[69 Limelight]

Looked up the lobe numbers from the cam card (3315 and 3316) in the Comp Lobe Master Catalog. Turns out they are Extreme Energy Hydraulic Roller lobes. Those Extreme Energy lobes with quick ramps and short seat timing get the job done. Wonder what it would have done with more ignition timing. Guess we'll never know.

[Steve C.]

Note the very nice power band, rpm numbers from peak torque to peak horsepower.


.

[SD455DJ]

Cliff, Awesome!!! With 8.8:1 compression that is amazing. Congrates on straightening the SD out and making it as powerful as it should be.

Just to add to the SD dyno results, Dan dyno'd a factory stock '74 455SD engine build a few weeks ago with the original Y cam (224/236), but with new .030 forged Diamond SD pistons pressed on the SD rods with 9.4:1 compression. The heads had been cut before and the decks shaved so the pistons were .005 in the hole. Got the quench at .040, so should be pump gas friendly. It pulled 410 hp at 5000 rpm and 525 lbft torque at 3400 rpm. It was interesting to see how the factory cam would perform.

Dennis

[vidguy]

Exciting and informative thread. Really fun project Cliff. Thanks. Lot's of spirited opinions, I like that..
The results are outstanding. I for one, appreciate the mostly "as Pontiac built it" approach especially in regards to Cylinder Heads. 42 years later it's rare to see a build and dyno of any Make true to form with factory heads.

Out of curiosity I looked up other Makes big cube rebuilds and dyno results in stock head form with factory offerings (block and heads for that year generally) and it sure looks like Pontiac was doing it right and that your build was a real good one, as this motor you built had huge power advantages over all of them.

[Cliff R]

I actually believe that the head porting done prior to us getting this build hurt the torque curve rather than helped it. They probably accounted for a few more ponies for peak HP, but with the cam used here we needed to keep signal (vacuum) up at low rpm's since it's street driven. Other goals included taking advantage of the Super Duty heads and making at or close to 1hp/cid which we achieved, even with relatively "low" compression.

Jeff had some dyno sheets of a 455 build dyno'd there recently with the same cam but 10 to 1 compression and 260cfm head flow and it make 20 more HP and 20 ft lbs more torque with a very similar power curve. So for sure another point and a half of compression would have helped a lot.

Also correct that these are "XE" lobes, but not to be compared to the flat XE lobes with shorter seat timing events and woln't make nearly the power the roller version will make in this application........Cliff

[critter]

I tell you there's 470hp in it. Just gotta tweak it a bit. Almost identical to what I had before I put the Eheads on. Congrats on a great engine Cliff and whomever is the owner. You're going to have a lot of fun with that.

[Skip Fix]

"I actually believe that the head porting done prior to us getting this build hurt the torque curve rather than helped it. " I figured with this much effort and especially SD heads you all would have flowed them to see if they had some holes in the flow curve that maybe needed some "touch up". And to at least get an idea the numbers.

[Cliff R]

I have no doubt we could have put some high test in it and cranked the timing up, then chased to power some more. NOT the goal here, just wanted a solid build on this engine and stayed conservative with the tune.

The last effort on this engine was done by a very well known Pontiac engine builder, and what I would call "high end" but used antiquated parts and "old school" methods in several areas. The result was an engine that refused to idle, required race gas, wouldn't stay running at low rpm's, not very user friendly for street use, and didn't last but a few hundred miles.

We went a completely different direction with it to meet the customers goals, but still wanted to stick with a roller cam set-up, and upgraded rods/pistons/ring packs, and make around 1hp/cid while maintaining the "stock" appearance........Cliff

[Cliff R]

The Super Duty heads in stock form are PLENTY for the power level we were looking for Skip. I've done several of these and a couple of HO 455's and they do NOT need any help in the heads for 1hp/cid. The added head flow for previous port work wasn't needed here, we just had the valves and seats re-worked, springs checked, and cleaned/assembled. Had to ditch the overheated and hand bent factory guide plates and went to KRE's laser cut plates and used 5/16" pushrods.......Cliff

[Skip Fix]

Cliff my point was not getting more flow for more HP, just making sure the original porter had not made it worse or created some turbulence at a specific lift-easy to do on pontiac iron heads! Why I'm not a porter! I can port match and clean up castings but shaping a port my brain just can't always figure out.
Cool motor build! Since I'm a round port kind of guy

[wovenweb]

Originally Posted by Cliff R

Hoping for close to 1hp/cid and 530-540tq for peak numbers. We won't be chasing the tune really hard for best numbers, just going to run it in on the dyno, check for leaks, and make a few pulls on it. I'll put the dyno sheets up after we're done......Cliff

Originally Posted by Cliff R

Another quick metering rod change and 2 degrees more timing and it made 457.8hp and 533.4tq. Dyno sheet from the last pull attached.

Sometimes it pays to stick with experience.

[Cliff R]

"Cliff my point was not getting more flow for more HP, just making sure the original porter had not made it worse or created some turbulence at a specific lift-easy to do on pontiac iron heads!"

Understood, but we had no intensions of changing anything there and they were done by a Pontiac engine building "guru" with decades of experience so we just left all that alone.

My experience with at deal has also taught me that more likely than not you are going to check that deal out and NOT like what you find and open up a another big "can of worms" trying to straighten all that out, so we chose to just "run what you brung" so to speak with the ported heads.

Looking at the graphs from the dyno runs they were very smooth and no big dips anyplace in them. The ported heads simply weren't needed for what we were doing here, and I suspect that the big runners slowed the air down considerably at lower rpms and may have hurt our torque numbers slightly, but that's just a guess on my part after seeing the results and comparing them to others that we've done with unported but very well prepared stock heads.........Cliff

[Cliff R]

"Cliff, Awesome!!! With 8.8:1 compression that is amazing. Congrates on straightening the SD out and making it as powerful as it should be."

Thanks Dennis. For sure Pontiac didn't but nearly enough cam in these engines but I'm sure the EPA was the big stumbling block there.

So with a little bump in compression and a stock cam they are over 400hp/500tq without grumbing too much. Can's say I've ever seen a dyno sheet of a stone stock one?

They would have been a solid 1hp/cid if the factory could have but the RAIV cam in them with the high ratio rockers and a little more compression, but the 80 something degrees of overlap and not enough squeeze would have made them impossible to get thru emissions.....IMHO......Cliff

[Skip Fix]

For me I just like to know for myself what the numbers are on my heads-even fairly stock ones.Just can't help myself

[Cliff R]

Agreed Skip, but it was NOT my engine, and there was no need to spend more of the customers money since we were not going to do any additional port work anyhow.

IF they were mine, we would have flow tested them......FWIW......Cliff

[SD455DJ]

So with a little bump in compression and a stock cam they are over 400hp/500tq without grumbing too much. Can's say I've ever seen a dyno sheet of a stone stock one?

Cliff - I'll try to post a copy of the dyno sheet soon. Dennis

[pontibeast]

The standard bore 455 I am working on right now made 390HP with stock rebuilt 4X heads that were 114cc and a crappy 262 XE cam. I have gotten my 6X-8 heads ported and am putting in a Stump Puller hybrid setup so I will have to see what improvement it makes. It won't be really accurate as the 390 was on an engine dyno and I will be chassis testing once done but hopefully it will give me an idea of how the engine likes more compression and cam.