Doing a 3.4 swap! My 2.8 had a flat heat shield installed between the block and the manifold gasket, without a gasket between it and the block. The only gasket was between the manifold and the heat shield. I thought, "That's not good!" Metal to metal = exhaust leaks! what is that shield for, and do I even need it? Seems superfluous to me! There is the rounded shield over the manifold which protects the wiring, tubing, and whatever, and keeps oil off the manifold, but that flat one between the gasket and the block doesn't make any sense! Can some one (in-the-know) tell me what it's for and if I even need it on my 3.4 application?
If I do need it, shouldn't it have another gasket to prevent exhaust leaking?
I'm not "in the know on the recalls" but the sheild keeps the oil from getting on the manifold.. the other one(rounded one) really will not. the metal to metal.. non issue , cars and trucks used to never have exhaust gaskets at all at the head . if it leaked you decked the two mating planes.. the shield itself is a gasket as the metal is soft(enough) use'n 2 gaskets would cause it to leak as the heating cycles would back off the bolts/studs g.m. added it for a reason.. and the 3.4 swap doesn't fix that reason.. the reason is the exhaust running under the engines,, and the converter gets mighty hot.. lots of fwd cars the exhaust runs under the engine but the hot converter(s) are down stream, out of line of dripping oil..
[This message has been edited by E.Furgal (edited 08-13-2012).]
The real reason that shield was installed was to prevent a fire in the event the engine threw a rod through the block. The shield would prevent engine oil coming in contact with the cat and exhaust system. Head, shield, gasket, manifold.
Originally posted by Indiana_resto_guy: The real reason that shield was installed was to prevent a fire in the event the engine threw a rod through the block. The shield would prevent engine oil coming in contact with the cat and exhaust system. Head, shield, gasket, manifold.
True on L4 engine... V6 shield is up on the head to keep bad cover gasket from dripping oil on exhaust and cat.
Yes, Fiero Cat is a target for any oil leak. Cat makes heat to to its job and runs 800-1000*F as normal operation temp. Ever higher when engine runs rich or you "poison" it. Any oil hitting the cat will be a big problem and cause engine fires.
Small exhaust leaks, like shield/head joint w/o gasket, won't be an issue.
Side note... Watch AC hoses... AC can leak oil too.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
I removed it from mine, it seemed to have been a nice spot for leaves and other tinder to get stuck in.. I don't have a cat and I run high flash point synthetic oil so I don't see any good it was doing besides causing a manifold leak.
Please scroll down like 3/8ths of the way down in the provided information to a letter dated April 18, 1990 to Mr. Michael R. Brownlee. Third paragraph sentence begins with Specfically, . . . . .
Letter is from GM to NHTSA.
Even though the recall TSB 88-C-24 does not specifically call out tossed rods, it is a solution to all problems addressed in GMs investigations. No recall issued by GM mentions specifically to the problem of thrown rods, even in the L-4 engine that I can see. The blanket statement of "If combustible materials come in contact with the exhaust manifold, an engine compartment fire can result. Engine compartment fires can spread to the passenger compartment and cause injury to occupants." is clearly intended to cover all instances of oil and or fuel coming in contact with any high temprature heat source in the engine compartmet, specifically the exhaust system.
(forgot to add link)
[This message has been edited by Indiana_resto_guy (edited 08-14-2012).]
Okay, I have a CAT delete, and I run Mobile 1 oil, so I guess I'm okay to leave it off. I know allot of guys do leave them both off. Randy Enerson (3.4 swap on this Forum, left his off because he is using Felpro rubber valve cover gaskets, and so am I. I just want to get some more opinions on it. I'm feeling like I can safely leave them off...?
quote
Originally posted by sco77:
I removed it from mine, it seemed to have been a nice spot for leaves and other tinder to get stuck in.. I don't have a cat and I run high flash point synthetic oil so I don't see any good it was doing besides causing a manifold leak.
I forgot to mention: Randy Enerson has the Fiero Store stainless steel headers, which substantially run much cooler. I might mention too, concerning harmless exhaust leeks, that they are not harmless with these light gauge stock ports. My stock end port was burned out around the flared edge that meets the cast iron flange, do to exhaust leaking, and the flange literally fell off when I removed the manifold. Leaks create heat at the leak...not good! Funny thing though, that flat shield (between the manifold gasket and block,) showed no evidence of leaking!...? I'm one of those guys who like to know why for everything and the sensible reason for everything...lol! And make my decisions based on the answers.
[This message has been edited by hypo327 (edited 08-26-2012).]
After reading all comments, I still see no practical reason for having that flat shield between the block and the exhaust gasket! I don't want leaks, even if they don't hurt anything. They sound terrible! And if exhaust manifold gaskets aren't necessary, why do they have them...just to stop any leaking noise, or what? I'm not driving a truck or a D-8, but I thought even they have exhaust manifolds...!?
The round shield obviously keeps the heat off the other hoses and what-not, at the firewall, but my manifolds are going to be welded (continuous fillet around the flanges and inside,) then ported and polished. That should keep the greatest amount of heat down compared to the stock manifolds with all their obstructions!? If I go to the expense of Jet Hot ceramic coating, will that take care of any heat concerns?
[This message has been edited by hypo327 (edited 08-26-2012).]
I'm not "in the know on the recalls" but the sheild keeps the oil from getting on the manifold.. the other one(rounded one) really will not. the metal to metal.. non issue , cars and trucks used to never have exhaust gaskets at all at the head . if it leaked you decked the two mating planes.. the shield itself is a gasket as the metal is soft(enough) use'n 2 gaskets would cause it to leak as the heating cycles would back off the bolts/studs g.m. added it for a reason.. and the 3.4 swap doesn't fix that reason.. the reason is the exhaust running under the engines,, and the converter gets mighty hot.. lots of fwd cars the exhaust runs under the engine but the hot converter(s) are down stream, out of line of dripping oil..
Just as an up-date to this thread: Furgal is right. I installed the flat shield against the block on my 3.4 and have had zero exhaust leaks. And it's there if ever my valve cover agains the firewall ever should leak, even though I have the dry neoprene blue gaskets, which have never leaked on my 2.8 and now my 3.4. So, it's just some extra cheap insurance against possible fire from a possible oil leak. I like to know it's there!
