I'm finishing my budget build this week. 1988 350 .040 over 9.6 comp. with vortec heads. Machined guides and 981 springs ( possibly without dampened, shop didn't machine guide width for them, but they did lower seal height .200). I'm running a comp xe274 and keeping the ccc E4me. My question is what mods do I need to do to this carb during rebuild to handle the 350 with this cam? Carb is from the 305 L69 I'm my 1987 Monte Carlo SS. Also is it ok to run the 981 springs without a dampner? I've read that it's ok because of the width of the guides on vortecs? Any help is appreciated.
xe274 and the e4me
- Thread starter breakneck88
- Start date
i would call comp and ask them. a friend of mine took a gm performance parts 350, added a set of vortec heads, comp xe262 and a 750 double pumper. he also ran the 981 springs. with a 3k converter and 4.11's he shifted religiously at 5100. he started bumping the shift points up and eventually pushed a pushrod through a lifter. i dont know what you intend to use the car for, but this might be of some help so you dont run into the same problem.
You don't need to make any carburetor modifications. You already have the large window jets.
If the carburetor has been taken apart by someone previously, you should get the proper tools/gauges to set up the carburetor properly, especially the min/max travel of the primary needles. Apart from that, you may need to adjust the dwell of the mixture control solenoid after setting the timing, idle speed, and throttle position sensor voltage.
If you have a GM shop manual, all of the carburetor procedures are well documented.
You do have opportunity to change to narrower secondary needles from an older quadrajet or from the aftermarket. There are several different thicknesses and tapers to the secondary needles available.
If the carburetor has been taken apart by someone previously, you should get the proper tools/gauges to set up the carburetor properly, especially the min/max travel of the primary needles. Apart from that, you may need to adjust the dwell of the mixture control solenoid after setting the timing, idle speed, and throttle position sensor voltage.
If you have a GM shop manual, all of the carburetor procedures are well documented.
You do have opportunity to change to narrower secondary needles from an older quadrajet or from the aftermarket. There are several different thicknesses and tapers to the secondary needles available.
981 springs work just peachy on Vortec heads with the inner dampener coils removed. Done it several times personally. You're good to go on that one.
BUT.... the computer controlled Qjet system is not likely to play nice with a cam that big. You can try it if you like, but just like most computer controlled engines, things get dicey when the duration starts going above 220* @ .050.
I'm talking about idle and part throttle drivability here. When you smack the throttle wide open it'll still sing like it should. Just that driving around on the street is likely to be borderline miserable. The ECM is shooting for stoich mixtures (14.7:1) which is just going to be too damned lean on a carbureted setup with a semi-lumpy cam.
Are you dead-set on running that cam? I could suggest a few that would probably work better with a bit less duration and a wider LSA.
BUT.... the computer controlled Qjet system is not likely to play nice with a cam that big. You can try it if you like, but just like most computer controlled engines, things get dicey when the duration starts going above 220* @ .050.
I'm talking about idle and part throttle drivability here. When you smack the throttle wide open it'll still sing like it should. Just that driving around on the street is likely to be borderline miserable. The ECM is shooting for stoich mixtures (14.7:1) which is just going to be too damned lean on a carbureted setup with a semi-lumpy cam.
Are you dead-set on running that cam? I could suggest a few that would probably work better with a bit less duration and a wider LSA.
