samdjr74

So my mechanic is telling me my seats are shot on my 80' heads and the best thing to do is replace the heads with something modern and a little less restrictive instead of dropping huge amounts of money into the stock heads.

At the same time my engine of course is old. Mileage is low but the seals are dried up, it leaks, etc. So now I'm thinking of replacing it with a new GM crate motor as I can get one for $1500 and have the car back on the road fair quick, plus I can save the original L48 for future rebuilding.

But there's something to say about keeping it original and all numbers matching. Plus I know I can have the engine built up for more HP then the crate motor puts out. (It's putting out 260 which is still better then the stock 190 the car came with) But a rebuild takes time and could cost more

Just wondering what some of you folks did in this situation and if you liked the results? I'm leaning towards the new GM motor but I want to way in everything.

Revi

It all depends what your final goal is. Do you want a 300hp engine or a 600hp engine? How much can you afford to spend?

How do you know your current L-48 is making 260hp? Gross, net, rwhp???

The L-48 has poor flowing heads (with small valves), intake manifold and low compression. The only way for your original L-48 to make more horsepower than a typical crate motor will be by replacing the carb, intake manifold, heads, cam and possibly the pistons. The only "numbers matching" item that you will have left will be the block.

samdjr74

I'm not looking for high horsepower, I'm not going to race my vette, it's just a cruiser. The new engine I'm looking at makes 260HP, the stock engine was rated at 190HP new so even with the bottom line GM crate engine it's 70 more HP's over stock.

Revi

No, your stock engine was rated at 190hp (Net) and the new crate engine is most likely rated at 260hp (Gross).

190hp (Net) is approximately 230hp (Gross).

samdjr74

Ok, even at that I'm looking at a slight increase if anything from the original to the new crate engine which for the HP is fine by me.

Revi

Then the decision you need to make is how much money you are willing to spend for a 30hp increase.

My $.02 cents, if you are going to all of the trouble of pulling the engine and either rebuilding it or replacing it, you might as well go for more HP. A 300-350hp (gross) engine won't be that much more expensive and will still be a reliable cruiser with a bit more fun added in.

samdjr74

Well I'd like to keep the budget under $2K which is why the base engine looks good. There's another engine, right at $2K putting out 290HP and 320 ft lbs of torque which would be a nice step up from stock. But is the extra $500 worth the 30 more HP's, that's a tough question.

REELAV8R

Numbers matching on an 80' is not a major consideration unless this is a well kept and complete car now and you intend to keep it that way.
The GM motor your considering is a good base motor and capable of being upgraded later should you want to. It comes with a warranty and is all new.
Your current motor has low quality components by today's standards. For any decent HP >350 it will require replacing most everything save the oil pump and block. And if your gonna rebuild the motor why only go half way, may as well pump up the HP and put in quality components.
Cheapest, quickest route is to store the stock motor, and put in the crate GM motor. Then when you have the time and money, rebuild the stock motor if you want to retain the numbers matching block.

TedH

The only difference between the 260 and 290 Goodwrench engines is you get more cam in the 290 engine. I would get the 260 engine from Summit and order an equivalent Crane Energizer or Comp High Energy cam/lifters. the engines come without intake so you have only to pull the valve covers and front timing cover, pull the cam/lifters (loosening/removing pushrods & rockers) and put your new bumpstick/lifters in their place (I use the assembly lube that comes with the cam).

You have to do cam break-in even with the OEM cam so a little extra work for the $200 cam kit and you save $300 off the engine price. But, you have the time investment so your time has some cost/value.

It is really a wash when you come down to it (time=money). Save some time or save some $$$.

the 260 engine is not only gross but also that is rated with good carb, intake and headers/dual exhaust. the stock 190hp L48 had to breath through the restrictive converter, cast iron manifolds and other restrictions. The 260 engine is essentially the base L48/300hp engine with about the smallest RV cam available.

samdjr74

Good info, thanks. Even if I run a stock 260 motor without swapping cams I'm ahead of the gain. I already have a good Edlebrock intake and I'm running headers with side pipes which I plan to reuse both no matter which decision I make.

68post

My choice would be a "Vortec" GM crate engine over any of the lesser GM crate engines. More compression , better heads - by far and away , and a roller cam setup also = more HP and more upgrade potential too.

Install it with a good/used performer vortec intake ( I bought mine for $60 & shipping), a set of headers , and an HEI with the proper advance curve , and you'll think the power has doubled from the L-48 even with the stock vortec 190* @ .050 cam !

NONE of the factory crate engines come with a proper cam in my opinion, although the vortec crate is intended for a direct replacement into a truck application.
$.02

96 lt-4

The vortec is a good upgrade.That being said I would consider buying the GM crate motor and replacing the heads/cam(or buy heads/cam for your engine).Some 64cc aluminum heads will give you more compression and better flow.Match to a mild cam and you have the perfect street motor with some pep.Aluminum heads are cheap enough new and used ones are a plenty.

7t9l82

a matching number motor on an 80 corvette is worth exactly zero to someone with a brain. people are ate up with "matching numbers" because on some cars it matters a lot,but not every car. put yours on a dyno you will probably have 75 rear wheel horsepower, you want that?
turn your engine into a coral reef and put a crate in it and be done.

jb78L-82

That's probably true today but who knows in 20 years? Folks probably said that about a 70/71 with the base engine and automatic 20 years ago-not true today.

The one 80 that may be worth more original down the road is the limited number of L-82's (about 5,000 cars)-last of the L-82 and about 10% of total production that year. How many of those L-82's are left still intact and unmolested? Probably not too many...

7t9l82

20 years from now all collector cars may be worth zero, due to many reasons.

jb78L-82

I try and be more optimistic…..

7t9l82

Live for today.

samdjr74

Thanks all, great info and advice. I think the new crate motor will be the way to go. for the price I can't go wrong and modifying the motor down the road will help with the upfront budget.

sledz

I am on the fence with mine since it is the weakest engine they made, but it's an excellent condition 75 convertible and I want to keep it stock... I guess.....
I always hear about people saying they can put a crate in and keep the original, I wonder how many original engines are really put back in or even sold with the car.

jb78L-82

i just rebuilt my 66,000 miles L-82 into a 355 with AFR heads, Howards roller cam, and 10.2:1 compression-could not be happier! She is a beast now…..