I'm not sure why there's this negative stuff about the Edelbrock RPM heads,
yes there is probably certainly better aluminum "racing heads" out there,
depends on what you need & possibly a bad casting here & there maybe too,
really depends on what your end goal is, what your experiences actually are,
but for "bang for the buck", middle of the road price range,
IMO the RPM's are pretty damn good... I've had nothing but good luck...
I haven't heard very many negative complaints about them,
especially when it came to the castings quality...
But that's just in my little world, others may have had different experiences...
I had tried the Alum. Stealth heads that were professionally ported,
by the same guy {Mark Lowe},
that barely could break the 10.00 barrier,
mid 9.90's only about a 1/10th better than my Iron heads,
most of that was because of weight saving over the iron heads only...
By the way it took allot more port work, parts were inferior to the Eddy's also,
just to make them "as good"
{slightly better after allot of porting & parts changes}
as the Eddy RPM's were stock/std OOTB/Flow rates...
anyway back on subject at hand the RPM's
I don't have dyno #'s, I rarely ever dyno-ed any of my combos...
I have real world track #'s mostly on a 90*+ to 100* days
at a couple of test & tune days at Sacramento Raceway,
that car in this thread was only equipped with a 4pt roll bar &
frame connectors & added torque boxes,
couldn't really run it in races it was too fast for the safety equipment it had,
I wasn't willing or maybe too stubborn to back off either,
it was really merely my street/strip car/toy, not my racecar... Anyway
In my opinion, the Eddy RPM's in either open 88cc or closed 84cc,
if they were properly set up, checked & cleaned up,
{I don't & wont run anyone's heads right Out of the Box}
I would change to the proper springs, retainers, locks,
to match your needs & camshaft etc. {if necessary}
IMO they are a great choice, for middle of the road type builds,
many engine builders will say the same thing too...
Now please don't quote me this is going off my memory,
not meant to deceive anyone if a few facts were off,
inadvertent & not intended as such...
Just the near 70#'s in weight saving alone, will improve performance,
less weight on the front end, less wear on brakes & shocks,
better cooling/heat dissipation {albeit marginal},
but cool down times were far quicker, less heat soak, same everything else,
I went from running @ 190*-200*- high of 210* {with Iron heads},
to never really over 190* ever with the new alum. heads
The RPM's better flame travel & more complete burn with angle plugs
& heart shaped combustion chamber designs
{some certain cheaper brands header clearance issues},
the RPMs have stock intake, exhaust port & rocker shaft locations,
but improved port design {see IQ52's many posts} over the factory 906
& other OE Iron heads...
There's nothing wrong with the heavy OE Iron 906 heads,
if ported "properly", but stock there's no comparison,
even to the OOTB Eddy RPMS,
unless they {the 906's} are ported they are still heavy & 40 years old
{they can be made to be pretty damn good}
& the Eddy heads can be made to flow allot more than what they are OOTB...
Some 40+cfm in my case, more in some other cases
I had a set of very good 906's fully & professionally ported buy Mark Lowe
{may he rest in peace}
IIRC they flowed in the 315cfm range, 3520# 68 RR 479ci/6bbl
ran low 10.00's best passes, thru the mufflers, we tried for comparison sake,
some of the then relatively new at the time alum. Eddy 929 84cc heads...
I had tried the Stealths & had issues {wont go into that here}
basically the RPM's Out of the Box flow #'s & 2.14 & 1.81 valves,
might have been 10-12cfm better flow than OOTB #'s
by a little cleaning up in the pockets, short side radius clean up, there was
a slight lip under the valves in the pockets, where it was machined/cut from the factory
& we went to a 50* back cut on the valve job IIRC {this was about 10 years ago now}
we just changed the valve springs, retainers, locks & added lash caps
& Smith bros. 3/8" & proper length pushrods
{on the Stealth's you need to grind a bunch in the push rod passage area outside &
next to the intake ports, if you use 1.6:1 rocker &/or 3/8" push rods},
{different set up than the pushrods that were on the 906's too, differ length}
& my 1.6:1 Crane Super Gold rollers, that were used on all my heads,
I just changed stuff to match my camshaft & for proper rocker geometry...
The car 60ft went from 1.33 to 1.29 IIRC, front end lift/weight transfer,
was far better too,
the 330ft times were where it really was better,
made up most all the improvement in my et, in the 1st 660ft,
the head design was way better in the low to upper midrange, from 3500-5500
partially because of better spark, intake & exhausts port floor design
{that's what Mark Said & I saw anyway}
the et went from 10.0's {10.02 -10.04's} @ 129 best
{about 127mph average normally},
to 9.77 @ a best of 135mph best
after a jet change had to go up 6 jet sizes,
larger squirters #31's IIRC & the pink accel. pump cam with 50cc accel. pump
on the center carb,
she was really wanting more allot more fuel with the RPM's at the hit & down low
WO throttle it was OK {had {Promaxx adj. jets in the outboards},
with the only other change, was the cleaned up Eddy 929 heads & valve springs etc...
The car hit the tire way harder,
had to do some CalTracs, shock adj. & air pressure adj. too,
partially because of the weight taken off the front of the car...
It had even more in it, but didn't want to veer to far, from the comparison,
it needed a gear change {less gear ratio}
& converter change eventually {more converter},
but I was running decent & was going to be testing N20 after that point
& the comparison were way different...
Using the RPM's, way better than the iron-heads,
hands down night & day better...
I went the best of 8.58 @ 156mph with a single dominator & 300 shot, but that's
a whole other ball game, not the best way to compare parts,
unless the same parts were used with the same tune up etc.,
I sold the car not very long after that,
I have a very similar build now today too, less cam & less port work etc.
very happy with the parts choices, even if some are kind of outdated now...
That's a real world experience,
I did a similar comparison when I did the Stealth heads too,
I didn't have anywhere near as good of results,
But the new Stealth's are better than the original design too...
Much like a copy of the Iron 906's except Alum. & in many ways, even OOTB flow rates...
But IMO still nothing like the RPM's, but the Stealth's also have straight plugs
& look allot more like OE style cast iron heads when they're painted,
if that's a necessity...
sorry for the rambling, I'd suggest listening to IQ52 he's the cylinder-head expert
anything he says is like gold or gospel in my mind,
not very many people, a very select few, I would say that about
{my buddy departed friend/professional head porter, Mark Lowe was also one of them also}
doesn't mean the OE style 906 Iron heads are bad "at all"
it's just not what my personal choice would be or
what I'd run in a performance application,
especially if it's properly set up...
That's what great, different people have different likes & preferences,
even different experiences...
The world would be boring as hell, if we all liked the same thing,
if we all built the same things...
I love all the new tech, all the better parts & welcome change with open eyes,
some have been great experiences & some not so much...
To each their own, I'm not saying my stuff or my opinion is any better,
or that someone else's opinions & experiences are wrong,
it's just what I have done & had success with...
It's far more than just the engine or just which heads,
it's about the whole combo, how everything works together...
that's my $0.02 cents
