4.1 overbore Q

[turbo buicks]

alright guys im in kind of a dilemna. i picked up a 4.1 stage 1 block supposed to be std. turns oout its .005 over std. no prob, but no im faced with a few options i cant decide on. option A: find .005 over pistons and rings. (anyone got a clue where to get these i would prob buy them right now), option B: guy i got it off of tells me "id try my hardest not to bore it out if i were you" so i do a minimum std overbore .10 or .20 and try again to find piston/ring combo for this (again, anyone know where i could get this) option C: bore .035 over to a 4" bore which opens up a large selection of piston/ring combos. my question is, has anyone had any probs boring their 4.1 stage 1 block (siamese cyls) to a 4" bore? how much more room do i have to go bigger should need to in the future?

thanks

 

[Black Car]

What is your actual bore size? 4.005?
You will probably have to order pistons from Diamond, Ross or Weisco or other piston mfgs.
My 4.1 was bored to 4.005 and I had Weisco make the pistons for that bore size. Any mfg of pistons can make them for what ever your bore size.
Just money.

Gary

 

[Lee Thompson]

4.1 std bore is 3.965

Doubt that you will find .005 oversized piston without being custom made. First thing I would do is have it sonic checked. There is no fixed answer as to how far ir can be bored without a sonic sheet. Best of luck--sounds like you are going to need it.

 

[Alky V6]

I've been out to 4.047 without problems.

 

[yullose]

Bah...

.005 is nothing.

Put a set of standard size pistons in it with file-fit rings and run it a little loose.
Might be a little noisey when cold, but I bet she screams like a beast.

I ran a 427BBC many years ago that had around .013" skirt to wall clearence. It rattled like a diesel when cold, but she revved to the moon on the dragstrip.

 

[Lee Thompson]

There you go

Bah...

.005 is nothing.

Put a set of standard size pistons in it with file-fit rings and run it a little loose.
Might be a little noisey when cold, but I bet she screams like a beast.

I ran a 427BBC many years ago that had around .013" skirt to wall clearence. It rattled like a diesel when cold, but she revved to the moon on the dragstrip.

There's a man who thinks like I do.

 

[DR BOOST]

i had my block sonic checked and run 4.065 withno problems.

in your case i would just run std pistons.

surej

 

[49-blues]

I have a couple sets of 4.00 stage2 pistons-what piston height do you need? Diamonds and Ross.

 

[boostingbuick]

Mine is 4.030

 

[750H.P.V6]

I would tell you to keep the bore size as small as possible because this will allow you to rebuild the engine multiple times in the future and good Stage blocks with a small bore size are hard to come by. You can go bigger with the bore if you like but I wouldn't go any larger than you have to.

Pistons will more than likely be custom anyway due to bore, stroke, rod length, actual deck height of your block, desired compression ratio etc. Rings in almost every size are available from Total Seal in standard or zero gap. BTW, some good advise from above would be to have the block sonic checked to establish the actual cylinder wall thickness.

Neal

alright guys im in kind of a dilemna. i picked up a 4.1 stage 1 block supposed to be std. turns oout its .005 over std. no prob, but no im faced with a few options i cant decide on. option A: find .005 over pistons and rings. (anyone got a clue where to get these i would prob buy them right now), option B: guy i got it off of tells me "id try my hardest not to bore it out if i were you" so i do a minimum std overbore .10 or .20 and try again to find piston/ring combo for this (again, anyone know where i could get this) option C: bore .035 over to a 4" bore which opens up a large selection of piston/ring combos. my question is, has anyone had any probs boring their 4.1 stage 1 block (siamese cyls) to a 4" bore? how much more room do i have to go bigger should need to in the future?

thanks

 

[turbo buicks]

wow, lots of good info in here. 49 blues, ill get back to you. im getn all my parts from Dan at DLS so i ask him b4 i buy anything. 750hpV6 thats what the guy who sold me the engine was sayin about the rebuilds and stuff. what do std/gapless rings from TS cost? i assume they would be custom? from what ive seen, off the shelf TS GApless are expensive, might just use a std one.

 

[stagemonster]

I have a simese 0016 block thats bored to 4.125 i havent used it yet. Iam probley gonna put 6 sleaves in it and make it a 4.00 bore

 

["More Boost"]

is a 4.1L crank same stroke as 3.8L? 3.400 or no?

 

[750H.P.V6]

Yep. They're the same.

Neal

is a 4.1L crank same stroke as 3.8L? 3.400 or no?

 

["More Boost"]

so, you go from 3.8L to 4.1L on bore size only? that cant be.....plz

 

[yullose]

From 3.800 bore to 3.965 = .165 over... So yes, it's done with a bigger bore.

 

[750H.P.V6]

What he said.

Neal

 

["More Boost"]

ok, u see thats why i asked, because i didnt know. :biggrin: thanks guys

 

[TexasT]

ok, u see thats why i asked, because i didnt know. :biggrin: thanks guys

Realize the 4.1L is a siamese cylinder block placing the cylinders closer together and allowing for the larger bore(Similar to the Chevy SB 400). It is a different configuration than the '109' and other 3.8L blocks. I wasn't sure if you knew this and am just throwing out an FYI.

 

["More Boost"]

thank you, i appreciate any and all input. information is your (my) greatest tool. so the more i get the better. :wink: