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Old 04-19-2004, 10:21 PM
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BBC heads

hi,wow,first let me say,what a great site!
i am looking for some info on heads,really on the fence about choosing my heads.the most popular seem to be aluminum heads.i seen some edelbrock performer plus aluminums that sure look sweet.and what a great match since i used the performer plus cam,valve springs,performer plus intake,1407 750 carb and true roller cam all from edelbrock!
but to tell the truth,i'm afraid of them,2 grand is a huge hunk a change.what if my car overheats,i don't get them torqued right,the heads warp,crack,i strip bolt holes... oh the horror!
currently using stock heads,casting number ,336781 oval port open chamber,118cc chamber 256/114cc ports,think like 1.88 int and 2.25 exh.i had these heads reworked (not polished,basic rebuild)and had to install special springs per edelbrock and put in perfect circle something because the umbrellas wouldn't fit over the something.(see why i had someone else do the heads? )
if i don't upgrade my heads is it a fact that i will never realize the true potential of my efforts in rebulding this motor?maybe a better question would be,would it be like a night and day noticeable difference with the eddy heads?
is there an alternative?geez 2 thousand clams would sure buy alot of upgrades!
i'm asking mainly because i think i should be getting a lot more power out of this combo than i am getting,granted it's in a heavy car,65 belair.but shouldn't i be close to or above 500hp?this thing i would think,should scream...

Thanks for any advice anyone can give me!

here is my current setup:

1976 454 casting 361959
bored .30 over
edelbrock performer plus cam 7162
edelbrock performer plus intake 7161
edelbrock carb 750cfm 1407
speed-pro .280 domed hyper-t pistons
edelbrock true roller timing chain set,set to 0
stock cast iron oval port heads casting # 336781,with edelbrock recommended springs,
roller tipped rockers
standard hei distributer/accel super coil
timing currently at 38 total
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Old 04-20-2004, 06:53 AM
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if your on a budget, keep the 781s
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Old 04-20-2004, 11:08 AM
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The 781 is a good casting head. 500 hp should not be a problem with that motor. I would look into how much it would cost to get the ports and combustion chambers cleaned up, and use the heads you have. I would think that if you did a little porting a polishing on the 781's, they would probably outperform the as cast edelbrocks and you would have alot less money in them. Another thing to consider is that the edelbrock heads have a 290 intake port and the 781's have around 250. At low lift(.100-.400) the stock 781's flow close to the Edelbrocks. Above that the edelbrocks take off, but I see that your cam only has 560 lift anyway. What good is a head that flows really well at .600-.800 lift if your cam only has .560? The smaller ports in the 781's will allow for much greater port velocity at the lift and RPM range that you will be running which will make for a more responsive motor.

Good luck
Adam

Last edited by firestone; 04-20-2004 at 11:23 AM.
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Old 04-20-2004, 04:11 PM
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One other option, is go get a set of the new AFR oval port BBC heads. They are $1800 a set assembeled with CNC ported combustion chambers. They have a 265cc runner, which would match your motor very well, and even with a smaller runner, they signifigantly outflow the Edelbrock heads. These heads would be your best overall bet. The only bad thing about them is that they are not available yet, so you would have to wait. Another thing about them is that they have a .300 inch raised exhaust port, so a stock header may not fit. They also offer a Fully CNC ported oval port head, but it has a 290 cc runner which may be getting a little big for your application, and they are around $2300.

Adam
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Old 04-20-2004, 07:45 PM
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hey all thanks for the advice.i believe i will go ahead and have these heads ported and polished at my local speed shop.i was really surprised and happy to hear this.

now on another note...

Adam,
Quote:
but I see that your cam only has 560 lift anyway.
i understand the point you were making in reference to the edy heads but would you say that my cam is pretty conservative?i tried to accomplish a build with good low end out of the hole torque.
i remember putting it together and actually worrying endlessly that i had so much lift that the valves would hit the pistons. now im wondering if maybe i should have researched more.this was my first build and i really liked the total package,matched parts thing edelbrock had going on.i guess what i was really thinking,was that it felt safe
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Old 04-20-2004, 07:55 PM
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I know of several people with racing engines making upwards of 600-650 HP N/A with those 781 heads with minor porting work. GM did a great job of making these heads right from the factory.
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Old 04-20-2004, 09:50 PM
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I am pretty happy with the 781 heads I am running. I did a port blend mostly on the exhaust ports concentrating my efforts on the valve bowl and the short side radius. I also did a little bit of a blend in behind the intake valve. With a fairly conservative 268h and flatop pistons it is a really torquey setup. You are right, with the 268h (.520" lift) cam it had a mile of room to clear the piston valve reliefs. I had .160" clearance with a .039" head gasket.( I did also shave the heads and deck the block .050" total though.)There is a lot of literature available on porting, especially these heads. Sorry do not have any web links, but maybe somebody else does.
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Old 04-21-2004, 12:54 PM
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I wasen't saying that the cam you were looking at was too small, I think it is just about right for your setup. I was just saying that if you compare a set of ported 781 heads to a set of unported Edelbrock heads the 781s will probably flow better at .550 lift and below. Above that the Edlebrocks would probably take off. My point was that since the 781's will probably flow at least as well as the edelbrocks until .550 lift, and your cam has .560 lift, there may not be any performance improvement going to the edelbrocks over a set of ported 781's in your case. If you had a bigger cam (something around .650-700 lift) and were running the motor to 7000+ RPM, then the edelbrocks would be the better choice, but in a lower RPM application the ported 781's will probably perform better.

Adam
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Old 04-21-2004, 02:25 PM
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If you took those 781's right now and did a basic bowl blend they would make the same power as the Edelbrocks.The RPM heads should only be about $1700 assembled and ready to run,and they will save you about 75# of weight.As for durability,the aluminum heads are way better.The 781's are prone to cracking between the valves when the engine runs hot and has big valves in it,and the Edelbrock heads have much thicker decks and ports and have better valve seats.In reality even in the very matter of being overheated or torqued down wrong the aluminum heads are way stronger then the GM iron heads,and if you did manage to break one they can be much more easily repaired.If you didnt already have a bunch of work in the 781's I would ay the Edelbrock heads would be a very good upgrade,but at the point you are at now,I would run the 781's and get my moneys worth out of them.ood luck.
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