2.8 versus 3.4 reliability

[signalb]

Hello,
I have a 1986 Jeep Comanche with the 2.8 and am thinking about doing a swap to the 3.4 liter. What i am concerned about is the aluminum heads on the 3.4 and their reliability versus my iron 2.8 heads. Also since the 3.4 is basically a bored and stroked 2.8 would it be safe to assume that its less reliable? I know that a 3.4 is more powerful but does that come with a price?

[pocket-rocket]

You could go with an iron head 3.4 out of an F body if you are worried about reliability of a bimetallic engine, although I wouldn't say a 3400 (the aluminum head version of the 3.4) is any less reliable than the 2.8 as long as you take care of the LIM gasket issue.

On a side note, welcome to the site!

[86FieroSEv6]

In my long experience I have found that the reliable ones are usually the ones that were properly assembled and maintained. The unreliable ones were usually the victim of some sort of neglect, whether it was a crappy assembly or lack of maintenance.

[geoffinbc]

Agreed there is zero reliability with these engines. Even a lot of neglected ones go forever as long as they see a few oil changes. Like any engine once they lose oil pressure or overheat due to lack of coolant they are toast.

I had a heater hose blow in my Trooper and lost coolant in the heads which caused the heads to crack between the valves and coolant to fill the combustion chamber on the #5 cylinder. The truck still ran good once all the coolant burnt off in the morning and I drove it for a few months while I built up my 3.2L for the swap.

Regarding your swap. If your looking for a drop in replacement that looks and works just like your 2.8L then a 3.4L from a Camaro or a GM Crate engine is what your after. An aluminum head 3.4L (3400) is by no means a drop in replacement. It will take some serious work and fabrication to make it all work.

[signalb]

So just to be sure, the 3.4 from the 93-95 camaros have the iron heads? I assume I can use the flywheel from the 3.4 and simply replace the intake, water pump and timing chain cover off my 2.8? Any thing else major I need to know about doing the swap?

[robertisaar]

So just to be sure, the 3.4 from the 93-95 camaros have the iron heads?

yes.