stlregal

I am in the process of buying some Mondello Aluminum heads with 7111 RPM Edelbrock Performer Manifold that will be ported to match... My current setup is a 350 olds casting 395558 2 .30 over...stock dish pistons (the guy that build my motor didn't tell me that I had could have bought flat head pistons to bump up my compression).....3711 Edelbrock intake manifold,non-posi rear-end 2.76 gears,HEI distributor,stock stall converter,and a 350TH transmission with shift kit....I quess my question is will these heads bump my compression up... or do I have to take my engine apart again and buy heads? Can the heads be ported to improve performace on my current setup?

coppercutlass

Those heads will have to be machined to get a decent cc to make compression i think they come with 77cc chambers. What size is the dish this could be a big deciding factor also what cc is the dish.

stlregal

I believe they 64cc 6a heads... I fould this online...

.In 1970, the 350's had 9.0 CR with a 64cc head. In 1971 the CR dropped to 8.2 with the same cc. This was accomplished with a "dish" in the piston. This carried over until 1973 when the CR dropped again to 8.0 BUT with a 79cc head. This means that the dish was gone but the large chambers in the head caused a further drop in CR. Going from the stock 79cc heads to the earlier 64cc will bring the CR up to around 9.2 but with the thicker head gaskets than stock you can figure on about 9.0:1 "true" CR. This will definately wake up that motor and with a cam, 4bbl, and dual exhaust you should get 250 HP net easily as long as the bottom end is in good shape

captjim

If stock replacement pistons were used (23 cc dish and 1.595 p/h) and a .040 gasket, with 68 cc heads Cr is 7.8 to 1. Even if you milled the heck out of the heads, there would not be enough compression to use any cam at all, negating the value of the heads. There is just no working around those pistons.

stlregal

Wow the guy told me @ Mondello that it would bump uo my compression and and get me to aleast 375hp....

coppercutlass

The 6 heads where 70 is it's low compression its a 14 cc dish if the block is 70 I think they went to a 23 cc dish in 71. I would invest in better pistons and re work the 6 heads .

cutlassefi

X2, Mondello just wanted to sell you a set of heads.
Even if you had the 7cc forged piston, a .020 deck with a 77cc Edlebrock head your compression would only be about 8.6:1. With those heads I'd run 10.0:1 no problem.
I have a guy who bought an 11K motor from Mondello. It was supposed to be a roller 455, it was a flat tappet 425. Then they redid it, and made it an 11:1 455. Now he has to use octane boost.
Steer clear of Mondellos, it's amazing they're still in business. Jmo

If you want to better the performance, change the gear first, or;

you can make 350+ with the #6 heads or get the flat tops (Probe makes one that is .030 over and would work well) and the Edelbrock heads. Mill em a little and you'll make upwards of 400 with the right combo, but a better gear would help a bunch.

Again jmo.

stlregal

ok thanks... this really helped me out... now I know what I need to do

captjim

I can barely decipher this post. You did read where he stated that it was bored with replacement pistons??

coppercutlass

x2 with cutlassefi from all the stories i hear mondello isn't even an option for me . If those pistons are .030 with stock dish they are 23 cc if not bigger. sorry cptjim when i read stock i thought he said stock pistons lol read right past the .030 . The best bang for the buck is the speed pro rebuild kit it has every thing new bearings, oil pump, flat top pistons etc. etc. for around 600 bucks cant beat that. The advantage of the probes over the speed pro's are the strength but the speed pros get the job done from most street strip setups from what i have seen.

Run to Rund

You need much more cam and rear gears to justify those heads. More compression would help too. Some have posted that mechanical fuel pumps won't fit on small blocks with Edelbrock heads. The big intake ports are a poor choice for a mild engine; there is a reason Olds used smaller intake ports on the small blocks. When they designed the W31, they tried big block heads and decided on big block 2" intakes and 1.63" exhaust valves in small block heads instead.

coppercutlass

I was writing my fixed mistake as you posted this lol sorry .

captjim

Please explain how/why the Probes are stronger.

coppercutlass

Probe pistons are just better . lighter better ring pack more moder design sorry i chose stronger for lack of better words to describe a products quality. There is nothing wrong with the speed pro's but the probes are just better i think from what i have seen. That is speaking from a design stand point the speed pro's will withstand high hp but the advantage of the probes comes with a price. Im not a pro but i know i would choose the probes over the speed pros if money allowed but for now im happy building what i build with what i can .

stlregal

I do have a
Comp Cam High #42-229-4 Gross Valve Lift .456 Duration@ .050 Lobe Lift .2860 in there..

z11375ss

Those heads will not fit without machining them to fit the fuel pump. OR, you could put in an electric one. I had a nightmarish sequence of events to get them to work on my small block and ended up with about 350 hp. Not worth the time and effort.
I found the original thread. Read it and weep. I did. Hope this helps you make the right decision to stay away from these heads.
This even has some advice from good 'ol Norm. Wow! It's an old one!
https://classicoldsmobile.com/forums...-way-pump.html

stlregal

Wow they didnt even tell me that

cutlassefi

Yes you'll need to use an electric pump. I would shoot for 10.0:1 with any aluminum head.
With the right cam and combination it will make a good, more efficient package. Erson did a roller for guy in Va. with Edlebrock heads on his 350, .030 over, RPM intake, he gave them the cam spec to do for him, 226/234 at .050, .544 lift on a 112, 9.8:1 compression, 700 Holley.
I would've used different lobes and/or stagger but he still got 350hp and 400lbft of torque, and it's very pump gas friendly, could run 89.

