[STEELCITYFIREBIRD]

I run dual quads, progressive, never fat, reverse mounted, front carb is primary.(2 600 holleys on a 428, 10.5:1)

So what do you have for piston to head clearance?

Pistons?

Have you tried a diet of high octane racing fuel?

[pmd400]

Originally Posted by pastry_chef

Unfortunately yes, I was thinking that last night.
Before that... the cam must be degree'd, or at least measure the intake tappet lift at TDC and report here or to Chris.

LSA comments in the crapper. The CRITICAL matter is the intake closing point. This cam "correctly installed" will close the valve within a few of the Voodoo 703 Paul Carter dyno'd or the cams that Len C and Jones suggested.

Examples:
268 deg in at 107 centerline
274 deg in at 104 centerline

I'm sure you probably know but the gas rating is not the same as USA.. your 98 is about the same as USA premium.

I put the 703 in a 9.2:1 455 that was basically stock with iron D-port heads. It made 400 HP from 4700-5200 RPM, and made like 528 ft. lbs.. According to the customer, it makes 14" of vacuum at 5000 ft. elevation. Works his brakes good. It has a real good idle also. The Lunati description of the 702 cam as being choppy idle is totally wrong. I put that cam in a 328 and it wasn't choppy. It will be baby smooth in a 455. The 703 was smooth in a 455. The 704 has a slightly noticeable idle in a 455. The 702 will probably come out somewhere in the 108°-109° range if you install it straight up. But there are so many variables that could affect the cam timing that it is best to degree them. The Voodoos are especially sensitive to where they are installed. They like to be advanced at least 4-6°.

Less compression ratio

[pmd400]

Originally Posted by STEELCITYFIREBIRD

I run dual quads, progressive, never fat, reverse mounted, front carb is primary.(2 600 holleys on a 428, 10.5:1)

So what do you have for piston to head clearance?

Pistons?

Have you tried a diet of high octane racing fuel?

Pistons are trw forged. 0.005 in the hole. 0.040 head gasket. 94cc Chambers. 6.7cc valve relief. 4.18 bore, 4.21 stroke. Comes in right at 9.5:1

[pmd400]

Originally Posted by Sprocket

I ran a 223/231 110 LSA cam for over 15 years in my 9.3:1 iron-head 455 in the Texas heat. Zero detonation. As in none, whether it was 91, 92, or 93 octane from the local pump. This was in a heavy 4200 lb car with auto trans and air conditioning and four passengers. I was able to get my car to 13-flat in the quarter mile without trying (no testing or tuning beyond street feel tuning and a vacuum gauge) and that time was achieved consistently on a 102-degree day. So the idea that 220's is too small, or a 110 LSA is too tight, is just plain B.S. The cam is just another factor in engine building. Move one direction or another, be it with duration, lift, centerline, or lobe separation, is relatively insignificant incrementally. Overworrying about the cam ignores all of the other factors that comprise an engine's performance. Unless it is ground wrong or somehow just way off in "size", a cam is not going to make or break an engine any more than the carb, distributor, heads, converter, etc.

Back to the OP's situation, something is wrong with his air/fuel delivery or ignition curve other than just the cam unless there is something physically wrong with the cam, i.e. bad grind initially or degenerative lobe syndrome.

Do you know what duration at .006? Do you know intake centreline?
Thanks

[1968GTO421]

Not exactly relevant to the OP's problems but I found this description of the Pontiac 455 by Cliff to be one of the best I have found (having friends with 455's) :

"Once again as it relates to this topic. The 455 is a HUGE engine, it has long stroke with heavy internals and fairly long connecting rods. The heads and intake system are somewhat restrictive for that much CID. By design they will try to throw all the power at you very early in the rpm range. So basically they are very good at torque production and excellent mid-range characteristics, but seriously lacking in upper mid-range and top end potential.

