[beertracker]

I realize there are several factors involved in selecting a cam and static CR is just one. If a cam manufacturer recommends a CR of 9.5 and your 455 only has 9.1 CR can you use the cam in your build? Are there any problems with this such as lower vacuum and poor throttle response?

Or put another way how close to cam's CR 9.5 must the engine CR be? Ideally they should be the same but is there any lee way? I do not want to over cam.

Thanks,
bt

[pastry_chef]

If you are talking about an online catalogue don't worry. That information is very generic and is not even specific to a certain size engine.

Can you post the cam numbers?

[steve25]

The bigger your combustion chamber the lesser your vacuum will be from a base line level.

The problem with catalog Cam spec's are the generality of them!
When the application says the Cam wil work with a 350/400 /428 and a 455 cid motor but requires a minimum 9.5 compression , that would be for the smallest cid they list in a application .
If you where to look at things in a apples to apples way a 455 makes 11% more cylinder pressure then a 350 and does 11% faster!
A ball park way of looking at this all is that once again in a apples to apples way the 455 can make due with a compression of 8.5 while the 350 would need 9.5.

This faster cylinder pressure rise also has a effect on rate of timing advance needed!

[PunchT37]

Steve and Pastry are correct. Catalog instructions are generic and based mostly off the small block chevy.

One can get away with running a 230 @ 050 cam in a 8.5 to 9.0 to one 455 and as high as mid 240's in a 9.5 to 10.0 to one iron head 455.

[beertracker]

Originally Posted by pastry_chef

If you are talking about an online catalogue don't worry. That information is very generic and is not even specific to a certain size engine.

Can you post the cam numbers?

Here is the cam I was looking at Voodoo 268/276, http://www.lunatipower.com/Product.aspx?id=1776&gid=287

After reading the comments I wonder if Voodoo 276/284 would be too big? http://www.lunatipower.com/Product.aspx?id=1777&gid=287

Thanks,
bt

[pastry_chef]

Originally Posted by beertracker

Here is the cam I was looking at Voodoo 268/276, http://www.lunatipower.com/Product.aspx?id=1776&gid=287

Good cam, here is a 455 dyno result.
http://forums.maxperformanceinc.com/...d.php?t=776169

Depending on your car weight, rear gear and torque converter stall a Voodoo 704 might be good for you as well.

[steve25]

Yes that would be too big unless you had a 4 speed and at least 3.42 gears in terms of everyday go anywhere street driving!
That Voodo Cam is basically a RA4 Cam and back when that Cam was used in a production 10.5 to one factory 400 motor Pontiac would not sell the RA4 motor to you without 3.90 gears and on top of that no A/C!

I like to look at it this way ,a 455 is 13% bigger cid wise then a 400 so if the factory wanted you to have 3.90 gears for the street then for a 455 the minimum gear would be 3.39!

With that voodo Cam if you ran Rhodes bleed down lifters then if would make for good everyday street pick for even 3.23 gears as it would behave very nice below 3400 rpm, in fact much more like a factory 068 Cam!

[beertracker]

Originally Posted by steve25

The bigger your combustion chamber the lesser your vacuum will be from a base line level.

The problem with catalog Cam spec's are the generality of them!
When the application says the Cam wil work with a 350/400 /428 and a 455 cid motor but requires a minimum 9.5 compression , that would be for the smallest cid they list in a application .
If you where to look at things in a apples to apples way a 455 makes 11% more cylinder pressure then a 350 and does 11% faster!
A ball park way of looking at this all is that once again in a apples to apples way the 455 can make due with a compression of 8.5 while the 350 would need 9.5.

This faster cylinder pressure rise also has a effect on rate of timing advance needed!

Does the apples to apples comparison apply to stall converter rpm and axle gear ratio?

Since the 268/276 (part # 703) cam shows 350 engine specs as 2200-2300 stall and axle ratio of 3.23-3.42 doesn't this mean a 455 engine can run with less (lower #) axle ratio and less stall converter because the 455 will produce more torque that the 350 engine?

Thanks,
bt

[beertracker]

After reading the comments and looking at the Voodoo 704 276/284 cam specs http://www.lunatipower.com/Product.aspx?id=1777&gid=287 This is a weekend, pump gas street car
I take it this is not a good cam to run in a 455 with 9.1 or 9.5 CR, headers, 6x-8 ported heads, 2300 rpm stall converter, 2.78 axle ratio. I don't think the addition of rhoades lifters would make this work. Is there any one on this forum in their right mind who would run this combo? I doubt it and will cross this off the list.

Thanks,
bt

[Sprocket]

The cubes are fine, 9.5:1 CR with iron heads is fine, 245-260 cfm porting is fine, headers great, the converter is okay, but the rear axle ratio sucks for the rest of the combination. It's a 455, so it will still build torque, but you will likely get dusted by "quick" cars and need a lot of real estate to catch up and then blow them off the road. Not the most ideal situation.

[steve25]

It's not just a matter of steeper gears getting a motor into the Cams power band and making more torque that provides increased performance, but overall the motor gains rpm faster and that has a big impact on performance also and should not be overlook!

[ponyakr]

http://www.lunatipower.com/Product.aspx?id=1777

Just curious if you really want that much lift & a 110° LSA, for a weekend street car ?

The old 041/Rhoads combo, is hard to beat for a mild mannered 455 street engine, IMO. Will it make max upper rpm power ? Of course not.

