Small block cylinder head question

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rod7515

rod7515

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I have a 360 that has been stroked to 408 and currently have a set of J heads with the larger valves in both intake and exhaust. These J heads have been slightly ported before i bought them. I was wondering if I would see any gain by going to a set of x heads.
if no real difference in gains what heads would you recommend that would get me some gain. The cars not on the road yet but I know the bottle neck will be the heads. I will be running 10.5-1 compression, solid roller comp cam with .575 lift on both dual plane edelbrock intake.
Thanks for your thoughts.
Rod
 
As it has been explained to me the only difference is at a max port effort. About 12 cfm because the x head was designed for the larger valve and the water is farther away which allows more porting. There are so many better/cheaper options out there. They are both open chamber heads, to go and buy a core set of x heads will be about $300-$350. Then they need to be rebuilt, and will probably need harden seats installed. You can get 275-280 cfm out of an x head, but a cnc ported aluminum head is cheaper 40 lbs lighter as good if not better. What carb are you running
 
I am running a Sean Murphey built Holley 750 that flows to 830 cfm
 
rod7515 said:
I have a 360 that has been stroked to 408 and currently have a set of J heads with the larger valves in both intake and exhaust. These J heads have been slightly ported before i bought them. I was wondering if I would see any gain by going to a set of x heads.
if no real difference in gains what heads would you recommend that would get me some gain. The cars not on the road yet but I know the bottle neck will be the heads. I will be running 10.5-1 compression, solid roller comp cam with .575 lift on both dual plane edelbrock intake.
Thanks for your thoughts.
Rod
Click to expand...
10.5 compression (depending on which heads of course) .575 lift solid roller and dual plane? I think that's the wrong intake for the cam and compression.
 
I could be wrong on which I take I have on it. It's been almost 3 years since the motor was done. It's an edelbrock but I cant remember for sure which one but it was recommended by the engine builder so I'm sure I'm ok there. And it will be changes to my 2x4 setup once it's broken in.
 
Depends on your goals for the car...but a ported set of edelbrocks would put you in the high 10's more than likely, depending on the rest of your setup.

For what its worth, my old 410 stroker combo was 10.8:1 compression, small comp solid roller (XR286R) and ported Edelbrocks...it ran a best of 10.5 in street trim, but would normally run 10.7's (3200# Barracuda, 727, 4.10 gears).

Edit: I also ran an Air-gap duel plane intake when I first built it...It ran high tens with the Air-gap, then I switched to a Victor and it picked up ~ 2 tenths.
 
toolmanmike said:
10.5 compression (depending on which heads of course) .575 lift solid roller and dual plane? I think that's the wrong intake for the cam and compression.
Click to expand...
He never said which one he has (although I’d shreak if it was a regular Performer. Also, FWIW, as reported by a few memebers the RPM is best for double duty. Flyfish shows 2 tenths gain between the RPM & the Victor. I can’t for the moment remember the other members name who tried the RPM to M1 switch and found a tenth on the M1 over the RPM. (IIRC) Slower ‘60, higher mph. Again, IIRC, the 360 was in an import running low 11’s.

The RPM-AG dual plane torque advantage on the street would be well appreciated.
 
rumblefish360 said:
He never said which one he has (although I’d shreak if it was a regular Performer. Also, FWIW, as reported by a few memebers the RPM is best for double duty. Flyfish shows 2 tenths gain between the RPM & the Victor. I can’t for the moment remember the other members name who tried the RPM to M1 switch and found a tenth on the M1 over the RPM. (IIRC) Slower ‘60, higher mph. Again, IIRC, the 360 was in an import running low 11’s.

The RPM-AG dual plane torque advantage on the street would be well appreciated.
Click to expand...

I went from an airgap to a single plane( weiand excellerator) on a flat tappet 416 that ran 10.70’s at 3350 pounds and saw next to nothing ET wise( maybe couple or 3 hundreds). Stage 2 Hensley ported eddies, TTI step headers, 727.
Thats been my experience pretty much generally with intake swaps. Unless the one coming off was ultra wrong for what was going on, all i have ever seen is very minimal differences. Or none.
2 whole tenths is 40 or 50 horsepower on a 10 second car. Thats a ton. My 416 i only ran 6600 max and the car was relatively heavy so the dual plane wasnt hurting much.
I ran a 1025 race demon on that combo, nicest carb i have ever owned, i was stupid getting rid of it.
 
and with all that info, take a hard look at what the car is going to be used for...
what are the type of gains are you looking for ? street car or race car
 
rumblefish360 said:
He never said which one he has (although I’d shreak if it was a regular Performer. Also, FWIW, as reported by a few memebers the RPM is best for double duty. Flyfish shows 2 tenths gain between the RPM & the Victor. I can’t for the moment remember the other members name who tried the RPM to M1 switch and found a tenth on the M1 over the RPM. (IIRC) Slower ‘60, higher mph. Again, IIRC, the 360 was in an import running low 11’s.

The RPM-AG dual plane torque advantage on the street would be well appreciated.
Click to expand...


