[rexs73gto]

I want to add a bit here . I've run a 455 +.30 over for about 5 years now & it has a RA IV cam Crane factory blueprint , & it idles fine , has a nice loop to it & it's or was in my 73 GTO with 4 spd. & 3:73 rear gears. I get about 16 mpg's & it was running high 11's . I was running the 1:65 rockers & the car ran great. Ido have E-heads on it right out of the box which gives it about 9.6 comp.???? I think. I do run it on 87 pump gas to. I know what the lift is but right off hand don't know what the dur. is but I usually get funny looks & comments when I say I'm running this cam because it's an old cam. But I've run this cam in several 455's & a few 400's over the years & it always seems to work good. & by all rights this is a 30+ year old cam design & works great for me.

[Cliff R]

"Cliff, Jim, With the knowledge you have now, of using the 041 cam in a 10:1 455 street engine. Are there somethings you might experiment with to make the 041 cam even better? or is it at the edge of doing the best it can, for what it is???"

For sure high ratio rockers really help that cam. I ran 1.73 Ford rockers on mine, pretty sure Jim ran Harland Sharp 1.65's (1.71 actual ratio) on his. It's also a huge cam, even in a 455, so if you want great idle quality Rhoads lifters are really going to help it. I would add here that I ran mine for quite a while with std Johnson HT-951R lifters, then swapped in the Rhoads lifters and immediately saw about 2" vacuum improvement at idle speed. The car ran no quicker with them, but my converter "flashes" well past 3000rpm's, so they are well pumped-up by then anyhow. They did improve idle and off idle smoothness, so I did see a benefit from them on the street and driving around in the pits. I would also add that an engine that idles smooth and strong against the converter also makes the car easier to stage without coming up against the brakes, so another side benefit for using them if you are a "foot-brake" drag racer.

The 041 cam is just a great cam for the 455 engine, maybe by coincidence or the fact that the engineers at GM really did know what they were doing WAY back in the 1960's. As good as the 041 cam is, it's not the best choice for the smaller 400 engines in most cases. Even in the big 455's, it really likes to be at least 9.5 to 1 compression, and 10 to 1 is even better. My old 455 with iron heads was right at 10 to 1, and it would manage any octane of pump fuel that I wanted to put in it. One of the first years I attended the Norwalk race with that engine in place I entered the street car race that required that we go off the track and run a 20 mile loop, then return to the track, fill up with pump gas right before we got back, and make 3 runs without shutting the engine down.

It just so happened we stopped at a station that only had 89 or 90 octane, no 92-93. It was one of the hottest days I can ever remember at Norwalk. LOTS of the other participants were dropping out with overheating issues, and one guy blew up his engine (high compression) making runs when we got back.

My 455 never even thought about running hot, overheating, and made three perfect runs back to back without shutting it off. After that experience I'm sure I could have ran closer to 10.5 or even a bit higher compression and still easily managed pump fuel with that engine.

Shortly after those runs we pulled the engine for the KRE head testing and HPP/Popular Hot Rodding articles that followed:

http://www.hotrod.com/how-to/engine/...-dyno-results/

http://www.hotrod.com/how-to/engine/...track-results/

With the new heads and higher compression ratio the engine still easily managed pump fuel, but I didn't play around much with anything less than 92 or 93 octane.

I still kept the original iron head testing in the back of my mind and decided to build the next 455 with smaller 76cc chamber heads, bigger cam, and 11 to 1 compression. Working directly with Dave at SD we got one of the first sets of his KRE ported heads and teamed them up with his "Old Faithful" camshaft. It turned out to be a great success, and the current 455 easily runs on 87 octane fuel at 11 to 1 compression. I even tried adding higher octane fuel to it at the track, and it slows it down a few hundreths, so it really likes and runs well on lower octane fuel.

This sort of throws a monkey wrench into the proverbial "brick wall" theory of 9.5 to 1 compression for pump fuel, and I think the folks that make that remark are talking about 92-93 octane, not 87 or 89.

I certainly do NOT recommend for folks to do the "high compression pump gas deal", but we have shown that with careful engine building, and full control of timing/fuel curves that you can EASILY manage pretty high compression in one of these engines. It involves tight quench, and the right cam more than anything else. Of course you have to be able to keep the engine cool, so a small radiator and electric fans may not be in your future with that deal. I tried a big single electric fan for a while and it kept killing the battery trying to keep the engine cool on race days in really hot weather, so I went back to the stock set-up and all has been fine since.

