I have a problem. I have had my fiero for going on a year now and have never driven it. I bought it with an engine problem (2.5 white smoke). Took the head to my machine shop only to find it cracked. Took my spare head from a parts car and low and behold it is cracked too. I am wondering a couple things.

First, what cars/trucks have the same cylinder head (casting number 767)?

Second, what possible upgrades, if any, are there available instead of a stock head, and what mods have to be done to make it work? I have read that s10 heads work with 87-88, but not the earlier engines.

any input would be great. Thanks.

Welcome to the Forum!

There is a lot of information about this on PFF. Here is just one thread.

https://www.fiero.nl/forum/Forum2/HTML/116541.html

Then engine in my fiero is an "R" vin. That link does help assuming there is no difference between the 88 head and the 84 head. I have an 84 and from other posts I have read the heads are different.

again, I have 767 casting and vin R in an 84 fiero. If there is anymore information I can collect to help make the hunt easier please let me know.

Go to the search function.....type in '84 head'... and set it to 'entire forum + archives'.

Shitloads of cars have the 767 head, 1984-1986. Citation II, Celebrity, Ciera, Century, Pontiac 6000, Fiero, S10 MY 1985-1986 IIRC.

ok, so from what I have read, the s10 head will work on 84 fiero provided I use the intake from the s10. I was planning on doing an adapter plate for the throttle body so I can use the stock one.

Here is the kicker though. I havent found anyone able to answer which push rods to use or if I will have to buy different ones. If anyone has this info please let me know. Thanks.

Don't bother with 87+ head, there's too much to swap.

Usually I wouldn't want to do a swap either. However, I am not inclined to put a crack-prone head (i.e. the factory head) back into the car. I have heard the s10 head is stronger. So basically, if it is going to be a lot of work please prove it to me. Tell me what needs swapped. I will determine if it is going to be too much work.

quote Originally posted by irish_motorhead: I am not inclined to put a crack-prone head (i.e. the factory head) back into the car.

I don't believe the early Fiero duke heads are known to be "crack-prone".

I work part time at a machine shop ( I work on the service side) and the guy thats been working there for 40+ years said they had lots of problems with 2.5 heads cracking back in the 80's (hence both of my heads cracked).

quote Originally posted by irish_motorhead: I work part time at a machine shop ( I work on the service side) and the guy thats been working there for 40+ years said they had lots of problems with 2.5 heads cracking back in the 80's (hence both of my heads cracked).

It's possible I suppose, but I'm just going by what I've read here over the last 14 years (and the fact that I've been daily driving and autocrossing my own '84 duke hard with no problems for three years).

It seems to me I've read more complaints in this Fiero forum about Quad4 heads being prone to cracking, which is quite interesting... considering these engines didn't originally even come in Fieros!

So I wonder... Were the damaged duke heads your co-worker was referring to cracked because 2.5 heads are actually fragile, or were those particular engines simply abused? (Run low on oil, coolant, etc.)

He said they would crack mostly due to overheating, but even mild heat would cause cracks. I don't intend to let my fiero ever run hot, but I can't control the reliability of say a cooling fan temp switch.

And my question still remains. What is needed for the s10 head swap? I know I have to use the intake manifold and make an adapter plate for the throttle body, and I probably need different push rods. Does anyone here know which push rods and if there is anything else I have to do for the swap? I am a mechanic and am not afraid of a good deal of work, but I do want to be sure it will all mesh after it is put together.

I am finding information for 87-88 dukes, but not for '84.

https://www.fiero.nl/forum/A...090219-2-085295.html

[This message has been edited by Gall757 (edited 03-07-2013).]

Well at this point I will probably get 2 heads. A standard vin "R" head with a 767 casting number, and a 90-93 s10 vin "A" head. I will put the 767 head on my fiero for now and use my spare engine to see what it takes to make the s10 head work. I will post what I find. I know the head gasket part numbers are the same so at the very least it should mate up just fine. I will use the intake and the adapter for the throttle body. I will let you all know what I find with the push rods/rockers and/if there are any other mods that have to be done. Hope to hit up the junk yard sunday.

