Opinions on rod and main bearing clearences
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Chevy guy rebuilt engine
Engine in our GN has 78,000 miles and was rebuilt by a Chevy guy 14 years ago/39K miles ago. The original owner had it done. Going thru old paperwork .30 over, main bearing cl..0027 and rod bearing cl..0026, deck clearance .023, cylinder head vol.48cc, CR 8.4:1 , crank endplay .004 , rod side clearance .012, valve spring pres. 1.7@120lbs and 1.25 @ 275lbs,... Original owner bracket raced her every weekend and every chance he got. Now most don't believe bracket racing is true racing. He liked running /racing the car on a consistant basis during racing season so she was tuned for consistancy and perseverence. He'd rather be on the track racing then in the garage fixing. He consistantly ran low 12's usually 12.1 .. He was happy and content with the times and racing at that level. This with a stock turbo @20psi, old ford supercoupe injectors 30lbers, Conley Mag4 chip 32 degrees timing @ WOT, nothing but C16, MT's Drag Slicks and tubes, Hooker downpipe, Hurst line loc, .. This motor has close to 40K since it was rebuilt and still running strong (not even a headgasket replaced since rebuild)and a Chevy guy actually rebuilt it, this is probably the only LC2 Mr. Gibson ever rebuilt.
Well even a blind squirel finds a nut every now and then, even a Chevy mechanic gets lucky with a LC2 with such loose tolerances every now and then.
Engine in our GN has 78,000 miles and was rebuilt by a Chevy guy 14 years ago/39K miles ago. The original owner had it done. Going thru old paperwork .30 over, main bearing cl..0027 and rod bearing cl..0026, deck clearance .023, cylinder head vol.48cc, CR 8.4:1 , crank endplay .004 , rod side clearance .012, valve spring pres. 1.7@120lbs and 1.25 @ 275lbs,... Original owner bracket raced her every weekend and every chance he got. Now most don't believe bracket racing is true racing. He liked running /racing the car on a consistant basis during racing season so she was tuned for consistancy and perseverence. He'd rather be on the track racing then in the garage fixing. He consistantly ran low 12's usually 12.1 .. He was happy and content with the times and racing at that level. This with a stock turbo @20psi, old ford supercoupe injectors 30lbers, Conley Mag4 chip 32 degrees timing @ WOT, nothing but C16, MT's Drag Slicks and tubes, Hooker downpipe, Hurst line loc, .. This motor has close to 40K since it was rebuilt and still running strong (not even a headgasket replaced since rebuild)and a Chevy guy actually rebuilt it, this is probably the only LC2 Mr. Gibson ever rebuilt.
Well even a blind squirel finds a nut every now and then, even a Chevy mechanic gets lucky with a LC2 with such loose tolerances every now and then.
I'm not clear on your terminology. Doesn't a booster plate turn your oil pump into a high volume pump? What are you referring to as the booster plate?
J-B Racing
Forced Induction
- Joined
- Sep 16, 2003
- Messages
- 2,466
Like Don Says
A Topic with lot`s of opinions. I personally prefer .002 - .0025 on ALL...
And I use 25/50 Penzoil...:smile:
A Topic with lot`s of opinions. I personally prefer .002 - .0025 on ALL...
And I use 25/50 Penzoil...:smile:
You're using a dang good oil there, Joe.
J-B Racing
Forced Induction
- Joined
- Sep 16, 2003
- Messages
- 2,466
I THINK MR J-B RACING IS EXACTLY WERE ID LIKE TO BE .0020 - .0025
I HAD MEASURED THE CRANK AFTER CASTILLOS MACHINED IT,I ONLY HAD
.0015 CLEARANCE WHICH IS WAY TO TIGHT.SO I TOOK IT BACK.I SHOULD GET IT
BACK TODAY. WHICH OIL SHOULD I USE TO BREAK IT IN?
I HAD MEASURED THE CRANK AFTER CASTILLOS MACHINED IT,I ONLY HAD
.0015 CLEARANCE WHICH IS WAY TO TIGHT.SO I TOOK IT BACK.I SHOULD GET IT
BACK TODAY. WHICH OIL SHOULD I USE TO BREAK IT IN?
I use 30 wt. non-detergent with a high pressure additive if running flat tappets. Changed out after a few ring seating romps on the freeway and street. There are some oils available now for break-in use only. One is marketed by that football coach guy. He runs racing teams too. Name escapes me at the moment.
BlackBandit
God loves Buicks!
- Joined
- Mar 29, 2003
- Messages
- 2,437
Don,
I think the booster plate is a thrust plate that provides more thrust area for the gears to ride on so you don't bleed as much pressure in the pump. The HV pumps give you a new thrust surface for the gears but also give you taller gears to increase the amount of oil they can move.
FWIW I built my engine a little over .002 on the rods and mains. I opened the oil feed hole in the middle mains up to match the block and used the TA duel groove duel feed coated bearings that restrict the oil to the cam a little. I went through the front cover and radiused the corners and got rid of casting flash. Pretty much the "earls front cover mods" write up on the "other" site. I made sure no gaskets hung into oil passageways and that's about it. I run 0w-20 and have 20-22 psi hot idle in drive and it jumps up to 55-60 while I'm cruising. (~2100 rpm) I pretty much drive in the city and love to get into the boost so when I say hot idle that's what I mean. I also haven't installed the oil cooler yet but I do have a relocated oil filter. The system holds about 6 quarts.
Also, I agree with Don. People make these engines out to be some mystical beast that requires voodoo magic to build. They're no different than any other engine. Build it for it's intended purpose (in our case forced induction) and address any inherant issues like the oiling system and you'll be fine. That's my .02. HTH james
84BuickGNYorkPA
Daily Driving Buick V-6 Turbo's 1979 - Present
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- Jul 5, 2005
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- 1,840
Interesting thread, I've always heard tight, tight , tight. Good to see all the different responses....
Chuck
Chuck
- Joined
- May 26, 2001
- Messages
- 9,208
There are many different responses because there are many different "builds" for different situations and use.
The problem here is the owner should NOT be telling the shop what clearances he wants, it should be the other way around.
The shop owner/machinist should question the car owner about how he is going to use/run the car and decide accordingly. This is true if the shop has experience in the type of engine desired.
Many shops have and can build NA engines, but have no experience in blown, turbo or NOS builds.
As Don stated, an alum block has different "specs" than an iron block, and the same is true of a street vs. race build.
Even the Buick specs are different. Many people quote the factory shop manual specs as what came in our turbo motor. This is not true, the turbo 3.8 bottom end is not set up the same as the 2 barrel carb engine in the 1960's. Even the Buick P S book has different "set ups" for various racing conditions.
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