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#61
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Won't know the final cc on my heads until the machine work is done, I suppose. I am going to start a new thread on cam selection, maybe you an help me with my cam choice?
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REDGOAT 70 1970 GTO 400/350 TH400 |
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#62
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All you have to be is open minded and be able to do common math with the ability of common sense. Each brand or engine group has it's quirks and/or deals that need to be addresses. I good automotive machinist can work on just about anything, but specializes in what he loves.
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#63
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It wasnt my intent to give you my suggestion on approximate compression and cam choice. You have decisions to make not me. You want highway gearing and good idle with strong performance best I can tell. You want no worry fuel choice too it appears. Generally this suggests a modest cam choice and modest compression. The more you push boundaries the more issues you have to overcome. The following combo works well in my wifes 69 bird convertible @ 3800 lb with driver full tank. 2.56 gear with powertax posi, non sticky regular BFG TA Radial 255/60-15, T400 2200 stall convertor(A freebie B+M from a parts car). 406 CI 9.7 compression home ported 1969 #46 heads with large valves, crower 60916 hyd cam and P65 dual quad with 1" 4 hole spacers topped with two 750 AFB's. Car has been driven thousands of miles since 2004 when this combo went together including the 1000 mile drive from our old home to our new home. Around town gets 12-14 mpg (carbs set tandem or progressive) and highway it gets 15-16 mpg. Performance is very good, idle quality very good(Deb says sounds too stock), around 15-16 in idle vacuum neutral (800 rpm) and in gear about 13 with a 750 rpm idle. Not a racer but it has gone down a track a few times with a best of 13.05 104 mph and spinning 60 ft times in the 2.20's. Certainly enough there to go mid twelves with traction(probably better with gear swap). Car only uses 1st and 2nd down the track. Recently sold the Dual quads and for now my RPM 780 holley are on there until I can put together an EFI. Car seems to run the same maybe a tid weaker up past 5000. Car usually runs on 93 no issue if stuck with 92 but 89 has worked ok except when hot it lightly pings from around 4k rpm up, and pushed hard and could probably tune around it If I wanted. Our combo is not your combo. A 428 or 455 would have different results. There are choices that could net better or worse results. I'm not going to dictate what I think you should run. Thats your choice your decision to live with! Cliff fwiw you seem to have good gas in Ohio. All our trips regardless of vehicle the fillups in Ohio net us our best MPG.(even fighting Cleveland, Columbus, Cincinatti traffic) NY gas we lose 2mpg. TN maybe 1/2 to 1 mpg. |
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#64
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"Cliff fwiw you seem to have good gas in Ohio. All our trips regardless of vehicle the fillups in Ohio net us our best MPG."
Yep, it must be good. When my son Matt first got out of the Air Force, he worked here for most of the summer. I sent him to town regularily to fill the fuel cans for the Ventura, as I don't drive it to town that much with the DOT's in place. I specified 89 octane, or 92-93 if they were out of it. It ran fine, and we even raced it a few times. Right before Norwalk this year, I sent him to town to fill the cans, and reminded him to get 93 octane instead of 89. He said "what?". Yes, 93 octane......then I find out he's been filling them with 87 octane all summer long! Well, the 11 to 1 compression engine never minded it a bit. The only problem I noticed is that on the very hottest days, when I had the engine really hot, it would try to "run on" for 1-2 seconds, but not every single time. Never once pinged at any load, rpm, etc. One comment on the 400 engine with an 067 cam and early small chamber heads. We have customers managing pump fuel with early GTO's and that set-up. Some have minor problems, others none at all. A few have upgraded to the larger 068 grind, or the Crower 60916 Bruce mentions, and a few on up to the 60243. None of those with the larger cams have reported any issues anyplace, and some of those engines are in excess of 10 to 1 compression with iron heads.....FWIW.....Cliff
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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#65
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1970 Bonneville Convertible |
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#66
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93cc will get you just under 10 to 1 in a 455. My old 455 had 6X-4's at 91cc, and TRW flat tops at zero deck. It was right at 10 to 1 compression. With the Crower 60919 (RAIV) cam it had no issues anyplace on pump fuel, and we ran it on 89-90 octane quite a bit.
