Anybody here take this motor apart? Need to do a headgasket on this motor, so I'm doing my research right now. The question I have is in regards to setting valve lash/push-rods. Documentation I have states that the push-rods are torqued to 11ft/lb plus 90* rotation. One thing I haven't found is if there is a pattern or a specific proceedure on what rods to torque. I know w/ the Fiero 2.8l, you have to rotate the engine and torque certain rods @ certain times. Anyone have any info? Thanks.

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-jason
'87SE
'88GT (5spd)
'90GTZ

just crank the rocker arm bolts down to the proper specs nothing else needs to be done. Be sure to use new bolts

You must use new head bolts as the originals have been "yielded" during assy. Also as mentioned above just torque the rocker arm bolts to the spec.....the rockers themselves are not adjusted. I think it might be wise to get new rocker arm bolts also as 90 degrees rotation will stretch those bolts quite a bit. I remember seeing many of them break when someone tried to reuse them. Just a thought.

[This message has been edited by David DeVoe (edited 06-21-2004).]

Right, I'm ahead of y'all on that one.... Noticed the manual called for new rocker arm bolts, soo that is a moot point... but I'm glad y'all mentioned it, thought! Shows attention to detail. I'm hoping that info will be useful to other people too. I tell you what, these specs are crazy. 35ft/lb for the initial torque on the head bolts, right? 130* extra rotation on all bolts. On top of the 130*, the 4 center head bolts take an additional 30*. WTF?? 160 degrees of rotation on top o fhte 35ft/lbs?!? If ya don't use NEW head bolts, I can almost guarantee those bolts will snap if reused. Thanks for the replies!!

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-jason
'87SE
'88GT (5spd)
'90GTZ

I used ARP studs in the heads - can be used over and over

If you use ARP studs make sure you get a high quality Thread sealant. I lost a set of rod and main bearings when the sealant I used didn't take, and allowed coolant into the oil.

quote Originally posted by LFiero67: If you use ARP studs make sure you get a high quality Thread sealant. I lost a set of rod and main bearings when the sealant I used didn't take, and allowed coolant into the oil.

I plan on using red Permatex thread locker when I do the heads. I know GM has there own part number for the sealant/locker listed. Might just pick that up just to be on the safe side. Thanks all!

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-jason
'88GT (5spd)
'90GTZ

Those specs you quoted for the head bolt torque don't sound right to me. If you let me know what year engine you have I'll look up the factory specs at work. I work in the 3800 plant. The next dept. down the build line from me installs the heads and rockers or cardonic assemblies as they are known in the plant. I have the build books and torque spec sheets for most years so let me know which one you have and I'll get it for you.
During assy all the fasteners in the 3800 are torqued with computer monitored electric wrenches, making it simple to turn to yield or to a threshold torque value plus x degrees. Its kinda tough to duplicate that at home in the garage.

Head bolts:

Step 1 - Tighten all bolts to 35 ft. lbs.
Step 2 - Tighten all bolts an additional 130 degrees.
Step 3 - Tighten center 4 bolts in sequence an additional 30 degrees.

Rocker arm bolts

Step 1 - 11 ft. lbs.
Step 2 - An additional 90 degrees.

These are the specs I got for the 96 Bonneville Service Manual CD-ROM dated November 2000. Thanks.

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-jason
'88GT (5spd)
'90GTZ

Wow, thats a lot of degrees man, I'll look at the spec sheet tomorrow morning and let you know what it says.

quote Originally posted by David DeVoe: Wow, thats a lot of degrees man, I'll look at the spec sheet tomorrow morning and let you know what it says.

Thanks. Ya know, that is exactly what I was thinking when I read it at first, too. I know my Quad 4 is 26ft/lb + 90 degrees. To confirm what that CD-ROM says, I'll pop open my Fel-Pro head bolt set tomorrow. Usually they have the updated torque & pattern for those bolts packaged inside....

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-jason
'88GT (5spd)
'90GTZ

Hey, sorry it took so long but here are the factory specs right from a 96 build sheet, also part #'s for the head bolts.
For all models except the EV6 used in the APV head bolt specs are: 50 newton metres +/- 4 then turn 120 degrees +/-3 This yields the bolt and provides a permanent elongation of .002-.012.
The part #'s are 25533811 & 25527831.
Torque spec for the rocker pivot bolts is 15 nm +/-4 plus 90 degrees +/- 3
Hope this helps. If you ever need any more torque data let me know.

Wow. Newton meters? Is that what GM uses? That makes since, ya know, since they use metric for damn near everything else. Will have to check torque wrench since I'm use to seeing it in ft/lbs.... Well, tomorrow (or this weekend as NC is too damn rainy this time of year) I should have the heads off.

Yeah, the head gasket is in the process of totally blowing. Saw puddles of fluid in the lower intake (didn't smell like oil - had a sweet smell of Dex-Cool... and it was reddish). Upper intake was hand tight... WTF???? Fel-Pro gaskets were uses in the upper intake. Did GM use those from the factory?? I doubt it. Missing one exhaust manifold gasket thus far in the disassembly.... Oh yeah, the heads are IRON. That surprised me. I ASSUMED all new motors had aluminum heads. 3100, 3400, 3800 had aluminum. NOPE! Tested with a magnet. Stuck to the block, head, but not the lower intake (obvilously alum.). You 3800 SC guys, do you have aluminum heads, or cast iron?

