[70 Dream]

It looks like this thread has gotten out of control, I think it's time to close it out.

But I found out pretty much what I wanted to know, especially with help from Ron H, GeeteeoGuy, and Chiphead, but thanks to everyone else as well, I've learned something from all of you.

As mentioned, I will be starting a new thread in the next two weeks or so with my proposed combo, and I will look forward to getting it critiqued.

Sincerely,

The OP

[Thumpin455_GTO]

Bret you think you have it bad, at least people are relatively nice to you. I like most everyone here, including you even if you did buy the car I wanted. I tend to stay out of these threads anymore, but I figured I would chime in just a bit. I always get ostracized for my choice of fuel here.

Just down the road from Wake Forest in Raleigh, there are three E85 pumps. You can run any compression ration you can get with flat tops and whatever iron head you have with it. About the most you will get is 13:1 and that is well within the range of E85.

The biggest change you would need to make is the carb, and you could run your car on it. My 70 has been running it since 07, and Cliff has helped me out immensely with my Qjet conversion project. The nice thing about running ethanol is you dont have to worry about detonation, it runs cooler, its cheaper, doesnt leave nearly as much carbon in the engine, (straight ethanol doesnt leave any carbon) and can make more low and mid range power that pump gas easily.

The drawbacks are you use more and with low compression engines you will get worse mileage, also there are only three pumps in Raleigh with none in Wake Forest(that I know of). An increase in compression can make more power along with getting better mileage, just how much is something I am working on this year. Will let anyone interested know this summer.

Just saying. Its an option since there are three pumps not too far away.

Now back to the regular schedule of lurking and watching the drama/arguments.

[screamingchief]

Ahhh,it does'nt bother me in the least,most guys here know that already,so they know it's an uphill battle to really get under my skin.

The funny thing is,I've never personally had a problem running a relatively high CR combo on pump gas,no matter what make engine they may have been.

My first "hot rod" was a 396 with 10.5:1 CR,that engine was in my '70 SS nova clone,and that thing never saw drop one of anything but pump gas,and it did'nt have any detonation related problems the entire time I owned it,nor afterwards by the reports I got back on that car.

And I've tuned more than a few high compression pump gas pontiacs too.

So I dont really look at this issue as a brand specifc sorta thing.

The real pisser is the fact that I've never once in any of these CR threads said that a high CR absolutely cant be done on pump gas.

I know tons of guys who run 12:1 to 13:1 CR race engines on pump fuel when they are'nt actually racing them.

But the fact that I still wont come on here and suggest that everyone who asks about this has to do that seems to be a bitter pill for some here to swallow.

I usually just explain that in my days as working as an auto tech and doing side work & such,I've run into plenty of folks that have had their share of problems doing such.

And @ times I also go ahead and express my personal opinion that,for the most part,I dont feel it's absolutely necessary to push the CR envelope as hard as some here feel it should be pushed.

But that seems to make some guys here get all foamy @ the mouth & such,and then they start slinging the insults and derision in my direction,and then things tend to go downhill fast from there.

Like it's a crime around here to have a slightly conservative opinion on a given subject such as this.

The average car guy is just that,average,they're often not expert tuners,and they may not even be genius cooling system engineers either,for them every little detail item they may miss or skip leads them that one step closer to less than stellar results when pushing the limits like others seem to have no problem doing.

I mentioned the genII LT1 transplants,those are a pretty good example,guys around here used to like to get themselves a low miles junkyard pull-out and throw the GMPP LT1 carb intake and a HEI in there and think they're done,but much of the time they'd have absolutely no idea that a fair amount of additional work is needed to adapt their car's old cooling system to that of the modern engine's cooling system,so they miss the boat there,and guess what happens,they cant get the thing to stay cool,and it runs like $#! cause they saw nothing wrong with throwing a box stock one of those junk @$$ 1850/600 cfm holley or edelbrock carbs on there and a mystery HEI with ???? advance curve in it.

So then you gotta fix the cooling system shortcomings first,iron out the timing curve next,and then get the fuel curve tuning nailed down.

