[ap72]

Originally Posted by OMARS67

I didn't want a smaller cam because I hated running out of power. Yeah normal street was great but freeway was not impressive. Maybe it was my combo at the time. But .560lift on a 454 wasn't very impressive. Fun on the street but didn't pack a punch maybe a jab

As for this statement, a bigger cam is NOT going to help you. That cam is actually too big for your heads, a smaller one would better match your combo- or better heads to match your current cam and wants.

No matter how much you port them old BBC and SBC heads are NOT competitive with even the most mild aftermarket heads. I use a lot of factory heads because I'm a cheap ***, but I know that even a set of mildly worked offshore heads can stomp all over my fully done factory stuff.

Get into LS territory and some of the reworked factory stuff is SOMEWHAT competitive with aftermarket castings, but in the end even there the aftermarket has a nice margin.

[ap72]

Originally Posted by hcompton

You always want to shoot for lift in the 25%-35% of valve size. So .5 is just about right for a 2 inch valve. Yours are almost .2 bigger so .6 is perfect. .7 would still not be out of range. Less and the valve is a restriction in the intake track.

With small chevy the valve size of .6 is all you ever need with 2.02 valves for the most part. But big chevy can have a much larger valve and will need the lift to work correctly. lower lift will still run but it will not get effecient like it should at the cams VE rpm range. If that makes since. Sorry i know i left about three books worth of info out of that one. LOL

You're assuming the port isn't a restriction, and it also depends a lot on your throat size and valve seat.

NONETHELESS, L/D=.25 is in general a good target to hit with a good head on a hot street engine.

[hcompton]

Originally Posted by ap72

You're assuming the port isn't a restriction, and it also depends a lot on your throat size and valve seat.

NONETHELESS, L/D=.25 is in general a good target to hit with a good head on a hot street engine.

Not all bbc heads are bad flowing heads. Bbc was made years after the small block and chevy addressed a lot of the flow issues the small block had with the larger boore big blocks.

I agree its not worth the money or time to port small block heads. Aftermarket heads are so cheap. But maybe not bad idea with bbc heads since there are no real cheap options. Might be worth the cash to get them cut by a pro. Depends if you got someone that can port at a good price.

Larger ports do not grant blessed more air/fuel into the cylinder. Most of the time the opposite is true.

Throat size? Throttle plate? Rare to get turbulence in the carb do to high flow rate. Usally that can be seen with a vacum guage at wot. Single and dual plane intakes really remove most of the issues that could result in engines that have very long tuned single runner intakes. In the big chevy were only talking about single runner for a few inches. Well past the carb.

Valve seat? You mean valve size as measured at the seat? Or the seat insert itself. It should be cut back if bored to larger valve if it came from the factory with larger valves then it is already taken care of. If you talking about bad machine work. I would hope that is not going to be an issue.

The reason you rasie the valve to the 25% of lift in most cases the valve is considered to be out of the head. Or the head will flow the same as if the valve was removed from the head minus stem diameter. This is always a goal in any engine from an engine with 3000rpm tq peak up to 7000 rpm peak. You will get your best performance from the engine with proper lift ratio. Now with small chevy it is not always needed because the engine make the same power with a few more points of duration but in big block it plays a larger effect.

[OMARS67]

Originally Posted by vinniekq2

My tires are 27 1/2 inches tall. I changed my gears because I had 2.73 gears and a stock 4 speed.I gave the trans to a local kid. When I changed the gears I put a new posi,new half shafts,new springs so the car would not squat,all new bushings,cut the driveshaft and put in a TKO 600,and a scattershield etc. I only use a 3.50 gear for road racing, for me 4.11s would make first gear useless.

While you stuff the parts in your car better add the roll bar.That car will easily go better than 11.50s

im not sure what gears came stock in 73. i put 17 with a 32 inch tire in the rear. they were on my impala that i sold. it had 4.11 funny thing is the 383 with the 295 duration cam responded very well to the change in tire. it was a bit sluggish with the 15s.

[OMARS67]

Originally Posted by ap72

I was saying that you can't look at the duration as you would with a hydraulic flat tappet cam. For a hyd flat cam that .050" duration is pretty damn big for a street car, BUT when you factor in the lash on a solid cam and the more agressive lobes of a roller cam that duration really isn't that big of a deal. The drivability will compare with a hyd flat cam with duration in the 230's and as we all know- that's pretty typical for a mild "hot street" 454.

I'm not saying it's an RV cam but it's not as rowdy as you might think. It's about 20-30 degrees short of a full solid roller race cam.

yeah i didnt think that duration was very wild for the street, the lift maybe

[cdminter59]

Originally Posted by hcompton

Its a big block that cam is not that big. For a small block maybe but for big block its just normal big not high rpm.

@cdminter59 2800 - 7000 rpm range with a 454. What?? no not that high rpm and the big block will make some good power down low. Did you miss where he said its a 454 bored 60 over. that is a large piston it will take a pretty big cam.

It will be pretty tame since the car is very light and the motor will make alot of tq down low it will pull away from lights gently enough. Engine probably wont even notice the car is connected. But have you thought about an auto. th700r4 would be a much better choice than the muncie. If its numbers matching then pull it and set it aside. The big block will break it for sure at some point if you drive it long enough. Also the auto will be a half second faster in the quarter. Maybe more since you will loose tracktion alot with the big block and heavy clutch.

hcompton, I stated the operating rpms of the Lunati camshaft he has. Solid Roller Street/Strip 2800 - 7000 249/255 .663"/.680" 110/106 40110733. I said he would need a low enough rear end that when cruising at 55-60 mph he would be taching 3000-3500 rpms.