When torn down for freshening up, the bearings were in perfect shape. At that point it had quite a few years in service and hundreds of dragstrip runs......Cliff
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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#67
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Unless you plan to pull the heads anyway, do you really think it's worth the effort and money to pull the heads just to mill 3cc's? I doubt you'd gain more than a couple average HP. It'd probably be worthwhile to pull the heads, port them and also mill to get the desired compression at that point, but not just to mill a few cc's...I'd be more inclined to use a slightly thinner head gasket if that were the only goal, cheaper, easier and the same end result.
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#68
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"Funny how the N/A internal combustion V-8 engine shows so many similarities following a few basic guidelines for setting them up, no matter what brand they are........Cliff"
In the article BruceWilkie linked to earlier (post #45), the author uses two examples of good vs. poor (for CR purposes) combustion chamber design, the Cadillac Northstar and the Hemi. I recall him saying the 2000 Caddy redesign allowed them to get up to 10-1 SCR on 87 octane (the second example I know of in this thread after LT1s.) So it appears those more modern chambers that everyone begged Edelbrock for (in Pontiac heads) are also a big part of that ideal combo. Now we even have them coming into the market for the masses. --so, I'll try a brief recap, as the thread grows, of responses to the original question: I. Major factors/variables beyond SCR include: -Dynamic compression ratio /cranking compression (as determined by cam events like LSA and IC--NOT overlap as is often assumed) -RPM range the engine operates in (determined by gearing and driving purpose) -Quench distance (pistons down the cylinder) -head material (iron vs aluminum) -cooling system efficiency -fuel quality, in addition to octane -combustion chamber design I'm sure I missed some--did it from memory. II. The major points of contention seem to be: -Should a "safe" SCR (8-1? 9-1?) be observed by non-tuners, even those who read these forums and are trying to learn more about high performance? Is SCR even useful as a guideline, given the many other variables? -Should camshaft LSA be wide or tight for a Pontiac, and for what purpose (part-throttle cruising? drag racing? dual-purpose? remembering that this is the "Street" section)? -What is the useful limit of dynomometer data for street-perf vehicles? I'll be happy to edit omissions/inaccuracies if they're pointed out. Last edited by mechanic17; 02-17-2011 at 04:59 PM. |
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#69
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Scratch LSA please! Its the intake closed point that determines how many degrees of crankshaft rotation you are in compression mode. Stroke and to some amount rod length determine distance in compression mode. Yes hot exhaust contaminating the intake charge can affect cylinder pressure too. However cylinder pressure is mostly affected by the intake closed point. Cylinder pressure affects compression temperature ultimately affecting octane requirement.
Real kicker is exact seat closing points arent advertised. In fact advertised seat timing varies from manufacturers often clouding things trying to compare one brand to another. Area under the curve and valve seat angles play a role here as well as valve timings and lift curves overall on both intake and exhaust. LSA and ICL are coincidental centerlines of chosen valve timing events. Cams are NOT designed on predetermined LSA or ICL. (though looking at different brands shelf grinds you'd think so) |
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#70
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Bruce, you quoted the LSA comment from the "debate" section. That HAS been hotly contended here, and I'm only trying to provide a summation, not add a new opinion in this post. Do you mean scratch it from the top section (section I)?
Or would you prefer to reword either yourself (I'll edit it in)? |
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#71
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OK to reference LSA ICL and advertised numbers but intake closed seat time would be more meaningful/conveniant for honest compression comparison. Not many have ever posted results of simply retarding their cam timing say 2 degrees to trim a bit of excess cylinder pressure. More often than not the whole cam gets swapped. instead. You do see posts where cams have been advanced beyond spec to compensate for wrong cam choice(too big) in the 1st place. |
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#72
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Sorry Bruce, the "edit" button has now disappeared. I did get several corrections in before the time expired. But your post does make your correction clear.
