My 86 951 dedicated track car blew its head gasket. The shop got the head off, saw scored cylinders, and is recommending swapping in a used engine. I have not seen the scoring, and I don't know how bad the scoring is. I trust the shop, so the question is what to do on a technical front.

I want to get the engine re-built as a full race engine, but I won't have the cash for that until next year. I might get in 5 DE's before this would occur. Is it possible (or advisable) to just finish the head gasket job and leave the scored cylinders as is for now? Would I be able to get a few DE's out of it?

Essentially, I am interested in avoiding paying for two engine removal/reinstallation jobs if I can and avoid buying a second engine. If that is simply unrealistic, then I will bite the bullet on the used engine until next year. I suppose one advantage of this route is that I could then send the current engine off for re-build while I still run the used engine. I don't need an extra engine in my garage, though.

 

as these engines get a bit more rare each year (people trashing blocks) a spare block is not a bad idea.

I simply say do it right the first time - gather parts for the rebuild. Find a nice go kart track for your addiction.

 

spare block sounds like a plan- but i just pulled apart a turbo that ran great and when i pulled the head it had some scoring in the cylinders at the top- prob from a headgasket. The car didnt smoke and ran very well w/ 150psi on each cylinder. Up to you where to go. Depends on the depth of the scoring as well.

 

I had a HG fail and discovered scored cylinders when I replaced the HG about a year ago. I had to make similar choices to yours. I decided to button it back up and run it as is. Granted I haven't done any DEs on it, but I don't baby it either. I am sure compression is down, but at this point it doesn't really matter. I purchased a spare block and am in the process of having it built up as a replacement. That is something you might want to consider as well. Essentially buy a used block and have that built into your race engine while running on your scored block.

IMHO, you really need to know just how bad it is scored. There are some here that have been running on midly scored blocks for quite some time.

 

Hey Dan,

How bad was the scoring on that block, bad enough to catch a fingernail?

 

most of it was just visual but it had a couple good ones in each cylinder from the top and down an inch or so. You could catch your fingernail barely - i shipped it to australia!

 

I've always wondered why these blocks score more often on the front and rear of the bores. I would think that more stress is put on the sides? I have spare blocks but they can only be used for either a Sunnen bore or sleeving project. If my new rebuild goes south on me I'm through with the Alusil and #2 RB headaches forever and will do an LS6 conversion and never look back. The $$$/HP on these engines just doesn't work out. It's like living on the edge of an eroding cliff just waiting for the bottom to drop out.

 

If its wearing at the front and back of the bores, it sounds like the thrust is worn out on the crank. I agree that it takes some $ to get these running well though. Doubt i'll ever do a conversion though.

 

I've got a spare 86 block for sale with good bores. Car had 142k on it and was parted because of a lot of things including blown oil cooler seals. Would like to get $1250 for the short block. I can ship it just about anywhere in the states via DHL for $125....just have to get the weight down to 150lb and then ship the remaining bits in a seperate box.

 

You could always hone the cylinders. Thats what I did and just had a machine shop bore scope it after. I put new standard sized rings in it. Stock pistons I had beed blasted and balanced at the same shop. Make sure you hone it with the AN-112 kit from sunnen. Cylinders are like new. Mind you my score marks were more like a discoloration. You could barely catch you finger nail on them. After installing the pistons with the new rings I turned the motor by hand with some light weight oil in the cylinders and it didn't leave a line of residue as you would normally see with blow by. I haven't installed the motor in the car yet. All together with the cost of the machine shop visit and the sunnen kit I spent about $500. Although you can get short block N/A for about that much money, I kinda like keeping the motor that came in the car. My $.02

 

Send off the pistons to Swaintech, depending on how deep the scratches are, have them do a .004-.008 PC-9 coating ($28 each for "heavy film" .008) on the skirts.

Send pistons with block to machinist, he'll have plenty room to do two stage hone then Sunnen felt/paste procedure.....you're golden, figure about $40-50 per hole for machine shop labor.

So roughly $300 and you have a fresh block, fresh coated pistons all within factory spec.

T

 

BTW - agreed that minor scratches are no problem as long as the piston skirt coating is fairly intact.

On a microscopic level, these pistons run on a very rough surface, minor scratches should hold oil just the same.

T

 

I just refreshed my motor for the 2nd time. Total 175k miles, 45k since the last rebuild much of it track/abuse. The bores were worn, and cylinder #1 has some minor scoring.

I Swaincoated the piston skirts and that was it. I used stock rings, and the gap improved from 35 thou to 20thou. A little bit more than spec. Car runs strong and it makes good power.

I don't think looser pistons is a bad thing in a race motor (within reason) as long as the ring gap is reasonably tight.

Perhaps I am giving up some power to a perfect, spec motor with perfect bores, but for what I am doing I am not willing to pay the price for perfection.

I have a spare TurboS driveline if this one ever grenades. Based on the past wear rate I figure I can get at least another 5 years and 40k miles out of this block, before I have to do anything radical.

 

Update. I decided to just get the head gasket done, and that is working out so far. The compression ranged from 135 to 145 psi. I did the TWS DE this weekend, and over 10 20-minute runs, it used 1 quart of oil. There is no visible smoking, so I can live with it for a few more DEs.

 

Brett, just sent you a PM.