Hi all
I have RHS 67cc 194/150 with 170cc intake runner installed on my '73 L-48 with stock 4 brow dish pistons, Edelbrock performer intake
I am not pleased with the performance due to the compression ratio.

I have a chance to grab a pair of Dart (World Products Sportsman II) cast iron heads... 64cc 202/160 with 200 intake runner.

Questions are, is the 200cc runner going to be a problem?
Also curious about pushrod length.

Both my RHS heads and the Dart heads are almost new and were run with hyd cam and roller tip rockers.
Will the 64cc heads be a worthwile upgrade over the 67cc heads
I dont have much time to wait or I will lose out on the Dart heads

Thanks all
Bob

 

from what I know (or think I do) the darts would be a good deal, although 200 is a little high on a street motor, but it might be better than 170

 

The intake runner is the part I dont understand.
I really dont have time to research it because I need to grab them in a few hours or someone else will.

For $300 complete I may go pick them up anyhow.

 

I am using the WP Sportsman II heads on my 383. I agree that the 200cc runners may be a little large for a street 350. It depends on what cam profile you are going to use. A larger intake runner on a street 350 is going to see better top end and be a little worse on low end that a 170 or 180. If you have too small of a cam, the cam and the heads will be working on the opposite RPM range (not good for performance).

The 3cc difference will not make much of a difference in the CR (about .3). However, if you switch to the Fel-Pro 1094 head gasket (.015), you will have about 9.2:1 with the 67cc and 9.5:1 with the 64cc.

If the RHS heads flow well, you will probably get a little better low end power with them. I know that the WP heads flow pretty good, but I am not familiar with the RHS heads.

If you want to move up on the RPM range, go with the WP.

 

Buy them, I use that exact same head on 383 and I used them when I was 350 c.i. too. They ran great on my 350.

 

I've decided to pass on the heads
I have 3.08 gears with a M20 and I rarely see 5,000 RPM.

Theres really no way I'm going to get the performance that I am looking for without new pistons. It's a shame though.... $300 for basically new, complete World heads is a great deal

Thanks all
Bob

 

I would at least pick them up and flip them if you are not going to use them. When I bought mine, I bought them on eBay and they rarely go for under $500.00 for an assembled pair.

 

I thought about that but for me to drive 80 miles round trip, sell them, ship them and all the other .... It's really not worth it.

 

Bob,
Just estimating your compression. If I assume 67 cc heads, -5 cc for the piston valve reliefs, a .039" Fel Pro head gasket with a diameter of 4.1", standard deck height of .025" in the hole, I come up with 9.5:1.

Now if you swap out head gaskets to a Fel Pro 1015 at .015" thick you jump to 10:1. If I use .027 for a Victor Reinz head gasket I end up with 9.76:1. This is of course the above assumptions are correct. Your compression doesn't look too bad.

You have a Crane Z cam listed, which one is it? Perhaps it is too big or not degreed correctly or matched to your compression ratio.
In this case, I think a shorter duration cam ground on an early ICL will be a good match.

 

You don't post all your numbers with respect to the "estimated" C.R. but I would say you are in that area, the 9.5:1/9.7:1 again depending on the "actual" numbers. I'm assuming a "flat-top" piston here with 4
"eyebrows", like a TRW L2256F style!

For "openers" those RHS heads will out-perform the Worlds on your setup, providing you have a 350" unit. The cam choice is most critical on these types of builds.

Second, I would go out on a limb here and state:I don't believe you will ever get the "seat-of-the-pants" feeling you're looking for with a low-compression (9.2/9.5) 350 SB AND 3.08 gears. Those "small" SB's just don't produce enough "torque" to turn those rear gears! At least not to the point of being "comfortable".

One last note here, ANY pistons that have "offset" wrist pins simply
"eat up HP", it's as simple as that! G.M. never had a performance oriented unit with the "offset" pin option. ALL their "decent" units like the 327-350HP, 327-365HP, LT-1, L-82, had "centered" wrist pins AND forged pistons for added strength!