If you don't wanna use Rhoads lifters, the Howards 410051-14 has less adv duration, a 114° LSA, and less than .500 lift.

https://www.summitracing.com/parts/h...w/make/pontiac

If you don't want a Voodoo, here's a few more choices.

https://www.summitracing.com/parts/c...IaAusEEALw_wcB

https://www.summitracing.com/parts/crn-284281

If you don't mind payin a few more bucks, the Crower 60243 might be in the mix.

https://www.summitracing.com/parts/cro-60243

[Steve C.]

A repeat......

"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 degree 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 degrees."

Paul Carter
Koerner Racing Engines

And one of many related comments originally Posted by Paul Carter, this regarding the 110 lobe separation in conjunction with a Voodoo cam:

"We all know that wider lobe seps make less peak power than narrower lobe seps, but in a broader RPM range. More average power. Certain lobe designs, by nature, benefit from wide lobe seps, while other lobes benefit from tighter lobe seps. If you have a lobe design that when ground on a 110 LSA, has a power band as broad as another lobe design ground on a 112 or 114 LSA, why not take advantage of the extra power if your not running the cam out of it's power band in the first place?"

"Let me make one thing perfectly clear. When I talk about narrower lobe sep cams in big engines, I am specifically talking about Harold cams. Not Comp XE or anyone else's tight LSA cams. Harold did many things differently to his lobes. Things NO ONE ELSE DID! These subtle little things created lobes that when ground on a 110 LSA, gave the power band performance of a cam ground on a 112-114 LSA. Just look at some of the Voodoo lobes."

.

[beertracker]

Originally Posted by Sprocket

The cubes are fine, 9.5:1 CR with iron heads is fine, 245-260 cfm porting is fine, headers great, the converter is okay, but the rear axle ratio sucks for the rest of the combination. It's a 455, so it will still build torque, but you will likely get dusted by "quick" cars and need a lot of real estate to catch up and then blow them off the road. Not the most ideal situation.

Good post. It contains all the facts I need to make my decision. Thank you and my decision is made bt

[ponyakr]

Yeah it seems like MOST HFT cam threads wind up with Paul Carter recommending nothing but Voodoo cams & Cliff recommending nothing but Crower cams.

Hey, there ARE other cams out there. Not everybody insists on making the most power & torque they can possibly make & still be fairly streetable. "...I do not want to over cam..."

BUT, when max streetable HFT power is the goal, I'd say Rhoads lifters will have to be used. The use of Rhoads will allow you to order a custom cam that will POSSIBLY make more upper rpm power than available shelf grinds, but will still have enuff low end so that you could live with it, on the street.

By ordering EXACTLY the correct specs, + Rhoads lifters, you could have a cam with a really wide power range. What are the exact specs to order ? I have absolutely no idea. As I've said many times, the only way to know for sure would be to try LOTS of cams, in dyno, strip, & street testing, and compare each. And, until I win a multi-million dollar lottery, that will probably never happen.

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

http://www.bulletcams.com/Masters/ultradynemasters.html

[Baron Von Zeppelin]

I wouldn't go over the range of 450-I/465-E , and would still use Rhoads too.
Because of the 2.78 , Functional AC , Heavy Car
Would probably be prepared for an idle solenoid that clicks in with AC too.
Whatever keeps it civil for around town driving.

Your ported heads will still bring you good extra horses vs. stock
Lighter springs will be friendlier/easier operating than going to next level stiffer springs if your cam goes over .465

If you had 3.08 gears , I'd probably go up on the cam and springs.

A lot of these dyno builds probably weren't used in cars with 2.78 gears (fwiw)

[dmac]

Originally Posted by ponyakr

By ordering EXACTLY the correct specs, + Rhoads lifters, you could have a cam with a really wide power range. What are the exact specs to order ? I have absolutely no idea.

Do you mind if I quote this????????? I'm trying to think about a cam for my low CR 455//467 4.25 stroke with stock heads and trying to decide on anything from 8.1:1 cr to about 9.2: cr. Will never see 5000 rpm except by accident. I just want to be able to jump from ~60 mph to 90 mph to pass trucks and pull back into the slow lane going uphill in a 75 Ventura. Plus I want to save money on gas. I don't know if reading cam threads is any help when everyone else has 9.5:1 cr or higher and care more about 60 ft or 1/4 mile times.

[tom s]

Paralyses by analysis !Tom

[Baron Von Zeppelin]

Paralyses by analysis !

lol

I've got 6-7 engines that will need to be built.
Hoping for electric motor / battery tech to get more advanced/cheaper before then.
No Cams !

[ponyakr]

"...I'm trying to think about a cam for my low CR 455//467 4.25 stroke with stock heads and trying to decide on anything from 8.1:1 cr to about 9.2: cr. Will never see 5000 rpm except by accident. I just want to be able to jump from ~60 mph to 90 mph to pass trucks and pull back into the slow lane going uphill in a 75 Ventura. Plus I want to save money on gas...


A long stroke Pontiac is not the engine to use if you wanna "save money on gas". But, if you never plan to go 5000rpm, an 068 , a Howards 410021-12, or Summit 2801 should work. The low compression 455HO engines had the 068 cam. The low compression '73 D-port 455's only had an 067 cam. I assume an 067 would get better mileage than an 068. Also guessing that it wouldn't make much power past 4000rpm. But, that may be all you need for what you described.

https://www.summitracing.com/parts/h...w/make/pontiac

Next up might be something like a Lunati 10510312.

http://www.lunatipower.com/Product.aspx?id=1759&gid=278