RHS or EDDY

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Sportman

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I am going to replace the heads on my 408 in a few weeks and don't want to make a mistake. The motor now has a set of big valved J heads cc'd @71 they have had some port work on them but I do not know the extent. My motor is now 9.2:1 comp, and a street only motor.

Specs:

1974 360 bored .030
Wiseco -20 pistons
Eagle crank 4"
MP 248 - 484 Hyd cam (installed 4* advanced)
Edelbrock Air Gap intake
edelbrock 600 cfm (changing to 750-800)
4 speed
3:55 sure grip
28" tires

I want the car to run on Pump gas. Looking for advice on what heads to install for a healthy street machine. It runs OK now but just does not set me back the way I would like. I am thinking compression increase might help?????

Thanks
 
Ok from what I have read the Eddys will ned work before you should run them, even brand new ones are gonna have to have a good valve job done. If you like aluminum they have great potential but need work to produce really good power. If you go with the RHS heads contact Brian from IMM engines OU812 is handle here. He sells the RHS heads that he has done the work on for around $1600 I believe and they will out flow a Eddy out of the box. I think he can even make them whatever size chamber you want as well for your pump gas need. He does port work and your wallet is his limit. He isn't very expensive in my eyes either, plus he will answer any question you might ever think up. He's a good guy.
 
i would keep the ported J heads on a street machine. heads are really expensive and it sounds like you would be swapping a ported j for an as cast la-x yours should flow better at this point. plus don't you have to pay extra for the 2.02/1.60 valves in the rhs heads? i say leave the heads alone and work on compression and maybe more duration on your cam so you are taking in more air
 
If buying from IMM the heads are fully built with 2.02 intakes and a Comp beehive spring set-up. Those ported j heads will have to have had quite a bit of work done to match the IMM package - they flow 270cfm or so at .550".
 
Y ou need to know what the j heads flow now, otherwise in a ootb scenario ...you might end up with the same flow and only more money spent.
The closed chamber will bump up th comp a bit, but probably not much more or beyond the limit of what the current heads can deal with on pump gas.

I've run 9.7 - 10.1 comp with open chamber j's w/no issue and on pump gas 91

the other thing is....that cam is not a good choice for the 408 or much else anymore, and if you go some 1300 heads that flow more 'but at a higher lift'...you wasting ur time only lifting the valve .480....and when in reality you might actually see a whole .450-.460 lift due to lifter angle/push rod angularity.

either go with a bigger cam, or flow and port what you have to work better.
You can get the same big low lift numbers from a j head as you can an rhs head
remember most of these replacement heads are just that..
 
Exactly what OW&CG said.

I know it may seem like money thrown out the window, but take your J heads and put them on a flow bench to find out exactly where you stand. For a small price, adding more porting (If need be) to the J head may be better for the perameters your engine is in, what your doing in general, driving perameters.

3,55's and a 28 inch tire does not sound like a strip machine to me.
 
Between the two choices you asked about...

Buy the RHS head IMM does and don't look back!
 
With alot of people buying up the RHS heads,I wonder if there will be some Eddy heads coming up for sale in the future?(cheap)Hmm.:idea1:
 
pettybludart said:
With alot of people buying up the RHS heads,I wonder if there will be some Eddy heads coming up for sale in the future?(cheap)Hmm.:idea1:
Click to expand...

I doubt it. Most of my customers are starting from scratch or replacing stock heads. It's counterproductive to sell eddy heads for our heads in most instances.
For 500.00 you can get good power out of the eddy heads, and for 1200.00 you'll SMOKE the RHS heads unless they are fully ported, in which case they should still make more power due to the pushrod pinch area able to be larger.

Brian
 
Now I am really baffled....???? I think I will try a carb first, then heads and cam??? Still not sure what heads to go with.
 
Sportsman, how much work was done to them?
Can you have them flowed?
While the Edel. and RHS head can and will outflow the J head, you allready have port work done to them. Considering your not racing the engine, but simply driving the street, a cheaper route could very well be some more port work done the the J head. This would and should work out cheaper than purchasing ethier RHS or an Edel. head, and having work done to ethhier to make work. Which would include, really everything from start to finish. Valve guide, seat, port work, and how much to work well ontop of 400+ cubes?
 
Maybe he can quench the engine and run more viable compression, unlike the J heads, unless he has the quench dome pistons installed already (my guess unlikely)...

Another guess, porting will run 500-700 before any other residual items, seats/guides/surfacing/etc. Not to mention the heads become crack prone when you start to approach the RHS numbers.

Lots of different opinions... pick your parts, pay your money.
 
I really dont think he'll have a problem with the J heads cracking.

Since he all ready has them in use, he'll just need to put the same head back on the smae bank it came off of. Unless the heads have worn since it was rebuilt, then new guides wont be needed. But we'll assume this needs to be done. Just as a worst case and hope for better.
Same deal withthe valve seats. There less likely to have been worn out. Since he has the heads, it should work out cheaper. The big question is, what they flow now and what he can use in terms of cfm in the heads.
 
I know the J heads had been redone when I purchased them. Everything was new and the person I purchased them from said there had been $1,200 put into them, he bought them from the guy that done the work. I could see where the porting had been done but not sure to what extent, it looked as if all the runners were smooth. Beyond that I don't know about. They only have about 500 miles since I put them on
 
600 cfm, LOL. OK, typo! LOL!

Mad, At what cost?
 
Mad Dart said:
I have an awesome set of RHS Heads they flow 600CFM+ @ .550, I ain't bullshittin!
Click to expand...
600+ @ .550.....damn a cnc ported Stage V Millennium Hemi head from For Hemis Only flows 435 @.550.....
 
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