Despite the less than ideal design and parameters they are still EXCELLENT engines for powering heavy vehicles and they don't require a lot of gear or converter to get it done. In order to get the very best from one, we need to install a camshaft that will push some power up higher in the rpm range and spread out the power as well. Installing small cams on tight LSA's is going backwards here. This will pull power down in the rpm range, and improve VE and peak torque will be higher and occur earlier.
The cam is actually too good at cylinder filling too early in the rpm range. So on paper Straub actually did a very good job for you. Problem is that the 455 is a little different animal than a 454 BBC with much less stroke, bigger bore, shorter rods and HUGE port flow.

As I've put up on these threads many time, the 455 by design is going to try to make all it's power right off idle, it's undersquare and fed by heads with no more cross section than an "average" set of SBC heads. So dynamic compression will be high and early in the rpms right to start with. When you bring in a small cam on a tight LSA, it just takes what the 455 does best and makes it better."

[Cliff R]

Thanks for putting up that reminder here as to what is really going on.

I tried to help early on as I've seen this EXACT same thing happen many times as we build these engines, build carburetors/distributors for them, and have had quite a few driven or trailered in here for custom tuning.

Matter of fact some have cam from as far away as Kansas, Georgia, New York, etc. Of course we only get them after EVERYONE else within reasonable distance from the owner has already had a crack at it.

Without exception every single 455 build we've worked with that was doing the same thing as the OP's here didn't have enough cam in it, and that cam was on a tight LSA.

The absolute WORST one we had used the Comp 262XE cam in a 455 with 6X-8 heads, it pinged EVERYWERE but at idle, ran hotter than it should have, and didn't make chit for power anyplace. Even though one would think that a tiny little cam like that in a 455 would make TONS of low end power right off idle it did NOT. Instead it pinged so hard on pump fuel with "normal" timing/fuel curves in it that by the time we tightened up the mechanical spark curve and yanked out enough timing to make it happy ALL the power was pretty much gone.

The second worse example was a 455 Super Duty just about 9.3-9.5 to 1 compression and Comp XR276HR cam. That cam is WAY, WAY WAY too good at cylinder filling in one of these engines and it pinged at heavy part throttle, full throttle and even at light part throttle if we added more than about 10 degrees with the vacuum advance. We "crutched" the repair by adding really high ratio rocker arms to it, which allowed us to increase the total mechanical timing to about 28 degrees and bring it in a little earlier, and add a few degrees with the vacuum advance for "normal" driving".

Even after making it much happier on premium pump fuel it wasn't overly impressive anyplace, just did OK.

What folks should take out of this is that adding high ratio rocker arms also added some effective duration, and the engine LOVED it. So doing so tells anyone with half a brain that the dynamic compression is too high/cam too small/LSA too tight. I mention LSA here because tight LSA narrows up the power curve, pulls it down a few hundred rpms AND spikes it higher. So basically the XR276HR cam is an EXCELLENT cam for one of these engines if you really want to make some KILLER power (torque) at low rpms, but in the same sentence it very quickly raises cylinder pressure high enough that a 9.4 to 1 CR engine acts closer to 11 to 1 as far as octane requirements are concerned.

Far as the OP's troubles, the cam choice is "tiny" for one of these engines which is going to make it very octane sensitive at 9.4 to 1 compression, and the 108 LSA and reverse pattern is really filling up the cylinders effectively at very low rpms. I doubt if moving it around (later intake closing) will cure all the issues, and even if they did it isn't going to make any kind of respectable power much past 4000rpm's or so as it's just not enough cam for such a huge engine right to start with.......IMHO.......Cliff

[PunchT37]

Reading Cliff`s last post reminded me of when I was drunk and dumb. I ran a 455 with 62 heads with the comp P280h cam. Even with 25 degrees total, I ended up busting 2 pistons.

Both cylinders were ok. Must say something for the nickel content of Pontiac blocks? Or dumb luck? Yeah, that`s it.

