Hey all,
Getting back into the third gen life. Going to pick up two third gens....86 iroc and a 89 rs. IROC has a 305 TPI and the RS has a 305 TBI. Going to take the TBI engine and install it in the IROC. Less miles and a cleaner engine. The question is this....will I experience any issues with an engine swap like this and can I install a touch bigger cam into the 305? Looking for suggestions on Cam's and issues I might come across switching engines. Like power to the TBI and controls and harnesses? The RS is a coupe and the IROC is T tops. Looking to gut the Iroc and insert the RS into the body with some small mods. Cam, exhaust, breaks, love to install a manual trans if I can find one. Any help would be awesome. Thanks in advance. I'll post updates and photos.

 

Can't offer anything on the electronics side because my advice there would probably cause a major fire but in my 90 RS I'm swapping in an L98 cam and 081 heads. Also installed a set of flowtech mid-length headers (great kit, Can't remember part number). Should be a huge improvement over the stock L03. Good luck with the build!

 

I did some research on TBI upgrades and chips. Brian Harris' page. Very good information. Sounds like using a cam from a LT1 is suggested. I guess I still have questions. If you switch the cam, don't you have to switch out the pushrods, rockers, springs, and valves?? There wasn't much information on that. It was pretty much talking about the throttle body and upgrades. I want the car to have just a touch of tune, but not over the top mods. Small cam upgrade, headers, and sounds like I need to upgrade the TBI chip once I change the cam. Still learning, I just want to have a touch of cool and unique in a third gen car.

 

Depending on what cam you choose will determine springs and things like that. The L98 cam from what I've seen isn't big enough to change much and the 081 heads are rated to about .450 or .460 lift IIRC. Where the cams are roller, the lifters can be reused unlike flat tappet. Pushrod length should be the same but I may be wrong. As far as the valves, I'm leaving them stock sized because I don't want to sink a ton of money into the 305. Just want it to be more fun than the 170 angry little hp my L03 has 🤣

 

187 vs 081 head will not net anything with everything else stock. The L98 cam was the same cam used in the 90-92 speed density 305 TPI as well as the older 87+ manual trans TPI 305s.

 

Is it different from the TBI peanut cam? I've heard of tons of people running the l98 cam in tbi cars and figured I'd try it too.

 

I've got an L98 Cam and lifters for sale for $75 if you're interested.

 

I surely would purchase that set up from you if it's still available. I'm in the middle of head gasket and timing upgrade bc of a blown head gasket.. plz let me know. Text Me @Eight Six 4 seven six 2 one 8 four zero

 

So, I have been talking to a guy that programs the chips once you upgrade all your changes. He suggested a summit sum 8800 cam, changing the air filter to an open 14" for more flow. No one has still answered the base questions about what do you use for springs and push rods after you change your stock cam. Does changing your cam shorten the length of the push rods?? Do you need different springs (stronger) or just replace with stock new ones?? I'm planning on up grading to a newer timing chain. If your going that deep, shouldn't you?? I know these must be newb questions, but I'm still gonna ask. I want to do a good job and make sure I get something nice once complete.
Depending on this cam, do you need to change the stall speed on the automatic clutch? Sounds like you should if your going through the trouble to do the work. Right? Comments.

 

The cam manufacturer will recommend what valve springs to use. Remember, the stock heads are lift limited (.485 maybe?). Replacing the timing chain is also a must. As for converter, that again will depend on the cam. Chances are you're cam will still be mild and not necessitate a converter swap.

 

so fast…..does that sum-8800 cam Amount to much? Was planning on that, new springs,14”air cleaner mod, pens timing chain upgrade and installing heads off of an 86 iroc onto a 92 305 tbi and getting a programmed chip from Brian Harris. Supposed to be able to program you a custom chip once your mods are complete! Thoughts. Any suggestions?

 

Unless you data log and send him the files, you'll be dissapointed. It takes a lot to dial in a tune without having the tuner with the car.