Just bought some used Edelbrock RPM 340 heads... for my Magnum

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MopaR&D

MopaR&D

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I was about to purchase a pair of EQ Magnum heads for my build today when I came across an ad on Facebook for some used Edelbrock RPM LA heads for the same price. I didn't realize until after sending the money though that these are the stupid open-chamber ones meant for factory pop-up 340 pistons, and I'm putting them on a stock 5.9L Magnum short block. If I can manage 9.5:1 compression I'll be happy, is that possible without having to mill the heads or change pistons? Also any other potential issues you guys can think of besides rocker oiling (what would be the best solution for that btw)? The heads come with valves and springs but some of the valves got bent so they'll probably need a valve job and maybe guides checked... this was kind of an impulse buy because I knew someone else would grab them quick if I didn't but compared to buying new EQ heads and getting them prepped I think this is a petty good score no? They were $750 shipped btw and also include a set of head studs which is nice.
 
abdywgn said:
get an LA360 block and switch all your rotating assembly into it.
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I'd much rather not do that, this Magnum short block is in mint condition and I don't want to touch it. I'd much rather fab a custom oiling system for the rockers than go through the trouble of finding another block which I doubt these stock Magnum pistons will fit in, it's really hard to find "virgin" SBM LA 360 blocks nowadays... then I have to worry about honing (at least), rings, etc.
 
I guess you could do the external oil line into the end of the rocker shafts, the rocker/pushrod end could get it's oil thru the lifter.
 
BigBlockMopar said:
What's wrong with milling the heads?
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The chamber "squish pads" are recessed .060" into the chamber so roughly that much would need to be removed to make them closed chambers, and then the chambers themselves would be super small since even the open-chamber 340 Edelbrocks are listed as having 65cc volume, only 2cc more than the normal closed-chamber ones.

@abdywgn I'm thinking I might try one of the methods mentioned in this thread:
Magnum block mdded to oil LA heads?
 
MOPEkidD-3 said:
I was about to purchase a pair of EQ Magnum heads for my build today when I came across an ad on Facebook for some used Edelbrock RPM LA heads for the same price. I didn't realize until after sending the money though that these are the stupid open-chamber ones meant for factory pop-up 340 pistons, and I'm putting them on a stock 5.9L Magnum short block. If I can manage 9.5:1 compression I'll be happy, is that possible without having to mill the heads or change pistons? Also any other potential issues you guys can think of besides rocker oiling (what would be the best solution for that btw)? The heads come with valves and springs but some of the valves got bent so they'll probably need a valve job and maybe guides checked... this was kind of an impulse buy because I knew someone else would grab them quick if I didn't but compared to buying new EQ heads and getting them prepped I think this is a petty good score no? They were $750 shipped btw and also include a set of head studs which is nice.
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Hey, I happen to be selling a new pair of those “stupid” heads on here, lol.
Good luck with your motor
 
604B1duster said:
Hey, I happen to be selling a new pair of those “stupid” heads on here, lol.
Good luck with your motor
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lol sorry no offense, I only called them stupid because they aren't exactly what I wanted... one of the big reasons for me for going with aftermarket heads is having closed chambers, also seems weird they have a completely separate model type just for factory high-compression 340 engines, I doubt there's much demand for those...? And on anything else they're pointless vs. closed chamber, just takes away the ability to build quench unless you get special pistons that come above deck. But I could be missing something here (that happens often lol)
 
Haha No offense taken. I have a fresh matching 340 short block, so if I don’t get a decent price I’ll just keep them.
I’ll be watching for updates on your engine
 
604B1duster said:
Haha No offense taken. I have a fresh matching 340 short block, so if I don’t get a decent price I’ll just keep them.
I’ll be watching for updates on your engine
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I don't remember if I started a thread on it yet but I will post details, currently I have the Magnum short block sitting with the lightly-used oil pump out of my old 360 and the special main cap bolts installed for a windage tray; now I need to save money for machining the heads, new camshaft, timing set, and all the small stuff.
 
I believe some of the early magnum blocks are drilled for LA oiling. not sure how big of a pain drilling a block would be.
 
Baxter61 said:
why dont you just sell the heads and get the heads that you need?
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I may end up doing that depending on how they look, however it would be a bit of a downgrade since it's not every day you come across Edelbrock SBM heads for $700 per pair and I can't afford more than that; I'd be stuck going back to iron EQs which was my initial plan anyway.
 
vitamindart said:
I believe some of the early magnum blocks are drilled for LA oiling. not sure how big of a pain drilling a block would be.
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They were, my Magnum is pretty late build though it's a 2001 MY. I think I will most likely just do an external (from the block) oil feed directly to the rocker shafts, drilling 6" into cast iron sounds like a bad time.
 