Thanks, Gary in N.Y.

P.S. Back to the C.R. for a moment, there are other ways to "boost" it some, such as milling the heads, altering the head gasket thickness, etc. Some 5cc's of the heads will get you 1/2 point add'l! I do have some of these smaller units making 360+ HP and 385 Ft.Lbs. torque with a 9.75 C.R., and run fine on 93, but they have a few "fancy" pieces inside! These are all 100% stock-appearing also with the stock cast exhaust manifolds and Q-Jet carbs.

 

It can be tough to get my car going from a slow roll with my 195 heads. If it's your daily driver I'd say no, but if it's your weekend car, go for it.

Also, if you barely see 5K rpm, definitely stay away. You'd have a 4K-5K rpm power band. My enigne likes to be above 3500 before it really starts to make power.

 

From his description, the pistons appear to be the stock L-48 dished pistons with valve relief, which are about -12cc. A -5cc piston is a flat top with valve relief.

 

Good catch, I missed the "stock" part. Yes those are at least -12ccs if not more. The set I took out of the kids '76 L-48 cc'd at -16cc's.

OK, if they are -12ccs, worst case is 8.8:1 with the .039 head gasket.
You could swap out head gaskets and use with a small cam like the Z-252 or Z-262.

 

Ok, heres all the info

Stock '73 L-48 block- 4 brow dish pistons (12cc?)
Pistons were measured .025 below deck
RHS 67cc heads- 195/150-170cc intake runner
Felpro 0.40 head gasket.

Crane Z Cam
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,800-5,800 RPM
Intake Duration at 050 inch Lift: 218
Exhaust Duration at 050 inch Lift: 230
Duration at 050 inch Lift: 218 int./230 exh.
Advertised Intake Duration: 268
Advertised Exhaust Duration: 280
Advertised Duration: 268 int./280 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.459 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.486 in.
Valve Lift with Factory Rocker Arm Ratio: 0.459 int./0.486 exh. lift
Lobe Separation (degrees): 112

Crane 1.5 roller tip rockers.
Edelbrock performer intake/Qjet
Long tube headers through stock exhaust.

Thats about it.
Thanks guys

 

You can swap the head gasket out and move up to about 9.2 CR, but you would still only add maybe 20 hp. It's up to you if it is worth the time and effort.

Have you gone through the other items to make sure that the whole setup is tuned?

 

The pistons have to go, no question about it. No matter what you try you are not going to be satisfied at all. Engine has to making very low torque as well as horsepower.

Not a real good combination all around, in my opinion, mainly because of those pistons

Harry P.Hunter

 

Yup, it's tuned properly.
I'm done with it for now. It goes really well but it's certainly not anything like my '70 El Camino SS LS-5

Oh well, it is what it is.
Thanks for all your help guys!

 

You should match the camshaft to the compression ratio. I would get a single pattern camshaft with about 210 degrees duration. This will shift the torque peak down in the RPM range where it is more accessible. You spend a lot more time at 2500 RPM as opposed to 5500 RPM.

BigBlockk

Later.....

 

The heads aren't really going to buy you anything. 200cc is about as big as I'd go for the street...and that's assuming a 350 that's putting out 425+ HP. They're even on the edge of being a bit much for a 383.

I'd have to agree with the flow here that either you need to make some changes to match the heads, or cough twice and pass...

 

I'm a little late getting in on this one...but I think you'll have to look at the whole combo a little moe in depth. The 200cc heads aren't going to necessarily make it a pig....there wasn't that much there to begin with. I've run 207cc heads on a sump piston 350...but they were milled to 55cc and were very nicely ported. Low end power wasn't an issue...but I had a 4 speed and 3.36's and an LT-1 cam in it. But it also had a single plane intake.

At this point, I don't think they are worth a whole lot in extra performance unless they have been cleaned up and ported well to improve flow. You need some compression in that dude.

JIM