After that they usually were'nt too bad @ all,and the upside there was you did'nt have to mess with the optispark junk anymore.

But with those deals most guys did'nt even know which was the inlet or outlet hose for the LT1 engine,and they're usually completely clueless about what to do with the steam lines or such,and the first thing they'd do is pitch the surge tank,and that's often a big mistake unless one takes some specific measures to account for that,see the LT1's reverse cooling systems were'nt as simple as some guys like to think they were,there were some hidden little tricks to that cooling system beyond just changing the direction the water was flowing.

Anyhow,I really dont care what CR any of ya'll use from here on out.

Swim @ your own risk.

And dont try to blame me if you drown.

Bret P.

[Cliff R]

"I really dont care if your BS meter is pegged Cliff,because to me that's as much a matter of your reading comprehension skills as it might be a matter of my writing composition skills."

Save us all the "drama". Every single time anyone challenges or critisizes anything you post, you have to go into all that useless, waste of time, too long to read crap.

Instead, why don't you tell us about the last engine you build with a high compression ratio that manages pump fuel with zero issues anyplace. Tell us ALL the specifics of that engine, Pontiac, Chevy, Mitsubishi, who gives a crap, just DIRECT results from actually doing it.

How about the dyno and track numbers from that engine, and how well it worked on the street in long term use on 10 percent ethanol fuel(s).

How about just some SPECIFICS about the last one that you actually tuned, or helped someone tune that was having trouble managing pump fuel effectively.

Your problem Brett, as I see it, and this is just my opinion, you don't actually do anything when it comes to these topics.

Unless you are out there right now, with todays fuel, building, tuning, evaluation, making changes, working DIRECTLY with customers on engine projects, helping them make the most power possible on pump fuel, etc.....then maybe you should just stay off of these topics?

You do EXACTLY what I expect from someone who critisizes your comments, you attack the messenger, instead of telling us about all the great things you are actually doing related to the topic at hand.

Dragging in the Chevy engine stuff was a poor choice on your part, IMHO. Those engine were built and designed to make great power on piss-water fuel, and they don't need a knock sensor, CCC, googy cooling system, or fuel injection system to do it. Get your hands on one and do some testing, or better yet, stick to Pontiac engines, at least you have had some experience with them at one level or another since I've reached puberty!.......LOL.

Anyhow, sorry to get off track some, it was expected.

If anyone would like any results of DIRECT testing, engine builds, parts selection, tuning, etc, feel free to PM me or send a not to my email via the website. I'm out there every single day doing this for a living, and we are still learning, and getting great results as well.......Cliff

http://www.cliffshighperformance.com/

[screamingchief]

Originally Posted by Cliff R

"I really dont care if your BS meter is pegged Cliff,because to me that's as much a matter of your reading comprehension skills as it might be a matter of my writing composition skills."

Save us all the "drama". Every single time anyone challenges or critisizes anything you post, you have to go into all that useless, waste of time, too long to read crap.

Instead, why don't you tell us about the last engine you build with a high compression ratio that manages pump fuel with zero issues anyplace. Tell us ALL the specifics of that engine, Pontiac, Chevy, Mitsubishi, who gives a crap, just DIRECT results from actually doing it.

How about the dyno and track numbers from that engine, and how well it worked on the street in long term use on 10 percent ethanol fuel(s).

How about just some SPECIFICS about the last one that you actually tuned, or helped someone tune that was having trouble managing pump fuel effectively.

Your problem Brett, as I see it, and this is just my opinion, you don't actually do anything when it comes to these topics.

Unless you are out there right now, with todays fuel, building, tuning, evaluation, making changes, working DIRECTLY with customers on engine projects, helping them make the most power possible on pump fuel, etc.....then maybe you should just stay off of these topics?

You do EXACTLY what I expect from someone who critisizes your comments, you attack the messenger, instead of telling us about all the great things you are actually doing related to the topic at hand.