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#73
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Mech,
I think you did a pretty good job summing it up. The various discussions/arguments could jump off from any one of your points. The important thing from your post is that several parameters have to be considered when choosing a SCR for an engine. When modifying an engine, you become the design engineer. You have to make sure that all the parameters are accounted, so the engine operates properly in the intended application. You can't just boil it down to a SCR and leave it at that. The original poster (hi harry!) would be better served by us if we suggested entire engine combinations for his application, instead of just throwing compression numbers around for 4-odd pages. So guys: Suggest entire engine combos for both 9.5 and 10.5 compression ratios..... And then we can pi$$ about the fine details in the context of a proposed combination.
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I could explain all this to the girl at the parts store, but she'd probably call the asylum. White '67 LeMans 407/TH350/Ford 3.89... RIP Red '67 LeMans. 407/TH400/Ford 3.25 Last edited by chiphead; 02-17-2011 at 09:38 PM. |
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#74
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You sure do like to take a fellas words and twist them all around to suit your whims & views,dont'cha. I never once said there was a problem getting a SBC live on pump fuel @ 10:1. (please feel free to point out where I have said such) I just said to deny that more factors are involved in doing such beyond the influence that a reverse cooling system brings to that dynamic is more than a bit misguided. You mentioned the modern SBC chamber design,and guess what,so did I,please go back and re-read my reply post to mechanic17,I already pointed out that very same feature as you are now pointing out here. You mentioned how the shorter SBC stroke affects that deal,well guess what,please go back and re-read my reply to mechanic17 again,I already said that too! Again,I NEVER said there was any major problems running a carb equipped SBC @ 10:1 anywhere in this thread,even the carb/HEI equipped genII LT1's. (again,please feel free to point out where I have said such) All I said was it takes careful parts selection,and the proper tuning,just like any other engine requires to do the same. Which again is exactly what you're saying... 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. You read into another fellas words only what you wanna read into them,and that I have absolutely no control over. Often it seems to me that you dont care to hear anything from anyone that has a tendency to think for themselves,all you ever seem to want is a crowd @ your feet hanging on your every word.I told you guys this was gonna turn into a p!ss!ng contest. And surprise surprise,now it has. Funny thing is,I have'nt once expressed an opinion pro or con on this whole compression ratio debate in this thread,I've intentionally stayed away from doing such purely because I knew where all that drama would wind up going sooner or later,as it always does in these sorta threads. All that about the LT1 was about was the fact that I personally feel it's probably one of the more over-rated SBC engines out there,simple as that.And the fact that there are far more reasons beyond that reverse cooling system that lets that engine operate @ 10:1 CR on pump fuels. ![]() Have fun guys. Bret P. |
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#75
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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
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REDGOAT 70 1970 GTO 400/350 TH400 |
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#76
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#77
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However large or small my part of that blame may be. I knew what was gonna happen before I ever posted a single word in this thread. ![]() So to you & the rest of this threads readers,I'll say this loud & clear in plain language. I'm sorry. Just dont wait around too long for the other fella(s) to do the same... I say that as I dont recall ever seeing 'em do such publicly here on this forum. Yep,I admit I went a bit OT with the LT1 ,but I just hate that GM took one of the simplest & easiest to work on V-8's of all time,and made it an absolute nightmare to work on,all in the so-called name of "progress",and that just so happens to be one of my pet peeves,so when mechanic17 mentioned those engines as it relates to this topic,it just struck that particular nerve @ just the right moment,so to to him I'll also throw an apology his way,sorry dude,but you gotta admit they aint exactly a cake walk to work on like the other SBC are.I'll stay outta your next thread(s) too,if you want my opinion or advice on anything by all means please feel free to PM me or such. Bret P. |
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#78
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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. |
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#79
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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. |
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#80
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"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/
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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