[1976 Grand Prix 455]

Originally Posted by Baron Von Zeppelin

The 5th or 7th digit in VIN is an engine identifier code.
Usually a car parts website can decipher it, if nothing else.

If you can see 6X cast in big raised characters on the center exhaust ports of the cylinder heads - it is not a 301.
Seems like 01 was the 301 cylinder head casting.

Several other little things are different with 301 also, but the heads will tell real quick and easy.

I don't think it's a 301 and I'd be surprised if that engine was even released for 1976. I was just making a joke since the car is lacking in the options department.

[ponyakr]

Decent 1.65 alum rockers are near $300 & more, depending on which you buy. Before I paid that much, I'd be absolutely sure that I was gonna run those same rockers on the future 455 build.

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

https://www.summitracing.com/parts/s...QaAoLKEALw_wcB

https://butlerperformance.com/i-2445...cp3053-16.html

I ran stock, well used rockers on all my bracket racing engines. Only broke 1, thru many years & lots of passes. So, your $300 might be better spent on something other than 1.65 roller rockers, IMO.

[KEN CROCIE]

How 'bout we forget the mechanical stuff for a while , and concentrate on the tune up. Get a carb rejetting kit from one of our Q-jet specialists here on the forum. re-curve the dist, to get the most response from the lo compression 350. These two changes will make a much larger improvement than 1.65 rockers, maybe 4-5 tenths in the 1/4. 1.65RR will generally yield an improvement of .1 to .2 sec ET with the small cammed 350. Throttle response will be greatly improved. 1.65 rockers will definitely allow the pushrod to clear the pushrod hole in the head with stock lift cams. keep the stock air cleaner with the stock cold air induction package. Make sure the flapper valve in the air cleaner stays open. Install a true dual exhaust system. Get a 3" system to be ready for the 455. disable the EGR system and make a block-off plate for the manifold. Make sure the exhaust flapper valve stays open.

[ponyakr]

"... 1.65 rockers will definitely allow the pushrod to clear the pushrod hole in the head with stock lift cams..."

So, now I'm curious. EXACTLY how much lift is the most you can safely run, with no chance of any pushrod rubbing ???

Am I to assume that the popular 068 & 744 clone cams can safely use 1.65 rockers ?

How about the 041 clones ?

How about this Howards, with a 1.5 rocker lift of .450 ?

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

If .450 is too much, how about the Crower 60239, with a 1.5 rocker lift of .419/.422 ?

http://www.wallaceracing.com/cam-specs.htm

[1976 Grand Prix 455]

Originally Posted by KEN CROCIE

How 'bout we forget the mechanical stuff for a while , and concentrate on the tune up. Get a carb rejetting kit from one of our Q-jet specialists here on the forum. re-curve the dist, to get the most response from the lo compression 350. These two changes will make a much larger improvement than 1.65 rockers, maybe 4-5 tenths in the 1/4. 1.65RR will generally yield an improvement of .1 to .2 sec ET with the small cammed 350. Throttle response will be greatly improved. 1.65 rockers will definitely allow the pushrod to clear the pushrod hole in the head with stock lift cams. keep the stock air cleaner with the stock cold air induction package. Make sure the flapper valve in the air cleaner stays open. Install a true dual exhaust system. Get a 3" system to be ready for the 455. disable the EGR system and make a block-off plate for the manifold. Make sure the exhaust flapper valve stays open.

I bought a curve kit but do not have it installed yet. Who should I contact about a rejetting kit for my Q-jet? I also need a rebuild kit for it.

I also have headers and a Pypes 3” mandrel bent X pipe system ready to be installed.

[ponyakr]

"...Who should I contact about a rejetting kit for my Q-jet? I also need a rebuild kit for it..."

Cliff.

https://cliffshighperformance.com/

[Baron Von Zeppelin]

Ken Crocie was part of the legendary Pontiac go-fast supplier "H-O Racing Specialties".

