I have a 88chevy g20 van with a 305 v8 engine. I purchased a rebuilt engine from Jasper engines. That was in NYC. I moved to Florida of 2014 of April. I still have a warranty on the engine. Problem is it's been giving me he'll. The engine has been hesitanting and stalling. I can not go no more than 35 to 40 mph. I changed the tune up kits and still the same. My father in law is saying it could be the timing chain. Because the van is not sounding right. The engine only has 20,000 miles on it. I could even feel the van loosing power.
What do you think is the problem. A mechanic who deals with jasper engines is going to check it out.

 

I guess start with the basics. Check all the spark plugs to make sure they are firing. Check the timing for sure, and make sure it is not getting starved for fuel. Bad filter, clogged filter, bad Carb....? Does the 88 have the TBI or a regular carb? If its TBI then check your fule pressure and make sure the injectors are spraying proper and the secondary injector is working....