Hopefully someone has dealt with something similar. My L69 305 is getting tired and leaky.

I'd like to basically jack up the carb and distributer and put a mild 350 crate motor in there. Keeping my cc qjet, and HEI electronic dist.

Question is: is there enough "play" in the computer that it could control the 350's few extra cubes?

This little 305 just lacks a good torque and hp curve being under square such as that motor is. Bore is too small, stroke is too long.

 

Reports of success are numerous. GM put out a kit that included a ZZ4 crate engine, upgraded air cleaner (you already have that), upgraded exhaust, and a chip. The chip was more of an upgrade for LG4's than for L69's.

Hopefully, I'll be able to add my success report soon.

 

Wow I didn't think of the computer at all. I'm doing a LG4 305 to 350 swap. I'm keeping the Q jet and stock distributor do I have to change the computer or chip? If I don't will it throw off a bunch of codes?

Good topic.

 

Worked pretty good for me while I used the CC stuff. Just used a '87 L98 knock sensor in it.

 

yeah, i'm trying to do that same swap now. What mods did you guys do to the carburetor? I'm just gonna have it rebuilt, and take it somewhere to get it tuned I think.

 

Tune the secondary rods, hanger, and AV tension.

 

I didn't have to do anything to mine, just needed a basic rebuild and the tuning that goes with it afterward.

Mine was on top of an L69 before the 350 though, and from what I've heard, the L69 had a good setup as it came from GM, so I left it alone. Worked pretty good for me.

 

The nice thing about the kit that five referred to is that it was smog legal in all fifty states. The bad news is that the kit was disco'd some time ago.

With all the information that's available, it shouldn't be too difficult to come up with a smog-legal duplicate. Check out the GM Performance Parts catalog. The kit is still listed, along with all the parts that go into it.

 

I kinda thought it was discontinued.
Sounds like the consensus is that a fairly mild crate 350 should bolt right under my carb and pretty much be plug-n-play?

 

I got the p/n's of the knock sensor & module from the kit parts list and ordered them from www.gmpartsdirect.com . Didn't want to take the chance on the 305 parts not working properly.

You may have to do some secondary tuning, along with basic idle & choke adjustments, but nothing major. The L69 chip should be decent. The EGR won't work because the ZZ4 heads don't have the exhaust crossover passages, but if you keep the solenoid electrical connector attached (no vacuum needed), you probably won't have any problems. You might encounter partial load pinging problems, in which case you can opt for the PROM that GM put in the kit which deleted the EGR, or plumb exhaust up to the intake manifold using the ZZ4 intake's hot air choke boss, or back off your base timing.

 

Well, I wasn't thinking of a ZZ4. Something a bit milder actually. I'd like to keep the EGR and everything else intact. I'm sure I'll also have to transfer my intake over to maintain the low rise to mitigate any hood clearance problems.

 

The knock sensor & module from that kit will work with a CC carb'd 350, that's the message.

The ZZ4 intake, available from GMPP, maintains sufficient hood clearance, and EGR capability. So do the EGR versions of the Edelbrock Performer and Weiand Action+.

 

Keep in mind of the Vortec and 1988 L98 iron head bolt patterns on the heads on the crate motor. They both differ from the traditional intake bolt pattern and will require a new intake manifold.