These heads are dated from 9-18-70 and 10-21-70. They are casting number 3946074, 118cc combustion chambers. Are these what they call "D-Ports"?

I am thinking about using these on my motor next winter whenever I go the 8-71 blower route. With some porting I would imagine these heads will flow quite nicely (I imagine they flow half decent without porting).

What do you guys think? This will be cheaper than getting the Edelbrock heads.


[Modified by bence13_33, 5:42 PM 2/20/2003]

 

I believe you call those oval ports.
John

 

John:
No, an oval port would refer to intake ports...the ports in the picture are the exhaust ports. Some of the L88/ZL1 aluminum heads have what they call "D-Ports" the "D-Port" refers to the shape of the exhaust port.


[Modified by bence13_33, 5:57 PM 2/20/2003]

 

It doesn't look like it. I have "D" ports on my L98 and you can certainly see that the exhaust had the "D" shape.

 

those are L-88/ZL-1/LS6/LS7 2.19/1.88valved 118cc chamber open design aluminium round exhaust port heads.

those are nice heads, I wouldn't attack them w/ the die grinder unless you really know what you are doing. Chances are you will make them flow less. I've seen that happen (flowbench proven), the work looked very nice but the bench proved they flowed less, basically destroying a good set of heads.


[Modified by Twin_Turbo, 6:46 PM 2/20/2003]

 

OOOPS :banghead: :banghead: I didn't look at your picture too long. As soon as I opened the post my Wife called me for dinner...............
John :bb

 

These are the exact heads I have, but they are iron. They can support 800hp without a problem.

:cheers:

 

Corey:
Do you by chance have any flow numbers or anything? So in stock form they can support 800 horsepower. My goal is 750-800 horsepower with the 8-71 blower.

 

These heads are 325CFM and 119CC, I'm not sure of the flow numbers. But I do know these heads are used on the iron rectangle port 502's and 454 H.O.

 

Yes those are so called D-port heads. The exhaust port was originally round and flowed terrible. People figured out that if you welded up the floor of the port so it looked like a D the flow was much better. The later heads almost always have a D port of some sort it is that much better. Chev. never made an iron head with those ports but every after maket head builder does.

 

These heads are D port with 325cc intakes . They can be taken out to 340cc and with a normal aspirated engine that would be a mistake. No bottom end torque but with a 8-71 they will have lots of low end torque. Flow changes with boost. These heads full ported will probably not flow over 325cfm in the intake and 205 on the exhaust and exhaust is where power is made.
Sorry have to go, Class calls

 

I'm back. Anyway with say .625 lift these heads normally aspirated would flow say 310 cfm maximum so horsepower is Flow x .254 or .257 x 8 cylinders. So in theory these head could support 310 x .254 x 8 = 629 horse. But intake loss if 20% would reduce these flow number dramatically. And intake flow losses of 20% is normal. If it approaches 25% get a new intake. This does not take into account exhaust flow. These heads with limited 205 exhaust are meant for very ammature competion.

 

Here is some info I found from another thread.

Description Open Chamber LS-6 & LS-7 Service Head, 425hp, approx $700
Casting # 6272990 (equiv 14096188, 6260482, 366250, 3965774)
intake / exh valves: 2.19" / 1.88"
Material Cast Iron
Combustion Chamber Open 118cc
Intake Runner 325cc
Intake Port Type Rectangular
Exhaust Port Type Square
Flow: valve lift /Intake /Exhaust
.05 32 24
.10 69 53
.20 125 103
.30 183 140
.40 233 176
.50 264 198
.60 292 204
.70 - 207

 

Shane, sorry for the confusion, I guess I couldn't really tell by the picture they are "D" ports. They certainly have better heads than these on the market, they are proven to make good numbers, I've seen it with my own eyes.

:cheers:

 

Good information Corey 68. You basically backed up what I just said. My numbers come off a flow bench. I have access to one and sometimes like to play. Your exhaust went only from 204 at .600 to 207 at .700. It does not warrant the extra lift and valve train wear to go from .600 to .700 just for 3 cfm.
The intake flow is down from what I ran 292 vs 32? I think 7 but can't remember for sure but it was 325-327 for ported stock 325cc intakes.
The intake is the big killer. Yes 20% reduction in flow is normal and some poor intakes take 25%. We flow heads without a intake but this is what really kills the heads.
A head say that flows 300cfm is good for 609 horse but put an intake that takes away 20% of it's flow and you are down to 240 cfm and only capable of 487 horse. And this doesn't take into account the carb restriction.
Anyone who really wanted to get serious can buy their own flow meter. A good accurate one is about $650-$700 AMERican with very good accuracy. All you need besides in a good shop vac. I use a professional flow bench but apparantly these new flow meters are extremely accurate.
I don't spend much time developing a combination anymore since I went with the 8-71 blower. Everything changes and I have finally found more horsepower then I can put to the pavement. I am going slower then I did 10 years ago with alot less horsepower but at that time it was all useable to the tune of 10.28 on the street.

 

Great Info :cheers:

Norval, so what single intake would you suggest to accompany these heads? I have a L-88 hood, so I have the added clearance, and I'm running the CC 294 duration and .650 lift.

:cheers:


[Modified by Corey 68, 8:04 PM 2/21/2003]

 

The first intake I tried with heads like these was the stock high rise LS6 intake with heavy porting and the center divider cut down like the L88's . I also run a cheater nitrous system with this setup and with a 850 double pumper and 2 inch drop base element under the stock 75 hood. I really like that intake setup. Later I switched to a victor junior, same carb, same nitrous system and the car slowed down.
If I was going back to a combination I would go back to the old heavily modified dual plane LS6 intake.
I still have both intakes on the shelf and someday I might put them to use.
Both have built in cheater nitrous systems. No plates just the spray bars mounting right into the intakes with the cheater solenoids mounted very close, within a few inches so they hit quick.

 

Out of curiousity how good is the stock aluminum 454 H.O./ 502 H.O. dual plane intake? I'm going to run it to break in the engine to I find a single plane that will work best. I have a friend that is going to get me a killer deal of hos N.O.S. 2 stage system. I'm just trying to find an intake that will breathe to 6,500rpms and put out good numbers. This will be a weekend car at the most.

:cheers:

 

Those dated aluminum BB heads may be worth $$$$$$ to a 'restorer'.
Try checking with the Chevelle and Camaro sites; I bet you can sell them for more than a new set of bigger port heads.
my 2c.
:yesnod: :chevy :chevy :yesnod:

 

Dunno, are they the same ports as these? :confused: