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Itsjust a 305 07-11-2019 07:40 AM

Main and rod bearing clearances
Look for somw help again it seems like my bearing clearances seem a lil tight. My main are betwwen .0015 and .002. I have not checks rods yet bc i ran out of time last night. Was wonding about if this was ok or if i need to get a set of that has the +.001 . my crank is .010 on both mains and rods.

Note this is what i would call a hot street motor and the plans are to u a 100-150 shot as a o **** button at the track when running heads up.

Motor specs are
Copy victor jr intake
Worked over 210cc intake procomp heads
3.5dome pistons at 4.04
3.5 stroke crank thats has a .002 gram bal
Came is 243 int./249 exh at 50 with a .600 int and exh on a 112 lob
Running a .040 head gasket

MouseFink 07-11-2019 08:00 AM

Rod and main bearing clearance between 0.0020” and 0.0025” is ideal.

2001Blazer4x4 07-11-2019 08:46 AM

It's fine but I would stay away from 20W50 oil. Use good old 10W40.

MouseFink 07-11-2019 09:58 AM

I have used Valvoline 10w-30 All Season Motor oil in every car I have owned since 1965. I have never had a problem that could be blamed on the oil when using 0.0025” - 0.0030” rod and main clearances.

I spun out rod bearings on two different occasions in my 1969 Pontiac Firebird 400 but that was due to excessive engine speed over 5700 RPM with stock 1969 rods. I resized a set of used 1972 stock rods that did not have a spit-hole, using ARP 3/8” rod bolts, and that ended that problem.

Stock 1955-1963 Pontiac forged or 1964-1971 Pontiac cast spit-hole rods with stock rod bolts are undependable more than 6,000 RPM.

You can successfully use up to 0.0030” rod and main clearance if you have rods without a spit hole in the rod cap. The lack of a spit-hole forces more oil across the rod and main bearing surfaces.

ericnova72 07-11-2019 10:38 AM

The .0015" is a bit on the tight side considering you plan some nitrous use. If it was mine I'd get the +.001" clearance set and use just 1/2 of it, this would put you at .002"-.0025" clearance.
Splitting sets to fine tune clearance is quite common in the high performance and race engine scene, so don't de worried about it.

Be honest with yourself about that nitrous amount.....the power gets addictive and often leads to stepping it up....more than a few engines have been toasted due to the owners upping the jetting to the max the solenoid will flow.

If you're the type that this would be a possibility, then use the full +.001" set(actually, it would be a .009" under, or sometimes called a .010x")….and makes sure you've got the added RING gap to also handle more nitrous.

If using stock rods, even with ARP bolts, don't run them on the tight side, get the additional oversize there for sure if it measures out tight. Slightly tight a thr rod will only ba acceptable with a race type rod with 7/16" capscrews.

Itsjust a 305 07-11-2019 10:51 AM

Im running h beam rods 7/16 bolts and i been there and done the need more power. My truck is being set up for the 11.00 index class here. And i only have jetting up to a175 shot.

I thought the clearances where a but on thr close size. I well check my rods before i order my +.001 bearing

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