Edelbrock RPM Head compatability issues.

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trigger_andy

trigger_andy

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Ok I have a 1970 340 that I plan on getting rebuilt soon. I found a pair of Edelbrock RPM heads on the UK eBay site and won them. Only now do I realise that the 340 Heads(#60179) differ slightly from the 318/360 Heads(#60779) The 340 I have will be getting bored 30th and have the correct pistons to keep the 10.5-1 comp ratio.

1, Will these heads be OK to use on the 340? Or would I be better off building the late 70's 360 I have and fitting the heads to that? I really want to keep the 340 though and build that (I have a 6 pack set up to go with it too!)

2, I dont have any of the Rocker gear, ie arms and shafts for the Heads. Would a set off of a 318 be up to the job or would I be better off investing in a roller tiped gear? (Cash is tight)

Thanks in advance guys!
 
The 60179 heads have slightly larger chambers - and were introduced because Edelbrock failed to anticipate how many guys were out there still running factory pistons that protruded slightly above the deck and this created some clearance issues on the original offerings which were P/N 6077 - which have now become P/N 60779. Unless I somehow missed it, you don't really state which P/N you won on e-bag. In either case, as long as you build a true flat top engine you'll have no clearance issues and I think there's only about 2 cc's of combustion chamber volume difference between the two part numbers anyway.

Stamped steel rockers don't know if they're off of a 340 or a 318 - all the same. Run them until you can pony up for some good ones.

Ray
 
Sounds good, I think I would go with a Ross forged flat top piston and try to stay under 10.5 on todays gas, and for $$ savings see if you can find a set of used adjustable 273 rockers.

Back compression, also depends on cam, gearing etc in car. I know you can get buy with a little more compression with these heads, and I think the smaller chambers will raise you over stock pistons.. So be carefull not to go to high for a street car.. Do the bore size, chamber size with the pistons to figure the real compression for static ratios. PS how much and what cam are you gonna use?

You could also if money permits get a set of adjustable set screws from Isky or crane for the rockers (273 type), and I think new chrome mopar shafts are like $60 a pair.

I am thinking with non stock heads and depending on cam etc you may need to go adjustable. But if you do this you also need the cup style push rods too.

Should be a nice power plant sounds good!
 
Wow! I really appreciate the fast and informative responce guys!

Ok, I realise I was not to clear on what heads I bought. I bought the #60779 Heads. The pistons I bought are the Federal Mogul Flat Top Forged 10.5-1cr,with 2 relief's. (L2316F-30.) Will these protrude over the top of the Block?
As the heads I have are two cc's smaller than the #60179's will I have compression issues and be unable to run on pump gas?

As for the cam well I have not desided yet but I'm looking for something fairly mild. I'll not be taking the Duster up the strip much if at all, well maybe a few runs to see what she'll do. It has a 8 1/4 open with gay gears, Im guessing 2.7** odd. I'll be running a 340 Quadrojet untill I get the six pack restored.

Any idea's what hp/torque it will make and what she could do up the 1/4? Its a 727 column shift.
 
Here is a compression ratio calculator:

http://kb-silvolite.com/calc.php?action=comp

What you have bought is the closed chamber version of the edelbrock heads which is definitely better then the 340 version because you can build an engine with a quench combustion chamber. A quench combustion chamber will greatly resist detonation allowing you to run on pump gas with good compression. What you want to do is have pistons that are zero deck and then run a .039" inch head gasket for good quench.

In some cases the positive deck pistons can be milled but I'd call the piston manufacturer or a reputable machine shop to determine if that is possible with what you have.

If you can't mill the pistons and they are above the deck like a stock 340 pistons then thicker head gaskets will give you the piston to head clearance to run those heads.
 
Thanks 340! I've saved the Comp Calc. Cheers!So all is not lost. I got the heads at a great price and I could not afford to but another set. Is there a way to find out if the pistons I have will protude outta the block or will they deffo stick out?
 
Whichever head you have, figure out piston/head clearance and buy the appropriate gasket.

Try to zero deck the pistons, then the head relief won't matter. If they stick out slightly, buy a thicker head gasket if you are going for a quench set up.
 
trigger_andy said:
Is there a way to find out if the pistons I have will protude outta the block or will they deffo stick out?
Click to expand...

I would start by finding the "Compression Height" of the pistons. That is the distance between the center of the wrist pin and the top of the piston. If it has a stock 340 Compression Height it will stick out of the block. How much is a different story because block Deck Heights vary from one engine to another even within the same year engine block. The factory was sloppy when it comes to those specs.
 
trigger_andy said:
Thanks 340! I've saved the Comp Calc. Cheers!So all is not lost. I got the heads at a great price and I could not afford to but another set. Is there a way to find out if the pistons I have will protude outta the block or will they deffo stick out?
Click to expand...

From what I've notice so far, the flat top pistons that protrude from the block normally have a camfer of about .060 around the top edge. The ones that don't protrude are squared to the side.
 