Dragging in the Chevy engine stuff was a poor choice on your part, IMHO. Those engine were built and designed to make great power on piss-water fuel, and they don't need a knock sensor, CCC, googy cooling system, or fuel injection system to do it. Get your hands on one and do some testing, or better yet, stick to Pontiac engines, at least you have had some experience with them at one level or another since I've reached puberty!.......LOL.

Anyhow, sorry to get off track some, it was expected.

If anyone would like any results of DIRECT testing, engine builds, parts selection, tuning, etc, feel free to PM me or send a not to my email via the website. I'm out there every single day doing this for a living, and we are still learning, and getting great results as well.......Cliff

http://www.cliffshighperformance.com/

It simply would'nt matter if I did everything you suggest,you'd just try/use some other way to shoot holes in anything I said,same as you've done here in the past when others have tried to do such.

Hell you even argue with Pdude and Pbody over this very same stuff,and those guys both build a ton more stuff than you do,so why In the he!! should I even make the slightest effort to appease your impossibly high standards to earn some "cred" with you.

We've been over this time & time again,I dont care what anyone else here thinks about me,it serves me no purpose,I know that the members here have minds of their own,and personally I feel they can make up their own minds on that deal.

It's not your job to make up their minds for them,,,now is it...

There,is that short enough for you?

Probably not.

Bret P.

[Cliff R]

Brett, FWIW, I probably turn down MORE Pontiac engine jobs than those guys are actually building. I actually send that sort of work in their direction, as we just don't have the time these days for it.

How many Pontiac engine only jobs do you think a small shop can turn out in a single year?...and....what percentage of those engines are designed to make "optimum" power on pump gas at relatively high compression ratios, my bet is LESS than the number I build here...FWIW.

Completely DIFFERENT deal stuffing an "small" XE cam into a 455 with a 20cc dished piston in it, than setting one up at or over 10 to 1 compression with flat top pistons and a much larger cam on a wider LSA. Both do great "Dairy Queen" burnouts, but one will propell your car into the 11's at nearly 2 tons, the other will be hard pressed to run high 12's with the exact same drivetrain parts.

In any case, that isn't what this thread is about. I've figured out the deal, and am comfortable with building engines with high compression ratios to effectivley manage this new fuel. I do NOT recomend this path for others, but only suggest that it can be done. The course of action for the car owner should guide the engine builder. For most, 400hp and 500ft lbs torque from a 455, and 375hp and 450tq from a 400 are MORE than enough power to get them to a car cruise, car show, and occassional trip to the track to spin most of the way thru first gear and blast off a 13-14 second run.

Since a few have taunted that the only reason I can do this is because we run KRE heads with aluminum construction and "modern" combustion chamber profiles....we built an iron headed 455 at just over 11 to 1 compression and are testing it this year, street and at the track on pump fuel. I'll let you know how it turns out?.....Cliff

[Mr. P-Body]

Guys,

Let it go! Suffice it to say, Ken and I build engines to what customers WANT. CAN we build engines with higher compression? Of course. Why do we "not"? (we do from time to time..., not including "race" engines) Because we're in business to make our customers happy. In the vast majority of cases, we are completely successful. NOBODY makes EVERYONE "happy". And those that don't make an occasional mistake, simply don't DO anything at all. Neither of us are interested in "one-upping" anyone else.

To the folks reading this:

If you WANT to "press the edge" of compression, by all means, knock yourself out! For those that want a low-maintainence "daily driver" without all the computations and added effort, and are willing to "sacrifice" a few HP for that, lower the compression.

It really is that "simple".

Let's move on to something productive...

Jim

[PONTIAC DUDE]

Jim. Couldn't have said it better myself. X 2

Pushing the envelop is fine for home builders & top of the class racers. But in this business, it's about driveability and customer satisfaction. Most that we build for never see the track and 15 hp wouldn't be felt even by a veteran racer. Especially with the built in torque the stroke and lower end head flow produces out of the box.

