I have a 1987 z52 L98 auto bone stock with 220,000 miles. This guy is my daily driver. I got a hold of a 1975 350 that was previously intalled in a 1980 monte carlo for a 100 bucks from a buddy of mine. According to him, it blew a head gasket and its sitting on my engine stand getting ready to be disassembled for inspection.

My plan is to build this engine as a budget 383 and using either my stock 128 heads or purchasing 113 heads with current stock tpi setup. Upon completion of build, just swap engines and maybe heads + intake and start the tuning process to minimize downtime. Obviously, I'll send the block to the machine shop for cleanup, clearancing etc. I don't really want to spend more than 1500 total for the project if possible.

What are the major differences between the blocks? I know that the 87 has a hydraulic roller setup and that I will need some sort of block-off plate for the mechanical pump. Will I be sacrificing anything by going to whatever the 75 had for cam setup? I will document the build as I go, if you guys give me the go ahead for the build.

I've been a fan of this forum for a few years and know that you guys will steer me in the right direction. I'm very excited about the prospect of building my first engine. I've been a helicopter mechanic for the past 11 years and believe that I can tackle this job with some help from you guys. I currently have several engine building books and videos that will help along the way. Sorry for making this post so long, but I wanted to make sure that you guys had all the info you needed.

Thanks
Hector

 

Personally, given the choice between the two, I'd be using the block out of the '87. It's a one-piece rear main, and a hydraulic roller cam as you had said.

My car is an '86, which is the last year for the flat tappet. If I were going to build up the motor in it, my plan would be to look around for a newer block that is set up for the hydraulic roller. I've heard and read too much about people wiping out cam lobes on newer flat tappet cams. I'm sure with due diligence, you'd be fine, but the less I have to worry about the better.

 

To begin with, the newer block has a one piece rear main seal and the older block is a two piece. That means that the cranks are not directly interchangable. There may be a way to adapt one to the other, but I've never walked that road. I always chose the correct block to begin with.

If you decide to go with a roller cam using the older block, you'd need to use a retro-fit setup OR have the older block machined to use the stock type roller cam and lifters.

$1,500 isn't going to be nearly enough once you factor in all that'll need to be done.

Jake

 

'74 & '75 were bad years. Someone in GM's penny pinching department thought it would save the company a zillion dollars if they stopped putting nickle in their cast iron blend. Nickle is what makes cast iron more dense or harder. So, starting in '74 cylinder bores started to wear out quick, heads cracked, cams went flat. Anything from GM made from cast iron turned into junk. This era went into the '75 year as well before someone at GM noticed a problem. Beware of any light blue GM engines.

 

So, I guess roller cam block is the way to go. Jake, I didn't plan on reusing the crank. I was thinking more along the lines of a 383 kit for the 75 engine (400 crank, longer rods and new pistons). Pardon my ignorance, I didn't know that flat tappets weren't as reliable as rollers.

Do you guys recommend that I do a stock rebuild on the 75 and sell it? Is that even worth it? How much can I expect to sell it for? I guess I'd have to wait to do the 383 conversion on my 87 block till I get another car or a newer block.

 

You can do a 383 build using the 87 block, you're just going to need to buy all the needed parts and pay for the machine work done to the block. Also, if the 87 block is the one that came in a Vette it should have 4 bolt mains, which is desirable.

Since you have the option, it's best to go with a roller cam valve train.

Jake

 

Thanks Jake, that makes perfect sense. I guess I'll do a proper rebuild on the older block and sell it. How much do you guys think I can sell that long block for?

I'll save up the money and come back here for some guideance on parts and such for the 87. Hopefully I can get it together in a month or so.

 

L98 blocks are all 2 bolt mains, but that doesnt diminish the fact that this is the better of the two blocks to base your build on. I used an 87 block for my stroker and ditched the original 85 block because of the added benefit of the one piece rear seal and the roller lifters...you'll end up having to do an overbore, just be sure your machinist checks everything over before you order stuff...

 

Just pulled my '87 engine out and it is a 2-bolt main.

 

honestly youd be lucky to break even after rebuilding it. THeres a lot of cheap Ebay junk selling for nothing so everyone will compare your rebuild with someone elses price.

Id sell the block for whatever you can get for it and move on.
Try to get a half decent head or at least some port work done to the 113s, they will choke the 383 as cast big time. They may be a touch better than your stockers but not by any means youd feel while driving.

 

Took the 75 engine apart and found blown head gasket between cylinders 3 and 5. Also found a cracked rocker. Some corrosion was built up on the upper ridge of most cylinder walls.

Tonight I'll take apart the bottom end and look for obvious damage and let you guys know how it went.