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Discussion Starter · #1 ·
So I’m currently building a 383 and am new to the scene I have 58cc L98 aluminum corvette heads and I’m trying to figure out what rotating assembly to go with I want forged parts incase I want to run boost in the future just trying to find a good set for 2pc RMS for under 2000 and trying to figure out a good cam for stock torque converter thanks
 

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I went with a balanced rotating assembly from CNC motorsports. It came with a balance sheet and all the parts measured up during assembly to give me good bearing clearances. They seemed to be the best deal at the time.

My kit was a scat cast crank with forged pistons but they also have complete forged kits. I got the 6 inch rods. Lots of research, lots of opinions... and after reading all of that I went with the 6 inch. I obviously had to clearance my block and also had to touch up the connecting rods a little for cam clearance. Nothing was hitting the cam but I didn't have a safe enough margin so I took a little off of like 2 or 3 rods. It had the scat ICR6000 Pro Stock I Beam Connecting Rods.

What block are you using?
 

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Look at the Comp XE268H or a spec equivalent from other makers. Cam’s of this specification are as far as a stock stall converter will be a reasonably happy experience for all involved. The aluminum L98 head will support about 350 to 360 hp and well into 400 ft pounds of torque. They just don’t have enough port flow to do much if any more and they are very thin castings, there isn’t a lot of thickness to port these bigger nor a lot of meat to support seat inserts for much larger valves. It is unfortunate but the L98 head is not a race piece, it was designed to provide the bottom and mid range torque on the TPI 350 used in the Corvette and Z28 Camaro engines of the late 80’s, early 90’s. Not a bad head but nether is a racers head.

Also, it’s small chamber drives you into either a thick head gasket, Chevy put .051/.053 inch between these heads and the block. That with the stock piston crown at TDC being .025 inch from the head deck has overly generous Squish/Quench clearance of .076 to .078 inch. While the thermal characteristics of aluminum will let GM get away with this, generally anything beyond .040 is not considered good form. For a 383 (appreciate I’m not doing the math for this installment) these small chambered heads against the need for a tighter Squish/Quench clearance is going to push a really big volume in the piston crown or a larger chambered aftermarket head. Add to this to get the Squish/Quench clearance down you need to zero deck the block, use a raised compression height piston, or run a thin steel shim head gasket which is generally not recommended between aluminum heads and iron blocks, I do it but I unfestsnd where this can get one into trouble so I use head studs and recheck torque a couple times a year for a street motor.

Now a boosted situation is different from a normal atmospheric engine. The forces and BTU loads go way up. Thin head gaskets and thin wall aluminum castings quickly surrender. Also, this likes a change with greater emphasis on the exhaust side which has to deal with a lot more product. So how you want to boost and how much are important up front considerations. If you’re talking about blowing compressed air into more or less a factory configured engine about 6 psi gets to be the limit, beyond that you need to design for the specific needs of the volumes, pressures, and thermal loads involved.


Bogie
 

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you need all your info, car type, driving style, and then start calling cam manufacturews. comp cams will talk with you for hours, they might tell you good stuff, they might confuse the poop out of you, but there is much to learn, and they have all the good stuff. I'd start with what is your goals? a 383, is a simple thing to build, my last one cost about $450 bucks, i used 400 sbc crank and rods.
 

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Dont add boost later. Either build a boosted engine or NA. Different cam especially for a turbo engine. The L-98 heads are ok for a mild 350 or perky 327. NA 383 or turbo I would want at least 200 cc intake volume heads and perhaps bigger for super charged. Build the entire engine on paper before ordering a single part.
Start with power requirements? Size engine you want to use? How you want to make the power? Heads?
 

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if your 383 is for a towing rig; I'd be okay with L98s, otherwise? Go get a set of Pro-filer All Americans OR one of the budget aluminum casting pairs and load em up with serious guts.
TBH if you want a camshaft recco? I'd go with Bullet, Mike Jones, Chris Straub etc
 

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For what it's worth, my Comp 270H in my 383, 3800 lb., 2400 stall, 700R4 with selectable lockup, 2.88 Jag IRS is a real pleasure to drive. It's a daily driver, not a race car but it will certainly lay plenty of rubber when I choose to. 2000 RPM at 80 miles per hour. And electric cutouts are a MUST! Videos and pics on my website.

 

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Discussion Starter · #9 ·
Look at the Comp XE268H or a spec equivalent from other makers. Cam’s of this specification are as far as a stock stall converter will be a reasonably happy experience for all involved. The aluminum L98 head will support about 350 to 360 hp and well into 400 ft pounds of torque. They just don’t have enough port flow to do much if any more and they are very thin castings, there isn’t a lot of thickness to port these bigger nor a lot of meat to support seat inserts for much larger valves. It is unfortunate but the L98 head is not a race piece, it was designed to provide the bottom and mid range torque on the TPI 350 used in the Corvette and Z28 Camaro engines of the late 80’s, early 90’s. Not a bad head but nether is a racers head.

Also, it’s small chamber drives you into either a thick head gasket, Chevy put .051/.053 inch between these heads and the block. That with the stock piston crown at TDC being .025 inch from the head deck has overly generous Squish/Quench clearance of .076 to .078 inch. While the thermal characteristics of aluminum will let GM get away with this, generally anything beyond .040 is not considered good form. For a 383 (appreciate I’m not doing the math for this installment) these small chambered heads against the need for a tighter Squish/Quench clearance is going to push a really big volume in the piston crown or a larger chambered aftermarket head. Add to this to get the Squish/Quench clearance down you need to zero deck the block, use a raised compression height piston, or run a thin steel shim head gasket which is generally not recommended between aluminum heads and iron blocks, I do it but I unfestsnd where this can get one into trouble so I use head studs and recheck torque a couple times a year for a street motor.

Now a boosted situation is different from a normal atmospheric engine. The forces and BTU loads go way up. Thin head gaskets and thin wall aluminum castings quickly surrender. Also, this likes a change with greater emphasis on the exhaust side which has to deal with a lot more product. So how you want to boost and how much are important up front considerations. If you’re talking about blowing compressed air into more or less a factory configured engine about 6 psi gets to be the limit, beyond that you need to design for the specific needs of the volumes, pressures, and thermal loads involved.


Bogie
I went with a balanced rotating assembly from CNC motorsports. It came with a balance sheet and all the parts measured up during assembly to give me good bearing clearances. They seemed to be the best deal at the time.

My kit was a scat cast crank with forged pistons but they also have complete forged kits. I got the 6 inch rods. Lots of research, lots of opinions... and after reading all of that I went with the 6 inch. I obviously had to clearance my block and also had to touch up the connecting rods a little for cam clearance. Nothing was hitting the cam but I didn't have a safe enough margin so I took a little off of like 2 or 3 rods. It had the scat ICR6000 Pro Stock I Beam Connecting Rods.

What block are you using?
I have a regular 4 bolt main gen 1 casting
 
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