[1976 Grand Prix 455]

Good evening all,
Hopefully this will be an easy one. I’m looking to replace the cam in my 350 Pontiac. I’m looking for something mild that I can race until I can beef up the rear end and drive train before swapping in a 455. The car weighs 4000 lbs with an open rear end. I’ll be adding headers and an x-pipe exhaust. I need something that won’t burn the tires off at the track or start braking things. Any advice would be greatly appreciated. Thanks in advance.

[Scott Stoneburg]

Whats the rest of the 350 consist of? The cam needs to match the rest of the motor.. Heads,intake,carb,converter?

[1976 Grand Prix 455]

It’s a bone stock 1976 350 with a 4 bbl carb and a stock converter in a Grand Prix. Sorry I’m just starting to learn Pontiacs.

[1976 Grand Prix 455]

Engine

[Dragncar]

Summit 2800
Summit 2801 does not come on until 3500 so you need some gear.

[Scott Stoneburg]

I would pick something in the same range as Dragncar. I like Comp Cams product. I have used them and never had any trouble. Look at the 252H or 260H

[steve25]

Well lucky for you it's good you are starting off with a 350 with heads like those 6X-4 castings that are on there with screw in rocker studs that you do not have to fear ripping them out like with the pressed in ones when a bigger Cam is used and more valve spring load!

A change in rear gears will provide you with a better all around performance gain then swapping out the Cam & lifters in that weight of a vehicle by far!

If anything all I would do would be to invest in a set of 1.65 Aluminum roller rockers and set those into the motor as you will pick up about .035" more valve lift which is about all the stock valve springs can handle, and then these rockers Cam be used on the 455 build.

The 1.65 rockers will also add 3 to 4 more degrees of duration to the Cam, but only over the nose of the Cam lobe so you will still have a good idle.

It's a win win deal!

Also that Intake with the EGR valve restricting the secondary's needs to go if you can turn up a used performer Manifold .

Also Exh wise if the Cat is still on there with it Y into it and out, that needs to go to the junk hep too!

[ponyakr]

The 2800 is the cheapest choice.

But, without changing rear gears or converter, I'd say that a Voodoo 250 would probably provide the biggest performance increase, at the track. They are said to increase cyl pressure, which really helps the low compression engines.

https://www.lunatipower.com/voodoo-h...8-250-256.html

"...all I would do would be to invest in a set of 1.65 Aluminum roller rockers..."

I think 1.65 rockers require removing the heads & grinding for pushrod clearance. Don't know if you want to remove the heads, or not.

"...A change in rear gears will provide you with a better...performance gain...by far!..."

I agree. A numerically higher rear gear will lower your ET more than a cam swap. But, you may not wanna change, now, to a gear you will not want, after you switch over to the 455.

A higher stall converter will also lower ET.

So, you'll just have to decide exactly how many changes you are willing to make, while still running the 350.

[chiphead]

Those engines in stock form are pretty weak sauce. Compression in the 8s, tiny camshaft, restrictive intake, lean calibration carb, emissions timing curve and pellet-bed cat converter. Put that in a heavy car with freeway gears, and 0-60 times are measured in afternoons.

If you are emissions exempt, I suggest removing or replacing the stock cat converter. IF going to headers and X-pipe exhaust, size it for the 455 so you don't have to re-buy the exhaust after the engine swap. The Voodoo 250 is a good choice for a stockish motor in a heavy car. While the cam may look small on paper, the factory cam in these motors is even smaller. Recurving the distributor and retuning the carb would really help throttle response. Beyond that, you'd have to start really digging into the engine, which you may not want to do, if the other areas of the car need work.

[ponyakr]

"...Compression in the 8s..."

Not arguing, but I think the CR was actually in the '7's. Advertised at 7.6 maybe ?

http://www.wallaceracing.com/cratio0001.htm

"...restrictive intake..."

Although they LOOK bad, it's been posted that the later Q-jet intakes actually flow just about as good as the earlier ones.

[1976 Grand Prix 455]

Good afternoon guys,
Thank you for all of the feedback. I do appreciate it. My short term goal is to get the car to a more comfortable ET for bracket racing at my local track. I'd like for it to run in the 16 second range as a 350 with minimal modifications to the engine. If it runs in the 17-18 second range I'll be just as happy with that. I'll be making my first pass down the track in it this weekend so I'll know about where I am starting from. I thought a cam swap would be an easy way to achieve that. It's sort of sounding like I might be better off installing the headers and X-pipe exhaust then start upgrading the rear end. My thoughts on that were updating the factory 8.5 to a posi with 30 aftermarket axles. I wanted to use a gear that would work with either 350 or 455 engine. I was thinking 3.31 or 3.42.. I don't want to run the car to death because I plan to drive it back and forth to the track.