The camshaft topic ALWAYS gets kicked all over the place on the Boards, so for the most part I sit back and watch the threads run. I have been paying close attention to folks who have came up WAY short in power with 455 builds, and they almost ALWAYS have chosen the smaller cams mentioned in this thread. I have also had a number of those engines brought here to tune, or set up carbs for them, and to date haven't been impressed in the least by any of them. I knew those cams weren't making the grade, so finally we had a professionally built engine by a well known shop try that deal, and we ended up getting dyno sheets on it, which prompted me to go public with the information. I certainly hope that it helps some folks out with cam choices for these engines......Cliff

[Steve C.]

When you see specific compression numbers touted in these cam discussions consider the cylinder head material, iron or aluminum, and consideration should be given to the chamber design involved.

"The design of the combustion chamber influences the performance of the engine and its anti-knock properties. The layout and shape of the combustion chamber has a bearing on the thermal efficiency and performance as well."

Typically a 'heart shaped' combustion chamber will tolerate a higher compression on some these aluminum heads. Iron heads and older style Edelbrock heads are a different ballgame. As an example, with the Edelbrock head and their 'regular' combustion chamber design some might suggest max of 10.25 with the 87cc chamber design and max 10.5 with the 72cc chamber design.

This for day-to-day type driving in all kinds of conditions for the average person, and as a precaution with unknown gas quality. And one doesn't always know how a customer would tune and drive the intended combo. Many will suggest for day-to-day type driving in all kinds of conditions, a potential for unknown gas quality and for the average person one still might suggest precaution.


.

[pmd400]

Iv read this whole thread, it's very interesting.
In a 9.5:1 iron headed 455, a cam with a 274 adv duration and 230 at .050 is considered to small. It doesn't make as much power as it should and is octane sensitive.

A crower 60919 has adv duration of 304 and .050 duration of 231. It makes great power but works best with 10:1 compression and rhoads lifters.

Is it possible that a cam with 230 at .050 and an adv duration of about 290 using standard lifter would be a good compromise? I understand that some companies also use a different lift point for advertised duration, so some cams seem to have a longer duration but in fact they are just measured at a lower lifter point.

Crower, comp, howards, lunati, melling all measure the advertised duration at 0.006 of tappet lift

[Will]

Originally Posted by pmd400

Iv read this whole thread, it's very interesting.
In a 9.5:1 iron headed 455, a cam with a 274 adv duration and 230 at .050 is considered to small. It doesn't make as much power as it should and is octane sensitive.,,,

I think this might be oversimplifying things a bit. Lobe centerlines play a very large role also as they determine valve opening and closing points in conjunction with the overall lobe profile. A fast-ramp cam like that might work just fine and have a broader powerband if modified to a 112 LSA and 108-110 ICL. Of course, the faster ramp cam will still have later opening and earlier closing points than a cam with similar .050" duration but longer seat duration ("slower" ramps) and the same lobe centers.

Isn't the point of a roller cam to minimize the seat-to-seat duration in relation to duration and lift off the seat? In that respect, a fast ramp flat tappet cam is an attempt to mimic the valve motion of a roller as much as possible. Of course it seems that running bigger rollers (as measured at .050" duration) than flat tappet cams is the way to go.

Which all comes back to valve opening and closing events and their relationship to other engine parameters being the key to whether an engine is a dog or a monster.

[nytrainer]

I happen to own a practically new (thumbs down in a friend's 455) Comp cam XE 262 cam (specs below).
To the gurus who can decipher the specs. would this cam work nicely in a 9:1 cr 350 with dual ex, iron manifold and q jet or is there no place for it in any Pontiac engine? I read all the posts in this thread but still can't answer that question myself.
Also, plans are/were for my 455 to get the 041 cam (9.8:1 cr 6x-4 with push rod holes enlarged) or should I be looking at the Crower offerings (619...). Car is a 4 speed with 3.23's. I'd rather do regular lifters and would be OK with a rumpity idle (but I do have power brakes). Are Rhoads a must? I think the ticking would send me over the edge. It's a once in a while cruiser car during nice weather.

[JLMounce]

I've been following this thread pretty diligently. As Cliff has suggested, that barrier at 9.5 SCR for pump gas isn't a hard and fast rule.

I didn't build the engine in my bird so I couldn't tell you exactly what cam is in it, however it runs on pump gas just fine. It's a 462 topped with #62's which should put it between 10.8-11.2 SCR depending on how it was built.

I suspect that the cam may be something along the lines of an 041, possibly with rhoads lifters. Though without taking the engine apart I just don't know.

This is great information for the future if/when I decide to do a rebuild.

[Will]

I'm no expert but I'd think that XE262 would probably work decently in a medium compression 350 with a mild stall (or manual) and mid 3-series gearing behind it. Good flowing exhaust will really help.

