[ponchjoe]

Nice car ‘76! I’d eventually add power to the drivetrain and leave it looking like a sleeper...
Very nice low mile car.

[77 TRASHCAN]

A problem with getting power out of a 350, is getting the comp ratio high enough to help out.
I'd just leave that 350 alone, period! Concentrate all $$$ on the 455...

[chiphead]

With a car that nice, I wouldn't modify the original engine too much or remove much of the original accys under the hood. I wouldn't do any mods to the body or frame that couldn't be easily undone. No minitubs, shaving emblems, removing seats or interior pcs trying to save weight. No cutting the dash for aftermarket gauges. That's happened to most of the classic cars and it hurts their originality and value. Just my .02.

Ideally you would set the original engine/tranny in storage and swap for a hotrod drivetrain you could modify without hurting value of car.

[ponyakr]

"...will the 3.42 gear be too much for the 350..."

From strictly a 1/4 mile standpoint, the 350 would require a lot more gear than that, for best ET. With a car that heavy, I'm guessing the lowest ET would probably be produced with 4.56, 4.88 or 5.13 gears.

But, those are obviously not street friendly. Any gear ratio in the 3's, or numerically lower, is just a compromise, to make the car more street friendly.

Just as an example: I ordered my new '69 GTO with 3.90 gears. 4.33 gears were available, and would have produced a lower ET. But, since it was my DD, I went with 3.90. I loved it. But gas was lots cheaper back then, & I did hardly any interstate cruising. 55mph was the speed limit on most of the roads I traveled.

You can use the calculator to figure your approx rpm, at different speeds.

Assuming 3.42 gears & 28" tall tries, your rpm will be aprox 2900, at 70mph, & aprox 3700, at 90mph.

http://www.wallaceracing.com/calc-rpm.php

So, you can see the compromise. Might be a little more rpm than many would like for interstate cruising, but less than would be needed to produce the best 1/4 mile ET.

So, I suppose you'll just have to decide how much highway rpm you're willing to tolerate, in order to run quicker on the track.

One option is to run tall tires on the street, & short drag tires, at the track. That will decrease your street rpm AND reduce your 1/4 mile ET, while using the same rear gear for both.

The trunk should be plenty big in order to get a couple of short drag tires in it. In '73, I towed my GTO to the track, with narrow street tires, then bolted on the drag tires, at the track. It's more work. But, it's one way you can lower street rpm and also run a lower ET, with the same car.

[steve25]

Please note that Running a Cam of less then .410" lift will keep you from having push Rod clearance issues when adding 1.65 rockers.

In other words the factory 350 cid Cam lift of .406" or less will not have issues with 1.65 rockers!

Just don't use Harland Sharp brand Rockers since they are over ratioed coming in at 1.70 or so.

[1976 Grand Prix 455]

So I'm just about sold on doing the 1.65 ratio roller rockers as the only "internal" upgrade to the stock 350.. I understand the concept of the 1.65 ratio, but not the real world physics of them. Here are my questions:
Regarding a Pontiac engine, I see a lot of comments about needing to machine the heads to accommodate the extra lift/duration. Does this same issue exist with a cam swap?
If so, what is the max lift these heads will accept without modifications?
How much lift will stock valve springs take?
Will there be issues with valves colliding with pistons?
Finally, does anyone have any literature on cam lift for this year and size engine? I'd hate to guess with this and guess wrong and these rockers wreck my engine or heads.

Thanks in advance.

[Baron Von Zeppelin]

iirc the base cams in mid-to-late 70's were less than .400 lift.
W72 cam was about only cam in that time frame with a little over .400 lift.

If you dig around on the www.wallaceracing.com website - think it has the cam specs for that application.

Pushrods lightly rubbing where they come up through the head , is the precaution area. Not really a factor with your 6X-4 heads and low lift.

Approx 10% gain on lift with 1.65 rockers
Should be in safe zone concerning pushrod rubs and coil bind.
No fault in investigating deeper yourself to feel certain.

[steve25]

With the low compression / deep chamber of the 6X heads you could run over .600" lift and not run into piston to valve clearance issues.

The push rod cup distance in a rocker will move about .090" closer to the stud with a 1.65 rocker over a 1.50 rocker .

The factory Cam base circle / Lobe lift for having .406" lift at the valve with a 1.50 rocker is .270"!

[Baron Von Zeppelin]

With 3.23 gear and 15" wheels on both my 77 Can-Am and 79 TA , around 60mph was 2700 RPM.