Ultimately I'd like to run in the low 13 second range with the 455. I'm planning to put it on a diet fairly early on to try to shed weight with a glass hood, gut the bumpers and 5 mph absorbers, aluminum radiator and aftermarket wheels. Not sure how much all of that will save in weight, but something is better than nothing.

[Skip Fix]

"The 1.65 rockers will also add 3 to 4 more degrees of duration to the Cam, but only over the nose of the Cam lobe so you will still have a good idle."

But usually heads will need grinding to accommodate that.

2801 in my fairly stock 400 in the 81 TA is a nice cam in a 400, would add a little lump to a 350.

[Stan Weiss]

Originally Posted by ponyakr

"...Compression in the 8s..."

Not arguing, but I think the CR was actually in the '7's. Advertised at 7.6 maybe ?

http://www.wallaceracing.com/cratio0001.htm

"...restrictive intake..."

Although they LOOK bad, it's been posted that the later Q-jet intakes actually flow just about as good as the earlier ones.

My Chilton's has 7.6:1 for every engine Pontiac offered in '76

Stan

[ponyakr]

"...I was thinking 3.31 or 3.42.. I don't want to run the car to death because I plan to drive it back and forth to the track.

Ultimately I'd like to run in the low 13 second range with the 455..."


Gonna take some gear, some converter and some power, to run low 13's, if the car + driver weighs near 4000lbs.

This calculator says it'll take just over 350hp, to run a 13.10, at 4000lbs.

http://www.wallaceracing.com/et-hp-mph.php

And, I'm assuming that the calculator assumes that the car will have the optimum gear & converter, for 1/4 mile duty. So, assuming more street compatible gear & converter, you'll probably need closer to 400hp/500 torque, in order to run low 13's.

No problem making that power, with a correctly built 9:1 CR 455.

http://lenwilliamsautomachine.com/455_Long_Block.html

3.42 gears would be better for the track. 3.08 would be better for the highway. This is assuming a 3-speed tranny.

[1976 Grand Prix 455]

Fortunately I live relatively close to the drag strip and can drive city roads if need be. So with that being said is it safe to say the consensus is upgrade the rear end and gears first then worry about a cam for the 350 engine? Since the 455 swap is a little ways down the road, will the 3.42 gear be too much for the 350 with a 250/256 Lunati Voodoo cam in it with headers?

[Baron Von Zeppelin]

I've never seen a 70's GP without factory AC before.
Looks like a super low mileage vehicle underhood - especially nice for a 40+ year old Ohio vehicle.

The "hairy-hose" that attaches to the air cleaner snout will bring good money if it isn't in bad shape.

Anything you remove from underhood will sell to someone restoring a Trans Am.
All the emission components, cat converter, EGR valve, spark plug wire dividers, all the little detail and knick-knack items that you will likely be removing.
Photo the stuff before you remove it to authenticate.
Every little clip and bracket and gizmo will sell.

I had a "mostly" bone stock 77 Can-Am , that is similar to a GP.
It was a 400cid though,,,
but a set of headers, recalibrated distributor, and a shift-kit really made a big difference in the car. It also had a shaker hood scoop like a TA.
With a 3.23 limited slip axle.

Might consider a TA shaker hood scoop (open scoop) for your GP, versus the money for a glass hood. Just cut a hole and use black flexible door edge guard around the cut edge.

Do find a 3.23 limited-slip rear. You probably have a 2.73 peg-leg.
Its not likely you will ever need aftermarket axles in your rig.

Wouldn't do a cam swap.
The low-lift cam in your 350 shouldn't cause any interference going with 1.65 rockers.
Its probably less than .400 lift

Trim the weight best you can and don't worry about aluminum radiator and aftermarket wheels. Save as much coin as you can to put into the 455.

[1976 Grand Prix 455]

Hi Baron, thanks for the input. I’m the second owner of this car and near as I can tell the only options it has on it is the 4 bbl carb and the Morokide vinyl (if that was an option). Please see below.

[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

[1976 Grand Prix 455]

It is the barest one I’ve ever seen too. Check out the front and rear bumpers.

It’s also very clean underneath. There is some rust on the frame but it’s very minimal surface rust. This car spent a lot of it’s life out of the weather.

[PAUL K]

Very cool car and a very cool project. Take your time and think about your goals. Enjoy!

3:42 will be great for the 350. You can have a lot of fun messing around with the 350. It will also benefit from most the moves you'll want to make for the 455.