Join Date: Jan 2000
Location: madison, AL, usa
Everybody responded with truth. There is far more capability in the current offerings than ever was available before. And special or rare intakes aren't required and off the shelf headrs are readily available.
However, if you are really wanting to do a cleveland headed small block, there are some things to consider.
1) if this is a 302/5.0L then the motor is very compression crippled. What I mean is that the clearnace volume needs to be quite small. Unless you have some small chamber 4V heads, or aussie 2V heads, or 302 Boss head, you are going to end up very low in the static compression department.
The open chamber heads 4V and 2V have combustion chambers around 76cc's. With the open chamber dome top piston configuration that was available for the cleveland, the compression ratio ended up 11.5 -12:1 When this same dome is used on a 302, the resulting compression is 10:1 at best.
In short, if you are using a open chamber head you are going to be looking at very low compression (8.8:1) if you are attempting to build with a conventional 5.0L piston configuration. If they fly cut it to clear the valves, it will be even lower.
If you use the 302Boss dome top you can acheive around 9.5:1 with the open chambers.
The closed chambered heads are about the only realistic alternative. Just something to think about. You dont just go to a junkyard and grab closed chamber cleveland heads (and they will be 4V heads). and aussi closed chamber 2V heads are not super easy to come by either.
2) No matter how you look at, it you are going to need special parts. intake manifold, headers, pushrods, etc. this stuff is not going to be cheap, unless you can find someone that already has the stuff. You are looking at 300-400 for the intake, and headers realistically wont be less than 300.00, pistons 300 +.
3) now the 4v vs 2V issue. Everybody is going to say you dont want to try the 4v route. I dont think that is necessarily the case. I have worked with both and the problems that come about from the 4v heads, are from the engine combination itself. the camshaft and peripheral components have to be right. You cant take a 275 cfm inlet capability, in a very large slow flowing port (that with a only a little effort can hit 330 cfm- thats the real port capability) stick some 1 5/8 headers, or even 1 3/4 headers, and then typical street machine camshaft in it, not to mention the low compression.
the 4v combination on the 302 needs to have very good inlet flow quality, in otherwords an intake manifold that can work with the huge head (holley strip dominator, parker funnel web etc. if a stock boss intake is all you can get, then so be it, though). the exhaust will need to be suitably large to work. 1 7/8" or 2" headers. even Ford recommended 2" as direct bolt on for the stock boss 302 mustang. then the camshaft will need to be very small, if its a hyd roller, i'm talking like a stock 5.0L cam (210/210/115). this is what will give you good low and mid range cylinder fill and recoup the torque. Do not cripple the air flow by looking at rpm ranges or headers based on hp, you will steer wrong very quickly. Let the the motor have access to everything the heads can do, then let the camshaft tell it how it needs to utilize it.
the 2V works the same way, but the components will be a tad smaller. the old BA stuff is ok. the strip boss was the better of the two, although we used the dual plane on the one we did. then the headers will need to be 1 3/4 and possibly 1 7/8, depending on the combination.
The aftermarket cleveland heads can really bring the port velocities into line, but then you are talking a hefty chunck of money.
What this all comes down to is what are the real gains. In hp/dollar terms it is a huge loss over a conventional windsor style motor.
In the looks department and specialness department the cleveland wins hands down.
a friend had one of the very first BA 2v conversions in a 65 fastback. We were young and dumb. It was all wrong. I think it ran low 8's in the 1/8. But man did it look good.
Since then I have been involved in some 9.2 deck builds and the big port stuff will work well on the very street oriented situations, but it has to be right, or it will suffer from all the woes that everyone is going to talk about regarding large port motors.
Last edited by buddy rawls; 04-27-2011 at 03:41 PM.