CNC Ported Heads on high 700rwhp Combo

Streetpwr281

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I’ve been researching various upgrades for my car including NSR cams, rods/pistons, etc. Came across Fox Lake $1995 special for GT500 heads incl full CNC porting, backcut stock valves, perf Valve Job, Bronze guides, Valve seals, decking, assembled, etc. Upgraded valvesprings or Férrea valves are addtl options. Seems like a good value.

Has anyone upgraded/cnc ported their 13/14 heads on a 700rwhp+ combo? Wondering if a better upgrade then cams on a streetcar where driveability is key but you want 800rwhp+ in a useable rpm range. Thoughts?


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biminiLX

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Myself and my tuner both prove you can make over 900rwhp without CNC ported heads. I only have a port match to a fully CNC ported intake. He has no head work.
We both have intake port work and cut/welded opening for KB BIGUN IC.
You’ll be money ahead on addressing the restrictions and on these cars the lower intake is next up after the TB.
I would only do CNC heads as part of a full build, meaning lower end, cams, bigger blower.
-J
 

biminiLX

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Ron the owner of Fox Lake has down great work for years. He’s on a short list I would use!
-J
 

Streetpwr281

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Yes you both are making big hp but with what I consider aggressive cams for a 100% street driven car. I agree on waiting til I upgrade rods/pistons and maybe I go CNC Ported heads and lower intake so that I can go w milder cams and still make big/broad hp and tq.


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Catmonkey

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I think a full port with mild cams is a big waste of money, but I don't think there's a down side other than cost. A multi-angle valve job would likely yield the same benefits for a lot less dough. The GT500 heads are not heads that need a lot of improvement for a moderate build, but with aggressive duration and lift in cam selection make porting beneficial.
 

Streetpwr281

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I think a full port with mild cams is a big waste of money, but I don't think there's a down side other than cost. A multi-angle valve job would likely yield the same benefits for a lot less dough. The GT500 heads are not heads that need a lot of improvement for a moderate build, but with aggressive duration and lift in cam selection make porting beneficial.

If I’m pulling motor for block hone/rods/pistons/mildish street NSR cams I’m doing the CNC Ported heads w valvejob while they are off. Efficiency improvements that lower boost and improve airflow are favorable to overall power w/o harming driveability. Expensive yes but at that point the wallet is already wide open. Now I just need to find $15k or so by next Fall.


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biminiLX

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If you’re going that far it’s a shame to neuter it on pump 93. Still, I’d do 11:1, ported heads and springs even if the cams are mild. Just don’t forget the lower intake is the biggest restriction.
Run a safe low timing tune around town and add timing/race tune when you have octane.
If I ever rebuild mine it’ll have ported heads and another point of compression.
-J
 

Streetpwr281

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If you’re going that far it’s a shame to neuter it on pump 93. Still, I’d do 11:1, ported heads and springs even if the cams are mild. Just don’t forget the lower intake is the biggest restriction.
Run a safe low timing tune around town and add timing/race tune when you have octane.
If I ever rebuild mine it’ll have ported heads and another point of compression.
-J

Yes absolutely porting the lower intake w heads. The system has to be improved. These are some of the trade offs of a true street driven (often) build. Probably have to limit compression to 10 to 1 and milder on cams. Goal is to run 93 pump most of the time and hopefully make ~ 875 - 900rwhp. And have a E85 race tune for half mile events or street callouts ~ 975 - 1000rwhp. Again, with pretty damn good drive ability. No it’s not the 1100rwhp+ some are making with more aggressive cams and compression but it would make me happy for my purposes.


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4VandHemiKiller

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I think a full port with mild cams is a big waste of money, but I don't think there's a down side other than cost. A multi-angle valve job would likely yield the same benefits for a lot less dough. The GT500 heads are not heads that need a lot of improvement for a moderate build, but with aggressive duration and lift in cam selection make porting beneficial.

Increased head-flow/port volume reduces camshaft duration requirements. So if mild cam timing is a build criteria, ported heads would be ideal.

Also while stock GT500 heads with their ~ 310/240 cfm flow numbers (@ 28") flow very well, picking up another 40/60 (I/E) with a Fox Lake port job would free up power, and the chamber softening Fox Lake does will make the chamber slightly less detonation prone.