True that. When I think dual plane I think a LD340 or the like. (I'm a bit old school) I was thinking more along the lines of stroker, compression, .575 roller and a big single plane intake to feed it. Hell may be even a tunnel ram. You never know which direction these guys are thinking till you ask. LOL
 
B3422w5 said:
I went from an airgap to a single plane( weiand excellerator) on a flat tappet 416 that ran 10.70’s at 3350 pounds and saw next to nothing ET wise( maybe couple or 3 hundreds). Stage 2 Hensley ported eddies, TTI step headers, 727.
Thats been my experience pretty much generally with intake swaps. Unless the one coming off was ultra wrong for what was going on, all i have ever seen is very minimal differences. Or none.
2 whole tenths is 40 or 50 horsepower on a 10 second car. Thats a ton. My 416 i only ran 6600 max and the car was relatively heavy so the dual plane wasnt hurting much.
I ran a 1025 race demon on that combo, nicest carb i have ever owned, i was stupid getting rid of it.
Click to expand...
I don’t consider 40-50 hp a ton on a fast car. Indicated by only 2/10ths. But it is significant.
The faster you go, the less 50hp means, as you know.
Your intake swap yielded no results? Then, IMO, that is the break point between which one it is you need. The future attempt to go faster may show a single plane as the intake to use.

As we know, It’s all in the combo, what ever the engine /car likes, that’s what you use.
 
toolmanmike said:
True that. When I think dual plane I think a LD340 or the like. (I'm a bit old school) I was thinking more along the lines of stroker, compression, .575 roller and a big single plane intake to feed it. Hell may be even a tunnel ram. You never know which direction these guys are thinking till you ask. LOL
Click to expand...
Always application dependent! LMAO!
IDK, the lift alone doesn’t say big to me. It points, “sizable” sized cam, for certainly not small. The duration @.050 figures can vary widely! So you never really know. As far as intakes go, 90% of the time, dual planes for the street.
 
rumblefish360 said:
I don’t consider 40-50 hp a ton on a fast car. Indicated by only 2/10ths. But it is significant.
The faster you go, the less 50hp means, as you know.
Your intake swap yielded no results? Then, IMO, that is the break point between which one it is you need. The future attempt to go faster may show a single plane as the intake to use.

As we know, It’s all in the combo, what ever the engine /car likes, that’s what you use.
Click to expand...
Eventually chassis and drivetrain ,will come into effectively into discussion here....
 
rumblefish360 said:
I don’t consider 40-50 hp a ton on a fast car. Indicated by only 2/10ths. But it is significant.
The faster you go, the less 50hp means, as you know.
Your intake swap yielded no results? Then, IMO, that is the break point between which one it is you need. The future attempt to go faster may show a single plane as the intake to use.

As we know, It’s all in the combo, what ever the engine /car likes, that’s what you use.
Click to expand...

Agree for the most part, but 2 tenths is HUGE on a 500-550 horse motor. Thats somewhere 8-10 percent of flywheel horsepower just swapping an intake( and its on a fairly mild combo, not exotic)
Our experiences are different. I have never seen two tenths swapping intakes on anything going from one production piece to another. So that really jumped out at me. I think it would most people.
Your experiences obviously are different. Thats cool.
 
B3422w5 said:
Agree for the most part, but 2 tenths is HUGE on a 500-550 horse motor. Thats somewhere 8-10 percent of flywheel horsepower just swapping an intake( and its on a fairly mild combo, not exotic)
Our experiences are different. I have never seen two tenths swapping intakes on anything going from one production piece to another. So that really jumped out at me. I think it would most people.
Your experiences obviously are different. Thats cool.
Click to expand...
Well, yea, it not wildly. Depends on where you start and end with a 50hp gain. In going down the s al, a lowly 250hp 318/2bbl. engine is hugely out done by a 340 6 pack engine. Which we know is more than that listed 275hp rating.

Still, IMO, 50hp going from 500 - 550 should be felt in the pants as well. It’s iust the ET difference seen isn’t something large as the first example.

Going way up the scale, 1500hp is no different that 1550hp when your behind the wheel. While it shows up at the stripe, the driver (unless acutely award and well acquainted with the car) will never know 50hp missing. The race (most) are won and lost at the line and then the first ‘60. And etc.... not beating that horse topic of which we all know so well.
yellow rose said:
Ummmmmmm...no the Yellow Cars go faster.

That's a proven scientific fact. Google it. It's there.
Click to expand...
I’m tempted to google that......

If I google.... fat chicks drive what color car....
 
Did someone say 408 Six Pack? Hey I have one of those.

IMG_24951.jpg
 
OK,, Ive learned a few things through this thread so far today. Ive verified my intake as being an edelbrock victor. So far the 2 heads that were said to be a better pickup is the promaxx or a set of edelbrock heads. No one actually said there would be a good gain with the x heads.
Then, and probably more important I found that Ive painted my car the wrong color as Ive gone white with blue stripes and both the red and yellow cars are faster with yellow (per Google) being the fastest! lol
As for how I plan on using the car it will be mostly a street driven car. But I hope to race it a few times a year.
Thanks for everyones help.
Rod
 
After searching options I chose this option for my 408. Giving me plenty of reserve for when I want more
20180330_212710.jpg
 
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