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Old 04-08-2005, 09:49 PM
Mopar4LIF Mopar4LIF is offline
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Default Tentative magnum head swap

My best friend from high school which has been many years ago now is finally ditching his 68 Chevelle in favor of a 70 dodge demon. We have been amassing parts for it for the last year, it is primarily goign to be a bracket car, we have the 340 shortblock rebuilt and he recntly bought the hughes cam HEH 3742 AL grind. We were looking for a set of heads for it when it dawn on us why not do a newer magnum head style swap with edelbrocks new cylinder heads. Now my question is what would be needed? the lifters that match the cam can be used with engines that oil through the pushrods. So we have that covered. The intake he has is a mopar m1 single plane. I am thinking we can drill holes in it to match the magnum heads. Then rocker arms and pushrods. Is this feasible? Also which does produce more power, a magnum design or a LA head?
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Old 04-08-2005, 10:02 PM
TK TK is offline
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X or J but we've been arguing this before.
you can do more with old heads, but, if your not porting, the magnums are the way to go (just my oppinion) sides, who like chevy valvetrain anyway, real engines have rockershafts
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Old 04-08-2005, 10:09 PM
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dwc43 dwc43 is offline
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Why not just use the edle LA heads and save your money and use a proven and better rocker shaft system of the look a like chebby rocker junk. You'll also need one point higher compression when using aluminum heads over cast.
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Old 04-08-2005, 10:44 PM
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Quote:
Originally Posted by Mopar4LIF
The intake he has is a mopar m1 single plane. I am thinking we can drill holes in it to match the magnum heads. Then rocker arms and pushrods. Is this feasible? Also which does produce more power, a magnum design or a LA head?
Theres a dude on the net somewhere that has a jig to mod the magnum head to accept the older intake.
The difference between the Edel. Magnum head and the older head is small. Peak flow goes to the Magnum while area under curve goes to the comando head.
MoPar used the generic rocker system to save money. When you use the Edel. head or *I think* the Magnum R/T as well, you need to go to a larger stud and rocker to fit. This is where the gerneric rocker comes in.
Unless your hard core about this build , the MoPar shaft style system isn't going to show it's bennifits over the generic type really. Though they are a better rocker system.
(Sub the word generic for chevy)
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Old 04-08-2005, 11:01 PM
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Quote:
Originally Posted by dwc43
Why not just use the edle LA heads and save your money and use a proven and better rocker shaft system of the look a like chebby rocker junk. You'll also need one point higher compression when using aluminum heads over cast.
Seems that the Edel. Magnum heads should be better than the LA Edel heads from what i read in the "riddle me this Roger" thread:
riddle me this Roger

I personally dont like using Chevy rockers, i told my dad about Edel using Chevy rockers and he was surprised, "why would they use those? there crap!" With modern materials and designs in the after market, im thinking that most problems have been elimated by now. right?
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Old 04-09-2005, 01:51 AM
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rumblefish360 rumblefish360 is offline
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Good note dst. The flow difference between heads are close. I took the specs out of there atolog. While the Magnum flows about 10 cfm more, it's at max lift. At .500, the 3cfm diff. would never be felt and haed pressed to be seen on dyno or track.
It's that area under curve that I like from the Comando heads. A tad cheaper as well.
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Old 04-09-2005, 07:58 AM
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The Magnum heads have a much better combustion chamber then the LA rpms. Its also much smaller at only 58ccs instead of 64 for the LA heads.

Rockers may not be shft style but they are plenty strong and about half the price. You'll need Chevy 1.6 or 1.7 rockers for a 3/8" stud.

The valve covers use 10 bolts so they wont leak.

The intake your best bet is to redrill the heads for the LA intake if you already have one or sell what you have and buy a Magnum intake.

Even though bolth heads flow about the same out of the box the Magnums combustion chamber will make more power.

What does your friends block have for pistons ? Remember bolth heads have closed combustion chambers. If the pistons are sticking out of the bore you'll need a thick gasket to keep the piston and heads from becoming to close of friends.
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Old 04-09-2005, 10:18 AM
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does anyone have anything to say about how durable the Eddi heads are....after kicking around a few ideas it might be easier to just go with them than porting the iron 302s and finding 1.7 ratio rockers. Any problem with using the eddies for a daily driver?
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Old 04-09-2005, 03:57 PM
Mopar4LIF Mopar4LIF is offline
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Quote:
Originally Posted by fastback340
The Magnum heads have a much better combustion chamber then the LA rpms. Its also much smaller at only 58ccs instead of 64 for the LA heads.

Rockers may not be shft style but they are plenty strong and about half the price. You'll need Chevy 1.6 or 1.7 rockers for a 3/8" stud.

The valve covers use 10 bolts so they wont leak.

The intake your best bet is to redrill the heads for the LA intake if you already have one or sell what you have and buy a Magnum intake.

Even though bolth heads flow about the same out of the box the Magnums combustion chamber will make more power.

What does your friends block have for pistons ? Remember bolth heads have closed combustion chambers. If the pistons are sticking out of the bore you'll need a thick gasket to keep the piston and heads from becoming to close of friends.
His setup is a 70 .20 over 340 block with .10/.10 steel crank. Reworked stock rods, that have been shot peen, big end resized, magnafluxed, with arp wave loc bolts. He is running a set of keith black hypers. Yes I know about a million people are goign to tell us we are idiots for using these, blah,blah blah. But with no intention of nitrous use and properly set up they should not be a problem. However this is where I am a little confused, how do you determine piston to valve clearance. The pistons are These
any advice. I would fear with the small cumbustion chamber of the magnums it would be problematic on pump gas to run them. I should add that he will on the weekends drive this thing on the street and doesn't feel like having to run to get 100 octane fuel. We figured we might be ok with the LA edel heads and the cam because of the combustion chamber size and the cam would probably bleed off enough cylinder pressure to be ok with the weekend driver days. The magnums with teh ultra small chamber woudl raise the compression sky high the only remedy which isn't a good one I could think of was use a thick head gasket or double up on them.
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Old 04-09-2005, 07:27 PM
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I would stick to the LA 340 heads with those pistons. They stick .016 above the deck and unless you run a gasket with a compressed thickness of about .060" your gonna have piston to head clearance problems.

Your going to need the RPM heads made specifically for 340s though. They have the clearance for those pistons.
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Old 04-09-2005, 08:53 PM
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Default LA Edelbrock RPM

They Ede's RPMs are for hi-compression 340's the Magnum's small chamber would give you to much static compression, unless you could figure your dynamic compression to keep you out of detonation. The right cam might allow you to get away with that much static compression.

http://kb-silvolite.com/calc.php?action=comp Try this web page

Remember in the early eighty's Crower had a line of cams that could be run with higher compression engines. When there were still a few still in the wrecking yards, that could then use the current pump gas without detonating the rod bearings right out of the engine...

Better to be for warned and informed than just guessing
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Old 04-09-2005, 10:21 PM
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Quote:
Originally Posted by hellhound
does anyone have anything to say about how durable the Eddi heads are....after kicking around a few ideas it might be easier to just go with them than porting the iron 302s and finding 1.7 ratio rockers. Any problem with using the eddies for a daily driver?
The Edel. heads are not a problem for everyday use. Just install them correctly, no rushing or cutting corners.
You'll be fine.
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