I ran a Comp 270 Magnum with Crane Hi-Intensity lifters (similar to Rhoads but slightly less effective at improving low speed characteristics by all accounts) in an 8.5:1 400 with stock log manifolds backed up by an M-20 and 3.73 gears. It was a bit soft on the bottom end but came on strong at 2500 and pulled well to 5000 where it ran into a wall. The XE 262 should produce similar results in a 350, maybe even be a bit better on the bottom end. That 400 would likely have pulled better on the top end with headers and something better than a 2" compression bent exhaust system.

The tighter the lobe separation the more the engine needs good flowing exhaust to make upper RPM power, in general.

[neill]

Originally Posted by Will

I'm no expert but I'd think that XE262 would probably work decently in a medium compression 350 with a mild stall (or manual) and mid 3-series gearing behind it. Good flowing exhaust will really help.

I ran a Comp 270 Magnum with Crane Hi-Intensity lifters (similar to Rhoads but slightly less effective at improving low speed characteristics by all accounts) in an 8.5:1 400 with stock log manifolds backed up by an M-20 and 3.73 gears. It was a bit soft on the bottom end but came on strong at 2500 and pulled well to 5000 where it ran into a wall. The XE 262 should produce similar results in a 350, maybe even be a bit better on the bottom end. That 400 would likely have pulled better on the top end with headers and something better than a 2" compression bent exhaust system.

The tighter the lobe separation the more the engine needs good flowing exhaust to make upper RPM power, in general.

So Will, would you install it @106 or retard it to 110 to match the intake closing angle of the 270 magnum? How octane sensitive was your 400?

[Will]

Originally Posted by neill

So Will, would you install it @106 or retard it to 110 to match the intake closing angle of the 270 magnum? How octane sensitive was your 400?

Heh, we're way off-topic for this thread but I wouldn't mess around trying to retard it. All that will do is kill off low-end torque and may not make any more higher up.

350s need all the help they can get in the lower RPMs.

That 400 drank a steady diet of 87 octane with no complaints.

The XE262 seems like it would be decent in a low-moderate compression 350. Not the best choice, but it shouldn't be bad. I wouldn't run it in anything larger.

[Cliff R]

I've had a couple of 400's in here to build carbs for and tune that used the XE262 camshaft, and it's not very impressive anyplace. The last one had 7K3 heads on it, so 8 something to 1 compression. One would think that a tiny cam like the XE262 would fair good there, but it was a complete "turd" everyplace, IMHO. It didn't even act like it had a "big" cam in it, idled with a "deep/heavy" sound, not the first hint of "lope" anyplace, power curve was flat and done early in the rpm range.

Of course I had no idea what else was done to the engine, it could have had .100" quench in it for all I know?

I have been around "low" compression 400's before, and they can be STRONG runners with correct rebuilding and cam selection. The 400 that used to power my Ventura had 6X heads on it and ran into the high 13's with a stock converter and 2.73 gears......Cliff

[Skip Fix]

"I didn't build the engine in my bird so I couldn't tell you exactly what cam is in it, "however it runs on pump gas just fine. It's a 462 topped with #62's which should put it between 10.8-11.2 SCR depending on how it was built."

Just because you cant hear detonation does not mean it is not happening. Go put it on a chassis dyno and load it make a pass, then drain the gas run it on 104 race gas and see what it does. Bet it picks up a bunch because it needs more octane

Cliff you got many 455s running 11.2:1 iron heads on pump gas for a street car?

Those 11.5 NHRA stockers using low compression 78 motors sure got it figured out! But the chassis and cam are definitely not too street friendly

[JLMounce]

Originally Posted by Skip Fix

"I didn't build the engine in my bird so I couldn't tell you exactly what cam is in it, "however it runs on pump gas just fine. It's a 462 topped with #62's which should put it between 10.8-11.2 SCR depending on how it was built."

Just because you cant hear detonation does not mean it is not happening. Go put it on a chassis dyno and load it make a pass, then drain the gas run it on 104 race gas and see what it does. Bet it picks up a bunch because it needs more octane

Cliff you got many 455s running 11.2:1 iron heads on pump gas for a street car?

Those 11.5 NHRA stockers using low compression 78 motors sure got it figured out! But the chassis and cam are definitely not too street friendly

I admit this is a possibility. However, I've had a bore scope up it's skirt and at least with the crappy resolution from the camera the piston top doesn't show any signs of damage. I was even able to pull the part number off the piston.





L2359 which corresponds to the Sealed Power forged slugs for 4.181 bore.

