clearance issues on a turbo build

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wannaberacer

Member
What do you guys recommend for main bearing clearances as well as rod bearing clearances for high HP turbo motors? I'm kinda thinking about running the mains a little looser than teh .0016" max recommended by the shop manual to maybe .0025. The rods I was thinking about .0025 too. What do you guys run for your turbo motor builds?

BTW: its a dart block, wiseco's and eagles...
 
I dont think thats a good idea. It may not seem like much but you definately want a solid and tight bottom end. If anything, make clearances the max allowed. Too much gap and you will not have the correct oil circulation and pressure. I ran minimum clearances on my talon engine, and it holds up extemely well.
 
yeah you need to keep your clearances within spec or you'll run into problems with the motor. I would run them on the loose side of what honda recomends but do not go past the max
 
I talked to the builder today, he still wants .0020 on the mains and .0025 on the rod bearings. What do you guys think?? This is on a dart block, gt40r, etc... I really don't expect to run the motor more than 20k miles before I freshen it up again. Is .0020 too loose??!
 
Blanco @ Mar 19 2006 said:
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Yes, that's way too loose. That's .0005" past the service limit for the rod bearings and right on the service limit for the mains. Does your builder understand that he's building a Honda block?
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Yea, he understands. He's the crew chief for a top fuel team. And he thinks .0015 is too tight for sure. He wants me to use thicker oil and run looser tolerances. I have a gt40r that is going on the car, and I'll be makeing about 700whp on high boost. He thinks with that kind of power the tight clearances can be a problem... Is there anyone out there making over 500whp that can clue me in???
 
He just built a good friends 4g63 with looser clearances than he suggested for me. And the 4g63 actaully runs the same main clearances honda's do. That motor has been running a gt42r for almost 8000 miles now with no issues... Is there anyone who has a built motor than can give me an idea if I need to go loost or not???
 
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