Hey I got a pair of those "stupid heads"..when Edelbrock started production on small block Mopar heads that all that was available...
 
stroked340 said:
Hey I got a pair of those "stupid heads"..when Edelbrock started production on small block Mopar heads that all that was available...
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Ah I didn't know that, makes a lot more sense now... if that's all they could make initially, might as well make them compatible with all the engines, not just ones with low-comp pistons. I guess they aren't so stupid after all :eek:

Also makes sense why there are a good amount of these that seem to be floating around.
 
I would suggest selling the heads for a profit and get Magnum style heads. I'm sure the EQ heads wouldn't be a down-grade compared to open chambered heads even if they are Eddys. You could use the extra money for bigger intake valves or minor porting.
 
the "t"-ing off the oil pressure port sounds doable. how about a fitting straight out the back of the valve cover for the line to attach to? a nut or flange on the inside of the valve cover with a thick seal and a thinner seal, washer and nut on the outside to keep the seepage down. OR, tap the inside of the rocker shaft and thread a fitting in from the outside with the seals only on the outside. watch out for 90 degree fittings, it is like adding length to the hose.
 
Think about this for a minute, mags oil thru the push rods, the oil then goes thru the rocker arm and down the springs.
How much oil do you really need up there?
I would think there would be enough oil to lube the rockers on a shaft, maybe I am wrong, but push rod oiling puts alot of oil in the top end of the motor.
 
sireland67 said:
Think about this for a minute, mags oil thru the push rods, the oil then goes thru the rocker arm and down the springs.
How much oil do you really need up there?
I would think there would be enough oil to lube the rockers on a shaft, maybe I am wrong, but push rod oiling puts alot of oil in the top end of the motor.
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the part of the rocker that the shaft rides against (although it would "float on a layer of oil) would need to be pressurized.
 
You said the edelbrocks have bent valves and will need rebuilt, I think you will spend as much to rebuild these, and trying to retrofit them, as you could just buy fresh edelbrocks in the magnum variety and no mucking around.
 
replicaracer43 said:
You said the edelbrocks have bent valves and will need rebuilt, I think you will spend as much to rebuild these, and trying to retrofit them, as you could just buy fresh edelbrocks in the magnum variety and no mucking around.
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Well we'll see what my machine shop says, they quoted me around $300 to do a valve job and install bronze guides in my old Magnum heads. These probably need about the same, plus replacement valves for the ones that got bent. A pair of new assembled Eddy heads is almost $1900 and I originally budgeted about a grand for heads... so going that route is out of the budget unless I want my car to be done in December. I've already done the "well since I'm gonna spend that much I might as well..." thing twice now; original plan was to clean up and bowl-port my stock Magnums, then I realized for the same money I could get a set of bare EQ Magnums, then I saw this ad for Edelbrocks for the same price lol.

If I can't get these heads to work with $300-400 of machining and some home-fabbed oiling mods I will just sell them. ~$1000 is my limit and I'm gonna try real hard to stick to it, my Duster has been dead for a year and a half now I'm determined to get that b**** running by the end of summer.
 
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Lelo Dart said:
I would suggest selling the heads for a profit and get Magnum style heads. I'm sure the EQ heads wouldn't be a down-grade compared to open chambered heads even if they are Eddys. You could use the extra money for bigger intake valves or minor porting.
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I already have someone on here interested in the heads and I'd feel like a jerk flipping them for profit to a fellow FABO member; if I was to sell them I'd seriously consider getting them machined first, might be able to squeeze out a bit of profit if they clean up nice and I can sell a pair of heads ready to bolt on and go.

Oh and I'm not really concerned about closed vs. open chambers for this particular build because I'm using factory pistons which come nowhere near close enough to the decks for it to matter... The weight savings is the main advantage to me as I'm building my car for handling.
 
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I bought a set of those junk Edelbrock open chamber heads damaged for 450.00. Never milled them and after repairing them, porting, and upgrading to a 2.08 valve have gone 9.70’s with flat top pistons in my 408. I’ll give you scrap price for them if you can’t unload them
 
pittsburghracer said:
I bought a set of those junk Edelbrock open chamber heads damaged for 450.00. Never milled them and after repairing them, porting, and upgrading to a 2.08 valve have gone 9.70’s with flat top pistons in my 408. I’ll give you scrap price for them if you can’t unload them
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HEELLL yeah that's what I like to hear. I get a real kick from taking supposedly worn-out cheap "junk" and making something good out of it. It's not optimal but for the price... there's a lot of potential still there, my thinking anyway.
 
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