Re: [DML] Re: Head mods

[<delornut@xxxxxxxxxxxx>]

Simply bringing heads or cams to just any machine shop might do more harm than good. For example stock Ford 302 heads  flow better as cam lift goes from a stock lift of .480 to .500 but any lift beyond that will cause a performance drop.Experiance with Ford performance modification would tell you what to do with the heads to overcome that. Someone with no Ford experiance may do something generic that would kill performance. A few years back Ford paid for a group of us 
to attend a crash NASCAR engine building course taught by Mark Vieau who owns a NACAR engine building company and supplies engines to several race teams. They've been running similar engines for years but they're still learning how to get a little more out of them. ( and yes, still learning new ways to cheat ) I don't claim to retain all that was covered in a very short time but I did learn a few things that convinced me radical engine tuning like cam changes and head modifications can do more harm than good without the proper experiance. One rule of thumb I remember is that exhaust flow 
should equal aprox 75% of intake flow. In other words some degree of back pressure enhances engine performance. Experience grows with trial and error. Different engine designs react differently to certain modifications. I'm sure that DMCH, for example, didn't simply send the heads out to be ported and polished. I'd guess the shop they went to did some extensive testing on a flow bench and it possibly took a few tries to achieve the best balance of performance and streetability. Most of us aren't in a position to play with more than one engine or more than one pair of cylinder heads. In the long run it's cheaper to go to the shops that have done the trial and error and offer a final product, for example DMCH's stage II engines or Don Steger's cams.

Bruce Benson

>> --- In dmcnews@xxxxxxxxxxxxxxx, "Steve Brodsky" <ASNAKEINTX@> wrote:
>> >
>> > Anyone have any experience/advise regarding head
> polishing/porting to
>> > get a little better performance? How about some larger
> displacement
>> > pistons?
>> >
>>
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