Probe pistons are made from 2618 alloy, mostly race stuff but more and more mainstream everyday. But I've been using the KB Icon 2618 stuff in all my latest 455 builds, really don't prefer to use anything else. That alloy is strong, light and retains good rigidity for great ring seal, plus uses a more efficient 1/16,1/16 ring pack. And they really don't need the extra clreance they used to in the past. I install the KB's in 455's with .0035 piston to wall, that's less than than those Speed Pro L2323 slugs require.

Jmo.

droptopron

I remember hearing someoplace that a change to aluminum heads is the equiv of a drop in one point in compression (ie from 10:1 to 9:1) because of the way they dissipate heat. Is there any truth to that? What is the science behind it?

coppercutlass

Does kb make slugs for tlhe sbo ????

cutlassefi

Aluminum is less dense than iron, retains less heat, yes better heat dissipation. Plus the Edelbrock head has a better combustion chamber/plug location.

CC, no KB doesn't currently make any 2618 stuff for SBO. But I talked to them at the PRI, they've had requests and are considering a few possibilites.

stlregal

so the Aluminum heads will work with out me having to pulll the engine apart and ordering flathead pistons?..And I now have to buy a electric fuel pump to make it work? are these heads worth it, or am I getting myself into something that I will regret dollar wise?

droptopron

But does any of changes in heat exchange have the same effect as lowering compression?

coppercutlass

The aluminum heads aren't worth it . Trust me buy flat tops and invest in your 6 heads and you will make more hp with that alone thab trying to buy the aluminum heads and trying to make them work.

coppercutlass

The best way I can put it is money wise. Those heads from mondello I'm guessing are over 2k . For 1000 you can have big valves put into your heads a little bowl work etc. It's what it roughly cost me. Let's say for 500 you buy new pistons and to remove and replace and balance should be under well under 500 . Doing this alone will bump compression and improve your stock heads and it should be capable of 400 hp I think with the right cam carb etc jmo .

cutlassefi

They don't lower compression apples to apples. The aluminum increases the tolerance to higher compression/lower octane.
But with that said, it's always been believed that all else being equal, at anything less than 10.0:1 an iron headed motor will make the same or more power as an aluminum headed one. But still the eselbtock heads flow better than a sbo head and have a better combustion chamber. Based on what youve said you will probably have to change your pistons no matter what head you use.

stlregal

so i guess I should just pull the motor and replace the heads... probe heads
edelbrock 600cfm switch to 750 holley
3711 perfomer w/ egr switch to 7111 edelbrock RPM perfomer
stock stall switch to 2200 hughes stall
stock rearend switch to 3:23 eaton posi
HEI switch to MSD 6al, balster coil, disti no vac adv.
Comp Cam High Gross Valve Lift .456 Duration@ .050 Lobe Lift .2860 switch to a cam with .520 lift?

droptopron

You are a bit all over the place. What are you trying to accomplish & how will you use the car? Is this a daily driver?

stlregal

yes its a daily driver i just want to be around aleast 375hp

380 Racer

hee hee.......he said eselbtock......Sorry Mark I couldn't resist.

stlregal

is this not a good setup?

cutlassefi

Are you o.k. Nick? Been hitting the NO2 maybe? That's what I get for typing on my iphone without my glasses!

If you're looking for 375 crankshaft hp then I think most would agree with this combo;
#6 heads, 2.00/1.625 valves, some bowl work, crossovers filled, divider welded
performer RPM intake, 670cfm or better Carb
Minimum 9.5:1 compression
.500+ lift cam, without the expense of the Edelbrock heads you could do a nice roller, more lift with less duration, broad power curve, no need to worry about oils, retain good drivability.
Good distributor and ignition, doesn't have to be MSD, get one with a vacuum advance
3.42 gear, 2400 or so converter.
1 3/4 headers

Jmo

coppercutlass

I think you should do some more research. There is alot of guys here with some great combos that are tried and true. My set currently goes like this I have a 350 with stock bore flat tops. and stock deck height. I have 6 heads with 2.072 and 1.63 ex. valves with some bowl work and they where milled .024 with a .040 head gasket i have roughly 9.75 to 1 compression. Im running prw roller tip rockers . Im running a comp 280h cam. Full length headers an x pipe and hooker aero chamber mufflers. with a 2200 stall and th400 with 3.73 gears it ran 13.32 at 103 in the quarter mile. That was with a converter that was too tight going to a 2800 stall. and a bigger carb i ran a 600 cfm going to a 650 double pumper. It ran good with the 600 no issues but i think im leaving some on the table with it.I also ran a hei from proform out the box . With it running how it did the hp calculator says im making 380 at the fly. could be better with a new converter. The hp calculator is just to give a rough estimate on the hp by the way.