Or any others without super rare heads like T/A. Which is the best factory head to start with for a good street strip setup? Also, without paying a machinist a small fortune in labor to get to flow well just mild machine work. What size valves to choose? I've read that running 2.02 valves actually hurts flow compared to 1.88 valves in certain combinations. Can anyone clear this up for me? This would be for a 340 on pump gas.
X, J, or 308?
- Thread starter kujo
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Salty Dog
Well-Known Member
Yes, since, in general, all small blocks heads for the 340/360 have the same ports with minor differences that are very small,. They will all flow within a few cfm of each other after the basic porting mods are done.
The 1.88 valve helps with air velocity which results in a better throttle response and possible mileage gains on stock engines or very mild cam changes.
The 2.02 is best suited to higher rpm useage. The difference in valves, performance wise is small. Like you mentioned, it is in the combonation of the build.
Locomotion
Well-Known Member
The above post covers it. T/A heads are exactly the same as other 915 heads, just have the intake pushrod holes machined in a different location.
Mild bowl porting will help the most with minimal work. But you need a good, accurate valve job without "sinking" the intake valves. The higher the seat, the better they will flow.
If any of the older heads need much work, like new seats, it can get expensive. New stainless nail-head valves that are back-cut flow better than the OEM tulip shape.
But if the work and parts start adding up too much, then you might want to price some aftermarket head assemblies, like the Indy/RHS MA-X. Gotta compromise between your budget and how much work the old used heads you find require.
Any of the heads you mentioned would work well. Just check for cracks. The 308's may actually make more torque because the do have slightly narrower ports. X heads only have 2.02" valves and are the oldest. 915's can have either.
Mild bowl porting will help the most with minimal work. But you need a good, accurate valve job without "sinking" the intake valves. The higher the seat, the better they will flow.
If any of the older heads need much work, like new seats, it can get expensive. New stainless nail-head valves that are back-cut flow better than the OEM tulip shape.
But if the work and parts start adding up too much, then you might want to price some aftermarket head assemblies, like the Indy/RHS MA-X. Gotta compromise between your budget and how much work the old used heads you find require.
Any of the heads you mentioned would work well. Just check for cracks. The 308's may actually make more torque because the do have slightly narrower ports. X heads only have 2.02" valves and are the oldest. 915's can have either.
perfacar
Well-Known Member
hi, on the flow bench and on the track, the 587 head will out perform the j or 915 head. if you use a nail head 1.88, sst valve, you will gain flow and port velocity. I have ran both heads. bowl blending does wonders to the flow output. just food for thought.
ir3333
Well-Known Member
i have heard x or j will support 400 hp,but don't have any first hand info...
Locomotion
Well-Known Member
I've gone 11.22 @ 116 + weighing 3,540 lbs + with 1.88" intake 587 heads and .474" lift.
perfcar and others have as good or better numbers as well. I'm sure that's over 400hp, but you may get some widely varying #'s depending on which formula you use.
YES! it will.
In lay man's terms, the amount of HP a head can / or will produce is cfm X's 2 for most builds. Not all builds. AKA some really serious HP hunting engines. It is possible to exceed the basic formula.
A stock head flows approx. 200 cfm. X's 2 is 400 (HP)
The less cfm flow, the more cam, compression it will need.
MoPar Muscle has a few articles on this.
I remember a chick did a 360 with Edelbrock and RPM intake, 750 carb IIRC and wacked out 400 HP. The thing behind it all was the cam was barely lifting mid 400's. This is NOT using the head at all and the head doesn't flow all that much at that lift.
In another example, the (Stock) Magnum head (1.92-1.60 valves) was used with a 280/.480 comp cam. Though the 1.6 rocker moved the lift up to .512, the head could still handle that lift. The engine made over 400 HP and the displacement was a mere 318.
Thanks for all the replies. I should have gotten the 587's. I could still probably pick them up if that's what I decide to do. What about the magnums. How do the stock magnums compare to the LA heads. When considerring the same machine work (minor blending) to each type head.
Salty Dog
Well-Known Member
Good question. Perhaps Shadydell might have a listing on the stock flow or maybe a mag/rag. A compro chart would be a good thing to have at your point since your shopping around. "Like!" the idea of Comparative shopping.
out of the heads mentioned the 308head will make the most power but be carefull they are prone to crack between the valves and with a little bowl and intake porting they work real good
Salty Dog
Well-Known Member
J head flow; http://shadydellspeedshop.com/jhead.htm
Magnum R/T not standard Magnum head flow; http://shadydellspeedshop.com/magnumrt.htm
Magnum R/T not standard Magnum head flow; http://shadydellspeedshop.com/magnumrt.htm
I have Magnum heads on my 360 truck motor and they make GOBS of power!
I purchased them from a Mopar performance dealer in metro Atl and he said in their stock as delivered form, they Out Flowed ALL other SB heads.
I have no Dyno figures to know the approximate power they are making, but I can tell you my 74 3/4 ton camper special LWB hauls ***! Dana 60 w 4.10 and suregrip.
