[MetalHead175]

Hey all, I'm finally getting my 70 Firebird back together and have changed routes again with the 455. Its going to be zero decked with forged pistons and rods and #96 heads giving around 10.5 to 1 or so from what I have calculated. I have a brand new Comp 274 but have since decided I want something significantly bigger with a somewhat lopey idle making good power. I have a full MSD ignition system for it, Hooker Comp headers, and an xpipe, 3.73 gears as well into a built TH400. Recommendations for valve springs as well please. Thank you!

[Cliff R]

What cc are the 96 heads?

Flat top pistons?

Head gasket thickness?.....Cliff

[MetalHead175]

Thanks for the reply Cliff. The heads are 96cc, they are untouched. Flat top Ross pistons, and .040 head gasket. Perhaps my 10.5:1 comp ratio estimate was a bit off.

[gtofreek]

I'd say more like 9.3-9.5:1 without calculating it.

[ponyakr]

Here's one CR calculator. Don't know how accurate it is.

http://www.wallaceracing.com/cr_test2.php

If you plug in your specs, it should be in the ball park. Here's a sample.

Bore: 455 + .030, Stroke: 4.21, Deck: .000, Valve reliefs: 5.5, Heads: 96cc, Head gaskets: .040 x 4.3 CR = 9.53

[MetalHead175]

I noticed the difference after I posted the original post. Would the 274 Cam be a solid performer then given that comp ratio? Or should I bump up to something more?

[Blued and Painted]

@ 10.5, No the 274 is not a good choice. I would be worried about blowing the ring lands off the pistons.

[MetalHead175]

Then what's a good cam choice and springs to achieve close to 500 horespower with those heads? Desktop dyno says I will be sitting around 450 hp and 500 lbs of torque with the 274.

[Cliff R]

Not even close. The last two dyno runs I witnessed with that cam in a 455 build were 412 and 414hp respectively.

Here is part of an email I received from a customer who bought a 455 from one of the shops who build Pontiac engines for a living. It used their "ported" 6X heads, 9.3 to 1 compression, and the XE274 camshaft:

" The motor continued to be a turd for that summer. A chassis dyno run netted 326 RWHP and 439 RWTQ, XXX was happy with that, I was not"

We witnessed a dyno run with a 455 using the larger XE284 cam and 7K3 heads, which are basically the same as #96's. It only made 430hp/499tq......Cliff

[Kenth]

A 041 cam with Crower 68404-16 springs will be hard to beat for your goals.

[Tim Corcoran]

OK the Ultradyne 255/263 on a 108 LSA solid lifter FT cam is a killer cam for your combination. This cam is available from Lunati and this is a perfect match for your combo and it kicks ass. You will need 3500 stall converter with this cam. Then your only problem will be getting her hooked up. And if you do some head work like in the bowl area and a good 3 angle valve job this will wake it up even more. Without some head porting I doubt you will get to 500 HP.

[Jack Ferris]

Originally Posted by Kenth

A 041 cam with Crower 68404-16 springs will be hard to beat for your goals.

Agreed. We have used this cam in so many street builds over the last 25 years and they all seem to run good in 400's and 455's. There is no doubt there are better cams out there. I have tried many different versions of them with little success, but unless the customer absolutely has to have the cam of their choice, and/or they are using untouched heads, I feel the 041 fits most combo's well.

[ponyakr]

Originally Posted by Kenth

A 041 cam with Crower 68404-16 springs will be hard to beat for your goals.

I used these, with Rhoads lifters, in most of my 455 bracket motors. This combo will give you around 500ft lbs of low end torque. But, if you want a lopey idle, you may have to go a bit larger. I liked this combo because it has a smooth idle below 1000rpm. We used stock 13" converters and launched from an 800rpm idle.

There are several versions of the 041. I'd use a Melling SPC-8, just because they are cheaper. Lots of guys like the Crower 60919. Although most of these cams have a similar duration @ .050 lift, they could have more duration above .050 lift than another brand. So some of these cams will obviously make more power than others.

That brings up a very interesting question(to me at least). Which of the, so called, 041 grind cams makes the most power ? Maybe Cliff has done some dyno and / or track testing with different versions of this cam, and can share those results with us ?

The CC # is 51-116-3

http://www.summitracing.com/parts/cc...TAIaApOO8P8HAQ

The Lunati # is 10511003.

http://www.lunatipower.com/Product.aspx?id=1755&gid=340

The Crane # is 969681.

http://www.summitracing.com/parts/cr...-fUaApzh8P8HAQ

The Howards # is 410051-14

http://www.summitracing.com/parts/hr...kjkaAqIN8P8HAQ

Edlebrock even sells a cam and lifter kit #7157. Don't know who the cam grinder is.

http://www.summitracing.com/parts/ed...REAaAt4X8P8HAQ

Summit has the original Rhoads lifters for the best price I've found.

http://www.summitracing.com/parts/rh...w/make/pontiac

[ponyakr]

In order to go a bit quicker to make a quicker bracket, I switched to a bigger cam and more gear. The car picked up about .3. It had a lumpier idle, but with the Rhoads lifters, would still idle low enuff to leave from an idle and cut good RT's.

I can't find a cam listed exactly like the one I had. It was a dual pattern with 244 intake and 253 exhaust dur @ .050 lift. It had a little over .500 total lift with 1.5 rockers. Comp Cams has two single patterns, which are very similar to these specs. So the cam I had may have been a combination of these two. This may be a little too much for the street. But I'm sure some of the guys on this site can recommend exactly what you need. As I'm sure everybody knows, you can have a cam ground to any specs you want. Bullet has a lot of profiles listed.

http://www.summitracing.com/parts/cc...7JYaAvEG8P8HAQ

http://www.summitracing.com/parts/cc...OQYaAhFH8P8HAQ

http://www.bulletcams.com/Masters/Hlobes.htm

[MetalHead175]

Thanks all for the replies. It will be a street/strip car mostly and it does not have air so the lumpy idle is ok. I will be porting the heads to try to get more flow, plus port matching with the intake and such. I will definitely look those cams over, sounds like a lot of great advice. Just from a quick glance, I like this one
http://www.summitracing.com/parts/cc...OQYaAhFH8P8HAQ but again, I know very little about picking out a cam based on duration and such.

[gtofreek]

Here's a VooDoo cam you may find interesting. Have not used this one yet, but have used several VooDoo cams in many different engines and they always work great. Your compression may be a tad low for this one.

https://www.lunatipower.com/Product....d=1778&gid=287

I have built several 455's with this cam; https://www.lunatipower.com/Product....d=1777&gid=287, and it is a beast in a 9.5:1 455 on the street. Doesn't have the radical idle they say it does, although noticeable.

[MetalHead175]

I've never used a Lunati Cam, can I use my comp lifters? I have a brand new in box XE274 with the new lifters, and would like to only swap the cam if possible.

[gtofreek]

You can use anyone's lifters.

We've been extremely happy with the VooDoo cams. They are designed by the same guy that designed the UltraDyne cams which worked great in Pontiac's, and the VooDoo's work even better.

[Blued and Painted]

Here is a side by side list of different cams i use for quick reference.
http://www.pontiacpower.org/PontiacCams.htm

If you want to get into the 500+hp you might consider e-heads or KRE's and a roller cam.

[MetalHead175]

I'm not opposed to stepping up to a roller cam, I am however going to have to stay with the iron heads for now.