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Price Motorsports old school high port exhaust port mod ala Cleveland high port

287 Views 1 Reply 2 Participants Last post by  The Mad Porter
I did a search through the way-back machine and found a few references to them and a lot of confusion of them compared to say the old MPG "plates" which are not similar at all. For those not familiar, you basically mill OFF the top of the exhaust port and then bolt on this aluminum replacement port to straighten out the flow. Am I going to do this? Maybe but really curious to see if anyone has actually done it and what the outcomes were. Then there is the fact they raise your exhaust ports up a notable amount which could create new issues with header fitment depending on application. High Port Exhaust
Now I know with aluminum heads being really the better investment of my money that these may be a waste of time to investigate but I think it is at least worth seeing if anyone actually has run them and the results. Roush and others did this sort of mod to the old 4V cleveland heads way back in the 70s for Pro Stock racing with good results on the Cleveland head which has similar faults to the 429/460 head. Not exactly the same limitations but the whole turn to clear the towers issues forcing the port to make that U turn etc..
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With a proper dual pattern cam the OEM exhaust ports both Passenger car and CJ will support a bunch of power.
800+ and 900+ respectively with our ported stuff back in the day we actually did comp port work.

The OEM port design works well especially when the typical for the era shock tower compatible headers which turn down abruptly off of the flange are used.

Filled floor and MPG port plates work best when there is 3 or more inches of straight primary before turn down.

Simply dropping them in with out shaping to accommodate them offers no benefit and with a crites style header hurts air flow vs a non filled port's flow column allowed to begin the turn IN the exhaust port.
I've tested crites header primaries on a bench and they kill exhaust flow on a filled port by 20+ cfm. They are among the worst for turn down right off of the flange. #8 is really horrid.

There is a reason John Kaase doesn't fill the floor of his SCJ / P-51 and SR-71 offerings.

Having said all of the above I feel that the high port plates helped to deal with the single pattern cams of the era which will choke the BBF.
An upswept primary really benefits from the elevated ports exit angle.

At one time I actually dropped the floor of a filled eddy / procomp style head to see if it helped with a header primary attached.
It did by about 10% if memory serves.

When pushing for every last high RPM HP the exhaust port needs to be as large as possible in both cross section and volume. Some of the best iron CJ's we did had the seat choke at about 90%. Head bolt boss cut way back for added cross section and sleeved with a brass tube. Didn't sound good on a bench and breaking into the head bolt bump showed little gain but at the track... It works.

Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
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