cspear1

Okay, I have had my 85' Z28 for about two years now. I've wanted to do something with the engine to make it run a little quicker. I'm not looking for a drag car, just something that gets up and goes when I want it too. The original 305 in it starts up and runs "fine" but its fairly slow and isn't too responsive when I punch the gas. I know the 305-->350 debate is never going to end so im not looking to start another thread about that, but would it be better to just fix up the original motor in it, or should i just look into replacing it completely. I have absolutely no knowledge of how to do an engine swap, but my dad is pretty knowledgeable. I'm just looking on suggestions of fairly inexpensive swaps I could do, and any tips people can give me on what all I should replace on a 305 if i were to just rebuild it. I'm really looking forward to working on this project, but as you can tell I am almost completely clueless at the moment. Any help and tips are greatly appreciated!

cspear1

And if I do end up rebuilding the 305(or even if i swap to a 350) would I need to replace the suspension/transmission/anything else/carb? I'm sorry I am completely clueless, if anyone could point me in the direction of somewhere I can read up on all of this kind of stuff I would be extremely happy!

NathanLewis

Personally, I would hold onto that engine as a means of transportation(if its your only car) while you searched for a better engine.


But the source of power lies with the intake and heads. I'm positive the stock 305 heads were terrible (correct me if I'm wrong anyone).

NathanLewis

no. unless you want to upgrade. it all bolts up.

Ronnie Brennan

one of the first things you want to do is find out if your engine is a normal 305 engine, or a 305 HO(high output) engine. You will be able to tell this by looking at the casting number by removing the valve cover and looking at the top of your head. You should see a casting number like 140........ or 141....... you can take this number and do a search on it and the search will tell you what head you have. If its a HO it should still work better than you say it is, so I would probably take it into a shop and have it tuned up. there's a number of things that could be causing your engine to not work good so get an estimate and go from there. Building a whole new engine will most likely be more expensive than just repairing yours, but it all depends on whats wrong with it. If money is an issue you can run what you got and start buying pieces to build another one with or put that money into yours. the 305 is a good engine when working properly. Its not going to give you a mind shattering amount of HP without a tonne of money, but it will do the job. U wont be a 10 sec car but you'll get from point A to point B in a Jiffy. When looking at building you have to set a goal. If you want 400HP wheel you have to also consider that you will end up rebuilding your transmission and rear end to handle the power among other things. You cant just slap a bigger engine in a car and say giddy up... You can do this but be prepared to be broke down every now and then from destroying your tranny and rear end ++ Its also a good idea to know what you actually have in your car for tranny and rear end. and build a motor based on what you have if you dont want to be replacing them.

five7kid

iTrader: (14)

You're wrong.

five7kid

iTrader: (14)

Okay, where to start?

First, in '85, the LG4, HO, and LB9 all had the same heads - 416's. They were 58cc chambers, had 1.84"/1.50" valves. The ports are the same as used in later L98 350's. With 1.94" intake valves, and if you really want to improve them, 1.60" exhaust valves, and some pocket clean-up, they are pretty good performance heads, for either a 305 or a 350.


Perhaps just look at the 8th digit of the VIN. H = lo-po LG4. G = HO L69. F = LB9. But, about the only difference this makes is the exhaust, as the LG4 has pretty poor exhaust. Even that doesn't make a whole lot of difference, as any performance build-up, including a 350 or bigger swap, is going to start with a complete replacement of the exhaust.

Okay, rather than re-invent the wheel, why don't you just go to the FAQ forum (you know, where frequently asked questions are posted), look for the thread that has a title about difference between 305's and performance mods, and see what it has to say.

For 350 swaps, if you can't find info about that by searching this forum, you probably aren't up to the task.

startat2

iTrader: (2)

Personally, if your going to pull the heads I would have them cleaned up as five7 said. If its not something you want to mess with, leave em alone. My first third gen I did intake, exhaust, and cam. It really woke her up. I added a small shot of nitrous later and still had no problems until she was totaled. All of these mods can easily be done in a weekend however, even if she is your DD.