The idea of posts is to answer questions & post what works for 95% of the builds. One off or pushing parameters can get a shop in trouble. This IS the street section. I'm not into posting my years of knowledge and pages of technical jargon. LOL. Basic answer to a basic question.

Even if you tell the dude he might have issues, put it in writing, you damn well know that he won't take responsibility for a phucked up engine when the pistons melt. All his buddies will hear how "Quote..... that dude doesn't know what the phuck he's doing."

It's the machine shop s fault.

You want to build pushing the limits of today's fuels and emissions leaning toward lower octane with higher ethanol content in the future to "TRY" and sucker the public into Greenhouse control. Go right ahead and live with your build.

But still hold to my post and been doing such for 15 years.

9.5-1 with 93 and 8.7-1 or under 9-1 with 87 octane. Can higher compression ratios be achieved with carburated engines and chasing all the engine senerios. Yes. But.................

In 40 plus years I have seen just about most of it with ALL Brands.........

Party On Dudes

[Superchief455]

Originally Posted by Mr. P-Body

Guys,

Let it go! Suffice it to say, Ken and I build engines to what customers WANT. CAN we build engines with higher compression? Of course. Why do we "not"? (we do from time to time..., not including "race" engines) Because we're in business to make our customers happy. In the vast majority of cases, we are completely successful. NOBODY makes EVERYONE "happy". And those that don't make an occasional mistake, simply don't DO anything at all. Neither of us are interested in "one-upping" anyone else.

To the folks reading this:

If you WANT to "press the edge" of compression, by all means, knock yourself out! For those that want a low-maintenance "daily driver" without all the computations and added effort, and are willing to "sacrifice" a few HP for that, lower the compression.

It really is that "simple".

Let's move on to something productive...

Jim

That about sums it up in a nutshell...... I follow the same "idea's" at my automotive shop since I'm the one ultimately responsible for the work. While i more often than not follow the business practices of P-dude and Jim I've also followed Cliff's "build practices" for other customers that felt they "needed to push the envelope" as well and have had no issues to date, but i also tuned and continually do the "up keep" with those builds.

When i built the engine for my fathers Trans Am he made sure he laid the "ground rules" down long before i ever touched anything. His words were " i know you and I'm telling you now.... I don't care what you do to this engine/car but there will be NO: solid anything camshaft, the only thing aluminum on this engine will be the intake and maybe accessories, My "racing day's" ended long ago kid so i don't want to hear race fuel or racing anything for that matter, and i better be able to drive it on the street or YOU will be doing what needs to be done to "fix it". Dad's (50 plus years as a mechanic) made him much like the "average customer" that just want a good performing engine with the ability to enjoy the car. He will "turn a wrench" now and again but has been retired for a couple years and not looking to relive his mechanical career on his play toy. He manages to "cruise" his 648 dyno proven hp 10.5:1 iron headed engine around any time he wants on 93 octane fuel and is actually more than happy with the engine/build while somehow i get stuck with the "up keep" job, but i guess that's what kids are for or so he tells me....lol.

If any of us have "paid attention" to the posts made by any of the the "professional engine builders" on this or any site about any build and take one piece of advice that any have given for any build it should be this...... Combination.... Combination.... Combination. This is the one thing that they can all agree on......LOL.

[Don 79 TA]

i dont know if it helps with these motors (that are on the ragged edge of compression) but in my jetskis i am pushing some high compression with no problems running 110 gas and heat coated pistons, which i was told i should be using 112-114...

sure for my 2 cycle not a big deal, i forgot off hand how much coating is, but add that expense up for 8 cycls, it could get costly, and as mentioned here there are many variables that play into preventing the pinging and damage

i don't know if coating pistons would allow you to say run .25 more in compression or not
but on the skis it allows us to run tighter ring gaps too

fuel quality also depends where you are as well
i'd love to run 87 octane that makes some nice power and has a killer idle as well


as i say...
live by compression.... die by compression...

