Which heads to run on 340

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bbizelli

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Alright so im currently planning a 340 build slowly gathering piece by piece sense im in no big hurry. I had a set of magnum heads i intended on using but after a trip to the machine shop i found out there cracked in between the valves in the combustion chamber on both heads. I have a set of 360 J heads if i had the J heads milled and the valves punched out to 2.02 intake valves will that make the comparable to the 340 X heads or which heads so i try to find? Any and all help is greatly appreciated! Thanks Guys!
 
If 2.02 valves are install into J heads properly, they will be BETTER than X heads every time.
 
Buy the time you get those J heads up to standards you'd be better of buying a set of aftermarket heads. The RHS heads are good and cheap, edelbrock heads if you want aluminum (what I have on my 340). Of course you could run the W series is your pockets are deep.
 
1970Duster said:
Buy the time you get those J heads up to standards you'd be better of buying a set of aftermarket heads. The RHS heads are good and cheap, edelbrock heads if you want aluminum (what I have on my 340). Of course you could run the W series is your pockets are deep.
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X2 I DID the rebuild stock heads trick "J's" what a waste of money, IMO get the RHS heads you'll be a MILE ahead!!!
 
what engine setup did you have 412 and did you switch to the rhs
 
345man2 said:
what engine setup did you have 412 and did you switch to the rhs
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No I paid WAAAAY too much to have them rebuilt, (I have 2.02/1.65 Manley severe duty valves) so I have to run them, I just have a few friends that have the RHS heads, and they really love them, I AM someday going to get a set (RHS well now they are Indy heads) from either IMM or MRL as soon as I can afford it.
 
How much are the RHS heads? What are the flow specs? Do you need a special intake for them or does a standard LA bolt pattern work for them?
 
bbizelli said:
How much are the RHS heads? What are the flow specs? Do you need a special intake for them or does a standard LA bolt pattern work for them?
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Standard LA bolt pattern for intake and exhaust so anything LA will bolt to it. Ootb they flow better then j/x heads but ported will make them run away for the stock stuff.
 
just a heads up on the RHS LA-X heads (standard la intake works but need magnum head bolts), not sure if its been covered elsewhere but im putting a pair on my 318 with comp 978 springs and i need to get special rockers to clear the retainers. supposedly the rockers are designed for this head. they cost $350 just for rockers no shafts and they still rub so i will need to grind a little for clearance. also im on my 3rd set of pushrods because no one can seem to tell me what i need and now im getting custom made 7 3/4" long ball and cup rods that should finally solve my issues. they have not been the direct bolt on i was promised. just something to consider, also a beehive spring might solve clearance issue
 
:Ddont blame you a bit 412 trying to decide which way to go myself
 
zinser72 said:
just a heads up on the RHS LA-X heads (standard la intake works but need magnum head bolts), not sure if its been covered elsewhere but im putting a pair on my 318 with comp 978 springs and i need to get special rockers to clear the retainers. supposedly the rockers are designed for this head. they cost $350 just for rockers no shafts and they still rub so i will need to grind a little for clearance. also im on my 3rd set of pushrods because no one can seem to tell me what i need and now im getting custom made 7 3/4" long ball and cup rods that should finally solve my issues. they have not been the direct bolt on i was promised. just something to consider, also a beehive spring might solve clearance issue
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This is why we use the beehive springs!! http://www.immengines.com/rhsheads.html
 
We also use PRW stainless rockers, and ball-ball pushrods because they use cup adjusters. This saves money, and makes pushrod choices SO much easier!!
Brian
 
under e bay 360 cylinder heads is a nice looking kit pro comp is just putting out i,m in th e same boat with you trying to build a 408 stroker there kit is nice based on rpm heads with air gap intake roller rockers and valve covers for 1500.00 do i stay with my j's there already 202/160 but need porting i have my crane cams roller rockers and an old weiand like 7545 intake we need justin or a head specialist to fully explain this to us like were 2 years old wich way to go ??????????
 
Listen to what Brian (0U812) posted above. He knows what he's talking about in regards to the Indy/RHS heads. I bought a set from him, with the PRW roller rockers kit. Although I'm still in the mock-up/clearance checking phase, these heads with the beehive springs and the 1.6:1 roller rockers, bolted right up, and there was no issue with interference between the rocker and the spring/retainer.
 
doesn't the J head have a larger combustion chamber then the X head tho? So it would need to be milled correct?
 
I see i just thought the J heads had a larger CC combustion chamber but i could be wrong i know the 318 heads have a smaller CC combustion chamber. Ill probably just end up using the J heads now and punch the valves to 2.02 i got a guy that does it pretty cheap and hes really good hes slower but he does really good work. Then gasket match, clean the bowls up and slight milling. This would make a pretty good head to run correct?
 
Send Wild n crazy guy,a pm. He does this stuff,for a fair price and he's good.
 
Do you know where hes located at by any chance? Im in Missouri kinda by St. Louis and prefer not to ship the\m somewhere. I will have to check my small block book but can i put 2.08 intake valves in J heads? Think i can but would also like to open the exhaust up to does anyone know if i could run 2.02 intake and 1.65 exhaust like the magnum heads? Just a thought.
 
Actually stock Magnums are 1.92 int,1.62 exh diameters.Unfortunately,The guy I mention,in California.
 
Check out JD engines,in Columbia.Did a thread search,found this.Might pm 68fishy,in your general area.
 
there seems to be a lot of confusion about heads here . these are casting number for 340 / 360 heads That are the same heads. " J " as far as I know are the same as "x"
just different casting numbers.
68 to 71 340 - casting # 2531894
1970 340 6 Bbl. T/A casting #3418915
1971 360 casting # 3418915
1972 340/360 casting # 3418915
1973/4 340/360 casting # 3671587
1973 360 w/air pump casting # 3671587

Cheers.
 
hope this worked , guys I have attached a pdf file . It is a page from my mopar engine bible . Read the whole page but pay attention to the fourth paragraph. 340/360 heads .

Cheers.
 

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Fyi everyone, the j head has a different short turn than a 894 x head, the j is a better head .imo

If I had to choose one to port and obtain the highest int flow numbers possible...I would use the 915 over the x.
 
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