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Captain Rehab
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32 Posts
Discussion Starter · #1 · (Edited)
Engine Clearances

Sorry 'bout the mispelling "engine",it was another 20 hour day.....my bad.
I'm about to assemble my 388 Stroker Small Block Chevy. I bought a balanced complete rotating assembly (Scat crank,rods,pistons,rings,bearings,flexplate & balancer). What is a a good clearance on rod and main bearings as well as piston to wall clearance and also ring end gap. Also,what is a recommended oil viscosity and brand. I'm putting the engine in a 1968 16' Cheetah with a 12JG pump and "B" impeller. Figure it is going to be spinning maybe in range of 5000-5400 RPM. (This is just a guess,may not be accurate).Running 9.7 compression,hydraulic flat tappet Comp XM278 cam.Aluminum 64cc heads2.02/1.60,750 Holley,Edelbrock RPM air gap intake,stock volume,high pressure oil pump, 8 quart pan and Rewarder headers.

Thanks
 

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Sit N' Spin
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1,345 Posts
I'm about to assemble my 388 Stroker Small Block Chevy. I bought a balanced complete rotating assembly (Scat crank,rods,pistons,rings,bearings,flexplate & balancer). What is a a good clearance on rod and main bearings as well as piston to wall clearance and also ring end gap. Also,what is a recommended oil viscosity and brand. I'm putting the engine in a 1968 16' Cheetah with a 12JG pump and "B" impeller. Figure it is going to be spinning maybe in range of 5000-5400 RPM. (This is just a guess,may not be accurate).Running 9.7 compression,hydraulic flat tappet Comp XM278 cam.Aluminum 64cc heads2.02/1.60,750 Holley,Edelbrock RPM air gap intake,stock volume,high pressure oil pump, 8 quart pan and Rewarder headers.

Thanks
Go high volume on the pump. Looser clearances need more oil volume than stock clearances.

0.002" - 0.0025" on the rod bearings

0.0025" - 0.003" on the main bearings

With these clearances I'm running Valvoline VR-1 20w-50 oil and seeing about 25-30 PSI hot idle, 55-60 PSI at cruise and 70-75 PSI at WFO.
 

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Sit N' Spin
Joined
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1,345 Posts
I'm about to assemble my 388 Stroker Small Block Chevy. I bought a balanced complete rotating assembly (Scat crank,rods,pistons,rings,bearings,flexplate & balancer). What is a a good clearance on rod and main bearings as well as piston to wall clearance and also ring end gap. Also,what is a recommended oil viscosity and brand. I'm putting the engine in a 1968 16' Cheetah with a 12JG pump and "B" impeller. Figure it is going to be spinning maybe in range of 5000-5400 RPM. (This is just a guess,may not be accurate).Running 9.7 compression,hydraulic flat tappet Comp XM278 cam.Aluminum 64cc heads2.02/1.60,750 Holley,Edelbrock RPM air gap intake,stock volume,high pressure oil pump, 8 quart pan and Rewarder headers.

Thanks
Go high volume on the pump. Looser clearances need more oil volume than stock clearances.

0.002" - 0.0025" on the rod bearings

0.0025" - 0.003" on the main bearings

For the initial startup and break in, I recommend the Joe Gibbs Performance Break In Oil. It's got lots of zinc for that flat tappet cam. Run it for break in and the first two hours of engine operation, then change the oil and filter.

With these clearances I'm running Valvoline VR-1 20w-50 racing oil and seeing about 25-30 PSI hot idle, 55-60 PSI at cruise and 70-75 PSI at WFO.

I'm running that exact same cam. You'll want springs with about 120lbs seat pressure and 310-315lbs open. Also, if you got the high energy lifters, take them back and get the Pro Magnum lifters. They're only about $10-$15 more and the retaining clips on those High Energy lifters have no place in a jet boat engine.
 

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Captain Rehab
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32 Posts
Discussion Starter · #4 ·
As far as pump volume,I've had alot of guys swearing the high volume will suck the pan dry and wipe my bearings. They keep recommending stock volume,high pressure. I've built many street engines as well as mud drag/bog engines and run high volume pumps and have held engines at 7200 rpm for a 12+ seconds and never dropped pressure or wiped bearings.

