Okay guys I have a problem with my 91 z-28 it had a 305 tpi and od tranny stock. I recently changed to a 355 tpi with a t-5 its really wierd ran fine stock but now its hard to start after driven for about 30 mins. Kinda seems like timing is off but it starts on 1st turn when cold. Some people say it could be plugs are to cold i am running 24lb injectors and a 100 shot wet nx kit. I have not yet changed the ecm prom from stock. If any one knows more please help! Questions are welcome.

 

I don't have an answer exactly, but if you are running the stock 305 TPI chip in a 355 TPI which has upgraded 24lb injectors, you may want to have a chip burned or atleast get a stock 350 chip. The stock 305 TPI chip still thinks you have 19lb injectors.

Just my 2 cents.

Hope this helps!

 

ive driven my fair share of old cars, and a couple of them had the same problem. started fine when cold, not so much after warming up. what i found helped alot was cleaning the battery cables (especially the negative) and the contacts on the engine where they meet. its harder to start a car with a bad ground, and heat can mess with electronics. plus, its a free test, or at least like a thirty cent test for the sandpaper. good luck

 

thanks guys will try both

 

You said that it is hard to start but can you explain how exactly? Does it not crank? Does it grind while cranking? Or does it crank fine but the engine won't start? Fuel smell out of the exhaust?

Check the temp sensor on the front of the manifold (under the TB). It's for the ECM. If it's bad or disconnected, the ECM will be flooding your engine when you're trying to start because it thinks the engine is at -50F.

Many things can be causing your hot no-start. We'll need more information to nail it.

Lou