[Cliff R]

Guys, I agree, it is really just as simple as that. Every engine builder has their own way of doing things, and none of us are trying to get one up on the other. I could give a rats butt about doing engines these days anyhow. Since I can pick and choose, we stick with upper end builds where the owner come to us wanting to make optimum power on pump fuel. They've done the 068 cam deal with dished pistons, or something close to it, and are ready to step up to the next level for power production and vehicle performance, not being content with just enough power to propell them to a car show or do a burnout in a hard right hand turn leaving Dairy Queen!

Since the goal(s) for the project open up many options for us, we are able to pick the parts and do what is needed during the build for a good end results. I also have FULL control of the tuning, as we build/tune the carb and distributor for every engine that leaves here.
I didn't jump on this thread to prove anything to anyone. I will ALWAYS recomend low compression ratios for most Pontiac engine builds, as most folks just want to get in their cars and drive around on occassion, and not the first care about making big power or running fast at the track, etc.

What is important for folks to know when it comes to the topic at hand here, is that the camshaft is a MAJOR player in the engines ability to effectively manage pump fuel, not just the "static compression ratio". SCR gets most of or all of the attention, and knowing what I know now about these engines, recomending 9.5 to 1 compression as the "ideal" place to be, or the highest compression ratio an engine can manage on pump gas, is a "retarded statement". There is no real mechanical limit for SCR in and of itself, and one can quickly get into BIG trouble at relatively low compression ratios with poor parts selection and engine assembly parameters.

PLENTY of information out there these days, folks should take full advantage of having it available to them. I say this because of the number of piss-poor engine combinations I'm asked each year to help folks out with. I spend a lot of my time listening to folks wanting help with their fresh engine builds that "run hot, overheat, and detonate" on pump fuel. The common denominator with every single one of them is that they are TURDS in actual use. It absolutely SUCKS to have a musclecar getting outran by a Dodge Neon with a big "fart pipe" hanging on it! When I get into the details of their build, there are a LOT of similiarities. Despite taking some flack for it, I've shared some of that information in public Forum.

In any case, I'm not here to argue with anyone about anything, back to the shop to get some work done. Warm weather is right around the corner, and we have 8 months work of work to get done in 6-8 weeks!......Cliff

[JSchmitz]

Originally Posted by Cliff R

SCR gets most of or all of the attention, and knowing what I know now about these engines, recomending 9.5 to 1 compression as the "ideal" place to be, or the highest compression ratio an engine can manage on pump gas, is a "retarded statement".

Cliff,

First, I'd like to ask, "Why don't you use the quote option in your posts?". It makes reading them a whole lot easier.

Second, Recommending 9.5:1 static compression ratio, with iron heads, is so common that it should be comsidered fact. IMHO. There must be a lot of "retarded " people building engines. Many, of whom, outweigh your level of expertise. So, I contest that, your statement is retartded. Can people get away with more? Of course! But, recommending 9.5:1, on pump gas, is just good sound advise. As with most things, some people have to brag about doing more with less. I always say, "The first liar doesn't stand a chance".

[mechanic17]

Whew, that was a solid 22 minutes of reading to get caught up. Brett, I'm happy to "shake your hand," so to speak, for my own part in the sideshow. Back where I come from (south of Boston) trash-talking and bench racing go together with cars like girlie calendars go together with them. You should hear the verbal abuse in our garage when we're actually facing each other after a few beers. So it all seems pretty normal to me. But you're right, this thread is approaching 2,000 reads because it's an important topic, so some of us (me) ought to cut the smack.

To add something new, lemme tell y'all about a non-success story I'm having that directly relates. '87 305HO transplant in a heavy car (non-LT1). I installed a xe262 cam as per the "recipe" that is common on the web. As I'm not yet able to spec my own cams, I usually just copy other people's success. This motor has an advertised SCR of 9.5 to 1 (right where P-Dude says 93 octane will work) and it ran great in the donor Z28.