All I had to do to put them on my LA block was buy the intake manifold (from Chrysler) with provision for carb, use AMC (jeep) lifters and custom pushrods made (not too expensive either!).
I got the heads for $200 each! Brand new! Years ago!
They are still going strong, no signs of Cracks anywhere.
If you can find a good set (heads, magnum) you won't be disapointed!
Mike
Found some info on the stock magnum head flow. Here it is: http://www.moparmusclemagazine.com/howto/mopp_0507_cylinder_head_porting/viewall.html
Hope this helps out someone else besides just me.
Hope this helps out someone else besides just me.
1wild&crazyguy
Banned
Ive flow tested some of the heads u mention.
''J heads'' in general can cover many casting numbers, the 1st version came as casting #3418915 and went through to #587 and 974# then to #596. The main diff between the 1st gen and later following castings are the exhaust ports where the factory was getting ready for air injection/smog requirements handed down by the epa and so they added bosses for the air injection ports to be drilled...though many were not=#974/587 both could have come with or without the air injection ports drilled. That boss can help bring up the flow number in the lower lift if properly blended.fyi
The 1.88 int valve 915 and 974 versions that I have flowed go around 210/215cfm and 140/145cfm exh @.500 lift.
I have flowed 'as cast/machined' 2.02 version #915's and they went 228/[email protected] & up . The '#587'...now the diff is who did the valve job here, cause ootb from aerohead machine they only went 203cfm....due to a crummy throat cut 'mainly', there was way too much under the seat for them to even go stock numbers...imo
fwiw.
I would go with either, and if want to go wild on them....have seats installed on both int and exh to raise the valves up and lengthen that short turn and then port them.
''J heads'' in general can cover many casting numbers, the 1st version came as casting #3418915 and went through to #587 and 974# then to #596. The main diff between the 1st gen and later following castings are the exhaust ports where the factory was getting ready for air injection/smog requirements handed down by the epa and so they added bosses for the air injection ports to be drilled...though many were not=#974/587 both could have come with or without the air injection ports drilled. That boss can help bring up the flow number in the lower lift if properly blended.fyi
The 1.88 int valve 915 and 974 versions that I have flowed go around 210/215cfm and 140/145cfm exh @.500 lift.
I have flowed 'as cast/machined' 2.02 version #915's and they went 228/[email protected] & up . The '#587'...now the diff is who did the valve job here, cause ootb from aerohead machine they only went 203cfm....due to a crummy throat cut 'mainly', there was way too much under the seat for them to even go stock numbers...imo
fwiw.
I would go with either, and if want to go wild on them....have seats installed on both int and exh to raise the valves up and lengthen that short turn and then port them.
perfacar
Well-Known Member
hi the one thing you all are missing , is port velocity. it is way more important over the big flow numbers. when I went to a super flow class, it was stressed, port velocity and port shape are everything, don't get hung up on big numbers. there is a window of valve open and close, if you have big number , but low velocity, very low cylinder fill. higher port velocity will put more air into cylinder. in stock class racing, we strive for port velocity, flow numbers do come into play. just food for thought.
1wild&crazyguy
Banned
What u forget... is with factory iron...the port velocity is huge the ports r pretty small
Very fast air...and its going one direction..
Very fast air...and its going one direction..
So, what characteristics of cylinder head design dictate port velocity?
In general, a smaller port. Shape of port and it's position can vary for grater air movement. In example, a raised port. I'll let 1W&C answer the rest.
1wild&crazyguy
Banned
yes, and a narrow port...like an LA port.lol..
bowl to runner as well, small runner big bowl.
In general one could be correct in saying that a given air flow through a given cc runner.
the high flow through a small port scenario.
thats why i say the LA port IS a high velocity port, to a point and then some..once u start pulling big ported numbers out of it...the port can only get so big, it's small still really when it come to port volume.
which head do you think has more velocity?
An rhs head flowing 244cfm @ 179cc's?
or a factory iron head flowing 244@ 160-165cc's?
bowl to runner as well, small runner big bowl.
In general one could be correct in saying that a given air flow through a given cc runner.
the high flow through a small port scenario.
thats why i say the LA port IS a high velocity port, to a point and then some..once u start pulling big ported numbers out of it...the port can only get so big, it's small still really when it come to port volume.
which head do you think has more velocity?
An rhs head flowing 244cfm @ 179cc's?
or a factory iron head flowing 244@ 160-165cc's?
So, which is more important velocity or flow? Would the 318 head you ported in the stcky with the [email protected] 129cc ports actually perform better than a head with around [email protected] 179cc ports?
It's combo dependent. You just can not compare heads in this fashion.
Velocity and flow work together and this is also combo dependent. This should also make you think and give it up to the stock eliminator and F.A.S.T. guys.
Velocity and flow work together and this is also combo dependent. This should also make you think and give it up to the stock eliminator and F.A.S.T. guys.
Robbie2734
Lambcharger
One of the best threads I've seen in a while, thanks guys
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