Hello everyone!

I have an 89 coupe with close to 135,000 miles on it now, and am thinking it’s time to get the old engine refreshed a bit, if I can afford it. I just want a nice reliable car, a little more power than stock would e nice, but I’m not looking for a race car! Definitely needs to be very streetable!

I’m thinking about taking the L98 out and taking it to a shop to be rebuilt as I’m far from a mechanic and I just don’t have the skills or tools to do much engine wise.

I’m thinking that while it’s out I should have it bored out a bit (383?) and all the new parts to go with that. I want new gaskets all around of course. It should probably have the heads machined to ensure they match the block. While it’s out, I’ll change the timing chain and gears, which I have been meaning to do a while anyway. I’ll probably powder coat some small stuff too. Anything else that I should do while doing all of this? I’ll probably change the intake at some point as well, but probably won’t have the money to do that along with all the engine work.

Any idea what a ballpark cost of something like this might be? Anyone have it done lately? Would it just be better to go with a crate engine?
Also, how hard is it to take the engine out of an 89? Should I disconnect it from the 6-speed first, or take the tranny out with the engine? I’ve taken engines out of regular cars before, but the Vette is much lower and I expect to run into some clearance issues. Of course the clamshell hood may help some!

Any opinions? I’d love to hear them!

Thanks in advance!

 

In order to get a 383 you need to get a stroker assembly in addition to having it bored. Strokers have their own set of troubles. You may see what the other guys here say about the L98 heads, but as far as I know they don't flow very well, and you may not come up with a whole lot of power as a result of alot of cash investment. If you did the rebuild yourself you would still need $400-600 for the machine work alone. If you pay someone else the work+parts will run at least 3 or 4k with the old heads still on.

I'd say heads and cam are going to give you the most bang for the $$. You will get alot more rpm.

But If I were you I'd run the motor as is. With as low miles as it has, you could have alot of fun ruining it before you tear it apart! You'll be suprised how many more miles you will get out of it. Get some bolt-ons, nitrous, whatever floats your boat. When you see your oil pressure some day at 10 psi, or black smoke coming out the back, then you will know it's time for a rebuild.

I would suggest learning how to build an engine though, if you have someone to help you. It's alot of fun and very rewarding.

 

Thanks for yout input, but I think you misunderstood my question!

The reason for doing this is not to increase the power. I just want to restore the power that has been lost over the years. If I can get a little more than stock along the way then that would be great, but it's not my primary concern.

This engine is really starting to seem weak to me. It has a slight miss that is getting worse, and uses a bit of oil as well. I'm hesitant to take it on long trips these days!

I want to keep it a numbers matching car, so running it until the engine blows and then replacing it isn't a great option for me.

I would love to do all the work myself, but I don't have anyone to mentor me with this, and I doubt reading it from a book would allow me to do a good job. So, it looks like I'll need to take it to a shop, or maybe someone that does it "on the side".

 

How about a fresh set of aftermarket heads and a cam, and that will take care of everything you just said you wanted. I'd also bet that your bottom end is just fine. You should do a compression check also, to see what is going on with your power loss. Maybe get it dynod for a baseline. I would check into other stuff before pulling the motor and dong a whole rebuild. It can get very involved very quickly and you could be without a car for a while.

 

If you just want to "freshen it up", first take it to qualified mechanic that can tell you if it needs a rebuild. Have a leakdown test done. There is a very good chance the top end is what is causing your issues. Rebuilding the heads is a ton easier and less expensive then needlessly doing the bottom end. Im a BIG believer in "if it ain't broke, don't fix it" especially if you aren't going to be the one doing the work.

I'd pass on the 383 personally. They are powerful, but temperamental. The connecting rod thrust angles are the same as a 400 which, if you do your homework, have their share of issues.

[Looks like I posted the same thing at biggrizzly at the same time.]

 

There are other possibilities. For example, are you still on the original Cats? Your exhaust may be obstructed.

You might have a compression test and replace wires and plugs while the test is done.

Does your area require smog testing? If so, does your car pass? If not, you might want to get it tested to see what level of hydrocarbons you're producing.

 

Thanks guys! That's exactly the advise I needed!

I see your point about testing things before just replacing them. I just guessed that at 135K miles that the bottom end would need something done to it. But, I'll certainly do a compression test and see what I can see there!

Can I replace the heads with aftermarket ones without getting the block machined? I thought when you replaced heads youd need to make sure the block is completely flat...

Nope... no smog testing here, just a visual inspection. The last time I had the car in the shop I asked the owner what he'd charge for a new exhaust system (just to see what he'd recommend) and he said that my exhause looked brand new and I probably shouldn't replace it...

 

It's never too late to baby the thing! 135k isn't that high unless you are trying to sell it.

As far as heads go, when you have the heads removed you can easily check the deck for straightness with a machinist straight edge. Also there is no guarantee that the new heads are flat either. They need checked as well again with the machinist straight edge.