Thanks
 

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Sit N' Spin
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1,345 Posts
As far as pump volume,I've had alot of guys swearing the high volume will suck the pan dry and wipe my bearings. They keep recommending stock volume,high pressure. I've built many street engines as well as mud drag/bog engines and run high volume pumps and have held engines at 7200 rpm for a 12+ seconds and never dropped pressure or wiped bearings.

Thanks
As far as pumping the pan dry, in regards to a Chevy that is pure BS. If it were an Olds I'd say yes. But Chevy's never had the oil drainback issues that the Olds has...on top of that you have an 8 qt pan, which I seriously doubt that it would pump THAT pan dry.

You will have to change the intermediate pump shaft (i.e. the shaft that connects the distributor to the oil pump) to the severe duty chromoly shaft (ARP makes them...shouldn't be more than about $15). Also make sure whatever distributor you use has a brand new cast iron gear on it.

Most high volume pumps only pump about 25% more oil than stock anyway, so are you saying that a stock pump is 25% away from pumping the pan dry? I highly doubt it.
 

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E-7 Sheepdog (ret)
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6,625 Posts
As far as pump volume,I've had alot of guys swearing the high volume will suck the pan dry and wipe my bearings. They keep recommending stock volume,high pressure. I've built many street engines as well as mud drag/bog engines and run high volume pumps and have held engines at 7200 rpm for a 12+ seconds and never dropped pressure or wiped bearings.

Thanks
You do not need a high volume pump with those clearances.

I run .0025 (aprox) all over mine, and have no trouble maintaining 58psi on 10w-50 synthetic above 4,000RPM, all the way to 5,400+.

Idle hot pressure is 23, plenty.

I've run this engine WFO for as far as 8 miles, not 12 secconds, 7 minuites.

Standard 5-quart pan, 2-quart K&N oil filter (I THINK it's the 6002 p/n)
 

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Sit N' Spin
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1,345 Posts
Smokin' is right...you don't ABSOLUTELY NEED a high volume pump. You CAN run one though and IMHO it is the better way to go. However, unless you're running an oil pan with stock capacity, the whole "pumping the pan dry" on Chevys is simply a problem that doesn't exist.
 

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Captain Rehab
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32 Posts
Discussion Starter · #8 ·
Thanks JetAholic,I'm still thinking 8 quart pan,the large K&N 2 qt filter,I've got an oil cooler with 3/4" water in/outs and 1/2" oil in/outs and HV/HP oil pump.

Thanks
 

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Sit N' Spin
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1,345 Posts
Thanks JetAholic,I'm still thinking 8 quart pan,the large K&N 2 qt filter,I've got an oil cooler with 3/4" water in/outs and 1/2" oil in/outs and HV/HP oil pump.

Thanks
IMO you don't need the high pressure pump. A high volume/stock pressure pump pops off (bypasses) at 60 PSI and will allow the pressure to increase another 10 PSI on top of that (mine hits 70 PSI).
 

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Registered
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Sorry 'bout the mispelling "engine",it was another 20 hour day.....my bad.
I'm about to assemble my 388 Stroker Small Block Chevy. I bought a balanced complete rotating assembly (Scat crank,rods,pistons,rings,bearings,flexplate & balancer). What is a a good clearance on rod and main bearings as well as piston to wall clearance and also ring end gap. Also,what is a recommended oil viscosity and brand. I'm putting the engine in a 1968 16' Cheetah with a 12JG pump and "B" impeller. Figure it is going to be spinning maybe in range of 5000-5400 RPM. (This is just a guess,may not be accurate).Running 9.7 compression,hydraulic flat tappet Comp XM278 cam.Aluminum 64cc heads2.02/1.60,750 Holley,Edelbrock RPM air gap intake,stock volume,high pressure oil pump, 8 quart pan and Rewarder headers.

Thanks
Id be interested to know how that cam idles with your set-up. I'm currently running a very similar build with cast (sportsman) heads and an xm270... and am very tempted to go bigger

You're having the rotating assembly balanced by a machine shop, right?
 

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Sit N' Spin
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1,345 Posts
I run the XM278 on my big block and I'm seeing about 5200-5300 RPM on an A impeller with an RPM Air Gap, Performer RPM heads and a Holley 750dp, 10:1 compression.
 
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