69CutlassAlex

What kind of general Horse Power increase will I see switching from 73 "J" heads to 69 Big Valve "C" heads?

442rocketdave

Its noticeable and if you fill the heat risers and mill off the exhaust and match the intake and exhaust you will see a significant difference. I have C heads and E heads and there is a pretty big difference especially with a larger cam and headers. The big valve C heads flow much better especially when you do mild porting job on them. In fact the C heads will out flow F W30 heads, W30 D heads have only72cc combustion chambers and will defenitely increase power, they also flow like the big valve C heads. But alot of people will say go aluminum and thats if you got a grand you dont need. A little clean up work and a good 3 angle valve job and you will be happy!!

cutlassefi

Not entirely true.
Most big block heads flow about the same, same size valves to same size valves, (except for J's). And of course they'll all flow better with a port job, Geez.
But if you are keeping the stock camshaft etc I'd be surprised if it made more than a 25hp difference.

IMO the old irons aren't worth the money invested unless you're trying to keep the original look.

442rocketdave

I took my E-heads C-heads F- heads and D- heads to Bud Crow racing he is a friend of mine and we spent the entire weekend flow testing the heads the C heads outflowed the other heads but not by much especially the F and D heads but there was a larger flow difference between the E heads and C big valve heads. At lansing there used to be a joke that the Lansing factory was built entirely out of E heads. I think your right that it will only make a 25 hp difference but milling the exhaust and pluging the heat passage makes 25+ hp difference.

69CutlassAlex

I installed a bigger cam and lifters about 2 years ago. Going from 73 J's to 69 Big Valve C's. And my engine most definately isnt stock looking. While I do appreciate the purists among us, I put a lot of money into the engine for performance and looks.

69CutlassAlex

Ive also added headers, new intake manifold, Carb, etc...

442rocketdave

Alex what cam do you have and intake a carb? just wondering what combo you have and what transmission and rear end? I like your car I have a 69 W30 I have had for 32 years and if your doing a valve job on those C heads I would either weld up the center exhaust or just cut them .100 and plug up the heat cross overs those two mods will net you 40hp+ then matching the intake and exhaust gaskets another 15hp. Not hard to do or very expensive and most machine shops do valve jobs ie. standard for 150 and performance for 200 if they do the job right like setting the spring pressure and height and a good 3 angle valve job you got another 30+hp. The total combo can net you 80hp+! Having the heads modified mildy will work really well with the Intake, cam and headers to make your car wake up!

69CutlassAlex

Im working with an Edelbrock 455 Performer, Edelbrock Cam and lifter set(.472 lift), and Edelbrock 750 cfm Electric Choke and 3 Speed 400 auto tranny.

cutlassefi

All while still using a stock cam? Do you have proof of all this because I don't believe it for a second.

Case in point, a recent 455 build;
850 Proform
RPM Air gap
10:0.1
Ga heads welded and filled, 3 angle valve job
Hyd roller, 231/234@.050, .565/.555 lift

It made 413hp on 91 pump gas. So you're saying it would've only made 350 (I didn't port match anything) if I didn't do the other stuff?
That's the stupidest thing I've ever heard. You're talking out of your butt again.

69CutlassAlex

Look at the post above yours. Im not using many stock components.

cutlassefi

I don't care, you're not going to net the types of gains he said, period. That's absurd.

69CutlassAlex

Yeah I dont know,thats why Im asking. I was just pointing out that I wasnt using a stock cam, like you asked.

442rocketdave

W:hat are you talkiing about!!! I never said anything about 350 hp thats dollars for your average valve job 150 dollars standard or 200 for a competition job and 85 hp I have got out of changing from small valve E heads STOCK then having the big valve C heads 3 angle valve job cc'd, cross over welded up and the exhaust shaved and match the ports! Of course the cam and intake helped along with the headers.

cutlassefi

Oh Jesus Christ.
Now you're saying you got 85 more Hp when you did all that plus a cam and header change as well?
That I believe but that's NOT what you said to begin with.
Christ, say what you mean and mean what you say. You're all over the board, again.

I'm now thoroughly convinced that most days you don't know whether you're coming or going.

442rocketdave

Mark Maybe I am not clear on that but He already stated he had a cam change and intake and carb and headers, that why the C heads with the mods would make that hp not with a stock intake stock carb and stock manifolds. One works with the other and the combo is how you make the power. without the manifold,carb, headers he would only make 45 to 50 if that.