Well i am currently looking to swap a built 355(with approx. 330-350 Hp) i have in my 81 z-28 into a 86 iroc-z with a carbed 305 in it now....what emissions components does the 86 have and which ones actually hurt performance? I figure the smog pump robs a few hp...any numbers? The 355 i have now has no emmisions on it so i know im going to have to disconnect the ecu cuase i don't want to have to buy a computer controlled carb and distrubutor. I can get an emissions sticker easy for it but i would like to at least have some of the emissions still on (to give it a little sleeper look).....so what emissions components can i keep that don't rob too much power when i swap engines? -Thanks

 

The only real problem is the small air cleaner & exhaust systems used on the LG4. The A.I.R. pump does not use measurable power (I have time slips w/ & w/o the pump to prove that - run-to-run variation was higher than the difference w/ & w/o the pump running).

You can pull the 305 out, swap over the attached equipment, and install the 350. Install new exhaust from the heads to the rear bumper (headers, y-pipe to 3" cat, 3" cat-back).

I'll admit you have me a little confused. Does the '86 have the CC carb on it now? If so, it will work just fine on the 350 as long as the cam duration isn't completely out of line (doesn't sound like it with the HP #'s you gave). You may have to recalibrate the carb secondaries, but that's just tuning.

The '81 engine will have a two-piece rear main seal, and the '86 one-piece; so you'll need a flex plate for '82-'85 3rd gen to put on the '81 engine.

 

Hey good call on the flexpate differences....i never even thought of that! As for the carb situation i just figured the cc carb on the 305 would be a little too restrictive on the 355 which i have a 650 DP on now...and i don't want to have to reprogram the computer to get the kind of fuel mettering and timing i want. What other kind of emissions does an 86 have besides the smog pump?

 

I was told that they didnt change the flex plates till mid year 86. Do you know for certain that all of the 86's had the one piece seal. If not I would check into that before buying new parts. As far as the cc carb it is around a 650 in stock form, and is actually a 750, but has a throttle stop on the secondaries you can grind off to allow it to open all the way. You would just need to change rods and hangers which isnt expensive. The timing you would however need to get a different computer/chip from the junkyard(computer)/gm(chip) to adjust it. Is the car a auto or manual. If it is a manual you could easily just stick with your demon, but if it is an auto you will need to get a kit for the lockup on the converter. I dont know what power differences would acutally be there if you used the cc carb compared to the demon but from what I have read if you have them both tuned well there shouldnt be a lot of difference and the cc carb will get better gas mileage.

Ben

 

One-piece rear main seal started in 1986 (some really early production '86s may have had left-over '85 engines w/two-piece). Roller lifters and center-bolt valve covers started in 1987, making the '86s real bastards.

The only thing the chip will do is give you a more agressive spark curve, which you may not need. Certainly it will run w/o codes with the stock chip, optimizing may lead to a chip change. You may get all the advance you need by setting the base more advanced (I'm running 10 degrees base right now, no pinging on regular gas, 9.5:1 compression). With the GM performance chip, you'll probably have to run premium.

The '86 doesn't have a lot of "emissions" equipment; A.I.R., EGR, cat, charcoal cansiter, filler neck restriction - most everything else is there to support the computer controls. Knock sensor is one thing you'll give up if you go non-CC.

 

Would the computer controlled distrubutor switch over too? Also does the aftermarket make any CC carbs that are high performance, any estimates on price?

 

I dont think that the aftermarket makes them but if you send it to jet they will fix it up. Not sure on the price though.

Ben

 

I have yet to see an 86 with a 2 piece rear main seal and the early flywheel. Seems like GM did a pretty good job phasing out the old.

 

Yes.

 

AllGoNoShow-

Holley has a cc carb for sale. Not sure if it is high performance, but it is a holley remanufactured cc one. Don't know if it would be good for the 355 or not. The price is around 300 bucks, depending on core. O'reilly is where I saw it, but I am sure other parts stores have it.

 

AllGoNoShow-

Holley has a cc carb for sale. Not sure if it is high performance, but it is a holley remanufactured cc one. Don't know if it would be good for the 355 or not. The price is around 300 bucks, depending on core. O'reilly is where I saw it, but I am sure other parts stores have it.

 

JET can redo your quadrajet with a phase 2 rebuild, which would be good for your car, for right at $250. I looked into for a time in my motor swap. The Stage 2 Quadrajet's, from what I read in Car Craft, are a NICE carb. I'd recomend it. You can contact JetChip Performance if you have any other questions about it.