Ok guys got a question that I think I already know what im gonna do for it but figured I would get some input, I recently purchased a basket case 88 z28 for 200 bucks, this thing doesnt even have a key (unless you call a shorty flat tipped screw driver a key) but I got it for me and my son to re build and with winter coming seemed like a good idea. So we drive the car home, only talking a couple blocks and the thing runs well as well as you would think a basket case z would run but I wasnt worried about that cause I had every intention of pulling the 305 building a 350 and doing a swap, anyway we get the car home it sits a couple days and the boy wants to do something with it so we go out and kinda give it a once over to see what we got I pull the air cleaner off expose the distributer cap and low and behold 3 plug wires are missing, yup drove it home on 5 cylinders so I go to the parts store get some new plugs and wires swap the stuff out get all the plug wires in the right firing order and wala this thing runs like a top and unlike the other guy on here that cant get the tires to roll I have no problems burning the rubber off the rims so anyway I get everything back together and now the car idles really high, I would tell you how high but like everything else on the car the tach is in-op, of course I can live with that cause im tickled that now I can take my time on a 350 build cause I have a runner, trans shifts smooth brakes work great only thing I have to do is get this idle down, my first thought was a vacuum leak but to date can not find one so I am thinking about timing just wanted to put some feelers out about it and see what you all think. Something else that I was really kind of curious about, this being my first venture into a chevy build ( have done fords and was a die hard mopar guy years ago) is there any easy way to tell the difference between a 305 and a 350 without getting to the casting numbers on the block? is there any obvious way to tell what I have because I have a feeling that this engine is not original, I was trying to put an exhuast under the car yesterday and found the cat was falling appart internally and literally had the exhaust blocked knocked that honeycomb **** out of the way and now it really is ready to run going to gut the cat for now just to get everything straight then buy a high flow before I put this thing all back together but I figured this was going to be a long project but now that I have good running gear it should move a lot faster than I thought it would.

Anyway any and all help is always appreciated and I would like to say thank you before this thing even gets going.

 

You didn't mention what type of carb you have. If it is a Holley, or Edelbrock, then have you tried the idle screw? If it is a computer controlled quadrajet, then the idle stop solenoid is probably stuck open since there is no computer control. This is probably due to the previous owner not having all the cylinders firing so he compensated by raising the idle. If none of these is the problem, then you should double check the timing. A simple timing light and a few minutes will confirm the setting. Also, is it a vacuum dist or is it still computer controlled? This will make a big difference. A very good way to check for vacuum leaks is to get some carb cleaner and spray the gasket surfaces while the car is running. If you come across a leak, the car will surge and almost die. This will tell you where you have a leak. As far as the size of the block, you can't tell just by looking. You will have to pull the numbers and see what it comes back to. It should be stamped on the block in back of the driver side valve cover, i.e. 5.0L or 5.7L. You should post some pics and let everybody see what you are working with and have a progress shot every now and then.

Have fun with the build and do it right the first time. There is nothing more frustrating than tearing apart a fresh engine for something that could have been fixed very easily.

 

It is actualy a tbi, the distributer does not have a vacuum advance on it if I remember right I will take a look later this afternoon and post. Can the castings be seen on the block from under the car or will I have to wait till I pull the engine to know what I have?

 

Now we are talking a whole different ballpark. You need to scan the car and pull up the trouble codes. (With a thourough tune up, you will have a pretty good runner until you get the other motor built). You can get a handy little tool at Autozone to do the scan or you can use a paperclip and jump terminals A and B. Do a search for the proper way of testing and the results you should get. The dist won't have a vacuum advance since it will be computer controlled.

As far as the castings, you should be able to lean over the engine and look at the stamping on the back behind the driver valve cover. It might be caked with grease but it will be there. It will be plain as day what size the block is.

 

do you have the dis set on top dead center I had the same problem and the dis was off buy 4 teeth that can cause the car to idle high or to run like $hit