Should I pick up a set of 5.9 magnum heads and replace my 360 J heads for my 360? Please help me out if anyone knows facts on how much they flow compared to each other. I know the magnum heads have a much smaller combustion chamber than J heads.
Thanks,
Dillon
They do have the smaller chamber, but thats not as important as a general as flow and durability, factory magnum heads are cracking sob's.
The j head with factory small intake valves flow around 213 cfm 'on a 1970's pos factory valve job'.....meanwhile the magnum flow around 208 cfm on the intake side with a 90's valve job and bigger valves.
as for the low lift being better with the magnum, well.. beside the fact that the valves are bigger with the magnum 'duh' u can factor in the valve job...
I have a tread on here called '360 head trip' and although it doesnt show the full potential and effect of a good valve job on low lift YET...'thread not finished'...it does show the j head potential and it's magnum *** kicking ability even 'as cast'....
I advise u keep what you have.
Yeah gotta get rocker gear, hollow pushrods, and lifters with oiling hole in the pushrod seat plus new valvesprings and retainers unless you're using a mild cam. The main benefit is the closed chamber which is much more efficient and allows you to run more compression (if you take advantage of the squish with zero-deck flat-top pistons). They also flow a bit better than J heads in the lower lift ranges and have smaller volume ports (higher velocity) with the exhaust's flow rate closer to the intakes than on J's (work better with single-pattern cams).
Really IMO it's not worth it, you'd probably get more bang for your buck porting the heads you have unless you're getting new pistons and cam as well.
EDIT: Almost forgot, most (if not all) Magnum heads pulled from an engine with any kind of mileage will have cracks between the valve seats...
He would get better flow if put a lil coin into the j's, if he just put larger valves in a had a blend done...they would destroy the magnums.
The exhaust flows more due to the better short turn/higher floor.
Split pattern cams mainly to work around exhaust manifolds, as thats what they were designed around 'look at 440/383 roadrunner/hp cams as well as 340 cam specs... i point this out because the factory ratio of 69-70% is good and does not need a split 'especially if a header is in the mix' as well as the correct size exh pipes...even with a 2.02 in the picture...it's still at 65%...then factor headers and it's not really any issue...w/o?...well then look at that split cam again.lol
food 4 thought..
btw, what is the magnums port volume?
I know the 2.02 j/x heads have a 155cc intake port and the 1.88 have a 160cc port-the bigger tulip valve eats a lot more bowl volume than the 1.88 believe it or not.., but my point is that the magnum is probably about the same 150-155cc and yet it has a shorter roof, thats not a flow helper...fwiw.:sign7:
I run magnum heads on an early LA 360. No complaints here. I have flat top pistons and my final static compression ratio is 10.58 to 1. My cylinder pressures run at 190 to 195 psi. I can run 89 octane with no problems. Great setup once it's together.
Jack
Ok, cool....now what advice are u actually offering here?](*,)
Keep in mind that if you go to Magnum heads, that you can no longer use an LA intake. The Magnum heads are very crack prone as well. You can buy Magnum heads through HughesEngines (I know lots of people are not fans but just throwing it out there) and get the LA intake pattern.
Yes the after market 'performance magnum replacement heads' are waaaaaayyyyyy better and imo totally diff ports, they actually do flow more than a stock x/j by around 10-15 cfm [comparing j/228cfm to rhs/eq@24'ish cfm.....but they are not the magnums he's asking about.
I'm happy with my Hughes Magnum heads, but I have a lot into them. I probably could have gotten just as good or better results from the RHS heads with the same level of porting for quite a bit less money. Mine have a lot more potential in them (as far as flow goes), but with the stud mounted rockers, I wouldn't want to push them much more than I already am.
Again....not even the same head, totally different except that they bolt up all magnum gear n such and cost $1600 from the to go to when buying.
I have two stock pairs I'd sell for $75.00/pair both came off good running engines with 130k on the one engine and 145k on the second.
EQ/RHS are the heads to buy if you want a good performing iron head (from $950.00 to $1,450.00 depending on who puts them together/parts used).
so one head u recommend has 150'ish port volume...and the other sports 179cc and growing once you upgrade the valves....so now the same group of people are cross wires here if this ''velocity'' is to be considered important.LOL:hello2:
Thanks for all the input! Next time I go to the junkyard I will probably pick up a set if they are there, because it's my friends neighbor's junkyard so I can get them super cheap. I do have a mild cam (.420 lift) with aftermarket lifters meant for oiling.
Well if thats your choice....good luck.:joker:
