head comparison

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rod7515

rod7515

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I know the bottle neck in the motor I will be running in my dart is going to be the 915 J heads. I did step up the valve size when I had them redone.
So heres my question:
What does a 915 J head flow stock? how much more with the larger valves. And how much would I improve the flow if I swapped them out for a set of x-heads? What do X-heads flow?
Thanks
Rodney
 
The X heads and J heads are pretty much exactly the same. Especially if they both have 2.02s. There will be no difference.
 
Depends on how much hp your looking for, 400 plus they become a bottle neck. 1.88 heads flow just south of 200 cfms and 2.02 are another 10-20 cfms. From what I've read.
 
By doing some porting work on the 915 J heads how much flow can I pick up? I dont want to have to spend $1500 plus for a set of heads when I will only race 3-4 times a year. I know I have over cammed for the heads that are on it. a solid roller with .575 lift on both! Just looking for options so I know what to expect when it doesnt go fast enough! lol
Rod
 
rod7515 said:
By doing some porting work on the 915 J heads how much flow can I pick up? I dont want to have to spend $1500 plus for a set of heads when I will only race 3-4 times a year. I know I have over cammed for the heads that are on it. a solid roller with .575 lift on both! Just looking for options so I know what to expect when it doesnt go fast enough! lol
Rod
Click to expand...

They can be made to flow 500 HP or so. Possibly more in the right hands.
 
From what I remember reading, 240 cfm with bowl porting and some deep gasket matching/port widening at the pinch rod.
Best to ask a pro.
 
rod7515 said:
I know the bottle neck in the motor I will be running in my dart is going to be the 915 J heads. I did step up the valve size when I had them redone.
So heres my question:
What does a 915 J head flow stock? how much more with the larger valves. And how much would I improve the flow if I swapped them out for a set of x-heads? What do X-heads flow?
Thanks
Rodney
Click to expand...

Measured Stock Cylinder Head w/Competition Valve Job

#3418915 'J' Cylinder Head

........................{1970 and 1971 Casting} ............ {1972 Casting}

Intake Valve..................... 2.02" .................................. 1.88"
Intake Bowl Size................ 1.75" {86.6% of Valve}

Exhaust Valve.................... 1.60"

Intake Port Volume............ 157 to 160 CC .................... 150 to 152 CC
Exhaust Port Volume.......... 71 to 73 CC

Intake Flow @ .450" Lift...... 213 CFM ........................... 190 CFM
Exhaust Flow @ .450" Lift.... 146 CFM

Intake Flow @ .500" Lift...... 220 CFM ........................... 196 CFM
Exhaust Flow @ .500" Lift.... 148 CFM
 
The previously reported stock head flows are fairly correct in our experience, but probably more in the 200cfm range (412HP). An X, J, O, or U head with the 2.02 valve with a bowl hog and porting or hand bowl work and porting generally will max out around 240-245 cfm @ .450" lift (about 505HP potential) and stall above that. We have J heads with no welding or epoxy that flow 292cfm @ .600" and 298cfm @ .700" (some 600+HP potential). It is too expensive to bother porting a J head to those flows and a ported aluminum head is recommended for those power ranges.
 
Being a stock 340/360 head can be preped well and not ported to save money, you can still use that head to run pretty quick. The 292/.509 cam fits right in there and is capable of running in the 12's easy enough.

I think the MoPar speed tips has this listed and the cam so designed with this in though, so to speak. LOL
 
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