[OMARS67]

Originally Posted by hcompton

Not all bbc heads are bad flowing heads. Bbc was made years after the small block and chevy addressed a lot of the flow issues the small block had with the larger boore big blocks.

I agree its not worth the money or time to port small block heads. Aftermarket heads are so cheap. But maybe not bad idea with bbc heads since there are no real cheap options. Might be worth the cash to get them cut by a pro. Depends if you got someone that can port at a good price.

Larger ports do not grant blessed more air/fuel into the cylinder. Most of the time the opposite is true.

Throat size? Throttle plate? Rare to get turbulence in the carb do to high flow rate. Usally that can be seen with a vacum guage at wot. Single and dual plane intakes really remove most of the issues that could result in engines that have very long tuned single runner intakes. In the big chevy were only talking about single runner for a few inches. Well past the carb.

Valve seat? You mean valve size as measured at the seat? Or the seat insert itself. It should be cut back if bored to larger valve if it came from the factory with larger valves then it is already taken care of. If you talking about bad machine work. I would hope that is not going to be an issue.

The reason you rasie the valve to the 25% of lift in most cases the valve is considered to be out of the head. Or the head will flow the same as if the valve was removed from the head minus stem diameter. This is always a goal in any engine from an engine with 3000rpm tq peak up to 7000 rpm peak. You will get your best performance from the engine with proper lift ratio. Now with small chevy it is not always needed because the engine make the same power with a few more points of duration but in big block it plays a larger effect.

whats the differences between 49 and 781 to other heads?? like 148. i have a set of 049 and 148. the 148 are 396 heads with a 110cc ported and fitted with 2.19 valves. were my 049 heads are stock no porting and 2.08 valve.and a huge 119cc. i measured with a caliper the inside diameter of the intake runner and found the 148 to be bigger. without flowing them i wouldnt know which has better velocity, wich is what i care about. and i really dont see any difference in design.

[ap72]

If you want velocity (which isn't always a good thing) then you may want to look into methods of fillin gyour ports with epoxy. Stock BBC ports (more so than SBC ports) can benefit from adding some material in the right places. Its very important to do it properly though and use the right material as you don't want it coming loose and going into your cylinder.

[hcompton]

Originally Posted by OMARS67

whats the differences between 49 and 781 to other heads?? like 148. i have a set of 049 and 148. the 148 are 396 heads with a 110cc ported and fitted with 2.19 valves. were my 049 heads are stock no porting and 2.08 valve.and a huge 119cc. i measured with a caliper the inside diameter of the intake runner and found the 148 to be bigger. without flowing them i wouldnt know which has better velocity, wich is what i care about. and i really dont see any difference in design.

Most ppl like the 049s as far as round port goes. Rectangle port is also popular option but usally not as important as it may seem.

049 are the larger as cast factory castings. 240cc intakes with 119cc exhuast. They will port well and flow well. 781 have the better shaped ports and flow very good as well. with 225cc intake volume. sometimes better for a low rpm build.

148 are 225cc intakes as well. But exhuast port volume is smaller than on 049.

Here is a look at some stock and after market heads tested. But the stock casting is ported by a pro.
Oval Port Big-Block Chevy Cylinder Heads - The Big O - Super Chevy Magazine

[hcompton]

Originally Posted by ap72

If you want velocity (which isn't always a good thing) then you may want to look into methods of fillin gyour ports with epoxy. Stock BBC ports (more so than SBC ports) can benefit from adding some material in the right places. Its very important to do it properly though and use the right material as you don't want it coming loose and going into your cylinder.

expoxy ports are for race engines only and it does fall out and go thru the motor usally doesnt do any damage but still not good.

velocity is always good until you get to the point where turbulence starts. At about .7 of mach speed of the air fuel charge. up until that point you want to speed up the intake speed as much as possible.

BBC usally you can go smaller ports if the shape is good so picking the good casting numbers is very important. also the exhuast ports are usally small on BBC heads and usally require more work than sbc heads.

[OMARS67]

do cast iron heads gain compression because of heat??? i was told to keep the compression 9:1 were aluminum i can go to 10:1 i understand the heat issue with iron vs aluminum. i just wanna know if the motor is 9:1 will i gain compression when the car reaches operating temp. or is it just that 10:1 will start to detonate because of 91 octane

[OMARS67]

completed my build. went for a 496 stroker kit from scat (492 only bore .30) and used the same soild roller cam in question. i bought some brodix BB-2 305 R ports. i upgraded the tranny to a m21. its fantastic!!! i am going to play with the rear gearing. but deffinetly not sluggish!!

[KA67_72]

When I read your title, my first thought was you can never have enough motor. After reading the post, I think what you have will be more than adequate. It may be grumpy and annoying at times but worth it. Link us to some video when you have it together.

Kevin

[vinniekq2]

I second the request for a video.we need more videos here.

[OMARS67]

oh vinnie weres the trust!!! hahaha but i will get you your video. im still workin out the details oil leaks, hood replacment, etc.