Hello everyone,
I would like to ask about adjusting the valve lash on my 68 302. I have rebuilt the engine and now have it back in the car and running. While the engine was still on the engine stand I adjusted the valves using the John Hinckley and Duke Williams method which you can find on the CRG Research Group website. (start on TDC and turn the engine 90 degrees 7 times adjusting 2 valves at each 90 degree position at .027). Now that the engine is running and somewhat broke in (there are a couple valves that are a little noisy) I am going to adjust the valves again. The cam I installed is the Federal Mogul Speed Pro 30/30 grind part # 53059 12002 and the rocker arms I used are the Comp Cam 1.5 ratio roller tip stamped steel rockers.
Here is my question......Is the Speed Pro 30/30 cam Identical to the original cam where this adjustment method would still work, and are the Comp Cam rockers different in some way that this adjustment method would still work? I think the method is fine but would it change the .027 clearance?
Thanks in advance to everyone who replies.

 

If memory serves they called it a 30/30 cam because the valve lash was .30/.30 and those solid lifter cams are a little noisy. Back when I ran a solid lifter L88 cam in my 427 I'd sometimes get a couple that were a little loose and I'd just give them an 1/8 to 1/4 turn or so with the engine running 'till they quiet down to match the others. I ran that motor so hard I was adjusting the valves every weekend. lol Did the same with my roommate's '69 Z28 302. With solids it's better a little loose than too tight or you'll be bending pushrods or breaking rockers when you wind her up and those 302's do like to wind.

 

Thanks Y2K,
I usually adjust them at .030 also, but the method I was talking about takes into account that the stock rocker arms are actually a 1.3 ratio, not 1.5 like GM advertised. That's why they say to adjust them at .027 instead. I was wondering if the Comp Cam stamped steel rockers I used would also adjust at .027 or if they are actually a true 1.5 ratio.

 

You might want to email comp Cams with that question.

 

Stock rocker ratio is 1.5. Are you running iron heads? You want to set your lash with the engine hot. Are you using poly lock adjusters or standard nut? Standard nuts will lose their lock thread after a while. On TDC with iron heads, I would say go .029 intake and.028 exhaust hot. Keep an eye on the depth of the nut on each rocker stud. If an adjuster nut is deeper on the stud threads than the others, that is a sign something is bent or worn.

 

Thanks Al Loyrat,
They are the original iron heads and I didn't use poly locks because they wont fit under the stock valve covers.
I readjusted the valves over the weekend and it now runs and sounds great. For some reason number 1 and number 4 valves were a little loose. I originally used the EOIC method when the engine was on the engine stand. This time I used the 90 degree method which I think is the best method to make sure the cam is on its base circle.

I chased this car for about 30 years which my ex father in law bought new at Harry Mann Chevrolet in Los Angeles (68 Z28 RS). Its been sitting for about 25 years and has 67000 original miles, original paint and interior, all #s matching and extremely well documented. He told me he used to adjust the valves with the engine running. He would use cardboard to deflect the oil to keep from making a mess.

 

I worked at Harry Mann in the 70s! Nice car BTW.

 

I heard Harry Mann Chevrolet was a premier Corvette dealership back in the day.