pontiac 461

[sameoldthang01]

ltjs44 If i can run p1 or 93 that would be great. Indiana here. The guy who is porting these heads will be doing a valve job after. He says that the out of the box heads are most of the time needing some kind of attention. They should be done in a couple 2-3 weeks.

I still have to choose a cam and the machinist even brought that up so I have to narrow it down soon, Thanks for the help!

[tjs44]

With your rear gears and stock converter I would do like 236-242 @50 on a 112 with as much lobe lift like 380-400.I would run 1.65.My self would run hyd roller with 150 on the seat.Note,all my builds except one have been stick shift.The one auto was a 455 with a 245-252@50 on a 110 with 400 lobe lift and the guy had 3.08s and a turbo 400 and is a beast to drive around town.I would not drive it for anything.It had KRE 290 D ports.FWIW,Tom

[mag2555]

To the OP, depending on the out come of the porting work done to the heads and the resultant exh to Int ratio you may not want to run anything more then 1.5 rockers on the exh side of this motor for the highest power output, not to mention fuel mileage during street usage!

The greater stroke then bore size of these under square 4.210” 455s make for much higher piston speed and in turn a bigger shove to pump the exh out!

Talk to someone like Mike the Cam guy here on this site, or Stan Weiss on the Ames Pontiac forum site .
Stan can run you some numbers or you can get his program and run some numbers yourself.
The cost these days of a computer program is cheaper then having to buy another Cam, no less sitting out the big wait time as it seems to be for parts these days

[mag2555]

To the OP, depending on the out come of the porting work done to the heads and the resultant exh to Int ratio you may not want to run anything more then 1.5 rockers on the exh side of this motor for the highest power output, not to mention fuel mileage during street usage!

The greater stroke then bore size of these under square 4.210” 455s make for much higher piston speed and in turn a bigger shove to pump the out the exh per any given amount of compression.

Talk to someone like Mike the Cam guy here on this site, or Stan Weiss on the Ames Pontiac forum site .
Stan can run you some numbers or you can get his program and run some numbers yourself.
The cost these days of a computer program is cheaper then having to buy another Cam, no less sitting out the big wait time as it seems to be for parts these days

[sameoldthang01]

OK thanks. Indeed I know the cam is going to be the make or brake deal on this. I had no plan on using 1.6 rockers being I recall the max lift is .550 on these heads.

[ec1]

Don't over think the cam on this. Tom is steering you right. You can be happy with anything from a stock ram air 4 cam to even a touch bigger than what Tom suggests ... I was surprised 2 months ago when Crower had solid flat cores on the shelf and the cool face lifters. Got a custom solid flat done up right away. 455 Pontiac engines aren't nearly as sensitive to getting the camshaft exactly correct as the 389/ 400 engines. Availability seems to be more of a problem lately so pick something quick!

[ClassKing]

To the guy who said Pontiacs factory rated at 10.75 never were, ya gotta back up. After building over a thousand Pontiacs as that's all I do, I've seen the factory allowable plus and minus tolerances. This is why we, the older group who were there, would see two identical equipped new GTO's and one would run 13.60's and the other barely broke 14.50's. The Cr can easily be as high as 10.75, but I've also measured one that was 9.80. So, just to be clear ya got to watch making statements like that as it could mislead guys from the truth. Cheers

[ClassKing]

You should forget about porting the heads since your going to run the factory intake, it will just be a waste of money, also the factory manifold will limit the HP back to no more then 460 with the Cam I bet your concedering running.

Man, that's TERRIBLE advice. A factory Qjet intake on ported heads can make HUGE power. Don't know if you guys are familiar with NHRA Stock Eliminator...there are Pontiac 400's there running almost ten flat, with a .470 lift cam. Please be careful replying when you have no experience on that particular matter.

[sameoldthang01]

Thanks for the reply. Classking what camshaft would you pick for my setup? 1.5 or 1.6?

[ClassKing]

There are two things to consider when wanting more valve speed. More power or longevity. My approach on most street engines is to be conservative so the springs last longer. So I design cam profiles to make great torque at low rpms unless the customer has a different goals. IE: Hardcore strip but streetable and doesn't mind the maintenance. versus the guy who is plenty happy with an 10 or 11 second car that never needs that kind of maintenance.

Of course the other aspect is the modification work needed to clear the pushrod holes.

Also, there's not enough improvement over a 1.5 with a 1.6 to shake a stick at. If you want more valve speed dive in. 1.7 or higher.

As an an example of my approach to to long living pump gas street engines, my King Street series of 455's, stock stroke, stock rod length, has made 626 lbs ft at 3000 rpm. WITH a 1.5 rocker.

[Stan Weiss]

The only way to relate valve speed to rocker arm ratio is when talking the same lobe. I believe Butler has a hyd roller that gives the same valve lift curve using 1.5:1 as the Pontiac HFT 041 does with 1.65:1

Stan

[ClassKing]

The only way to relate valve speed to rocker arm ratio is when talking the same lobe. I believe Butler has a hyd roller that gives the same valve lift curve using 1.5:1 as the Pontiac HFT 041 does with 1.65:1

Stan

Um, if you haven't seen behind the curtain, JBP doesn't know a cam from an axle. Now someone could have told him something and or maybe he's got someone working there that's trying to learn, but quoting JB is like quoting a politician. What you must do, every time you hear some "amazing" sheet from them is to dissect it completely. If you didn't know, this was the guy who ran hidden nitrous for years trying to look like he was as good as us. Until Clay Phillips caught them in St Louis at a match race. Genie was out of the bottle at that point. Then not being able to compete N.A. then had to turn to boost. When you don't know much, boost it! Then brag

[Stan Weiss]

The only way to relate valve speed to rocker arm ratio is when talking the same lobe. I believe Butler has a hyd roller that gives the same valve lift curve using 1.5:1 as the Pontiac HFT 041 does with 1.65:1

Stan

Um, if you haven't seen behind the curtain, JBP doesn't know a cam from an axle. Now someone could have told him something and or maybe he's got someone working there that's trying to learn, but quoting JB is like quoting a politician. What you must do, every time you hear some "amazing" sheet from them is to dissect it completely. If you didn't know, this was the guy who ran hidden nitrous for years trying to look like he was as good as us. Until Clay Phillips caught them in St Louis at a match race. Genie was out of the bottle at that point. Then not being able to compete N.A. then had to turn to boost. When you don't know much, boost it! Then brag

Function - the hidden math. Got you like to go off on tangents.

Stan