symonds86

does anyone know what the spec is for how much the crank should move forward and back? mine seems to be excessive compared to other motors i have built. my motor is a 68 302 block with a scat crank (347). the onlt number i can find on the crank are 11 12 but i might have missed the others if they are there. im thinking i wanna throw a set of main bearings in it before i drop it in the car anyway, since i bought it used. anyone know what main bearings this thing would take?

thanks
guys

Portmaster

Around .007 no less than .006 not more than .009

Portmaster

You would have to mic the crank before know what mains to use

symonds86

ok thanks i get the dial indicator out and measure it but i think mine has more. thats just by eye though but we will see

symonds86

well i measured and it was .070!!! so i took the thrust bearing cap off and found this


also i think my crank is f'ed



i heard this motor run before i bought it and it made no odd noises, so what caused this? most of the wear is in the rear facing thrust. i took the rest of the mains off and there is no more than normal wear on them. so i need some help figuring out where to go from here. do i need a new crank? and how do i make sure it doesn't reacure.

thanks for the help

Portmaster

how does the thrust surface on the crank look? If it's smooth and polished looking I'd put a new thrust beaing in and check the endplay again. You may have excessive clutch pressure, someone did some serious riding of the clutch, or bad trans install. 070 is some serious endplay and could cause you a lot more problems. What transmision was behind that engine.

symonds86

it had a t5 behind it, but now that you say that he said he had alot of clutch problem with it, mostly that it wouldn't hold on a launch just slip. the surface is polished so now i gotta figure out what bearings i need for her and hope for the best. if i need to get a diff crank for some reason it would have to be all rebalanced right?. thanks for the help. i am more of a diesel guy so this balancing and high performance stuff is kinda new to me. If i can't pull the hood off, pull the heads, replace the sleeves, roll some bearings in and send her out, then i got something to learn lol. but thanks again

Portmaster

If the thrust side of the bearing is nice and smooth just pull the bearing out of the cap and look at the backside of the bearing for the size. I would try a new thrust bearing (and the rest of the mains) and check the endplay then go from there. Yes you would need to rebalance the crank and rotating assembly if the crank need to be replaced. If the thrust surface is nice and polished smooth you may be OK.

symonds86

ok thanks i'll look for the size

symonds86

ok the bearings are clevite 77s standards. what type of bearing are you guys running?