Inliners International Forums General Discussion Hi Performance Were there any of the GMC 302 with 7 mains.

The GMC uses a gear drive from the factory, Cloyes did make a suitable performance multi keyway set. Also, the later 250/292 six cylinders that are raced in Comp and other classes have had Jesel belt drives, so I'm sure they can do one for the GMC. You'll just need to decide when making the cam cores if you are going to make the barrel larger, and will you also make the snout larger as well so the cam gear can be made to fit that. The GMC crankshaft only has a snout the same size as a SBC, and many SBC Comp racers upsize the cam journals to BBC and also make their cranks with BBC size snouts as well.

Timing gears are the same from the 216-292 and GMC even though some were fiber they will interchange. There are some with straight cut teeth all steel that are said to be stronger. Some add a bolt in the gear/cam seam to assist the key in holding the gear in place. Most later sets have steel crank gear & aluminum cam gear. A lot will depend on how hard you lean on the cam.

a good set of all steel gears would be good. I may just have to do a belt drive

I believe a belt drive would require a reverse grind cam. Is that something else you can do in-house?

Yes, a custom reverse pattern cam would be required. You actually will see a significant gain in HP by going away from the gear drive and using a belt system.

pk ive torn the motor down out of the car and its got some great parts. Rods are Crower, Pontiac rod bearings

Great pictures, Thanks! Please keep us up on what you are doing here and noting the parts and modifications you find. Too many of the speed secrets of these engines are not in the books.

I agree awesome photo's, It sure is clean on the inside.

looking for an adjustable steel cam gear and a set of 4 bolt mail caps. I can make the main caps if I have to but if someone has already spent the time. I would rather support them. If Not We can make several sets

Greg,
I am not as familiar with the GMC's, but does your engine have more than a standard amount of head studs?
Second thing. Correct me if I am wrong guy's. Doesn't the GMC use the same timing set a 235/261/250/292? If So 12Bolt has adjustable timing sets in stock. Oh wait, I see you want STEEL cam gear also. Those are in the works.

All the GM sixes from at least '39 (216) through 292 and the 153 & 181 fours can use the same timing gears. There are different numbers but those designate fiber, aluminum, steel. and teeth pitch. I think the 151 Iron Duke may us the same set. Those cranks can interchange with the 153-181 but the cam can not because there is a different valve order.

Yes, there are 2 more studs in between the 2 and 3 and 4 and 5. They did not help , the head was dancing it's a$$ off. This motor has been setting since 2005 or 2006 and was probably built before 2000.

Cloyes Made a steel-to-steel timing get set MANY yrs. I know this firsthand Because I have the Last set, they ever made I got (84) and to the best that I know of They never made any more. They Used to make them for UPS And a cording to Cloyes the reason they stopped Because UPS started having problems with cam Brakeage instead of the gears over time.
So, I got the last set he said they had, and They sent them to me as an experimental Use ONLY..

that's neat. I've had a few parts over the years from GM that were kind of one-off. I am going just to build some main caps unless I can find some. one of the CAPs on this engine moved and was close to getting a bearing.

You'll need to make your own caps. You'll also need to dowel them to keep them from walking around. The Stovebolt and GMC blocks of that era don't have a register like later engines have to positively locate the caps.

that's obvious, these mains were moving. The head gasket was leaking between 2 and 3 and 4 and 5. They put 4 extra studs in this area and it didn't help. They didn't understand back cutting the studs

Looking at the pics I can see several things that could have been done better....Sounds like you're on a better path for sure!

I am looking at getting a cometic gasket made, not sure if it will happen this year.

You could machine the block to accept a fire ring or "hoop". And be back to work.

It should already be o-ringed for the copper gasket. Plus, companies that make MLS gaskets like SCE only rank that style of gasket a step or so above a composition gasket, while they rank the copper several steps above that. So you already have a much better gasket now so you are really backing up in comparison.

The Hoop I am referring to is different than a o ringed deck. The block gets machined with a step. The hoop goes into this step and creates a impenetrable wall. Not at all for street use.

Yes, I make them for all the LS stuff I'm doing now. His block should already be o-ringed for the copper head gasket any way, and is better than the MLS gasket he is thinking of using. A fire ring or hoop is good if he wants to step up and do that also, it's common for the LS and diesel performance stuff also. It's even better if you cut receiver grooves in the head. Since he mentioned he had a CNC, it shouldn't be any problem for him...

There is also a U ring that is used in F1. It is energized by combustion. It's much like a fire ring but open to the inside. At this power level, I think there is some other problem. The Studs were not back cut.

Going to a 55 mm tool steel cam and dropping valve weight by over half. The compression ratio was close to 16 to 1 with a .060 gasket and with a .040 gasket it's out of sight. I believe that the biggest problem was water distribution and flow
We are going to do a new billet head this winter.

The crank gears were the same, but the cam gears were different between the 235/261 and the 250/292. I just looked and they are slightly ever so different, right at the hub, or am i imagining this?