[scott70]

I had my 455 freshened and dynoed awhile ago. It has 253cfm #64 heads, stock iron intake, Qjet. 9.71-1 comp. Crower hft with Rhoads vmax lifters. 1.60 rockers.Had 1 3/4" headers on the dyno. Is it normal for this combination to make peak hp and torque that low in the rpms? Finally drove it fthe 1st time yesterday since completing the semi restoration. The cam I had ground so it's not off the shelf.

[steve25]

Yes it is 100% normal and that brutal amount of torque below 3500 is why a 3800 lb car can do well with only 3.08 rear gears!

It’s also telling you that at 3500 rpm your combination of Cam and cylinder head is maxed out!

Oh, by the way it took 240 intake cfm out of that 253 cfm to make that 491 hp .

[scott70]

On the video It made peak trq was 570 at 3400. Im going to check cylinder pressure soon to see what it is,,hopefully not real high.. I mix 100av with 93 pump gas. Cruising in 1st gear the tires went up in smoke going WOT so I cruised in 2nd gear and the same thing happened,,,completely broke loose and went to around 5000 rpms and let off. Muncie m21 with 3,31 posi . I guess it doesnt hurt anything having peak #'s that low? .Would of it been better to have a bigger cam or is that good with my muncie and rear gear combo?

[AG]

Originally Posted by scott70

I had my 455 freshened and dynoed awhile ago. It has 253cfm #64 heads, stock iron intake, Qjet. 9.71-1 comp. Crower hft with Rhoads vmax lifters. 1.60 rockers.Had 1 3/4" headers on the dyno. Is it normal for this combination to make peak hp and torque that low in the rpms? Finally drove it fthe 1st time yesterday since completing the semi restoration. The cam I had ground so it's not off the shelf.

Nice BSFC numbers.

[Navy Horn 16]

If you want to make more power, you've got to get better heads. Not that what you have there is a slouch by any stretch...that's a screaming motor.

It's doing everything it can down low, it's falling off because the heads/intake can't support any more. And that is a pretty small cam. Hard to tell which one you are bumping up on first.

I love me some 100LL too. Just got some from the airport yesterday. I probably don't need it, but I LIKE IT!!

I'll bet that motor is really good on the street too.

[Formulajones]

I like it Scott, looks good to me. Nice torque curve, should be a fun street car to drive.

With just 9.7:1 compression and that camshaft, I wouldn't think you need to run the AV gas. Should be fine on pump with some tuning. In fact I'd put a lot of effort in that area so I wouldn't have to mix gas if it were mine. That's a pain in the a$$ and gets expensive, and will only get more expensive now. You'll be needing extra money for tires every 6 months

[Formulajones]

If it makes you feel better, Your numbers are right in line with many of the 455's built decades ago with a RAIV camshaft, similar head flow, and similar compression, and from the looks of your build, that's pretty much what it is. Your cam just looks like a very mildly tweaked version of the RAIV so I would expect the peaks and the numbers to be right where they are.

[scott70]

I just figured Id put some AV in for the lead and a little octane insurance. I have a small airport about 1/4 mile away from me. Driving it ,,,it doesnt act like its lacking any power! I plan to take it to the track (1/8th) and compare it to past tries. Just street tires and baby launches. Watch the MPH.

It just seemed weird to me that especially the torque came in at 3400,,,seems really low rpm for a "semi high performance" motor. But from the sounds of it Im all good.

[Formulajones]

Originally Posted by scott70

I just figured Id put some AV in for the lead and a little octane insurance. I have a small airport about 1/4 mile away from me. Driving it ,,,it doesnt act like its lacking any power! I plan to take it to the track (1/8th) and compare it to past tries. Just street tires and baby launches. Watch the MPH.

It just seemed weird to me that especially the torque came in at 3400,,,seems really low rpm for a "semi high performance" motor. But from the sounds of it Im all good.

Sounds like a plan, go have some fun with it

[68lemans462]

Originally Posted by scott70

I just figured Id put some AV in for the lead and a little octane insurance. I have a small airport about 1/4 mile away from me. Driving it ,,,it doesnt act like its lacking any power! I plan to take it to the track (1/8th) and compare it to past tries. Just street tires and baby launches. Watch the MPH.

It just seemed weird to me that especially the torque came in at 3400,,,seems really low rpm for a "semi high performance" motor. But from the sounds of it Im all good.

I wouldnt be complaining! Nice job looks like FUN!

Sent from my SM-G981V using Tapatalk

[mchell]

Originally Posted by scott70

I had my 455 freshened and dynoed awhile ago. It has 253cfm #64 heads, stock iron intake, Qjet. 9.71-1 comp. Crower hft with Rhoads vmax lifters. 1.60 rockers.Had 1 3/4" headers on the dyno. Is it normal for this combination to make peak hp and torque that low in the rpms? Finally drove it fthe 1st time yesterday since completing the semi restoration. The cam I had ground so it's not off the shelf.

Wo.....that’s a lot of power from that combo!....with BFSC numbers that look like something from a perfectly tuned race engine?

The engine wanting to drop off that early is a bit odd, but Pontiac’s are tractors not Ferrari’s

I have a buddy that just dynoed his fresh 455, 64 headed combo(no port work other than clean up) and his made 384hp with BFSC numbers in the high 4’s and lower 5’s(mostly 5’s).....068 cam I believe. Basically a stock build.

[72projectbird]

Jesus that thing is making some power!

Not bad at all!

[mgarblik]

Giant, flat torque curve. Heavy car with little rear gear will love this engine. HP numbers are for bragging rights on a car like that. Torque makes the car move!! Should be perfect for the application and last a long time with the low RPM peaks. As said, for more HP, a 455 needs more cylinder head..

[Formulas]

So given the transmission used and RPM drop at shift what RPM should he be shifting at ?

Might be useful info with his new build to set up a shift light and rev limiter

[Navy Horn 16]

Originally Posted by mgarblik

Giant, flat torque curve. Heavy car with little rear gear will love this engine. HP numbers are for bragging rights on a car like that...

Bingo. 471 foot pounds at 5400 RPM is nothing to complain about. Just because it's "past the peak" by 2000 RPM doesn't mean much.

That's 65 more foot pounds than a Coyote motor makes at it's peak (6K rpm).

Good luck keeping traction on your 2/3 shift with street tires. That's the problem you are going to have.

[steve25]

The only thing I might play with if you want to place your power band up a bit higher would be to try the rpm performer, but even with the power you have now it’s time for good hd U joints even if you don’t have posi!

[65CatCoupe]

I would expect it to have traction issues in 1st and 2nd as you saw. Bigger question is how does it feel in 4th. 4th gear at 50 mph/2K rpm should pull strong till things get scary.

[scott70]

I would think shifts would be made at 5500 at looking at the dyno sheet? U-joints have been upgraded to HD. Connecting rods upgraded and autotech forged pistons.The pull in 3rd and 4th are very strong,,,yesterday was the 1st time out in a couple of years. The car was finished a few weeks ago and didnt beat on it too hard. The the 2.20 1st gear and the 3.31 rear its a little tall geared taking off but with the trq it doesnt seem to care to much. I was cruising in 3rd at about 3000 or less rpms and floored it and it did not break loose but pulled like a train til 85mph then i let off.. Only drove it about 15 miles round trip. Its the original motor,trans and rear end to the car.

["QUICK-SILVER"]

Those "Stock manifolds" log or ram air?

And what kind of pipes (size/mandrel/crush) are bolted to and behind them?

1/8th mile info in sig with this engine?

I like it
Clay

[promptcritical]

That's great street car setup. Congratulations.