Hi all, just a quick question regarding big block heads. I am currently running the Edelbrock Performer RPM package (carb, intake, and cam) on my 402. I was planning on finishing the engine off with their Performer RPM heads. Does anyone have these heads on their 396/402 that can maybe shed some light on if they are any good or should I opt for Brodix or Trick Flows? I am currently running 396 stock closed chamber oval ports from a '67 L35. Edelbrock claims with my current setup, adding their heads will net 50-75HP. Does this sound realistic? Also, I was planning on adding roller rockers, how much could I expect to gain there as well? Thanks in advance.

The intake is good,,,their carbs and cams leave something to be desired. The heads you have will go well into the 10's, you might want to look to Lunati or Comp or Crane or Isky for a better cam choice and I think that I'd use a HP750 if you're after performance. I think Edelbrock makes a good street carburetor,but if its performance you want, I'd choose Holley. I wonder why they'd tell you 50-75hp with the swap :rolleyes:

What will your compression ratio be before and after the swap?

Rod

Which RPM head? It looks like they list the oval and big port both as RPM heads now.

I'm running the oval port edelbrock heads. For what I'm doing, they worked well. Took 66 lbs off the front of the car.

Here's a dyno graph before and after. Before are stock LS5 heads (open chamber 2.07 valves) and a comp 270H (219/229 @050) hydraulic flat tappet. After is with the delbrock heads and a hydraulic roller, 224/230 @050.

http://www.corvetteforum.net/c3/zwede/71corvette/drivetrain/dyno10.gif

So I gained about 70 rwhp, but don't know how much was cam and how much was heads.

CR right now is 9.5:1, with the help of Desktop dyno, I'm estimating the CR to drop down to 8.5:1. I was planning to use the RPM oval port heads which have a 110cc chamber volume vs. the 96.4 my L35 closed chambers have.

Edelbrock has a set with 100cc chanbers but I don`t know anything about them or if they will work with your pistons.

You should consider looking into the 100CC version. I know that guys have used them on 454 motors with .100 domes, I would think they would fit with the 402 motor .180 domes but couldn't get a straight answer on this when I had looked into it a while back.

Edit _ SS, you beat me to it.

I do know the 100CC heads are angle milled so most of the cut is done off the plug side. I am inclined to think that with a normal deck ht of .015 or so and a .039 - .041 head gasket, their should be edequate clearance on a std 402 piston motor.

I think the 100cc are Performer and not RPMs, also I think they are designed for TBI only...

BTW, I'm using Speed Pro Forged pistons with a .182 dome, basically a similar profile to the stock L34/L35 piston. These have a lower CR, stock piston was about 10.25:1.

personaly it would be a waste of money to go to the heads if your looking at reducing weight or just have that kinda money to blow then do it. the bbc heads are very well designed heads that have since the start have been able to run very well into the 10's with very minor porting and bigger valves.

i wouod take the money and spend it on a roller cam set up and better carb.......if most would take the time to truely dial in there combos you would see gains of 50 hp just in that alone. specially for the folks who just put parts on and expect them to work right out of the box.

jmo

Originally posted by Nvr2Fast:
I think the 100cc are Performer and not RPMs, also I think they are designed for TBI only... Actually, here's the deal on the 100 cc edelbrock heads:

I have the 100 cc heads and they turned out to be regular performer rpm heads that they angle milled. This actually turned out to improve flow and it tilted the valves slightly (chevy high performance found these to flow marginally better in their testing). They have a casting number of 6045 which is the perf rpm. Also, for the BBC, the performer and performer rpm is the same casting and everything is identical. Only difference is the performer has a drilled passage for exhaust crossover.

I hear that recently the performer tbi 100cc head has a new partnumber so they may have changed the casting, but atleast the older ones were just angle milled performer rpms.

IMO, the Edelbrock RPM heads are TOO big for a street 396-402.

A properly set of OEM ovals (bowl porting, 2.19-1.88 valves) will flow as much (if not a little more) than a the RPM "Rovals" with a smaller port.
Rovals=290cc. OEM ovals=255-260cc.

Spend your money on a set of 215, 063 or 290 "semi-open" ovals, install a solid flat tappet cam and a HP750 Holley. You'll make more power for about the same amount of money spent. ;)

...what Darren said.
What are your performance goals? Even if you never plan on going to the track,what ET would want it to run?
My 454 costs me $2500 to build,and I'm using stock closed chamber heads with 2.06/1.72 valves

I personally think the compression loss alone would not be worth it.
Why not remove your heads and have the higger valves installed and do a little clean up in the chambers..valves are cheap..$100 or so,followed by cutting the seats for the bigger valves,etc.
Total cost might be about $800 or so.
You'd get the HP/breathing benefits of the larger valves,and keep your compression up,and cost half the money too.

Well, I think you guys have me convinced...After messing with desktop dyno, and listening to all the great comments, I think I might just stick with my stock heads and do a little porting and upgrade the valve size...I have casting 3917215 which has 2.06/1.72s, I'll probably upgrade to 2.19/1.88...
Basically, I would like to get my car in the mid-upper 12s...
Do you guys think I can hack these numbers retaining my Performer 750 carb?
Also, I contemplated a roller cam, I know some of you fringe upon Edelbrock cams, but they just came out with an RPM roller for BBs. I would think changing to a roller valve train would probably net me about 25hp or so.

