Magnum heads porting template P4876413 - feedback ?

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dfoyl

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I'm rebuilding a set of Magnum heads, and am looking to have them ported to flow a little better than stock (about 10-15% better is my goal). The MP Magnum Engines book lists a porting template, has anybody here used it - or if not, have they any specific recommendations to improve the stock production Magnum heads. Intake is the Professional Products Crosswind Airgap-style unit, exhaust is 20+ y/o Genie extractors.

Thanks,

Dean.
 
Never heard of that exhaust.

The porting templates will probably provided more than your goal of flow. Your build may or may not be able to use the additional flow.
A basic porting job will probably meet your goals of improved air flow.

Bowl porting and gasket matching and valve seat comp. angle cuts.

The porting template are not a full blow port temple, but a bit more along the same lines that I described above. MoPar made the tempates for a guide to improve the head, not maxamize it. That would require a pro that has had time to work on several sets and understand what the limits are and whats possible for the head. Also whats to far.
 
I have used the porting templates on two sets of heads. They work well and will keep you out of the water jackets. Expect to spend about 15-20 hours of porting to do a good job. The biggest flow restrictions on the magnum heads are in the bowls (which the temples open up alot) and the intake port pushrod pinch area.

I have done port molds of the magnum (and W2) heads and it becomes obvious where the problems are. I have also cut up a magnum head and the porting templates do a good job at safely maximizing the bowls.

Be very careful at the pushrod pinch area. There is not alot of cast iron there to cut.
 
Thanks guys, that's exactly what I was hoping to hear.

Dean.
 
the porting templates do a good job at safely maximizing the bowls. /
They work well and will keep you out of the water jackets.
Click to expand...

The 2 best key sentences. These are the two pit falls that turn good heads into door stops or less useful items.
 
I did a set of magnum heads using the porting templates.

I ended up making more power at the wheels than the 380 crate motor does at the flywheel using the same cam and intake.
 
The bad news is these porting templates are no longer available from Mopar, and there are no plans to make any more.

Does anyone out there have a set I could borrow or buy for my Magnums...

Dean.
 
Try ebay.

I found a brand new never been used set for $15.
 
I would be interested in finding a set as well... I am having trouble finding someone who has the templates... been on my ebay search for quite some time with no hits.

Does anyone have a set they could scan. I am ready for my winter porting project...
 
The fall issue of Engine Masters has an article on porting magnum heads. The did it in stages with flow numbers after each change so you can go as far as you want to.

They didn't go crazy bowl blend, perfromance valve job, gasket match, some simple contouring. Took the intakes from 202 to 236 cfm and the exhaust from 151 to 213 cfm. They figure the improvements were good for 50-60 HP.
 
I still have my set of magnum porting templates. Due to their lack of availability, I'm interested in not "losing" them.

Scanning them may not yield good results, they are transparent plastic with small black arrows printed on them.
 
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