I am curious what changes they made to the engine in 87-88 so I can plan ahead for any other mods that might be required. Thanks.

I don't know what the problems are with putting a later head on an 84 engine, but if the only problem is the bolt holes not matching, that can be fixed. When I put a later head on my 88 duke, two holes did not match. I filled the old holes with mild steel rod, held in with JB Weld, and drilled new holes. The head has lasted 20,000 miles so far, with no problems.

Thanks topnotch. I don't think the bolt pattern will be the problem. The part number for the head gasket is the exact same. The only problem I can think if is deck height. If the deck height on the 93 s10 block is lower/higher than the deck height on the 84 fiero it will affect the push rod length. If it is the same then the push rods from the s10 engine should work fine. I suppose lifters could also have an affect on the height as well.

Another problem might be with the coolant line that comes out of the manifold on the fiero. If that is does not appear on the intake for the s10 intake than I will have to find a way to make it work, but I don't see that being a huge deal.

Topnitch, which head did you end up using? I am going to go for the 90-93 s10 head but if that doesn't work I may turn to what you did as a fall back option.

The problem isn't the head itself, or the exhaust (same manifold).

The problem is the intake. The intake ports are in a different position and are a different shape than the 84 head. "So? I'll just use an 87-newer intake" you figure...I mean, that Kurtakx guy must be a dumbass, look at all the red in his ratings bar.

So then you swap on the intake, and realize, "**** , my throttle body doesn't fit!"
At first you figure you'll cut a chunk of aluminum about an inch or so thick to use as an adapter.
Dismayed, you realize that the throttle linkage that actuates the throttle on the 84 doesn't bolt onto the 87+ intake, hell its not even the right shape. Now realizing that the intricate 84 throttle linkage is also tied into the cruise and trans kickdown functions (if equipped) you might decide to scrap the whole 84 throttle system; preferring instead to use the newer throttle body with its silky, cable-actuated side-pull design. Now the wiring harness plugs are wrong, you have to rip apart the interior to pull an 87-88 four cylinder Fiero throttle cable through, and your fuel lines run to the wrong place. This is all not to mention the need for attention to cruise/trans kickdown systems you might have. Now you've got somewhere, right? Well, not really. You no longer have the mounting hole for the dogbone/alternator bracket. If you're thinking its as simple as using the 87-newer dogbone bracket, keep wishing. When you do that, the ability to adjust alternator belt tension goes away because you no longer have a slotted bracket. How does the 87+ set tension? With a serpentine setup. Oh hey, cool, just swap crank alternator and water pump pulleys and gain a more reliable belt setup, right? Nope. The tensioner/bracket used on the 87+ mounts into the cover in the front of the block over the timing cover, an area where the later blocks are not compatible with the earlier blocks because the shape of the hole, bolt pattern, and number of bolts changed.


There are some other things to, but if you are willing to solve this many problems to go from one crack prone head to another crack prone head, you're willing to do all the problem solving it would take to just do an engine swap.

quote Originally posted by KurtAKX: So then you... and realize, "****"

Heh heh, I think you've made your point.

quote Originally posted by KurtAKX: The problem is the intake. The intake ports are in a different position and are a different shape than the 84 head. "So? I'll just use an 87-newer intake" you figure...I mean, that Kurtakx guy must be a dumbass, look at all the red in his ratings bar.

lol, all the ratings bar means is that you pissed off one of the cliques on the forum...

well fortunately I have a manual trans and no cruise control. So now the only things you have mentioned that affect my car is the throttle plate (still can adapt), the throttle linkage and the alt bracket, both of which I could most likely fab up mounts for. It wouldn't be the first time I had done that.

So please, if there is anything else please mention it. I told you that I will be the one to decide if it is too much work to make it worth it to me. I know it won't be a walk in the park but if everyone decided not to do something because some smart-ass know-it-all told them it couldn't/shouldn't be done this world would be a pretty lousy place.

Btw KurtAKX, just telling someone not to do something without telling them WHY and expecting them to just take your word for it is pretty much pointless. I don't know you from adam and without the info you just now gave me I had no reason to think your word carries any weight or authority on the subject.