I recently was over at the machine shop thats taking care on the finishing machine work on my darton 427 MID block. While I was there, I layed the crank in the block, put on a couple main caps, and installed one piston to see where the rod bolts would hit the bottom of the sleeve (Dave @ cartek-who i purchased the block from- informed me that the block might have to be clearenced slightly at the bottom of the bore due to the fact that the rod bolt would contact it). Sure enough, the rod bolt barely nicked the sleeve. I marked on every bore where the bolt hit and the machinist used the mill to make a small notch in the end of each bore....

My question is this: since we wanted to take off as little as possible on the bottom of the sleeve, we wound up with about .040 -.045 clearence between the rod bolt and the bottom of the sleeve. We thought that this would be enough, but I just wanted to ask if this was enough for my peice of mind.

The custom JE pistons we used reuired a tiny amount of clearencing as well just on the skirt to clear the counterweight. Once again, we didn't want to take very much off the skirt (this was a very very slight amount), so we set the clearence between the skirt and the counterweight to be about 0.040 as well. The machinist (who builds race motors for a living) thought that this was a good value. Any opinions out there? I've asked around and it looks to be a good value, but it never hurts to ask again to make sure...

I will be doing the final assembly soon...I really want to get this in the car and running soon

Thanks,
Conrad

 

seems that alot of people here like to see about .090 for the rod clearance and i dont know about the skirt clearance.

but thats on an LT1, i dont know much about the LS1's...

 

Yes, Conrad, that sounds fine. I always do around .050-.060 at a minumum but I like .100 if theres no danger of hitting water or something. That way if the rod bearing ever spins and "piggybacks" the other it still wont hit the block. .050 should be perfectly fine though.

 

thanks for the replys. since it was too tight to get to some of the clearenced areas to measure, we ended up using a peice of tig wire that was about 0.045 thick. Since it was a little tight but still passed through OK, the gap could be as high as 0.050 like you say. This motor will be recieving a healthy dose of N20 via the dp system i built for the car ( www.nd.edu/~caschenb/dpnitrous ) that I want to make sure everything is OK.

thanks again, and all replys are welcome.

 

The machine shop that is putting my shortblock together builds motors for the promod guys. He said that they want at least .060" clearance between the rod bolt and block. Sounds like you should be good.

 

no offense, but that doesnt look like the dp systems im used to seeing. maybe its just the picture...

 

that might be because its a noszle system by NOS. its turned out to be a great system and the fuel system i build works great in conjunction with it. its the same system that east side used to go 8.93 on a 427 somewhat similar to the one i am assembling.