Good daily driver/performance blend.
And probably the highest numerical axle you will be able to source as a full complete unit that bolts right under your GP.

3.42 or more, you'll likely have to buy an aftermarket posi chunk and aftermarket set of gears and install all that into your existing differential with precision calibrations.
In that case, i'd go higher like 3.55 or 3.73 - then plan on an overdrive transmission later with the 455 swap.

by PAUL K -- Take your time and think about your goals. Enjoy!

Solid Advice

[steve25]

Another thing that needs to be considered about your stock 350 is that it only has a 50 psi oil pump.

[1976 Grand Prix 455]

Originally Posted by steve25

Another thing that needs to be considered about your stock 350 is that it only has a 50 psi oil pump.

Hi Steve. Please explain.

[chiphead]

Rule of thumb is 10 PSI oil pressure per 1000 RPM. So with a 50 PSI oil pump, you shouldn't spin this motor over about 5500 RPM. Which is hard to do anyway with engine and tranny in stock form. Now if you put a cam in it, headers, gears and change tranny shift points, you may creep up on 5800 RPM at the track. That's risky on a stock shortblock. With that said, my early '70s stock-ish 350 would spin to 5500-5600 often and I never hurt it.

[1976 Grand Prix 455]

I'm not planning to go that radical with this. I'm thinking the 1.65 ratio rockers, headers, performance exhaust and a gear in the rear end. What ever she runs after that she runs. I expect I'll have to do some carb work of some kind as well.

Bottom line for all of this my car running 19 something @65 mph getting stormed by a guy running 12.0 @110+ at the finish line isn't going to be easy to judge. I don't mind being the slower car at all and giving the other guy a chance to sit on the starting line and think about it. lol I'd just like to get a little extra bump in performance and I don't plan to squeeze every bit of HP out of this engine that I plan to replace anyway. I'm anxious to return to the track and I don't want to blow the opportunity to get my 9 y/o little girl interested in cars and racing. Some of my fondest memories were spent at the track and working on cars with my dad.

[steve25]

Since he may be running used valve springs but with another Cam the motor may not rev clean to 5500 rpm anyway, but it's also the smaller 5/8" instead of 3/4" pick up tube that has me most concerned!

[steve25]

Also concider this.
Pontiacs test out for releasing a motor to go into production was that it had to run 24 Hours at 4500 rpm with nothing more then a oil and filter change at 12 Hours in.

I would assume that some short blasts to 5000 would be ok, but road racing could have the oil pan venting Rods, Bearings and chunks of Crankshaft.

[Bruce Meyer]

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 had a 76 GP with no vinyl top. Bare bones GP with 350 2 barrel. It did have A/C and buckets.
I agree with you on the hood. That's a real nice car. I would not make any mods that couldn't be easily changed back to stock.

[Baron Von Zeppelin]

76-77 GP's are very good looking cars, to me.

Never seen one as unique as this car.
It's so bare its practically an obscenity towards the GP nameplate. Like its giving the middle finger and bronx cheer to all the other ones built that year.
And with a classic sinister color combo to boot.

I'd be scrounging around relentlessly to find a factory buildsheet in this car.
Would tell if it was special order/customer , or funky dealer order.

Maybe the guys in the 69-77 GP section could assist on whether or not B-sheets are commonly found in these cars, and where.

My 77 Catalina Wagon had a B-Sheet. fwiw

[1976 Grand Prix 455]

Originally Posted by Baron Von Zeppelin

76-77 GP's are very good looking cars, to me.

Never seen one as unique as this car.
It's so bare its practically an obscenity towards the GP nameplate. Like its giving the middle finger and bronx cheer to all the other ones built that year.
And with a classic sinister color combo to boot.

I'd be scrounging around relentlessly to find a factory buildsheet in this car.
Would tell if it was special order/customer , or funky dealer order.

Maybe the guys in the 69-77 GP section could assist on whether or not B-sheets are commonly found in these cars, and where.

My 77 Catalina Wagon had a B-Sheet. fwiw

Even though it's Plain Jane, I fell in love with it as soon as I saw it. The body color and interior combo are perfect together! The dealer I bought it from said it was a trade in. The title said it was from West Virginia so the original owner may not have been wealthy so would explain the bare bone car. When I went back to the pick up the car and sign paperwork the next day said his phone blew up with people wanting to come take a look at it so I think I got lucky with this.

[1976 Grand Prix 455]

On a side note. If this is the lone 301 car produced in 1976 I'm gonna die. lol

[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.