340sFastback said:
I would start by finding the "Compression Height" of the pistons. That is the distance between the center of the wrist pin and the top of the piston. If it has a stock 340 Compression Height it will stick out of the block. How much is a different story because block Deck Heights vary from one engine to another even within the same year engine block. The factory was sloppy when it comes to those specs.
Click to expand...

I agree! The factory machining was all over the place. Not only did the block height vary from block to block, but they vary from end-to-end on the same block. I've seen them be .018" off from end-to-end.

If the L2316F piston has not changed in 15 years, you can have them cut down in a lathe. I cut about .020" or .030" off the tops of mine when I built my 340 in 1993 using L2316F pistons.

In order to accurately figure this all out, you need to have your block line honed, square decked, bored & honed (don't forget the torque plate!), grind the crank (or just polish it if it's OK), resize the rods, then do a trial assembly to see how high up the pistons stick out of the block. Then, and only then, can you proceed to cut the pistons.

Doing it any other way is a "duct tape and bailing wire" approach, IMHO.
 
The shop that is building my 414 did the following:

Deck Height = (stroke / 2) + rod length + compression height

Then they lined honed the block and decked the block to the Deck Height computed above. They didn't need to do any mocking up to figure it out. My deck height is 9.588" which was what KB recommended for the KB745 pistons I am using.
 
Thanks guys, loadsa great info there. Bang goes my cheap rebuild! Sounds like there is much more to this than I thought. Looks like I'm well outta my depth,again. I hope the shop I have doing the build can handle this kinda work. I'm in the UK and working on US V8's is not really there thing....
 
To save you a lot of trouble just send those heads to me. I'll find a home for them. LOL
 
lilcuda said:
If the L2316F piston has not changed in 15 years, you can have them cut down in a lathe. I cut about .020" or .030" off the tops of mine when I built my 340 in 1993 using L2316F pistons.
Click to expand...

Thanks for this advice. Can anyone comment further on weither these Pistons can still be milled down? And if so by how much?

Cheers.
 
If a swap in pistons are in order, ask them for there zero deck offering. I just can't think of the number right now. But they have a nice hyper-U piston with coated skirts. (anit friction coating)
 
A couple other options would be to run Cometic gaskets that can be bought in several different thicknesses so when you figure out how much the pistons stick out of the hole add that to .040 and get a gasket that thick. That'll get you at an ideal quench for best power and detonation resistance.

The other options is what a buddy of mine did. His pistons stuck out .020 and he added Mopar .020 shims under his Fel-pro head gaskets and that put him at .040 quench. Again ideal.

The Cometic gaskets are expensive (I think about $130 US dollars per set) but their the best and their reusable. Going the route of the shims is cheaper and even though the Fel-pro is a real good gasket it's not nearly as good as a Cometic.

BTW: What part of the U.K. are you in? My mum's from England and I have lots of family over there. Hope to be visiting again in the next couple yrs.
 
Cheers Fishy! So your mate had the same kinda set up as me? The Pistons I have stick out 20th too. So if I ran a 60th Gasket it would solve all my problems? It seems a little to good to be true, but I have little to no knowledge of these things? Would I have to get special push rod's to match or anything.
 
P rods should be order the like amount longer.
At .060 longer, you have run out of the lifters adjustabilty.
 
If you run .060" head gaskets that would work fine. I'd bolt the heads on with the gaskets and get a push rod measuring tool and then order the correct length push rod. The measuring tool is a push rod whose length can be adjusted. Also make sure the rocker arm to valve stem geometry is correct.
 
rumblefish360 said:
P rods should be order the like amount longer.
At .060 longer, you have run out of the lifters adjustabilty.
Click to expand...


Ah, its getting confusing again,lol! I've seen .054'' gaskets for sale. Is that within the Adjustable range. Some people reccon a .060th gasket would work but others not. I guess if I had a combination of shaving the pistons .020'' and running a .040'' Gasket would be a good compramise? I cant aford to blow another $400-500 on another set of Pistons but if I have to I guss I have too.
 
If you can shave .020" off the pistons safely then run the .039" head gasket. The other solution is to run the pistons as is with a .060" head gasket. Either way its best to measure for push rods.
 
The wonderful thing about aluminum heads is they pull heat from the combustion chamber allowing you to run mor compression without predetonation damage.
 
As was said, the heads you bought have the smaller closed chamber, rather thna the large open chamber of the 60179 head. The psitons you bought are the old school forged pistons that were designed to be above the deck at the blueprint height. But, never have I seen a virgin block that was anywhere near blueprint. In most cases they are anywhere from .020-.040 taller. If your shop has modern machines, they can do what was also said... they align hone to gegt the main bore exactly placed, then square deck the surface to whatever height you need. If they are milling it until it's flat on an oldschool miller, you may have issues. Those pistons are very heavy, and a bit thicker than they need to be. I would see where your block is in terms of height, then mill the domes of the pistons whatever you need to get them to zero deck, or flush with the deck surface. Don't spend on pricey gaskets that need special surface finishes... Just run the std Felpro blue at .043, and you're good to go. It will be pump (US) fuel friendly even with a conservative cam.
 
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