[DeTomaso] heads

[MikeLDrew at aol.com]

In a message dated 7/2/08 0 22 4, torbjorn.harlem at elverhoy.no writes:


> Since I new to the 351Cleveland engine I got some questions.
> 
> What the difference between 
> 
> a)       4V closed Chamber
> b)       4V open chamber
> c)       2V
> d)       Aussie.
> 
> I see the difference between the open and closed chamber, but what is
> the real difference in performance, torque  and revs.
> 
> >>>The 4V heads have HUGE intake and exhaust ports.   The 2v heads have 
smaller ports.   The closed-chamber heads have much higher compression ratio with 
flat pistons (10:1 or 11:1, as opposed to 8.6:1 with the open-chamber heads.

Generally, the 4V heads make big power at high rpm and/or with big 
displacement (377 or 393 inches).   The 2V heads make more low-end and midrange torque.  
 The Aussie heads offer the 'best' street performance for most uses, with the 
benefit of the closed chamber, and the smaller ports for higher intake and 
exhaust velocities.   However, reportedly the Aussie heads are flow-limited at 
higher rpm and/or bigger displacement.   Some people say the Aussie heads 'shut 
down' at 6000 or 6500 rpm; the 4V heads will happily spin to 8000-9000 rpm or 
more.

The problem with that, of course, is that your stock bottom end (crankshaft, 
connecting rods, pistons) will explode at 7000 rpm, so what good is that? :<(

For a street engine you're probably best off with Aussie 2v heads; if you are 
building a high rpm motor or a stroker or a race motor, the closed-chamber 4V 
heads would probably be better for you.   The open-chamber 4V heads are a 
poor third choice (that's what I have in my car), and the open-chamber 2V heads 
are great for holding doors open, or as a boat anchor. :>)
> 
> >And what heads should I prefer to use?
> 
> >>>See above.   How do you intend to drive your car?   Your car probably has 
> 4V closed-chamber heads (based on the serial number), and I would suggest 
> that for cost reasons if nothing else, you should stick with them.   
> 
> >Does the intakes fit  to them all or is the difference between them
> also?
> 
>>>The 2V heads have smaller intake ports than the 4V heads, so there are two 
very different kinds of 351C intakes.   You can put a 2V intake on a 4V head, 
although the intake runner is too small.   But you can't put a 4V intake on a 
2V head.
> 
> I get the stock intake and was not very impressed about it. Think I buy
> some with a better flow rate.  (Any ideas)
> 
>>>Again, it all depends on what you want to do with the car.   I would say 
that MOST Pantera owners use an Edelbrock 4V intake.   That doesn't make it the 
best necessarily, but it's very good in most applications.   If you are 
really getting crazy and trying to build a super-engine that makes 500 hp, it 
definitely will NOT be a good choice.   But if you want a 350-375 hp street engine 
it would probably be just fine--and VERY cheap!
> 
> >Going to use a 750 Holley as though is convenient and easy installation
> the first time. ( I'm  doing a totally restoration on the car)
> 
> >>>Unless you make a pretty radical engine, a 750 will probably be too big.  
>  Although it might deliver high horsepower at high rpm, it will probably be 
> sort of 'fat' and 'fluffy' at lower rpm, and actually deliver lower 
> performance (while using more fuel).   You would get better throttle response with 
> something like a 650.   And considering how expensive fuel is in Norway (more 
> than $10 a gallon?!), you should seriously consider a 600, if your engine is 
> close to stock.
> 
> Others who know much more about 351C engines (and there are many of those 
people!) should offer their opinions soon....

Mike


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