Mach shop gave Chevy clearances

[ThikStik]

This 3.8 rebuid has been a comedy of errors trying to get machine shop to do its job. Finally get stuff home and see that my rod bearing clearance is 2.5 on most rods. I got the old Chevy treatment-they obviously didnt take me seroiusly about the tighter clearances. Next time Im sending stuff to buick only person.

I wonder how long itll go that wide.

 

[broke1]

I use Howtons in Bham.From talking to other local TR guys thats who they use also.I remember when I had them build the sbc in my T they had 3 Stage 2 engines sitting there.They are the best ms in Bham for TRs.

 

[norbs]

is the crank turned on the rods, and mains? If so how much?

 

[ThikStik]

Yes , crank is at 10/10 on both. (they knocked it over and damaged journals after the initial polishing at standard!, so it was ground. Glad I saw damage.
If I could just get a .005 oversized .010 bearing Id be ok.

RE: Howtons, yes ill use them next time. They did mess up Brian Mayfields 1987 WE-1 motor years ago. Hes a tuning guru/chip burner around Birmingham.

Thanks

 

[norbs]

I have H bearings here in +1 oversize, they do make a +10 but nothing more. Your out of luck. Either try and redo the rods again or if you must even chrome the crank .010 , or get an other crank.

Looks like they made a big boo boo!

 

[ThikStik]

I wonder If anyone here has run like this, some are at 2.0 but most are at 2.5 like I said. The mains are a bit better, around 2.0 though one of them is a loose 2.5. I wonder if a tiny amount of milling down the caps could crush down bearing alittle more.

I HATE MACHINE SHOPS.

 

[Dusty Bradford]

Rod's are cheap. Since .025 on the rods is pushing it then just buy another set of rods and have them sized correctly. You could call Birmingham Piston though and see what oversized bearings they have though. It may be possible to make up the difference with different sized bearings.

The main is a tough one---- I have heard of engine builders using a combination of bearings to get the clearance where you want it. For example a +.020 on top and +.010 on bottom. Never done it myself though.

 

[Lee Thompson]

bearings

1-888-236-6079 Calico Coating in NC ask for Jerry.
IMO your best way to save what you have is to have a coating applied to the bearings. You will gain about .0005. He can apply it heavy also.
I don/t believe resizing the rods will do it. I have seen where Buick mixed std. and .001 under bearings to get the desired clearance, but .010 and .020 would be disaster. Any time a crank is turned undersize, ask the machine shop to leave it on the high side. Best of luck.

 

[frankg]

Mark the journals that are to wide and take the crank to the machine shop to have them polish it to a .003" clearance then use +.001 bearings on those journals and that will make it .002". They should do it for free if you told them that before. That motor would be fine as is though!! I've seen people build these at close to .003" and live for a long time with great oil psi. I try to set mine to .002" though. Frank

 

[Lee Thompson]

clearance

frankg---crank is already .010/.010 Do you have a source for .011 under bearings? Not saying they are not out there, just never saw a listing for them. Would be nice if someone does make them.

 

[Chuck Leeper]

TOOLS??

Originally posted by ThikStik
I wonder If anyone here has run like this, some are at 2.0 but most are at 2.5 like I said. The mains are a bit better, around 2.0 though one of them is a loose 2.5. I wonder if a tiny amount of milling down the caps could crush down bearing alittle more.

I HATE MACHINE SHOPS.

A couple things...
1. How did you measure the clearances? Plastigage, or dial bore gauge? The dialbore gauge is the correct way to make sure what you have. Plastigage is not the way to go...That stuff is kinda like "close enough is OK when using handgrenades"..
2. If the shop messed this up as bad as you are saying, I'd loosen the rod bolts and retorque. If they "rebuilt" them and didn't do the torque and retorque during the process of honing the big ends, then they likely won't be round when you re-measure them...I've seen some rods that had to be honed, loosened, re-torqued 4 or 5 times before they stayed round...
A rod bore set on the minimum dim can help w/ excess clearances.
Same on the mains.

I've not seen .001 under under sized brgs... The coating can help some. If they are .0025, like Frank said, RUN THEM!! The factory clearances, IMO, are too tite for a performance engine anyway.

The added clearances are a bit of an insurance policy. If you have a rod close up some under hi stress, you still have clearance. Set them tite, and you have none, and we all know what that does..

If you need some added oil flo, use a hi vol pump, or a plate...

Back under my rock...

PS: w/ the clutzes you are dealing with, I'd dial bore the cam brgs too!!

 

[Ormand]

In the front of the Buick "Power Source" book, there are clearances for a number of competition engines. Some have forged cranks and rods, but there are one or two with stock crank/rods. Clearances in the range of 0.0025 are used on some. I can't find my book, so I can't be more specific. BUT.. these engines all have upgraded the lube systems. The stock system, with restrictive passages in the front cover, plus the filter adapter and the stock oil cooler, just won't flow enough oil to support bigger clearances. If you clean up the oil passages in the block and the front cover, and use a "biggie" filter and a better than stock pump, you should be Ok.

 

[ThikStik]

1st off: Thanks gurus!

2nd, RE tools: Am using starrett telescoping gauge-then measure it with mic. Ive got great repeatability. Double checked this 20 times.

3rd, RE rod retork when resizing by shop: I just cant know if they did cycle. I , per the ARP instructions cycled bolts 4 times. Heres an example of a rod big end---@ 12/6 oclock=2.374
@10/5 oclock=same
@Part line=2.374-2.375

Just a hair more at parting lines.

This shows that there mignt be some room to tighten rod bores a hair??? Will this mess up balance?

THANKS GUYS-I can see workable options here.