[TCSGTO]

I’m surprised C Straub hasn’t shown up here yet to enlighten us. I don’t know how him and his crew get any work done since they seem to spend all day advertising on every other forum on the net.

[Cliff R]

His fan club is ALWAYS on here giving him all sorts of "plugs" with this sort of thing.

They have grown quiet for the moment, guess it's a tough pill to swallow when you tell everyone reading these threads how great Straub, Kaase, and other "big name" folks are, never missing a single opportunity to argue LSA and all sorts of links to folks who agree with your line of thinking, and in the next breath do your very best to degrade the efforts of folks who specialize in Pontiac engines and do this sort of thing for a living. Not to mention a few guys like me come on here and give a lot of our valuable time for free trying to help folks out the best we can.

Dave at SD has reminded me more than once why he doesn't spend a lot of time on here and that I should consider doing the same.

I was about ready to crawl back under my rock with this thread since I put up some very good information early on and it pretty much went on deaf ears, even though I was hoping it would turn out better than it did. Certainly it's NEVER much fun when you do all the research, spend the time/funds to get a good end result, and come up a little short in a couple of places..........FWIW......Cliff

[OCMDGTO]

Cliff, Your posts definitely do not fall on deaf ears and shlubs like me take it all in and are very grateful that you share your years of experience and knowledge on here!!

[TedRamAirII]

Originally Posted by OCMDGTO

Cliff, Your posts definitely do not fall on deaf ears and shlubs like me take it all in and are very grateful that you share your years of experience and knowledge on here!!

+1 ! ; )

[STEELCITYFIREBIRD]

Originally Posted by OCMDGTO

Cliff, Your posts definitely do not fall on deaf ears and shlubs like me take it all in and are very grateful that you share your years of experience and knowledge on here!!

[Grand73Am]

Originally Posted by OCMDGTO

Cliff, Your posts definitely do not fall on deaf ears and shlubs like me take it all in and are very grateful that you share your years of experience and knowledge on here!!

Ditto!

[Holeshot71]

Same here!

[skipp65]

Same here, I value everything cliff offers this forum.

[Cliff R]

Thanks guys and I assure you that I try my best to help out if and where I can.

With that said I certainly am not "all knowing", but at this point in my learning curve I've got a pretty good handle on this sort of thing.

I've also reached a point in my career where I really don't have "a dog in the fight" so to speak. So when I come on a thread and post information about what we've actually done with something, there is NO want or need to bash the efforts of other simply to send or steer any more work in my direction as we have PLENTY of it, and not looking for any more.

So basically just trying to help out here and there, and rest assured I stay on topics that I have PLENTY of direct experience with, and not "googling" everything up just trying to find folks who agree with my line of thinking, or to pat myself on the back, etc,.......Cliff

[chiphead]

This thread doesn't need to be 9 pages long. Just put a 230/240/+4/112LSA cam in this thing and be done with it.

[Will]

Originally Posted by chiphead

This thread doesn't need to be 9 pages long. Just put a 230/240/+4/112LSA cam in this thing and be done with it.

[dmac]

Love this discussion.

Cliff- you have mentioned cams for the 9.5 cr range, and consider them as 'low' CR cams. How about a discussion of what would be an improvement over factory cams for the really low CR 455 of 7.5- 8.5 CR from the mid 70s. For us who want to be able to use regular pump gas without worry there should be something we can do as far as a cam change. My next project in next year or two is going to be a 1975 Grandville with a 7.6(?) CR with low miles that I'd like to wake up without spending a lot of money- just maybe a cam change and convertor. Anything off the shelf from cam makers that would help?

[Will]

dmac - I seem to recall that bman put an 068 cam in a low compression 455 and it worked really well for him.

I've asked about this myself as I have a stone stock '73 455 in my Formula currently that I'd like to wake up without spending much money. I've decided I'll put the Summit 2802 in it. That will require I change the valvesprings out (Crower 68404 will fit fine) but everything else should be able to remain stock.