One thing of course working in my favor here is my location. I'm 4500 ft above sea level.

[77 TRASHCAN]

The answer to post 270 is post 279,,,still no, I've read it here several times. Just because a company makes a product, doesn't mean it'll work, even though most of us have trusted them for years,

You're getting this experienced info. from someone that does this work EVERYDAY!!!
The biggest things a lot of folks can't wrap their mind around, is not knowing how their engine performs in comparison (lets say a low comp 400 w/ an XE cam) to an engine that has a perfect storm of parts, and modifications performed by an experienced pro doing the job, all the way from the build to tuning your engine.

You let somebodies grandpa, (that's done machine work for 40 years, and maybe the machine work is... even very good!!!) select your cam, and he has no part in your engine tolerances, induction selection, or especially tuning the thing. You MIGHT have a car that you THINK runs pretty good. BUT you have nothing to compare your performance to.

I read these forums to learn! So that I don't make engine building mistakes that have been performed over and over for decades, because of lack of knowledge...

That XE262 cam would make a great boundry marker for your property.

[Cliff R]

Skip, I do have a couple of pretty high compression iron headed 455's out there on pump fuel, on is 11.5 to 1, and it's been fine so far. I haven't talked much about it publically, as both were done recently and don't have a lot of street or track time on them. Besides, I really didn't want to jinx myself. About the time I start ranting and raving about how good it works the guy will surely put a couple of pistons in the oil pan! But, so far, so good.

I also help out quite a few folks with Stock Eliminator, Pure Stock and FAST Class cars. I agree the Stock Eliminator "low" compression set-ups run amazingly well for what they are. I support more folks in Pure Stock and Fast these days than Stock or Super Stock classes.

Just got off the phone with one of those folks yesterday, he's running a couple of 68 Firebirds, the Pure Stocker has went 11.18 and the FAST Class car deep into the 10's. We were trying to find a few more HP someplace to get the FAST Class car into the 9's this season, so tossing some ideas back and forth......Cliff

[68azbird]

Maybe if that was 110 octane coming out the pump.

[Steve C.]

Terry Walter Precision Engines:

Pontiac .030-over 400
unported #16 heads - 2.110 / 1.770
9.2 compression
Comp XE262H hyd flat tappet cam
Factory cast iron intake
Holley carb
Factory long branch exhaust manifolds

365 hp at 5400 rpm
445 ft.lbs. torque at 3400 rpm

Chevy comparision:

Comp XE262H cam tested with Chevrolet 350
Bore+4.040" Stroke=3.480" 9.25:1Compression ratio
Dart S/R Heads Edelbrock Performer Manifold
Holley #3310 Vac. Sec. Carb 1 5/8" Headers

Max Torque 411 ftlbs @ 3600 RPM
Max Horsepower 330 HP @ 4700 RPM
Vacuum 18.5" Hg @ 800 RPM
20" Hg @ 1000 RPM


.

[bendutro]

Thanks for sharing Cliff, the firsthand experience is invaluable to guys like me that can't afford to build 5 different engines to sort the truth from the BS.

Not to throw a wrench in the discussion, but in all the CL/duration/SCR/DCR talk, I can't help but wonder if Rhoades lifters would help or not.

[llwta76]

Originally Posted by Cliff R

Skip, I do have a couple of pretty high compression iron headed 455's out there on pump fuel, on is 11.5 to 1, and it's been fine so far. I haven't talked much about it publically, as both were done recently and don't have a lot of street or track time on them. Besides, I really didn't want to jinx myself. About the time I start ranting and raving about how good it works the guy will surely put a couple of pistons in the oil pan! But, so far, so good.

I also help out quite a few folks with Stock Eliminator, Pure Stock and FAST Class cars. I agree the Stock Eliminator "low" compression set-ups run amazingly well for what they are. I support more folks in Pure Stock and Fast these days than Stock or Super Stock classes.

Just got off the phone with one of those folks yesterday, he's running a couple of 68 Firebirds, the Pure Stocker has went 11.18 and the FAST Class car deep into the 10's. We were trying to find a few more HP someplace to get the FAST Class car into the 9's this season, so tossing some ideas back and forth......Cliff

A iron headed streetable car over 11 to 1 ? I'm assuming on 93 pump gas? I'd like to hear how you've managed that trick. We all know about quench and smoothed chambers and such but there must be more in your engine building techniques for you to accomplish this. I'm all ears if you're willing .

[Skip Fix]

I looked at my post and to clarify I meant 11.5 second 1/4 low compression 78 stockers. They allow 89cc heads for the "stock" 6X chamber.