If i did the 1.65 rockers on the 350, i'd go with normal stamped steel units like the Ram4 used. NAPA was selling them, not sure about now.

H-O Racing used to sell pre-made pre-calibrated distributor recurve kits that were wonderful. Not sure anyone does that anymore.
Mr.Gasket re-curve kits are a crap-shoot unless you have access to a Sun Machine.

[Dragncar]

I had a 350, put 48 heads on it, 2801 cam, factory Q jet and intake, 3 tube headers. Ran great for what it was. That cam came on hard at 3500. Ran 15. 50s in a heavy Le Mans with 3.08 boot leg and stock converter.
Had a nice sound to it. Balancer broke and that was it for that experiment.

[steve25]

Pontyakr, its not the Cam lift at the valve that in and of itself makes for push rod clearance issues when going up to higher ratio rockers it's the change in the diameter of the Base circle of the Cam.

To gain more lift at the valve the part of what is done to the Cam lobs base circle is that the Cam is ground smaller, this in turn causes the lifter to start out at a lower height in its Bore thus making for more lift once the lifter gets off the base circle of the Cam.

This makes the valvetrain installed height seem shorter which draws the push rod closer to the rocker stud the same way as installing 1.65 rockers, but to a lesser degree that normally does not cause problems.

For instance the longer the valves are that you use over stock the less added push rod clearance you will need from going up in ratio and when running valve lifts above .450"

[ponyakr]

"...This makes the valvetrain installed height seem shorter which draws the push rod closer to the rocker stud the same way as installing 1.65 rockers..."

So, are you saying that the pushrod is closer to the head(less clearance), when the lifter is on the base circle, than when it's on the tallest part of the lobe.(max lift) ?

[77 TRASHCAN]

Rocky installed a set of stamped 1.65 rockers in what I remember as a stock engine. Part of the equation was using stock diameter 5/16" pushrods.

We know that the stamped rockers are in consistent, concerning their exact ratio, from one rocker to another, and that their time he ratio is a tad less than 1.65...

[1976 Grand Prix 455]

So I got her out to the track today. Ran about I expected for a 43 year old car. Too bad it has a nasty backfire through the carburetor. Did it all 3 runs and of course she waited until round 1 to backfire and quit running on the starting line. So instead of going down the track I’m cranking on the starter. Still had a good time. It was my first time out since 2012.

[77 TRASHCAN]

Amazing how crap only happens at the track, especially at the track!!!

A kit and some parts from Cliff will help your "original" carb. A 20 second et from your stock combo sounds about right. Wish I was closer to help/observe!

Stamped 1.65 rockers are still available from s verbal engine parts distributors, Melling and Sealed Power likely have them...

[1976 Grand Prix 455]

Originally Posted by 77 TRASHCAN

Amazing how crap only happens at the track, especially at the track!!!

I know right?? I was pretty much expecting it to do that. I think the car has sat so much that the gaskets and whatnot have gone bad in the carburetor. The back fire is really bad when the engine is colder so I was running it hot hoping to keep everything expanded and potentially helping with the backfire. Ah well, I got my baseline which is what I wanted. Now all I need to do is find some public scales to weigh the car prior to any modifications.

[77 TRASHCAN]

I was looking at the engine picture again. Noticed you gave a TH400 transmission. That's good to know.
Looking forward to your work on the car!

[1976 Grand Prix 455]

Originally Posted by Baron Von Zeppelin

Helluva Nice Car ! DAMN
Might not want to cut a hole in the hood for a shaker scoop on that one.

Never seen a 70's GP come factory without a vinyl roof either.
Assumed it was a standard item on GP
Maybe it was special ordered to "delete" it. ?

Probably safe to say it was likely a special order car anyhow.
Definitely the barest boned GP i have ever seen.

And I Like It

I know this thread is basically finished, but a little something I did find out about my car. I found the dealer acceptance sheet it that shows the options and price of the car.. The good news is the car is equipped with a Pontiac Safety Track rear end along with a couple of other options. The bad news is the gear is only a 2.41.