Hey guys. I recently picked up a 87 IROC 305 5 speed. It originally had an EFI 305, but the previous owner put in an older engine that's carbureted. It's got a high idle, but the tach is showing 2250 (it's not actually that high of an idle. MAYBE 1500). I picked up a tach from a parts car down the road, but it's reading way too high as well. I originally thought it was just a capacitor going bad in my tach, but this one is reading the same exact numbers. I have limited knowledge of carburetors when it comes to dirt bikes etc., but I've never messed with one on a car. I know that there's still an ignition coil and no vacuum advance. Also, if the car gets up to temp and I turn the key off, the car keeps running for a few more seconds. Anyone have any idea what my issue could be?

 

You say you have an EFI to carb swap , and no vacuum advance ? If it's still running the original ECM controlled distributor which it sure sounds like it is since there is no vacuum advance , This is an unfinished remnant of the swap work that was never done . You must get a vacuum advance equipped distributor in there if you have ANY hope of getting it to run right . Yea sure , it will "run" with the crippled EFI system distributor in there , but it'll never run "right" till you correct the unfinished business left to you by whoever thought that "run" was good enough .

Put the proper distributor in there , time it properly , and then see how many of your poor running gremlins go away .....

 

I'll give that a try. Surprisingly it runs awesome other than the high idle. When I bought it we started getting on it, and even my friend (he's been working on cars for 14ish years) wasn't sure if it was a 305 or 350 because it was running so good. Sadly, the block says 305 :P

 

Yeah you can't run the EFI distributor, you need a common large cap mech/vac advance HEI distributor.

High idle can also be from a vac leak, and just idle speed adjusted too high on carb. Check for vac lines not hooked up, open ports/nipples on the carb and intake. Check carb base gasket for leaks., etc

Tachs from V6 cars will not work on a V8. The reading will be high.

If you plan on owning an older car like these you need 2 tools... Timing light and vac gauge. Buy a digital advance timing light with built in tach. You can get them for under $100 now. And also buy a vacuum test gauge. They are about $20

Those 2 tools can tell you many things about your engine

 

I've got both those tools, just haven't had much time to get to under the hood yet.. The interior of this car was absolutely trashed when I bought it. I've been working on that and the floor pans. Also getting the ttops to quit leaking so rain doesn't ruin my freshly cleaned interior. I appreciate the replies. I'm 19 and learning to work on cars. I've also got a 87 RS with the 2.8 that I daily. Unfortunately, my engine started knocking last night. I guess it's time for a 350 swap :P