Builders......Main clearances checked what to do now.

[TurboDave]

OK builders, I'm now your grasshopper, your advice is needed

The Buick specs state for main bearing clearances: .0003 - .0018

The power source book doesn't really quote specs, however the builds in the front of the book all show clearances just over .002

I have carefully measured mine with both plasti-gage, and mic/bore gauge methods

As near as my eyes can see with the plasi-gage

#1 .0018
#2 .0015
#3 .0010
#4 .0013

Using mic/bore gauge method

#1 .0017
#2 .0022
#3 .0020
#4 .0020

This using the original crank (100,000 rather easy miles)(some racing but nothing quicker than high 12's) that was polished and measured perfectly with no discernable taper on the mains/rods journals.
These are new King bearings (std).


With the above measurements, my question is: what's the next step?

BTW, Rod clearances were all measured at .0017 - .0020 Good?

 

[LOT]

I'll probably get shot down but

I would try a set of .001 under and see how well the crank turns (without rear seal) If TOO tight --try .001 under half in block only. I would do the same with rods. I have a stage II block and when last assembled (4 years ago)--rods and mains are right around .001 clearance. Granted all has to be right for this to work. Great oil pressure with a stock blueprinted front cover. If a strictly race engine --disregard anything I have just posted. Best of luck. --Lee

 

[TurboDave]

Guess I should have mentioned, this engine will not be raced. Just street use with the usual WOT blast once in a while.

 

[m233roller]

With the above measurements, my question is: what's the next step?


If mic. measurements are correct == RUN IT !!!

 

[Just a Six??]

Lots of difference in the plasti guage to mic. Maybe get another mic to borrow if possible & try again to be sure?

 

[Mac in SD]

Dave,

I'd run it as-is. .002 is pretty damn good, IMO. That's what I always went with.

 

[Alky V6]

I agree with Mac in SD.
Use it.

 

[thadeal4real]

could run ok but the rods should be bigger i think thats what lot was hinting on but it looks good n square RUN IT
good luck

 

[m233roller]

thedeal4real,
What do you mean (the rods should be bigger?) If you mean they should be more than .002 GOOD LUCK.

 

[Two T's]

Hi dave I talked to a friend local and he also said you should be good nice visiting with you when I was down on vac by scott are you closer to putting it back in? Well you all take there down there see ya next time im down that way.
Tom

 

[Chuck Leeper]

Huh???

Lots of difference in the plasti guage to mic. Maybe get another mic to borrow if possible & try again to be sure?

R u suggesting that the mic is less accurate than that old fart's eyes???

RUN IT!

 

[TurboDave]

R u suggesting that the mic is less accurate than that old fart's eyes???

RUN IT!

At least I'm pretty sure about the mic's accuracy. They all check perfect on their "standard"

 

[Just a Six??]

At least I'm pretty sure about the mic's accuracy. They all check perfect on their "standard"

I dont know you personally but you seem like a pretty smart guy from what I read on the boards so I'm sure when your done it will run like a Champ!

 

[thadeal4real]

just specs lol

thedeal4real,
What do you mean (the rods should be bigger?) If you mean they should be more than .002 GOOD LUCK.

the rod clearances need to be bigger than the mains or you will starve the rods
too big no good bearing wash too small oil stays and blows out the mains its a fine line to walk

 

[STP]

If it were mine..I'd leave the rods where they are and try to tighten up the mains a tick. Like Lee said, try a .001 half in the block. You may have oil pressure issues with the rods and mains over .0015....My IMO of course.

Why did you rebuild? Low oil pressure?

 

[TurboDave]

If it were mine..I'd leave the rods where they are and try to tighten up the mains a tick. Like Lee said, try a .001 half in the block. You may have oil pressure issues with the rods and mains over .0015....My IMO of course.

Why did you rebuild? Low oil pressure?

No, the engine didn't have any problems when I removed it. I took it out about 15 years ago because I a purchase a really low mile complete motor real cheap, and wanted to save my numbers matching motor.. I probably should have left the short block alone but it had 100,000 on it so I stripped it down for cleaning and new parts way back then. Tossed the cam and lifters and rod bearings but kept most everything else.
It had no problems though, was running perfectly.

 

[m233roller]

I don't know why some of you guys (THINK) you might have low oil pressure with the mains at .002 ?? Iv'e built my share of these and have set the rods right at .017 -.018 and the mains at .002 and with doing the oiling mods to a stock GM front cover and running a 60lb. yellow spring every one of the engines Iv'e built have GOOD oil pressure. Like 22 to 28lbs. HOT- HOt idling in gear and run 50 to 60 lbs. at 2000 RPM and some of them have been going strong for some years now. My own roller cammed engine is going on 8 yrs. and almost 35,000 miles and still has excellent oil pressure and YES it has been flogged on pretty hard threw those years with LOTS of quarter mile passes. Just my 02 worth??

 

[STP]

Experience is the reason, Mike....Last I checked Buick didn't assemble them with .002 main'rod clearances. On a race engine? It's a different story. Don't turn this into a pissing match. Dave asked for opinions...

 

[Nick Micale]

Experience is the reason, Mike....Last I checked Buick didn't assemble them with .002 main'rod clearances. On a race engine? It's a different story. Don't turn this into a pissing match. Dave asked for opinions...

OK, Dave did ask for opinions and stated he is NOT building a stock 15 sec. GN.

Buick actually did some "special" work on the turbo engines according to the engineers I communicated with years ago who were involved with production in the '80's. The oiling system and bearing clearances were 2 areas that received special consideration.

I fail to see where Mike has said anything to turn this into a pissin' match?

His statement mirrors our experience with rebuilds and race engines as to clearances and oil pressure. Race engine may go more than .002", and still have awesome oil pressure.

Another bit of experience with MANY Buick V-6 and V-8 engines, is that we have not seen rod or main failures from the looser tolerances, but massive damage when the tolerance when too tight.

Remember, a .002" clearance is only .001" when the engine is running. So Dave's .001" is then .0005" when rotating, and Buick "factory" spec is down to .0003" and .00015" at 5000 RPM.

That would scare the hell out of me if it was done according to factory specs.

 

[STP]

Nick, reread the first sentence in Mike's last post....Basically, implying that the experience others had seen was incorrect. The word THINK is what I had a problem with. It's all good...Too each his own, but don't tell me what I as well as others have experienced is not correct.