Hey guys,
I picked up an 89 iroc a couple months back and just got it smogged today. I live in sunny CA so I get the pleasure of taking my cars to the smog doctor every other year. Long story made short, the car just barely passed smog. I did some routine tune up stuff and dropped in some seafoam, 91 octane and lo and behold it passes..........just barely. Max NOx(i think) was .41 and what does the car read........ .41.

Anyway, plans for the car are a 350 while salvaging the original 305 heads, hedman headers(with air tubes), well mannered cam and roller everything and porting/polishing where possible.

Considering that, would it be possible for the 305(to the untrained eye) be able to throw out emmissions acceptable for the 305 range?

What is the range anyway, i'd imagine the base(non-roller) 305 has the same range as the bigger cam roller 305.

So has anyone done this? Will the 305 heads put me out of range? Should I leave the 305 in and add some bolt ons(which wouldn't be so bad b/c the wife might drive it now and then - don't want it too quick for her small lead foot.

And finally last question, will my base TPI 305 block(auto trans car) have provisions for a roller cam/lifters?

thanks and my apologies for all the questions? Just trying to be smog legal and a little quicker at the same time.

 

Yea your '89 should have all the roller provisions, if not already equipped with a roller cam assembly. on the emission stuff no clue cause I never have to deal with it.

 

im sure you'll be able to pass emissions with a 350 but i think it would probably be better to just work with what you have. i would more look into just rebuilding the 305 with a cam and a little head work.

 

Yes you have a roller cam and provisions for it. All f-body V8s after I think 86 (so 87+) have roller cams.

Also, I got a friend in SF who smogs his 350 as a 305 every two years... no problem.

But it's a mostly stock L05 in place of his L03.

 

Don't the 305 and 350 engines have different cylinder heads? Is your car a 305/auto or a 305/5-speed/G92 car? Starting in '89 the G92 option consisted of more than just deeper gears. The '89-'92 G92 305 cars had the L98 style cam, N10 dual cat exhaust, and 3.42 (10bolt) or 3.45 (borg warner 9bolt) positraction rear ends.

You could see if you could find an L98 that was 100% stock (in good condition) and that would save you from going through the rebuilding process too. When my original engine wore out I got a remanufactured L98 long block from A/C Delco. Its been 8 years since I've had it and I've never had a mechanical problem with it.

I've also been able to pass smog too. Up to this point I've keep my L98 all stock with just minor bolt ons. I'm in the process now of collecting the intake parts, cylinder heads, and cam that I want to use with my car now. Ha ha I want more power now. I live in CA to and I know that the smog tests are a pain in butt. I think that the state is trying to balance the budget on smog tests because of all the extra 'fees' they keep adding every couple of years when its time to get another test! I got charged an extra $20 last year to have then just do a visual inspection of my EVAP canister!

 

If you use the 081 heads on a 350, watch out for compression in the 11:1 range, depending on your pistons. Look for a set of 083 350 tpi heads. They should be cheap and you won't have to worry about detonation. Good luck!

 

Thanks guys....good point made by all. The odometer reads 10,xxx miles. Steering feels like 110,000 and suspension feels like 210,000. Its definitely got the Chevy puff at startup and oil was on the plugs when I tuned it up.
Seeing that the slightly modded 350 is smoggable I'd much rather go that route.
The iroc is not a g92 car, wish it was, but its almost a base iroc, 115 mph speed, auto trans with 305 and single cat.
So probable set up will be 350 long block(its from an early 90's p/u) but not sure if tpibase manifold will bolt on(comments?)
Mild cam, still porting where possible, roller everywhere, hedman shorties and maybe flowmaster out back.
Stock 700r4 and converter and tall 2.77 gears(converting to disc though).

Should be a fun driver wouldn't u think? Well mannered, decent on gas and smoggable.

Thx

 

Yeah thats cool. The fact that it's not a G92 car to start with isn't that important, just gives us a point of reference. If it's the LB9 305 and not the L03 305 that would be better. The TPI induction set for the LB9 and the L98 is the same (with respect to the same year) the only difference being the chip in the PROM and the injectors. LB9's got 19 lb/hr injectors and L98's got 22 lb/hr injectors.

I have also have 2.77 geared posi disk brake rear in my car to. I'm in the process of getting parts together to rebuild the rear with 3.27 gears. You may want to change gears as well once you get your new motor finished up and installed. I've gone through the engine and trans in my car and now the rear end is next. The rear is original to my car and I have 195,000 miles on the body and that original rear end.

Check see if you have a borg warner 9bolt rear or a 10bolt rear. 2.77 is a 9bolt gear ratio. If your car is a non-G92 with the 305/auto combination it should have a 10bolt drum brake rear with 2.73 gears. This is the factory set up for this drive train combination - someone correct me if thats not right. But it's been a long time since any of our cars were at the factory it would be better to check and know for sure before you start ordering parts or chainging things.

It should be an easy swap and since you are doing just common bolt on mods (nothing extreme) the stock computer (with a L98 style chip) should be up to handling the task. You may want to change your injectors to. You can get the car to run with the 305 injectors though.

At this point, your car is representative of a lot of the thirdgens out there that have been driven (including mine) - somethings have worn out and its time to replace or rebuild them. If the injectors and all the sensors are working well, thats very good. You can save up money and replace things as you would like as your budget allows.

Can someone correct me if I am wrong on this. Do the 305's and 350's have different knock sensors? I thought you had to change that to if you swapped from a 305 to a 350 as well.

 

Yes, 350 and 305 have different knock sensors. Also, I'm pretty sure you're right about the drivetrain. My Formula is 305 TPI, auto, 2.73 10 bolt posi drum rear.