To the OP, just keep in mind the Fox Lake CNC program adds ~4CC to the combustion chamber, consider that when figuring compression.
Fox Lake has the best 4V/GT500 programs; IMO, and the most consistent valve train setup (lash adjuster preload).
 
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Streetpwr281

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Good info on the compression ratio w chamber volume increase. Will consult w Fox Lake and engine builder to get that right when the time comes.


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Catmonkey

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Also while stock GT500 heads with their ~ 310/240 cfm flow numbers (@ 28") flow very well, picking up another 40/60 (I/E) with a Fox Lake port job would free up power, and the chamber softening Fox Lake does will make the chamber slightly less detonation prone.
Except that the intake flow results are not quite that impressive. Here's graph that Slawco has on their port work for a GT500 head on the intake, which includes a competition valve job. For typical mild cam profiles, (.450" to .500") you might see 20 cfm on the intake at peak valve lift, but the exhaust is in the right range. It might be worth 25-35 horsepower on pump, which makes it a pretty expensive mod for the gain. And it will get much better results with more octane, which wasn't in the initial post.

What the graph doesn't show is how much of the increase in flow is from the port work vs. the valve job. IMO the increase in flow rates at lower valve lifts are attributable to the valve job. I'll admit Fox Lake has higher number on their website, but there is no indication of the pressure drop for the readings. I've been there, done that, so I know the price tag on one of these builds. I put my money in springs and chain drive components that can run more aggressive lobe ramp profiles within the range of duration for a streetable pump gas grind than you'll find in NSR grinds. Sure you can do both, but once you're looking at the estimated cost, you might want to draw that line in the sand somewhere. And like I said, if you have an unlimited budget, go for it.

OP, 4cc will be about a 1/2 point of compression on a 5.8. The stock combustion chamber could use some blending.

Slawco intake.png
 

4VandHemiKiller

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Except that the intake flow results are not quite that impressive. Here's graph that Slawco has on their port work for a GT500 head on the intake, which includes a competition valve job. For typical mild cam profiles, (.450" to .500") you might see 20 cfm on the intake at peak valve lift, but the exhaust is in the right range. It might be worth 25-35 horsepower on pump, which makes it a pretty expensive mod for the gain. And it will get much better results with more octane, which wasn't in the initial post.

What the graph doesn't show is how much of the increase in flow is from the port work vs. the valve job. IMO the increase in flow rates at lower valve lifts are attributable to the valve job. I'll admit Fox Lake has higher number on their website, but there is no indication of the pressure drop for the readings. I've been there, done that, so I know the price tag on one of these builds. I put my money in springs and chain drive components that can run more aggressive lobe ramp profiles within the range of duration for a streetable pump gas grind than you'll find in NSR grinds. Sure you can do both, but once you're looking at the estimated cost, you might want to draw that line in the sand somewhere. And like I said, if you have an unlimited budget, go for it.

OP, 4cc will be about a 1/2 point of compression on a 5.8. The stock combustion chamber could use some blending.

View attachment 1525686

Fox Lake's GT500 intake port is both larger and better flowing than Slawko's.

A set of Fox Lake ported GT500 head with stock valves (28" on 3.552 bore plate):

.100 - 100
.200 - 193
.300 - 260
.400 - 308
.500 - 337
.550 - 349
.600 - 354
 

Catmonkey

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Not all flow benches are the same either. Without before and after comparisons, you might not be looking at a valid comparison of the results. I'll leave it at that.
 

4VandHemiKiller

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Not all flow benches are the same either. Without before and after comparisons, you might not be looking at a valid comparison of the results. I'll leave it at that.

I’ve seen data on all of the major head porters heads from the same bench, Fox Lakes beat Slawko, Livernois, etc.

In fact, talk to Mihovetz and ask him about his trials with the different GT head porters. On his combo the Fox Lake program was worth 200-300 HP over the Livernois’.

Suffice it to say, I’ve also been down this road with numerous combos.
 
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biminiLX

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I’ve talked to Mihovetz and more importantly bought parts from Ron at Fox Lake for a long time. I’d have Fox Lake give me the Mihovetz cut if you’re paying the tab :)
I really haven’t looked at intake flow data but I do know it’s the restriction.
I’d like to see the combined flow but in my case I put the max effort into the intake with a CNC port, KB Bigun cooler and extensive porting/welding to the bypass area to open up the core area to flow.
Great plan good luck
-J
 

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