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-jason
'88GT (5spd)
'90GTZ

Yes, the specs are for all head bolts, no special treatment indicated. Just some info you don't need but may find interesting. The head bolts are designed to yield, that is permanently stretch, at a certain amount of load which in 96 was either 13k or 15k pounds. That is the purpose of the 120 degrees, to provide an accurate way to insure that the bolts stretch. Torque alone is not accurate because so much applied torque is lost to friction, and the amount of loss is difficult to calculate reliably while 1 degree is always 1 degree.

The manual I have is a factory helms manual for a 1999 Bonneville. It gives this as the tightening sequence for the head bolts.

1.Tighten to 50nm (37ft lbs)
2.Rotate an additional 120 degrees
3.Rotate the 4 center bolts an additional 30 degrees.

It may be different when they do it from the factory as it is the first time it is ever done. Hope this doesn't confuse you more. Just wanted to help.

Kris

Yeah, its quite weird how there is varing torque specs floating out there. BTW, why are the heads IRON? I figured they would've been ALUMINUM. What about the SC version of the 3800? Do they have iron or aluminum?

Here is a question for y'all. I know the upper intakes had a problem w/ vacuum leaks and cracked manifolds years ago... what is the new torque specs for that upper intake? When I took my upper intake off, the bolts were hand tight. Also, there was fluid collecting on top of the lower intake in the two recessed points. Almost seemed like a mix between coolant & oil. Saw red spots all of the lower intake as well. I guess my head gasket is going....

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-jason
'88GT (5spd)
'90GTZ

Jason, it is entirely possible that there is a service bulletin out about the center head bolts that I'm not aware of. Shop rat has a point. The specs I gave you are first time build that might explain the difference.
Theupper intake to lower intake specs are 15 newton metres =/-3. You're right there was some cracking in this area so you have to be a little careful wrenching on it. That also explains the relatively low torque spec. Also in my experience you get some joint relaxation after the engine has been thermo cycled a number of times. We've done tests that show as much as 40% torque loss in some joints. Another reason for using angle rather than just torque.

[This message has been edited by David DeVoe (edited 06-26-2004).]

quote Originally posted by David DeVoe: Oh yeah forgot to mention........all 3800 heads are iron.

Yeah, I imagine the specs ya gave were for the first time build. The Fel-Pro specs and the shop manuals I've seen are dated in 2000, so I guess they went back and reworked a few things. No biggie. Thanks though! I'll definitely keep your specs in mind regarding the upper intake.

Well, I yanked the heads today. I think I see where the coolant was leaking into the combustion chamber. It looks to be off #5 cylinder... which is where the PCM reader says there is the occassional misfire. Makes sense.... I can't believe how easy it was to pull the heads on this motor. My Quad 4 is another issue. To yank the head bolts on that motor, I have to put serious body weight into that breaker bar just to get it to barely turn. The 3800, no biggie! Just some effort was all that I needed. Must be that iron block, iron heads vs. iron block, aluminum head thing. Funny thing is, the Quad takes less torque and less angle of rotation (90*) than the 3800, but its harder to remove.

Why did GM do iron heads for this motor??? I figured they'd want aluminum for the heat dissipation.... They want durability w/ iron?

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-jason
'88GT (5spd)
'90GTZ

Beats me. One thing though, the engineers caution against overheating the engine as the heads crack relatively easily. I've never asked engineering why the iron heads and now I can't because Buick engineering has moved out of Flint. In fact the whole Buick site is slowly leaving Flint. I think the 3800 is doomed as we are down to 1 shift and that has historically been the precurser of closing the plant.
Jason, I have the torque data sheet for every fastener in the engine so let me know if you need anymore info. You can always pm me. I visit the forum almost every day as I have 2 Fieros in a constant state of fooling around with. Im building a spare 2.8 for my 86Gt right now, and thinking about getting a Series II SC for my SE. Thinking is easy lol.

quote Originally posted by David DeVoe: Beats me. One thing though, the engineers caution against overheating the engine as the heads crack relatively easily. I've never asked engineering why the iron heads and now I can't because Buick engineering has moved out of Flint.

You know... its funny you should mention that. My heads are cracked... both of 'em. Don't quite understand it as I didn't overheat the heads. Sure they'd get hot in stop and go traffic, but the heads haven't been w/o coolant. The only time the heads have been w/o coolant is after the headgasket/head crack had formed. Well, I'm off to find some heads for my 167k mile engine. Need this project done ASAP as I have a 2k mile road trip in 2wks. When it rains, it pours, eh?

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-jason
'88GT (5spd)
'90GTZ

Jason I probably dont have to mention this but any heads you buy must be pressure tested. The heads are the 3800's only real flaw in my opinion. Good luck on the rebuild.