IROC-BOB86

OK my car is a 86 Iroc-z 305 LG4 with a 9.5cr, Hooker shorty headers and 2.5 dual exhaust no cats and X pipe, 5 speed transmission, and 3.27 gears. I have a set of 062 vortec heads milled down to 58cc new springs and worked for higher lift cam. I also have a vortec edelbrock performer intake. What I would like to know is what cam would work the best for my set up. I'm looking at the Lunati #10120702 and comp cams #XM262H I would like to keep my cc carburetor but i do have a edelbrock 750 carb. and a HEI distributor if i need to use them. Any help with this would be helpful. Here is the specs for the cams.

• Comp Cam Advertised Duration (Int/Exh): 262/268
• Duration @ .050 (Int/Exh): 218/224
• Gross Valve Lift (Int/Exh): .462/.477
• LSA/ICL: 112/110
• Valve Timing 0.006
• RPM Range: 1300/5500
• Lobe Lift: 0.308/0.318
• Lunati cam Advertised Duration (Int/Exh): 262/268
• Duration @ .050 (Int/Exh): 219/227
• Gross Valve Lift (Int/Exh): .468/.489
• LSA/ICL: 112/108
• Valve Lash (Int/Exh): Hyd/Hyd
• RPM Range: 1400-5800

cardo0

Well if u truly have 9.5 compression I think those cams while will work great but u could do better with a little larger cam. Something more like 270 full duration and 220ish @ 0.050".

IROC-BOB86

I'm not sure about the 9.5 compression. Just going on the information given in the tech data for a 1986 Chevrolet Camaro Drive train List on this site.

cardo0

Okay those stock compression numbers are usually generous in that actual compression is normally found to be less. Then those cams u have chosen would be a better choice than my larger cam suggestion. But with those short duration camshafts u could tighten up the LSA for more mid-range torque. Maybe go as tight as 110* LSA - no more - though your 112* will be quite an improvement itself. With such a short cam the overlap wont be affected much at all and u wont lose much vac at all.

U have a very good exh sys and really dont need much extra duration on the exh side if any. I think a single pattern cam would be ok in your car. I would add 1.6 rocker arms just to your intake valves also. Since your rpm less

IROC-BOB86

OK thanks I was thinking to try the 1.6 rockers but on both sides. Do you think my cc carb. will work with the setup i have in mind?

cardo0

Ok i had to google a CC carb. Well thats just a computer controlled electronic Qjet. All the computer controls is the primaries venturies jets/needles/rods. That would be for idle to cruise rpm only. At WOT the secondaries are set by the size of the secondary rods/jetting and have no connection to the computer. The computer will go to "open loop" and use the maps for ignition only.

With the new cam and heads and free flowing exh u should get the carb/computer tuned anyways but that will just be on the primary side during closed loop. When u go to WOT u will not touch the computer fueling maps - just ign advance and u should have that tuned also. Ignition advance but not the fueling map as i dont expect u have any unless for the primaries.

Myself i dont think the electronic Qjets are really harmful to power at all. The hearsay blames emissions and fuel mileage for the extinction of the carburetor. Cost wise if u compare the cost of injectors, electric fuel pumps and regulators EFI is a looser. But i think reliability and easy starting may have won the argument for EFI. That and the ability to compensate for temp/density changes.

Hope this helped.

BTW i dont think added lift on the exh will gain anything for your engine - more so if u have a dual pattern cam with added exh duration.

Bill Chase

Oops