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Give this 502/509 Combo Some Thought

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Old 09-29-2016, 11:34 PM
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Originally Posted by I.C.U.Lookin View Post
600-650 with zz502 cam? I'd love to see the dyno proof of that. Lol
No, as it is it's probably barely 500 undressed. The 600+ was with a new cam.
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Old 09-30-2016, 12:13 AM
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Txhawk, whats this heat you speak of with the small chamber? I ran 107cc chambers, with a blower for years, never had an issue.

Thats a huge chamber compared to a big chief head, no issues there at some extreme power levels. I wouldnt worry about that .

Those heads can be improved, if you wanted to sink some money into them. One of the best areas to focus on , for the low lifts we run in marine, is the chamber, throat/bowl and valve job. Im sure those heads could benefit from a little unshrouding in the chamber. Typically, doing that, will knock out 4-5cc of material. You'll lose a bit of compression, but done right, the airflow gains and burn quality will more than offset that.

The 741 cam wouldnt do much for you over your current cam. Theres better options for an off the shelf cam, that will be easy on parts and last a long time.

Id lose the dual plane intake, and go to a single plane like you said.

As far as a 100hp gain from just a cam swap in a combo like that, is well, a pretty tall order. Ive heard before how swapping out a crane 651 cam with a "custom" modern hyd roller, will net 100hp gain in a 540. If that was true, the 675hp 540s with a set of 290 afrs , and 651 crane cams, would have made 775hp with a "custom" hyd roller? Where those builds at lol. Seems like the 651 crane did just fine when compared to some of the recent 540 builds around here. Even if its an old grind. And it does it without hammering the pushrod tips , breaking rockers , or pounding out the valve seats.

Have you considered some 55mm cams, 903 lifters, 600lb spring pressures, 1/2" pushrods, and steel shaft rockers for a 5800rpm combo?
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Old 09-30-2016, 07:50 AM
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{ Have you considered some 55mm cams, 903 lifters, 600lb spring pressures, 1/2" pushrods, and steel shaft rockers for a 5800rpm combo? }

Calm down, deep breath, its Friday
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Old 09-30-2016, 08:22 AM
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Not even close with that cam...bin said so it just be true lol


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Originally Posted by Baja Rooster View Post
I have a very similar setup with 9.6:1, ZZ502 cam, and Eddy Performer heads and manifold. I don't know how the Eddys compare to yours, but when I spoke with MK he said that 600 should be easy and maybe 650.
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Old 09-30-2016, 09:45 AM
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Originally Posted by MILD THUNDER View Post
Txhawk, whats this heat you speak of with the small chamber? I ran 107cc chambers, with a blower for years, never had an issue.

Thats a huge chamber compared to a big chief head, no issues there at some extreme power levels. I wouldnt worry about that .

Those heads can be improved, if you wanted to sink some money into them. One of the best areas to focus on , for the low lifts we run in marine, is the chamber, throat/bowl and valve job. Im sure those heads could benefit from a little unshrouding in the chamber. Typically, doing that, will knock out 4-5cc of material. You'll lose a bit of compression, but done right, the airflow gains and burn quality will more than offset that.

The 741 cam wouldnt do much for you over your current cam. Theres better options for an off the shelf cam, that will be easy on parts and last a long time.

Id lose the dual plane intake, and go to a single plane like you said.

As far as a 100hp gain from just a cam swap in a combo like that, is well, a pretty tall order. Ive heard before how swapping out a crane 651 cam with a "custom" modern hyd roller, will net 100hp gain in a 540. If that was true, the 675hp 540s with a set of 290 afrs , and 651 crane cams, would have made 775hp with a "custom" hyd roller? Where those builds at lol. Seems like the 651 crane did just fine when compared to some of the recent 540 builds around here. Even if its an old grind. And it does it without hammering the pushrod tips , breaking rockers , or pounding out the valve seats.

Have you considered some 55mm cams, 903 lifters, 600lb spring pressures, 1/2" pushrods, and steel shaft rockers for a 5800rpm combo?
The heat concern comes from the builder I had go through this engine. He builds mostly SC power locally for the marine crowd. He likes the combo for what it is, but had concerns about heat during long runs.

No, I haven't considered getting deep into this shortblock, it only has 15 hours on it. I freshened it up to basically get the boat on the water after major restoration. I haven't changed a thing other than up 2 jet sizes since this boat came off the trailer. 28P LH at 5000 is 79-80 MPH and 9-10% Slip. If I can turn it another 200-300 RPM's I would be thrilled for the current money invested in power and would likely see 5 MPH based on slip.

85 in this boat will be a handful. Its entertaining at 75.
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Old 09-30-2016, 09:48 AM
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I was looking at Dart BBC Oval Port Single Planes and noticed they state to mill .060" to fit GM heads. Is this a Dart thing or something I should expect in general.

Is the consensus to run a Dominator flange and step back to 4150 with spacer to run my 850?
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Old 09-30-2016, 10:48 AM
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Pretty sure your heads were made by edelbrock, the GM aluminum ovals? Cant remember
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Old 09-30-2016, 11:52 AM
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Originally Posted by MILD THUNDER View Post
Pretty sure your heads were made by edelbrock, the GM aluminum ovals? Cant remember
I think thats right. Some 502/502's had a GM stamped head and others edelbrock. These are the GM Perf Parts stamped oval ports.
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