The new vehicle had a rod-knocking SBC 350 with TBI, pretty identical to a truck engine of the '85-'95 era. I adapted a performer RPM to use the TBI and dropped in the cleaned up 305HO, and headers. Delete the emissions, cat included. Car's running hot, pinging, once it reaches operating temp--even at idle! 14 inches vacuum at best, which is right for that combo of parts. I burp the cooling system. Still hot, still pinging. Eventually I figure out the computer is putting too much timing in, so I rebuild a Holley 650 spreadbore and put in an HEI, taking the computer out of the equation. I set the timing about 10 BTDC, and check that it's not putting in too much. I even try doing without vaccum advance.

Now somewhere along the way I'm suspecting that I messed up with the cam, and that, as Cliff said a while ago, it's "way to good at making cylinder pressure at low RPMs." As I've learned here from Bruce, SC, and others, even though the LSA is 110 it's really probably the intake closing point to blame. My original idea was to get as much midrange as possible--the car is really just an experimental toy--and maybe retarding the cam would help at this point. You really can feel the balls in the midrange, too--but turns out, I may have wrecked the engine doing it.

Problem is, with all the pinging and running the car hot and yes, driving it around beating on it too even though I should know better, I think I hammered some bearings pretty good because now I hear that giveaway momentary rattle on startup. Idiot. I'll see what Lucas will do, but the writing is probably on the wall.

So if I'm right about this car (someone tell me if I'm not,) 9.5 to 1--even set by the factory (which probably means piston .025 in the hole and a .038-40 head gasket, old-style chamber, old style cooling system, just like our Pontiacs) is just too much for a poor cam choice. And that's with a small bore! Possibly the thing has carbon buildup or other inducement to pre-ignition that I haven't figured out yet. Like Brett said, timing curve, fuel curve--maybe--but I am pinging at idle, no kidding.

Not a hijack, not trying to make this about my car or SBCs either, just supporting a lot of ideas that have been thrown around in the thread. The stakes could have been higher--thankfully that motor was not a big investment. But the time to change it out is fairly priceless to me.

[PONTIAC DUDE]

If that 350 chevy is pinging at an idle. You need to check the degree of the cam and timing marks.

[mechanic17]

Originally Posted by PONTIAC DUDE

If that 350 chevy is pinging at an idle. You need to check the degree of the cam and timing marks.

P-Dude, I should have said the engine WAS pinging at idle as long as the computer had control of the timing (TBI systems will do that to raise an "unacceptable" idle). Now that I'm on a carb and non-comp HEI, it pings only when it is revved up in park (no load). And, under accelerating load, of course.

The cam is installed correctly--this was rechecked. However, I did not degree this one (in other words, either the chain, cam itself, or a tolerance stack could be contributing to an error.) Another, I suppose, argument for "non-tuners" to go easy on SCR. Engine tolerance for low octane fuel will vary because of these sorts of "built-in" problems. Naturally, the proper degree procedure would have picked up this problem, if it indeed exists.

My personal, current theory is that 9.5 SCR is combining with overefficient valve timing at lower rpms (3k and below) to create too much cylinder pressure. IF that turns out to be the case, (and assuming the factory claim of 9.5 is accurate for this engine) then 9.5 may not be a "safe" number after all, or at least not an "idiot-proof" one. And if it isn't, then we need to work out one that is for people who will insist on being conservative because they don't like to experiment with their cars, time, parts, and money.

[PONTIAC DUDE]

Originally Posted by mechanic17

P-Dude, I should have said the engine WAS pinging at idle as long as the computer had control of the timing (TBI systems will do that to raise an "unacceptable" idle). Now that I'm on a carb and non-comp HEI, it pings only when it is revved up in park (no load). And, under accelerating load, of course.

The cam is installed correctly--this was rechecked. However, I did not degree this one (in other words, either the chain, cam itself, or a tolerance stack could be contributing to an error.) Another, I suppose, argument for "non-tuners" to go easy on SCR. Engine tolerance for low octane fuel will vary because of these sorts of "built-in" problems. Naturally, the proper degree procedure would have picked up this problem, if it indeed exists.

