Anyone know for a fact what the stock 1973 pushrod length might be? All the catalogs list them as 6.850 (5/16") But...I've measured the ones that were in my engine, and they come out to, 6.875 (I've had this engine since 1988 and never opened till I did a quick rebuild)....I've ran the engine with the 6.850's and it's noisy. Or do different manufactures measure them differently?
there are alot of factors that detrimine the right push rod lenght. a rebuild can change the required length. things like valve stem hight, if the heads were surfaced, if the block was surfaced, will all have a effect on what length is required. best way is to get or make a adjustable push rod and find out what lengh keeps the rocker arms tip on the center of the valve stem.
Pushrods are measured two or three ways. There's gauge length, Actual length and theoretical length. You're likely measuring the actual length and the info you got may have been the gauge length. 6.875 vs 6.850 are the same length. You're only .025" short which is less than a 32nd of an inch. Nothing to sweat over.
When I did all the checks with the engine once it was assembled, I used the push rods that were in the engine, piston to valve clearance was good, and the marker on the valve stem was right in the middle. But I figured that since it was still apart, I'd put a little better push rods in, SO I took one with me to the speed shop, and they measured it, and checked a few different catalogs, they all came out with 6.850. So I figured that must be correct, re-assembled the engine, and fired it up. The top end was noisy..so I checked push rod length again toady, and found it to be short with the new push rods. So I checked around the net, and found most listings at 6.8550, for stock 1973 302 push rods...... I just came in for the garage, and pulled a set out of another 302, and compared them to the new ones, and they are longer, close to the 6.875's. So something is screwy somewhere....anyone need a set of 4130 5/16"X6.850 push rods? Frustrating, but I love building my own stuff!!
I am measuring actual length, and the factory ones are longer compared side to side with the Manley ones I bought. I find the top end pretty noisy with them in there, so tonight I'm going to swap them out with the factory ones and see how it sounds.....(sounds like a solid lifter engine with them in there)
That's what's confusing about buying pushrods. Some list them in the catalog as gauge length, some the actual length. Sounds like you may have also gotten a set that's .060 short. Many are sold in .060 short, std and .060 long. .025 short shouldn't have been an issue, unless the ones you replaced these with were on the short side already.
