[tom s]

About 5 years ago I built a pretty stock 455 pump gas engine for my Judge.455,9.5C,completely stock 48 heads except springs and 1 pc valves.I used a XE276HR on a 110 as I had it in my drawer.We ran a stock AL SD intake with Joe Shermans dyno carb and custom 2in Tyree 4 tube headers.The engine made 432 HP at 5200.That cam was [email protected] ran 1.65 H&S rockers.I put Daves new Stump Puller II in the engine with exact same intake and carb put replaced the 1.65s with 1.50s to keep the lift virtually the same.Because I wanted to know the performance as it will be in the car I used long branch 2 1/4 exhaust to about 2 ft of 2 1/2 pipe into Joes dyno mufflers.The engine made virtually the same HP 234 but at 5400.Joe figures we gave up about 15-20 HP with exhaust from the 4 tubes.We also ran no spacers as I cant run one with the 69 T/A RA pans.This cam was on a 112 put in at 107.He is going to pump it.FWIW,Tom

[pastry_chef]

Excellent information, thanks

Curious about the numbers lower down for both.

[PAUL K]

Great information....thanks for sharing.

[tom s]

He starts the pulls about 3800,peak TQ was right there on both.The SP2 was 500.I will get the sheets on this engine when hes done.Tom

[71 T/A]

Tom, you're saying the Stump Puller 2 was no better than the XE276 HR? I have the Stump Puller 1 in my 72 Formula and that cam is great, like the idle and power, especially with ram air manifolds.

[72LuxuryLeMansLa.]

Originally Posted by 71 T/A

Tom, you're saying the Stump Puller 2 was no better than the XE276 HR? I have the Stump Puller 1 in my 72 Formula and that cam is great, like the idle and power, especially with ram air manifolds.

Just a guess on my part but, with stock-non-ported d-ports there is a point where more cam wont net much result.....?

[grivera]

Not apples to apples but food for thought: http://forums.maxperformanceinc.com/...8&postcount=63


Btw, what timing made peak hp?

[tom s]

As I said,Joe thought at least 15HP because of the small exhaust,It made HP 200 RPMs over the smaller cam.Only 6 degrees more.Tom

[Will]

If I read tom's original post correctly, the engine with the SP2 *and* a more restrictive exhaust made the same power as the XE276 with headers.

The consensus was the engine would've made 15-20 more HP with the SP2 and the same headers/exhaust.

Did I get that right?

[Cliff R]

Too many changes to really make a comparison between the camshafts. The change in rocker arms was a BIG deal as it made the smaller cam very close to the bigger one with additional effective duration and added lift.

Below are a couple of dyno runs from a 455 with #96 heads and 9.3 to 1 compression. Even though they are ported to 250cfm, note that the same 276HR cam didn't make power high enough in the rpm range to really need that much flow, but the bigger cam really took advantage of it.

The cam was the only change made there as well.....Cliff

[AdamIsAdam]

Originally Posted by Cliff R

Too many changes to really make a comparison between the camshafts. The change in rocker arms was a BIG deal as it made the smaller cam very close to the bigger one with additional effective duration and added lift.

Below are a couple of dyno runs from a 455 with #96 heads and 9.3 to 1 compression. Even though they are ported to 250cfm, note that the same 276HR cam didn't make power high enough in the rpm range to really need that much flow, but the bigger cam really took advantage of it.

The cam was the only change made there as well.....Cliff

wow!

Cliff, what rocker size was this engine using, do you recall?

I would have expected more torque, no?

[steve25]

If this dyno test was done with the same Carb jetting then also take note of the smaller BSFC numbers with the second Cam and its greater power with less fuel!

The fuel went into making greater power and not out the Exh!

[tom s]

This engine is going in a 69 firebird for a track car.I put the bigger cam in in hopes to raise to HP curves to maybe kill off some of the low end to help blowing off the tires coming out of a corner.As said I wanted this engine on the dyno exactly like it will be in the car on the track.If everything looks good Joe is going to put on a HSD single plain to see if it has a effect either way.Again it is bone stock,not port matched.The engine is not ideal but did not want to chance hurting my 366 NASCAR RA V engine in the car so this was sitting in the garage doing nothing.I just swapped the cam and put a Canton pan on it.If looking for more HP I would have changed the springs to reuse the 1.65 rockers and maybe even the next step cam.Tom

[Skip Fix]

Tom how did the Canton pan go on?

[tom s]

No issue,I put tape in the inside and ran the dip stick against it,drilled the hole there and it works perfectly.Tom

[tom s]

Little more info,the engine was not able to use the single plane HCD intake.HP was a few less and at a couple hundred turns less?The other thing we found is it pumps 190-195 and I question if I can run our 91 gas.Going to get ahold of Dave and get his feel.He told me to put it in at 107 and now I question if that might be a little too much.Also on one pull he had a high RPM pop that I think is because of the cheap ass plug wires I gave him.He is going to put a set of 8MMs on and do some pulls over the weekend.Wont have any sheets untill he gets it off the pump.For those interested I will post up.Tom

[tom s]

Dave suggest to back it up a coule degrees.Going to have Joe do it while it is on the pump and he has time.Tom

[tom s]

Joe backed it up some,the engine liked it,now at 449 HP.Going to his place and get details and dyno sheets.Forgot to ask if it lowered the pumping compression.Hope to get it off the pump tomorrow.More HP than I need for the bird on the road track.Tom

[Formulajones]

Pumping 190-195 I've found very tough to run on pump gas. Had a couple of engines back East where I had easy access to 94 pump gas and these engines were still VERY sensitive with a conservative tune and cool temps.

Out here on our crappy 91?? No way. Hopefully retarding the cam a bit knocks that pumping number down enough for you to run this 91 cat pea we have.

[tom s]

Looks like it now pumps under 190 in all cyc.Dave said the cam was designed for highly ported heads.Tom