My personal, current theory is that 9.5 SCR is combining with overefficient valve timing at lower rpms (3k and below) to create too much cylinder pressure. IF that turns out to be the case, (and assuming the factory claim of 9.5 is accurate for this engine) then 9.5 may not be a "safe" number after all, or at least not an "idiot-proof" one. And if it isn't, then we need to work out one that is for people who will insist on being conservative because they don't like to experiment with their cars, time, parts, and money.

Had to do the over 100 post. LOL.

I also subscribe more to the ............ if over 185 cranking compression you might be more susceptible to knocking conditions. But not a general rule either.

[Ragtop Man]

It's a bit of alchemy. Scratch that. A lot.

Actual Pontiac CR's were listed high to give the NHRA racers as much advantage as possible, production CR's could be down by as much as a half-point versus published.

IMO, it is better to stay conservative on the CR, and bump the ignition advance, than to go hog wild on compression and retard the spark.

But, a lot of things affect 'spark knock'. The load on the engine (low numerical rear end) ignition system quality and tuning, carb mixture distribution and A/FR, cooling system quality and capacity, exhaust system restriction and tuning, high bleed lifters or standard, and most of all, quench in the chamber.

The last is the most important, because if the piston is too far down the hole, combustion will take place in the dead space between the head and top of the piston, but it can not tumble and swirl in the same way it does in the chamber. You get a lot of knock and detonation, overheating, and generally pissy behavior. It is significant, because most shops will just drop a rebuilder quality piston down the hole and call it good, then blame the crappy gas when it doesn't run right.

Not having built a 400, but having seen the board's typical advice, with an iron factory head of good valve sealing and port matching, 9.0-9.5 static, zero decked, is about right, depending on cam carb and headers. The E heads can take more, all other parts equal, 9.5-10.0:1 because aluminum rejects heat more than iron.

This assumes all the other factors are working right, too.

[big_gto]

This post is not related to high compression, but too much octane. My experience is with too much octane for the SCR as opposed to too much compression comes from my experience with my `73 GTO. Weighing at 3980 (with a ¼ tank of gas), It had a `74 455 std bore block, with a re-ring/bearing kit, an 068 cam, Q-jet, 5C heads with 80K miles on them. I added 4 tube headers & re-curved the HEI. With .055 thick head gaskets I had about 8.8:1 compression. I used 85 to 93 gas, as well as 100 when it was at the pump in Minneapolis back in 2001. What I experienced is that the higher octane, the harder it was to start the engine, along with wet spark plugs. No pinging even with 16 degrees initial timing. Even with 87 octane & 8.8 compression, the GTO ran 13.98 & 98.22 according to my G-Tech. The higher octane did not help, but just caused hard starting as the engine wasn’t developing enough cylinder pressure to take advantage of the higher octane gas. However, there was a noticeable difference in driveability between 87 and 93 gas. 85 octane was obviously not enough. What I learned is to build the engine based on what’s available at the pump, which is what I did. For a daily driver $3.00/gl is expensive enough. I’m not disciplined enough to be a slave to the compression. But according to my `74 Catalina with a 400 2bbl. the underhood tag recommended 91 octane with 8.0:1 compression so I was close to giving the engine what it needed most of the time.
Note: the 100 octane gas was $1.80 a gallon while regular 87 was $1.25!

[slowbird]

Why push the limit of pump gas at all? You can run mid 11s with a 400 in a 3550lbs car with 9.7:1 compression. So why push it? Anyone really believe that the extra half a point or full point is really going to make a difference?
I agree with P-dude and P-Body built it on the safe side and go have fun you will never miss the very little power that the compression would have given you.
Just my opinion.

[Ragtop Man]

FWIW, for a couple of years, you barely lay hands on the GM Performance Parts ZZ383 engine, which made 425 hp on pump gas with a 750 carb and 1-3/4" headers, and ran on 87 octane pump gas.

The alloy Fastburn heads did such a good job at homoginzing the mixture and burning it properly, it could handle just shy of 10:1 static and run like a striped a$$ ape.

Now, everyone is going to LS motors, which punch that up to about 11:1 static on pump gas (!!!)