After a little Googling, it would seem that these heads are '87 - '95 swirl port TBI truck heads, with a 65.3 cc combustion chamber. Depending on the poster and which site visited, these are either half decent heads for low-end power and fuel economy or the worst heads on the face of the earth. That being said, the guy at the machine shop has recommended aluminum heads for a propane engine mostly due to their heat dissipation properties, lighter weight and combustion chamber shapes. I guess a little more research is in order :clue: Anyone have any suggestions that aren't $1200 / head?
I think I'm going to like wheeling with you. :glasses:
Those guys from Petawawa don't wheel!!! They just build big ass trucks for a hobby!!!
Hope you get it out this year! Let me know when your ready to tune those shox!
The thing about those heads is that it is all about expectation levels. If you are going for quarter mile times they will suck. If they are going into a truck then not so much.
I'm not up on propane and I'm a little fuzzy on what I read about aluminum heads but IIRC when switching to Al heads ideally you want smaller combustion chambers because the aluminum does something that effectively drops the compression ratio. It doesn't numerically/physically of course, but the effective result due to the material and the heat soaking capabilities means that it is like the CR has dropped when comparing Al to Fe heads of the same chamber size. You can get away with more compression with Al heads or conversely you can setup for more compression via a milled smaller chamber - if that makes sense.
For heads - used Vette L98s and such are affordable. Why set on Al? For a car I could see it but for a Jeep, that ~40lbs you'll be saving in weight will not be noticed. You can research till you're blue in the face over at thirdgen.org. I have the same "eco" swirl port heads on my engine. I still haven't settled on which heads other than junk yard Fe heads. Thinking about Vortecs. The weight difference for Al isn't worth the hassle IMO and Fe block with Fe heads will tolerate overheating better if something should happen. For a Jeep that is my logic.
I will second what Chris is saying about the aluminum heads. Overheating is always an issue when wheeling. Fans go south more frequent in the extreams that we put them through. Also running mud, snow and long switchbacks tend to work an engine harder than at race day. Most track cars don't even see perating temperatures because they only go for 12 second shots. I'd have what you have rebuilt before sinking a ton of money into new heads.
Also I have heard of guys having problems with head gaskets when running aluminum heads on cast blocks. Aluminum expands and contracts faster than cast so when offroading, especially when going through water, I have heard of problems with keeping gaskets sealed.
If you still want to do the Vortec heads, do your research on it. IIRC it requires at a minimum changing the intake manifold to a Vortec compatible version. Spidey-sense is telling me there is something else as well but I'm too caught up in other things (stupid computers!) to go look for you.
Root Moose said:Like anything with this hobby, once you start changing one thing it leads to and, and, and...