 

well if your Nox was that high, whats the HC numbers? Alot of the Computer Friendly Cams are Smog legal and will say if it is or not. Also did you know that changing your spark plugs heat range can change your Nox,HC,Co numbers..... Say your Nox is Way high and HC is low, go to a colder heat range and you'll notice the Nox drop and the HC rise slightly. also works the other way around sometimes, the numbers will tell you if you have a misfire or leaky injector creating excessive HC's where a hotter plug might now compensate for that...

 

Thanks yaj and phoenix, I didn't consider the knock sensor but had done so on most other things. The classifieds are addictive and have almost all I need for the swap. Between that and craigslist all I need to do now is rebuild the 350 long block, get a roller cam/lifter set, knock sensor and prom chip.

Yaj, ur right on the rear gear....I'm sure mine is a 10 bolt but I already went out and impulse bought 2 bw 9bolts, rear disc too with prop valve....good deals are hard to pass up.....
yaj one more thing.....did your car stall on take off after the swap? I'd want a low power band for street use and am just learning about stall converters which idont think I'll need.
Thx again.

Oh will post later about the smog results......may be co or hc's that were at max....just can't recall now.....just was glad it passed and didn't worry about it considering the plans for the swap.

 

Just one thought for you. The early 90's p/u blocks may or may not have the holes for the lifter retainers tapped. If they are great but you will need your old lifters and retainers. My 89 p/u block was tapped but I have seen others that weren't. If I remember correctly all the pick ups had the regular hydraulic flat tappet cams until they went to the vortec engines in 96. At that point they were all roller cam engines.
The 87-95 pick up engines were all TBI and non roller cams but as I said some had the lifter retainers tapped and were ready for a roller cam with the lifters and retainers swapped in.

 

Thanks for pointing that out phoenix but going full roller was and is at the top of the list so I pulled the valve cover off the donor block and verified either through the push rod hole or some other way that its provisioned for roller liters. Forget the block number now but its one of those that are hit and miss like you mentioned.
Thx

 

My car had the L98 from the factory. When I put the new engine I bought in the car it was a stock L98 rebuilt replacement motor from AC Delco. At that time I still was running my original stock 700r4, stock torque converter, and 2.77 posi 9bolt rear.

That new engine really woke the car up. Ha ha my original motor had around 166,000 miles when I replaced it. The valves and piston rings were shot. I went through 3 cat converters that year because of all the oil that was passing through them. Oil was coming out around the spark plugs as well as the tail pipe. That engine had seen better days. The only other mods to my car at that time were 3'' flowmaster cat back exhaust, a new 3'' high flow cat and 1 5/8'' ceramic coated hooker headers. Those headers really woke the car up and gave it a deep tone.

Stock stall is around 1600rpm-1700rpm which is too low. About 9,000 miles after I got the engine installed the pump on the trans failed. This was about 175,000 miles. I've had a couple of transmissions in the car since then and I'm satisfied with the set up that I have now. I've got a Bowtie Overdrives level 3 700r4 with a 2400 rpm stall converter. I also have had a 2,200 rpm stall converter as well. I like my 2400 rpm stall better now. I've still got the same exhaust mods in addition to a 52mm throttle body, gutted TPI airbox, K&N airfilters, and Hawks Thirdgen ram air boxes. I didn't have any stalling issues with changing the converter stall and the minor upgrades I have done. Had a lot more torque from idle to 3500rpm and the car accelerates quickly through the rpm band. I'm still hitting that famous TPI wall between 4500rpm-5500rpm but those few intake mods helped so that now its not until I hit 5000rpm that I start really feeling a drop off in power.

With most long tube runner TPI set ups I find that 2,200-2,500 rpm stalls tend to work best. Especially with stock style TPI set ups you really don't need to run a deeper rear gear than 3.42's to get good street performance. I've just kept my 2.77's until I figured out what I was going to do with my drivetrain. I'm just going to make my car a fast street car. The most I am going to do in the future is upgrade the intake with aftermarket TPI parts and install a mild emissions legal cam and heads. With that set up the 9bolt should be able to take that with no problem.

The 10bolt rear that you have will also handle the power that you want to install. Just upgrade all the parts that you can. GM made so many 10bolt rears that as long as your housing is in good shape you can go in to the parts book and have a field day.

I'm not sure when they upgraded the 10bolt with 28 spline axles. I think the '90-'92 cars had 28 spline axles. I know that the '90-'92 cars with 10bolt rears and the G92 option had 3.23 gears (L98), or 3.42's (LB9), positraction and the PBR calipers with the 11'' disk brake rotors. Those rear's are just as strong as the 4th gen 10bolt rears. You wouldn't have to deal with the difference in width between 3rd gen and 4th gen rears if you use a 10bolt designed for a 3rd gen car. If you wanted extra strength you can install a girdle and weld up the axle tubes. All that still would be a lot less than buying an aftermarket 12bolt or 9'' rear end. It's not really needed for the power level that a mildly modified LB9 or L98 would be at anyway so might as well save some money until you need it.


The next place where I am going to have to drop some money to upgrade things is the brakes. I'm still running my stock J65 set up with the single piston calipers and 10.5'' rotors all the way around. Those brakes are ok but I would like something better.

 

Thx raj and that's not a bad setup you have. I don't think i'll go muchfarther than that besides some minor suspension mods. Still have paint to deal with not to mention a 92B4C that got put on hold b/c the iroc is much closer to being a solid daily driver than the B4c.
Will start a thread on the build(s) when I get the parts together.

 

Thats cool. The important thing is that you are keeping that thirdgen on the road where it belongs!