FNG

hi all. want to do a few things to my 77 L48 before summer and need some advice on heads.(i know. been beat to death). Will probably go with an xe 262 cam, Dynomax coated headers, recurve the distributor, 3.70 rear gears from 3.08s, and a 200r4 trans. car has 86,000 miles on it and has been very well kept. good compression in all holes. when i put on the performer manifold, there was no gunk at all in the engine. valley and heads very clean. i want to go with iron heads and have narrowed it down to s/r torguers or sportsman 2s.

question: how much will 67cc torquer heads boost my compression?? and will it be too much for a daily driver??

question: for 10 bux more each would the sportsman heads be better?? i think these come in 72 or 64 ccs. wil the 64 cc heads boost the compression too much?? will i lose any low end grunt because of the larger runners??

this thing will rarely see anything above 5 grand, and i want reliability as i drive this car most every day. love driving this thing even in its present state of sorry azz performance. not really looking to be the fastest kid on the block, just want to warm it up a bit and have good stop lite to stop lite grunt and let the o/d trans take care of the highway stuff. thanks for any input here , am a body man by trade but have friends that are mechanics, so can do most of this stuff myself with a few 12 pacs :D and some help from buddies. thanks again, regards, fng

Smokehouse69

Currently your assuming your L48 has about 8.5 to one compression with 72cc heads, going to 67cc heads would raise your compression to about 9.5 to one. Assuming that you have flat topped pistons with 6cc valve relief in the tops and a deck height of .010 using a Felpro Blue .039 thick head gasket.
That isn't too high for cast iron heads, many guys are running that high or higher with iron heads and 92-93 octane premium gas.
In my humble opinion I'd go with the smaller runners of the Torquer heads, with a 350 you want to increase torque in the drivable range. Now if you were building a 383 stroker or 400 sbc, the Sportsman 2s, while running a single plane intake and a bigger lift cam than the XE262.
I think the setup you have narrowed down to will be a very nice street performer capable of running through the quarter with nice times.
BTW, welcome to the forum!

redwingvette

L-48 engines came with dished pistons and even though the book has it at 8.5 comp but it is really closer to 8. The deck heigth is about .037 below and you can go to 64cc heads without any problem. Why do you want to use cast iron heads? Both are good heads if that's what you want.

tnt76vette

Just opened up my '76 L-48 for a head upgrade, and I found FLAT TOP pistons w/valve indents. I was, like Redwingvette, expecting to find dished pistons also. It has always run well on junk gas.....WTF? :crazy:

redwingvette

As a rule, pump gas will work fine untill you get above 10 with Iron heads. Also, it has to do with the cam you have. As long as you have the heads off you should check and see what the deck height is. Line up the timing mark at TDC an measure from the block down to the top ridge of the piston. Stock heads can be as high as 76cc and with a flat top piston Valve dish (6.1cc) plus the deck height (.037) and gasket thickness (.039) you will around 9.5.

FNG

thanks for the input fellas.

Smokehouse69. thanks for the advice. I was thinking the sportsman 2s might be a little big for what i want to do.

Redwing. going iron heads mainly for the cost difference. dont think that any better heads would do much for me with just the mild warm up that im looking for. could be wrong though. im not a mechanic.

TNT. your setup looks about like im doing except for the heads. How does your car run??pretty streetable?? do you like the 3.55s?? i thought about going with those, but the o/d in the 2004r should still give me decent freeway rpm.

thanks again for the input guys. regards, fng

Smokehouse69

If you have the choice I'd go with the 3.70's or even 3.90's if you are going to use a TH200-4r. With the 3.90's you'll end up with a virtual 2.61 rearend ratio for about 2300 rpm at 70 mph and with a 3.70 you'll have 2.52 ratio and about 2180 rpm at 70mph.
2100 to 2400 rpm is a good cruising rpm, I get better than 18 mpg with my ZZ4(your engine will be similar performance) cruising at 2600-2900 rpm, with my old TH400 and 3.08 rearend. I have a TH200-4r that I could have put in my car, but I decided not to for several reasons, one of the main ones was the 3.08 rearend I have in my car currently, it is too high to really work well with a TH200-4r.
I think a perfect match would be a 3.90 rearend and the TH200-4r.

