340 Heads Flow Rate

[erik70rt]

I just purchased a complete '73 340.  I know it has the J heads with the 1.88 intake valves.  If I port them, can they flow as well as or better than 340 heads with the 2.02 intake valves?

I don't want to purchase another set of heads if I don't need to.  I plan on building another 416 stroker. 

Thanks!

[Shane Kelley]

Just put 2.02 valves in them and you will have the same head.

[erik70rt]

What modifications (if any) need to be done to make the 2.02 valve fit? 

[1 Wild R/T]

When the machinist does the valve job he cuts the seat oversize & typically does a blend cut... However when he does that he will cut through the hardened seats so you should consider adding hardened seats... $$$$ Honestly I'd grab a seat of 90-94 360 swirl port heads... They'll need less work, they'll make more power & they are pretty cheap...

[RUNCHARGER]

J's and X's are the same. You can get a real nice valve job when going from 1.88's to 2.02's as the valves won't be sunk and after a blend they will be better than an X. Look for exhaust valve recession though, lay a straight edge across the valve tips to give you an idea what you have, they should be all even.

[Chryco Psycho]

I agree , the 87-92 308 swirl casting will make a Lot more power than a X or J  head

[erik70rt]

When the machinist does the valve job he cuts the seat oversize & typically does a blend cut... However when he does that he will cut through the hardened seats so you should consider adding hardened seats... $$$$ Honestly I'd grab a seat of 90-94 360 swirl port heads... They'll need less work, they'll make more power & they are pretty cheap...

Do you know the part number for these?  I was doing a little research last night and am finding parts like MP5007950 are discontinued.

[RUNCHARGER]

Casting # ends in 308. Not sure but I think they were available late 80's until 92 on 360''s.

[Chryco Psycho]

87-92 308 casting , last of the LA heads with rocker shafts

[erik70rt]

Anyone ever use these heads from Indy?

http://www.indyheads.com/images/maxlaxnewproductlinK.pdf

[gzig5]

Anyone ever use these heads from Indy?

http://www.indyheads.com/images/maxlaxnewproductlinK.pdf

No personal experience but I've read a couple good stories about those heads and the results.  On the other hand, I've read and heard a LOT of bad stories about Indy quality control and customer service.  They make some neat stuff but make your engine builder deal with them.

With the porting work on them you could be into a set of aluminum Edelbrock or ProMaxx heads and be ahead of the game, IMO.  Depends on what your goals are.  The new TrickFlow heads probably have the most potential and are ready to go out of the box.

[erik70rt]

I got the engine home and pulled the valve covers to check the casting numbers.  They end in 586.  Were these used on a '73 340?  I haven't pulled them off yet to check the valves.  I do see dual springs for the valve springs.  Are dual springs correct for a stock 340 in '73?

[gzig5]

I don't see that number in these lists, but that doesn't mean they are all inclusive.  Could you be mis-reading the number?

https://www.enginelabs.com/engine-tech/a-guide-to-mopar-v8-cylinder-head-and-block-casting-numbers/

http://www.mymopar.com/headcastnumb.htm

[bennydodge]

587 heads were used on 73 340's. Never heard of 586's?? Factory springs should be single w/damper. The 340 spring was stiffer and ran a little more pressure than the 318/360 spring. Basically a 360 head with stiffer springs.

[kawahonda]

Anyone ever use these heads from Indy?

http://www.indyheads.com/images/maxlaxnewproductlinK.pdf

No personal experience but I've read a couple good stories about those heads and the results.  On the other hand, I've read and heard a LOT of bad stories about Indy quality control and customer service.  They make some neat stuff but make your engine builder deal with them in the cost delta. Alum heads, if money is no object, are better, but honestly, there are many serious ported iron contended that cost several hundred less that will flow better than the RPM heads will. And chasing down such small weight savings on an ebody isn't worth it for most street applications...

With the porting work on them you could be into a set of aluminum Edelbrock or ProMaxx heads and be ahead of the game, IMO.  Depends on what your goals are.  The new TrickFlow heads probably have the most potential and are ready to go out of the box.

I don't really agree.

Running an aluminum head is GENERALLY more money in machining over EQ or Indy-X heads as I've been learning. We're talking in the several hundred range, if not more. You don't simply take RPM heads and bolt them up out of the box. Compare out of box-ported iron heads and it's pretty clear that iron heads have an advantage for $/horsepower.

For example, Indy-X heads are $1,100 w/ 2.02 intake valves, ready to be bolted out of box and flow highest at 266-267 CFM @ .550-.600 lift. You cannot say the same about RPM heads. RPM heads in stock form flow highest at 251 CFM @ .600 lift.

As always, the one thing that stands true with time, it's up to your reputable builder to choose what has worked with their experience. Mine loves the EQ heads for the $ per performance....I'm told the aluminum heads would be $1000 more for my specific application and simply "not worth it." I'd rather not spend an extra $1,000 that I won't get back...

My point is that aluminum heads cost more IN THE END. It's not "A little more". It's A LOT more. Don't look at summit price and think that's it. Don't think that RPM heads will magically outflow all else just because they are aluminum, because it's quite the contrary. They flow good, but Indy-X heads flow better out of box with much less $$$. EQ heads are dirt dawg cheap, and a simple stage 1 porting job will make them crush RPM heads according to my builder.

Can the RPM heads flow better? Sure...but like I'm saying...ADD THE COSTS UP and determine if that little more is worth it for your build.  What you THOUGHT was only $1,500 but turned out to be $3,000. Was it worth it?