320HP Magnum Crate w/ X-heads

Brooks James

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Im confused, the rating for the Summit engine is 320 hp.
I have seen several dyno pulls with a stock 360 mag short block with headers, holley 750 a dual plane stock cam, come in at 300 hp Summit advertises 320 hp with same set up, where is the extra 20 hp coming from ???
 

go-fish

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Im confused, the rating for the Summit engine is 320 hp.
I have seen several dyno pulls with a stock 360 mag short block with headers, holley 750 a dual plane stock cam, come in at 300 hp Summit advertises 320 hp with same set up, where is the extra 20 hp coming from ???


That's my question too. The bore on Summit's advert is 4.060". Says the cam is stock Magnum grind. stock heads.

I talked with my Dad a little more about the cam. He seems to think he will be happy with the stock grind. He wants to drive long distances and get good fuel mileage. He's older so his go fast days are done.
I told him those cam specs are at the bottom end of the spectrum and that is with the 9:1 compression and closed chambered heads. He's GOT TO HAVE the x-heads, for some reason, and the main centerpiece of his vision is the LD6B six pack. Okay, I says, fair enough but the stock magnum piston and it's height isn't going to work with the open chamber X-head. I consider the change to the KB dome piston is almost a have to. They are $400 and I would like to get at least that much out of the fresh Magnum heads.
I am thinking we can get away with a piston change (leave the little cam), pushrods, and that Mancini LA/Magnum rocker gear.
 

mgoblue9798

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That's my question too. The bore on Summit's advert is 4.060". Says the cam is stock Magnum grind. stock heads.

I talked with my Dad a little more about the cam. He seems to think he will be happy with the stock grind. He wants to drive long distances and get good fuel mileage. He's older so his go fast days are done.
I told him those cam specs are at the bottom end of the spectrum and that is with the 9:1 compression and closed chambered heads. He's GOT TO HAVE the x-heads, for some reason, and the main centerpiece of his vision is the LD6B six pack. Okay, I says, fair enough but the stock magnum piston and it's height isn't going to work with the open chamber X-head. I consider the change to the KB dome piston is almost a have to. They are $400 and I would like to get at least that much out of the fresh Magnum heads.
I am thinking we can get away with a piston change (leave the little cam), pushrods, and that Mancini LA/Magnum rocker gear.

If I could pick only one part to change in the magnum it would be the cam. You can get a cam 2 or 3 sizes bigger and not effect mileage and would be about the equivalent of the stock 340 cam. I run this Hughes cam in my 5.9 combined with EQ heads stock valve size, everything else stock no tune and it made a HUGE difference in the top end. Engine was a total dog and would fall on its face passing or towing before, now it is fun to drive and owns the interstate. With your carbs I would get a 110 centerline cam instead of the 114.
https://www.hughesengines.com/Index...Z2UgTWFnbnVt&level1=Q2Ftc2hhZnQ=&partid=30212
 

Heywodja

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Did you ever figure out what year the block was?
 

go-fish

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No. Been on a fire in Yosemite National Park for the last 10 days.
288A9C3F-4629-4471-AF6D-11FEA7321A74.jpeg
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I’m going to get the heads and intake from my porter in San Diego and take them back to Oklahoma probably by the end of August. I’ll measure how much the pistons are in the hole and get a cc on the head from the porter. I’ll try to work out the compression ratio.
 

Ironracer

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No. Been on a fire in Yosemite National Park for the last 10 days.
View attachment 1715957393 View attachment 1715957394
I’m going to get the heads and intake from my porter in San Diego and take them back to Oklahoma probably by the end of August. I’ll measure how much the pistons are in the hole and get a cc on the head from the porter. I’ll try to work out the compression ratio.
Thanks for Saving some of the National Natural Treasures!!!!!!
 

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