FNG

thanks again Smokehouse. already have the 3.70s. a guy i do business with occasionally had a complete rear end that he had gone through and the owner never showed up to get them. got a good deal so i think i'll keep those. 18 mpg is great!! best i have gotten is around 14. thats all around though. if i can get 18 on the road ill be exstatic :D thaks again for the advice. gonna get the heads coming tomorrow, cam is in stock locally. regards, fng

cardo0

Hello FNG,
My '74 was in the same situation after I broke my fan shrould at Las Vegas Speedway - The Strip. Great new raceway and just can't waite to visit that town again - your lucky to live there. My GM goodwrench 350 had less than 30K miles on it and didn't what replace the whole motor - lifter valley like new and cyl. bores still had hone marks. Also have installed 3.70 so your set-up is very similar except mine is 4sp. Yes, the performance was sorry azz and I keep my time slips for humor only.
I finally chose S/R torquers with 2.02 valves as I'm convined sportsman runner size is too large for streetble 350. Bought them from Performance Products (also called Performance Heads and Chevy Performance) out of Phoenix, AZ. (602-254-9586) and couldn't be happier with them. Assembled heads where $750 and pocket porting was just outstanding for only another $100. Valves were unshrouded too! Only dissapointement was misssing umbrella seals - valves had only stock seals but was easy to fix. Recommend umbrella seals with stock cast iron valve guides. Painting and shipping were free but must request color.
I tried to measure #1 cyl. volume @ TDC with short block in car but the seal on block with plexiglass wouldn't cooperate by springing leaks. Valve chambers averaged 69ml (cc). I feel very confident using these heads with only steel shim gasket (.015") and quesstimate my conpression ~9.0 or less but don't have time (or care to) explain here.
I like your choice of cam and headers though mine are a little different. I think your right keeping RPM < 5,000 as those cast pistons will live alot longer - too much wasted effort to do it all over again for a blown motor.
Really should mention that removing the motor and trans. together shouldn't be any more work than just heads and cam. I just didn't have the garage space for mine. Havn't started mine yet as the new core support doesn't match and may need a few mods to get it right.
Good luck and let us know how yours performs when finished. :seeya


[Modified by cardo0, 11:29 PM 1/12/2003]

nunus79

I've run out-of-the-box Sportsman IIs on a mild-built street Vette and they performed just as advertised. Netted 55 hp gain, World advertises 30-70 hp gains. World also claims that the SIIs perform just like the SR Torquers up to 3000 rpm, then from there it starts to shine.

Intake volume size can give an indication of intake velocity, yes. However, the shape and length of the runners also play a major role in velocity. As one of the magazines that tested the SIIs said, "World Products apparently did their homework" or something like that.....

I would hesitate using the SIIs in a 4400 lb truck used soley for trailer towing. But I would definately buy them again for a Vette or Camaro build without second thought. Easy horsepower.

.....oh yeah, I left out the important part.... off idle throttle response was EXCELLANT. No soggy-ness just crisp throttle.




[Modified by nunus79, 2:13 PM 1/12/2003]

tnt76vette

FNG havent had a chance to take it out since head swap (Michigan weather ya see!). It was very streetable b4 swap and I expect it will be the same now. 3.55 rear puts me at 3K rpm at 70 w/TH350. If you can swing it, an OD tranny would be the way to go w/3.70 or more gears. You would have the best of both worlds..........GOOD LUCK! :D :D :D

nunus79

Tom
How'd you get flat-tops in them holes? Some of those dished pistons kinda look like flat tops except for the raised edges. Maybe you hammered those edges flat with too many full throttle blasts!!! j/k :D :D :D
Have fun with your new found power. Hard to find that kind of power increase for the price you payed. Good deal.
Norris

tnt76vette

Norris: I assure you they are flat tops w/valve indents. Yes the work was done in the morning (ie: I was sober and not hung over, LOL), and I have witnesses....Just wish I would have taken some pictures because I dont think anybody believes me. Enjoy your warm Hawaiian weather as we're frozen just about solid back here in MI. :eek: :eek: :eek: