GTO camshaft

I have a 1968 GTO that has a Pontiac 400 crate motor in it. I was interested in getting the correct 1968 GTO camshaft for it, and was wondering what specs lift dwell etc. I am looking for. Thanks.

Hold on for our resident Pontiac expert, MrPbody.

Thanks for the segway, Maxwedge...(:-

Pete,

Perhaps the 400 was delivered "in a crate". I say that because there are no "true" crate engines for Pontiacs today, as in the sense "crate motor" is used to refer to new production 350 Chevys, 302 Fords, etc. There is one shop in Florida (Ken's Speed and Machine, AKA Pontiac Dude) that sells a 505 "crater" based on the aftermarket block and heads. BIG money... About the same as the 572 Chevy, though it will stomp a mud-hole in the BBC.

You need to know a few things about the engine before you change cams. On the center two exhaust ports (where they protrude from the head), there are fairly large numbers "cast in". We need to know what those are. If it really is a '68 GTO engine, they will be "16". There are a couple of obscure numbers, but 16s are far and away the most common.

With today's gas, the original engines WILL detonate. They have 10.3 (or so):1 static compression. The practical limit for 93 octane is 9.5:1, with 9.3 being "optimum". The original camshaft ("068", last three digits of the factory part number) is well suited to the higher compression, but will lose significant power with the more modern lower compression. When copmpression has been modified to be "street friendly", we use Comp XE262H as a "replacement" for the factory performance cam. This grind sounds much like the original and performs MUCH better.

Please offer as much detail about your engine as possible. The block casting number is on the back above the bellhousiong "flange", 7 or 8 digits. The installation "code" is a two-letter stamping on the passenger's side front of the block, along with the partial VIN and other foundry marks. The two-letter code is "key". The date code is on the back, next to the distributor. There will be a 4-digit alpha-numeric code that appears to be a "tag" screwed down. In reality, it's "cast in", but the screw heads may be visible. The first digit is a letter indicating the calender month (A=Jan, B=Feb, etc.). The second two numbers are the day of that month. The last digit is the last digit of the year it was cast.

On the driver's side of the carb, on the secondary airhorn, there is a 7 digit number, too. It will start with 7028 if it's a '68 carb. The last three will tell us the application the carb was originally installed on.

Jim

The heads are "16's". By crate motor, I meant that I ordered a Pontiac 400 ci motor from autozone or somewhere. As it is currently installed, some of the other numbers you asked for I haven't acquired yet, I checked the numbers once, and the block is mid 1970's, 1975 I think. I looked up that comp cam number on their website, and it seems to correspond with several grinds, so I was wondering what the specs are so that I would get the right one. This car is going to be a driver, not a race car of any kind, but I would like to simulate the performance I might have gotten from the car from the factory, so I was looking for a cam that would be similar. Thanks for your help.

Pete,

I understand. Unfortunately, you have a "remanufactured" engine rather than a "crater". In general, remans use "generic" parts, based on what ever the builder is getting a "good deal" on this week.

The Comp part number you're after is 51-222-4.

Jim

Thank you very much. Comp Cams website indicates that I would need to have screw in studs, and guides in order to use this camshaft. Am I likely to have those things with this motor?

Pete,

Yes. ALL '67-newer Pontiac V8s have guide plates. All the large valve/small chamber heads (16s of the '68 vintage are large valve/small chamber) have screw-in studs.

Another issue comes to mind. If "stock" specs were used by the rebuilder, your compression ratio is too high for "pump gas" (93 octane). They probably have the 8-relief "fits all" piston which helps SOME, but not quite enough. Installing the Comp XE cam COULD create a situation where detonation will be a problem.

If you notice ANY "pinging", be sure to double-check ignition timing. 12 "initial" and 34 "total". If it's okay, you HAVE detonatin.

The "fix" is either higher octane (mixing "race gas" with 93) or disassembling the engine and have the pistons "dished".

Jim

This post does not make a cam recommendation when the stock 10.3 pistons ARE used. Does Mr Pbody have a good cam for the STOCK engine?

Don't hold your breath for a response from Mr. Pbody. His last activity on these forums was May 14, 2012.

Hopefully someone else with similar experience will be able to address your question.

-Rod