Nvr2fast..I just had my 396 built up using a set of -063 oval port heads. Had the shop install the 2.19/1.88 valves, springs, etc. and roller rockers. Performer RPM intake, Holley HP750 carb, (+.060" overbore), Lunati 02005 hydraulic cam..9.25:1 compression..went 425HP on the dyno, and 440 ft-lb peak. I had been looking at the Edelbrock heads as well and decided against it, these head mods cost me some $$ for the machine work, but I am pretty happy with the results.

That sure sounds like a powerful 396 JTM60. Post some track times when the weather gets better. I'd sure like to know.

Hey JTM, if you don't mind me asking, around how much did they charge for the head work?

Nvr2fast,I have the same heads ( 3917215) on my 454...

mr 4 speed, did you do any porting on your heads or valve size increases? Also, are you using roller rockers or stamped?

Ed,my heads are totally stock..no porting,2.06/1.72 valves,and stock stamped rockers.
Best MPH was 103.9 and thats with no tuning.Out of the box 750 vacuum secondary Holley (other than the 2nd from lightest secondary spring) and a used $50 Accel HEI

I know it's comparing apples to oranges, but what kind of power are you putting out of that 454? Do you think mid to upper 12s is a realistic goal with some head work and possibly changing out the vavletrain(i.e. roller cam and roller rockers)?

I'm running a 3.31 posi, but hell, for you to break into the 12s with 2.56s, you did something right...lol

Ed,best guess using the typical formulas is about 440-450 HP at the crank..my car weighs about 4000 lbs.On a dyno,a duplicate of my motor with 2.19/1.88 valves made 490 HP/525 ft/lbs torque
Roller rockers aren't worth anything ET wise,but the proper cam will get you there.A solid cam in the 240-245ish duration @ .050 along with big valves is what it would take IMHO
Mid-high 12's with an M20/3.31's might be possible,but realistically,low 13's would probably be where its at,and you will need sticky tires too,especially with a 4 speed
The 12.99 was a best in absolute perfect condtions in regards to traction/weather.
Car was usually good for a 13.20-13.30 average with some wheelspin.
FYI,my username is confusing in regards to my current ride...the black cherry 70 is a TH400 car.

Everyone keeps telling me to ditch the carb too (Performer 750), I gotta say it's been a good carb for me thus far, mind you, the car gets driven almost daily during the warmer months.

graemlins/thumbsup.gif

Gotcha mr auto :D

BTW, what part of CT are you in?
Is that pic in your profile from Musclepalooza? I know that's LVD.

Ed,I'm in Hamden..right outside New Haven..about and 1.5 hour ride from LI/the city
That picture was at the LVD Nostalgia Drags

not too far from me...

..if you ever need any help,give me a shout via the board or email mr.4speed@lycos.com
..the garage is always open for beers too ;)

where is Red Hook btw?

Do you know where Rhinebeck, NY is? Next village north.
I'm about 45 min south of LVD

I just wanted to add that it`s my understanding that the bigger valves will not work with the stock style piston. Since the closed oval port motors used small valves, the pistons don`t have the reliefs for the big valves or high lift cams.

Let me say that I do not know this from experience and was told this by 2 machine shops when I was building a 396 years ago. I ended up just selling the motor due to lack of funds. I`m sure someone here can tell you one way or another if there will be clearance issues.

[QUOTE]Originally posted by mr 4 speed:
[QB] On a dyno,a duplicate of my motor with 2.19/1.88 valves made 490 HP/525 ft/lbs torque

mr 4 speed, can you tell me what heads were used and any other head mods? Thanks

Anthony,they where 290 castings with 2.19/1.84 valves and mild porting.
Its fellow TCer "cmt454"

...FYI,stock 396 325 HP motor (small dome) with #063 heads and big valves..with the 2nd design L88 cam..no piston/valve issues.
...needed 4.88's :D

Chris is correct, 290 castings with some bowl blending and some ushrouding of the valves. Nothing real involved. Peak torque was 531ft.lbs@3900 rpms. I am changing my entire combo. Brian recommended a new solid cam for me, which I have. Its a Comp XE 273/279, 236/242@.050 .570in and .580 ex. for the lift. Its ground on a 107 LSA and 107 ICL. I now have an 8" BTE 4000 stall converter and 4.10 rear gears. It should be interesting at the track next year :D

Pvt. Cowboy..I am just getting it all together in the car now..probably wont get it to the track until mid '05 or so. It should be interesting. Running a 3.31 so I am not expecting any earth shattering times.

Looks like the labor was around $1000.

Thanks Cris. I thought your motor would be perfect for me 70 but I think I`ll upgrade to bigger valves and do a little bowl work to the heads. Also, thanks for the valve clearance tip. I was tols by the 2 machine shops around here that it would be a problem but obviously they were wrong since people are doing it without problems.

Sorry guys, I miscalculated CR on my engine after going back and re-running the numbers using the specs provided for the piston, I came up with 10.01:1, which is exactly what the guys at Summitt said as well. I kept thinking 9.5:1 seemed awfully low for a stock type replacement domed piston when the orig. CR from factory was 10.25:1. Anyway, sorry for the confusion, this has also helped me a little as far as what direction I want to go for added performance...

First though, I would like to see numbers on the Dyno and the 1320' before I make any modifications...

Thanks for all the input too...