94 barrels in a 90.5 case bore

[cpalma]

is this as simple as turning the base of 94 cima/mahle barrels to fit a case bored for 90.5? wil warpage be an issue?

new 94 heads on the way and looking to use same bottom end and spacers as this is already decked for my desired c.r.

[ErikTheRed]

You need to have the case bored for 94's. Try to machine down the base of a 94mm barrel to 90.5 and see what you end up with.

(That last comment was fececious, don't try it.)
 

[pfer10]

You need to have the case bored for 94's. Try to machine down the base of a 94mm barrel to 90.5 and see what you end up with.

(That last comment was fececious, don't try it.)
 

April fools right?  You are up early or to bed late aren't you?

As for the original question yes.  There is one thing you have to check. It is explained down at the bottom of this page. http://www.lowbugget.com/pistonpage.html  I did this on my last motor.  Took the cylinders to a  machine shop that knew what they were doing and it worked out great.

[cpalma]

nope, don't want to be that fool, hehe. but a 96 od on the 94's shud stil cut it on my mild motor.

thanks for the link PF.....

[bauerbus]

Yes It can be done I did it myself on my lathe at home. the next time I'll make a plug that fits inside the bore becareful it can be done. Bob Bauer 

[sweet67]

Rimco will cut the base of a 94 down to a 90.5 for $50.  I'm running a set in my 2332cc daily driver.

[Marty]

If you want more case stregnth around the studs, its the way to go.
Yo may need to have the case "plunge cut" deeper so that the piston does not contact anyting at BDC.

[Tom Simon]

IMO the right way to do this is to strip the entire engine all the way down to the bare case and bore the cylinder holes in the case to fit a 94 barrel.

Turning 94mm barrels (to go into a case bored for 90.5's) leaves only a .03" wall near the bottom of the barrel. Not terrible, but certainly more fagile. The bigger deal is when you machine the case for bigger barrels, you also true up the deck at the same time. No offence intended here, but truing up the case can be the difference between slapping it together and crossing your fingers, and doing a quality engine build.

When you bore the barrel openings in the case, you ask to have the barrel spigot faces cut at the same time. The way Rimco does this, it trues up the barrel seating faces making them equadistant from the crank centerline, to get the barrels to the same height. As a result, you will be able to get your deck heigths and compresion ratios closer to equal, and you will be sure the heads will seal up correctly.

[ErikTheRed]

IMO the right way to do this is to strip the entire engine all the way down to the bare case and bore the cylinder holes in the case to fit a 94 barrel.
Turning 94mm barrels (to go into a case bored for 90.5's) leaves only a .03" wall near the bottom of the barrel. Not terrible, but certainly more fagile.

I agree with Tom-- IMO theres a difference between "its possible" and "its the right thing to do". 5 years ago or so, I had a used case that had been cut for 90.5's and I wanted to build a 1915, and I looked into the possibility of having the cylinders turned down.......certainly seemed the easier way to go. After a couple phone calls, I was convinced its much better to do it the "right" way and have the case bored.

[Marty]

I am assuming a new or fresh case is being used.
ANY 94mm turbo motor I build is done this way. Have not seen a single cracked case since I started doiung it.

[cpalma]

all your inputs are very helpful, just wanted to hear from the experts how it's best done before i decide which way to go. makes me feel better knowing it's been done w/ success, whichever method is later used.

the easiest and yes, more cost-effective route to take for me is having 94A cylinders cut at the base to fit my "used" as41 case and use the current 76 crank and w-125 cam inside.

but leaving the barrels alone and having the case done instead is stil an option. more expensive as there's only a handful shops here that i trust can do this for me. wil also take longer since if i'm cracking it open might as well save up for that 82 crank and better rods....

[pfer10]

I am assuming a new or fresh case is being used.
ANY 94mm turbo motor I build is done this way. Have not seen a single cracked case since I started doiung it.

Why would the case every crack down there?

[Marty]

Why would the case every crack down there?

Because there is not much material left around the 10mm insert when it is bored for 94mm. On many mag cases, the insert encroaches on the 94mm bore. On boosted and higher compression motors, the studs try to pull out and crack the case around the inserts - mainly around #1 cylinder spigot.
My prefernce nowadays is a CB tall deck case bored for 92's. The combination of under-borin the case and the tall deck allows for the full threaded portion of the studs to be sunk deep into the case and have much more material around the inserts.
I have seen 33 pounds of boost so far without one having any issues.

[2stroke]

ive done full 36psi passes with stock german headstuds, and an aluminum case with 10mm inserts bored properly for 94s, not a problem doing that specifically.

now it has racewears and n2o

[pfer10]

now it has racewears and n2o

You still have the turbo also?

[2stroke]

You still have the turbo also?

oh gawd YES