Changing studs to bolts on '86 32v engine

MarkRobinson · 12-22-2006, 10:26 AM

I know many have done this, but i have not, so looking for the tips to do so: I know it's not just removing the studs & using the S4 bolts & washers...anyone??

Mark

m21sniper · 12-22-2006, 01:44 PM

To what end? Studs are much stronger than bolts.

rhjames · rhjames's Garage

I agree... Why change something that's better than where you're going?

Every racing engine out there (that stays together) uses studs and nuts. Included in this is head studs (mounted in the block) and crankshaft main caps (again, mounted in the block). The only securement in the rotating assembly that is not a stud/nut deal is connecting rod bolts (however you can get ARP high strength bolts for just about any application....).

Any time you remove studs (or bolts for that matter) on a rebuild, you should always chase the stud/bolt holes with a tap, then oil the studs/bolts when reinstalling them (unless the manufacturer says otherwise). Of course, you'll do a good soapy cleaning/brushing of every hole, passageway, groove, galley....you get the idea....BEFORE you put it back together.

Leave your studs in, unless you somehow broke one--it is possible to do that, just make sure you torque the nuts using manufacturer's specs and tightening sequences.

regards---rhjames

m21sniper · 12-25-2006, 08:33 AM

You can see the extensive use of studs in this pic, including the full race main girdle.

It's no wonder these motors are 'bulletproof.'

rhjames · rhjames's Garage

That's great photo!!!!

Every 928 owner should have a poster of this hanging in their shop!!

Great Holidays to all.

regards----rhjames

m21sniper · 12-25-2006, 05:16 PM

It's been my desktop picture for about 2 years now, lol.

MarkRobinson · 12-27-2006, 05:28 AM

I think the sitting of my '86.5 car has deteriorated it's headgaskets to a degree, & I plan to replace them with Cometic MLS headgaskets: which are more prone to leaking than factory. Because of this, I want a way to remove the heads with the engine still in the car. With the 8-10psi of boost I plan to run & conservative timing + decrease in compression, I don't plan to break 600hp, & bolts will easily hold into this range: as tested before.

Mark (yes, great picture of the exploded 928 engine: have or know of a higher resolution of that one??)

m21sniper · 12-27-2006, 09:42 AM

email me at m21sniper2000@yahoo.com, i think i have a higher res version.

loose caboose · 12-27-2006, 10:43 AM

FWIW

Screwing bolts into aluminum engines, and subsequent gasket failures, led to the use of grade 8 studs set with red loctite at no more than 10 lbs and 48 hours time.

Aluminum is not nearly as aware of clamping force as is cast iron.

Upon teardown of ANY Aluminum engine, ...replace bolts with studs and a drop of RLOCTITE.

Tapping the boltholes is a real FUP! The threads enlarge and all goes away.

FACT!

MarkRobinson · 12-27-2006, 10:48 AM

I"ve done 4 headgasket swaps before: 1 on '86 928 due to deterioration, 3 on 944's due to t-belt failures: cars purchased with broken t-belts. 944's are easy to leave alone, but a hell of a lot of labor for the 928, S4's HG's hardly ever fail. Yes, I'd follow Porsche's specs for bolts if I went this route.

loose caboose · 12-27-2006, 11:08 AM

I trust you can do fine with any P project. Sounds good!

loose caboose

MarkRobinson · 12-27-2006, 11:10 AM

My only worry: the MLS metal gasket possibly leaking on the 928. If so, then you're in for 20+ hours of labor to swap if studded. With bolts, you'll shave 6-8 hours off that pretty easily. & with the power/boost I'll run, should work just fine as I'm not in uncharted territory here.

Thanks for the note John.

loose caboose · 12-27-2006, 11:46 AM

My opinion means nothing.

The engines teach us by how they reply to our efforts. Engines cannot lie. That is the truth.

Regards from here!

loose caboose · 12-27-2006, 11:51 AM

Time for old man to leave it to you young folks. Sorry to bother ya'll! Just a habit..LOL

rhjames · rhjames's Garage

I disagree about tapping the stud/bolt holes. you are just cleaning the threads, not enlarging them to the point of no return. Engine building 101. Restore everything to it's original blueprint specs will get you a more reliable engine.

BUT everyone has their own way of doing "it".

That's why you have the John Forces of drag racing, the DEI's of Nascar, and the Penske's of open wheel.

Some are just better than others.

regards--rhjames

loose caboose · 12-30-2006, 10:48 AM

Quote:

Originally posted by loose caboose
FWIW

Screwing bolts into aluminum engines, and subsequent gasket failures, led to the use of grade 8 studs set with red loctite at no more than 10 lbs and 48 hours time.

Aluminum is not nearly as aware of clamping force as is cast iron.

Upon teardown of ANY Aluminum engine, ...replace bolts with studs and a drop of RLOCTITE.

Tapping the boltholes is a real FUP! The threads enlarge and all goes away.

FACT!

My post regards the original GM alloy motors circa 1982. My engines won only two major races but One was at Darlington Southern 500 1982. I had the best driver and we got it done.

Tapping the boltholes with a rounded tap workd very well back then. The Tap cleaned and compressed the surface and we were able to clamp the studs fine.

Valvoline and Cale Yarborugh would agree with me...but that was a long time ago.

Sorry to interfere here.

loose caboose · 12-30-2006, 12:04 PM

Apologies to Mark and All!

Wife just reminded me that back then is not Now!

I think my old ways just got in the way.

Never let old Mechs get on the Net..LOL

I'll enjoy my 928 and shut up!

rhjames · rhjames's Garage

What John said.......I said.

use tap for cleaning, not reboring or rethreading.

Note: production assembly line engines are not custom-take-your-time-builds.

Blueprint build? Yes. Did the factory take the time to do this? Doubtful. Can you? Probably.

Run a tap in the holes, then wash everything with soapy water, rinse, wash again. (IF you've never done this before, Carl Fausset has a great video of him getting wet on his website).

As for Mark cutting time off a head gasket swap, how many times are you going to R&R the heads in a particular car? Aluminum "bolt holes" don't last long if you take them apart/put them together repeatedly, as opposed to iron blocks and such.

If this is a race set up, I really question your race strategy (no one in the professional ranks of drag racing---where motor tear downs are a round by round affair---uses anything but studs/nuts), but if your just trying to beat the recommended change out time (for a service customer), maybe you can save him a bunch of bucks by just dropping a used, or reman, complete engine......there was a "reason" for the blown headgasket (and more damage than just the gasket failure?), wasn't there?

Just a thought......

regards---rhjames

Old mechanics never die, they just get a new Peterbilt......

m21sniper · 12-31-2006, 08:34 AM

A 928 is not a drag car, and apparently you have to pull the motor to change the heads on a studded 928 motor. Which is his rationale for the bolt conversion.

rhjames · rhjames's Garage

I didn't figure he was building race motors, but if you repair the head gasket problem once, why would you change to bolts for easy head change in the future? (fix it correctly the first time, so to speak?)

Any how, yes, the later 32V engines did use bolts instead of studs for head removal. Head removal is equal to engine removal with a studded 928 engine. I just wouldn't change a good thing unless I had a specific goal in mind. With regard to Mark's above posts, I would guess (that always gets you into trouble) that he is doing R&D on his 86.5 and might be testing head gasket (brands) to see what will stay together on his turbo car. If he's just hunting a problem (leaky headgaskets), then no, I would do the changeout without disturbing the stud/nut arrangement.

No big deal......

regards---rhjames