Hey everyone. Some of you may know me from my thread about fixing up my dad's '68 race car. It has a nom L88 engine that I have removed for rebuilding after sitting for the last 15 years or so.

My goal is to be able to run the engine on pump gas with hopefully no machining changes to the engine or the heads. It looks like some people have dropped less aggressive cams in and didn't piston heads in to achieve this. I have seen some info about this before, but many of the threads are older. Any suggestions on where to start?

Here's what I began with, mouse nest and all. That missing cap on the valve cover will come into play later...


Covers and carb removed. Valves look pretty good for storing for so long.
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They appear to be '67 heads from the casting number. I could be wrong though. I've also seen "401" stamped in a couple places, what is that stamp for?
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Some mouse made a home on the far side of the engine at some point.
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Aluminum intake number
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Had some fun on a Sunday morning a couple weeks ago.
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Those heads are L88 castings. It shouldnt be to hard to make a replica L88 with that engine. What are the block numbers? Is that vac adv can connected - i cant tell from the pic if there is a vac hose on the nipple or not. I cant read the intake casting number either. I see the intake is installed with studs so at least that has been modified. I dont know what to think of that heater hose - though the L88 cars were heater deleted.

Now the bad news. I see snow on the car in the pix. That means freezing. U will need to have both the block and heads pressure tested before rebuilding. Leaving water in a block in freezing weather can destroy them beyond repair - though im sure someone would buy them and try to market them. Y maybe able to press test engine before disassemble to save u some effort. They may press test ok who knows? But u better find before rebuilding as u dont want to chase block and head casting cracks after u rebuild them.

Cool car and good luck.

 

I can't tell from the photos if the valve retainers are Titanium or aluminum......
If they are aluminum....make a nice wall hanging out of them....they are unreliable for street....

You can make this motor just about anything you want......
I would run a nice Hydraulic roller and some 10.25 to 1 pistons and it will do what you want.....and look bone stock doing it.

That is all! Good Luck!!!!

Jebby

 

In the beginning of this post You state that this is a numbers matching L-88. I tried to look at your other posts but You have posted so many recently I'm pretty lost on just what You have. It would appear that Your Father was a very informed C3 collector of performance Parts. So what's the story on this Car ? If its a numbers matching L-88 then its one of the most sought after Corvettes ever produced. Obviously the car is not original as it was raced but who raced it before Him? If the Car was raced by a famous Driver it could be worth ten fold more than a car that is original, which in it self is worth a mint.
The 3904392 Cylinder Heads are very rare and very sought after. They only came on 1967 L-88 and L-89 Corvettes. Of which there were very very few sold. It will be assumed that this set of Heads was sold across the parts counter. Although there were very few cars that came with Racer Heads on production cars there were many that were sold at the parts counters, probably a lot more than anybody thinks. You need to pick up the Book "Corvettes by the Numbers" as it has a wealth of information identifying parts. It lists these Heads as 67 only, but the L-88 cars really don't apply to any of these rules. The date codes on the Heads need to be earlier than the date the body was.
You are talking about rebuilding the engine to make it run better. But by doing so You might be de valuing the Car dramatically. I think You have some Home Work ahead of You before You do anything more. If the car is proven to be a real L-88 Its is probably worth enough that You might want to just leave it alone. Odds are that it is not a L88, and if so then rebuild it with modern components and leave the rare parts to the collectors.
There is a wealth of information de coding Parts and Cars right here. And people to help.

 

Intake manifold 3933198 is correct for the 1968 and 9 L-88 Corvettes. I can only make out the 393 portion of the casting number in the picture. Many Many of these were sold across the Parts counters many more than came on original cars.

 

Sorry if there was any confusion, this is a non original motor to the car. No vin on the block either, but I've been told by people that knew my dad that it was an original 427 big block car but he added the L88 components. As far as I know he was the original person to race the car, he bought it in '72-3 and I have no idea who owned it before him.

Oh and the intake is stamped 3933163, sorry for the poor picture.

As far as rebuilding it goes, I'd like to keep all the outer components as close to how he had them as possible. I'd like to swap internal components to achieve being able to run on pump gas so I can easily cruise around. I have fond memories of growing up watching him race and the sound of an L88 engine gets anyone's blood pumping. I know the heads have a good amount of collectors value, which is why if like to avoid being to machine them, but they have more sentimental value to me then monetary value. And besides, we have a spare set of nos ones tucked away.

 

Thats what I'd do.

 

It is to be expected not to be a real L-88 or L-89 as there were so few made. And the ones that are were Raced and Wreaked. Since Your Father owned it since almost new probably about everything done to the Car was probably done by Him. This makes the chase on the Cars History much easier. If You Join the NCRS for $40 they can look up the Dealer who sold the Car. Now your only missing a Year or Two.
There still really isn't any way to document what options these cars came with with out the tank build sheet that's certainly long gone. Never the less there are lots of clues. You can run Serial Numbers along the remaining drivetrain. BB Cars had Different U-Joint Caps. Holley equipped cars had a single fuel line.
But all this doesn't really matter if the Car is worth more in sentimental value than it is to a collector. As long as its not rusted out it should make a great project. I would check that out before starting any project. This is one area where sentimental value can overrule common sence, only to end up with a lot of time spent a car that will end up, rusted out. Pictures of the Garage show this car probably spent most of its time inside and is probably OK.
I would still shy away from those Heads. They are what is considered Closed Chamber Heads. ( in this case very early ones) In in 1969 the open chamber head was introduced the first emissions designed heads. The design reduced compression 1/2 point yet made more HP. Modern aftermarket heads do the same thing just that much better, but for the most part they are designed for flat top pistons.
Since the Engine has been modified I would consider nothing original and there for no catalog of parts giving You compression ratios accurate. I would CC the Chambers, Heads, and measure the Head Gaskets before You start to see whats going on in there. It might be possible to cut some of the dome off the pistons and use thicker gaskets to keep the parts you have.

 

When you have the cylinder heads looked at by the machine shop....make sure they have a quality seat/guide machine like a Newen/Serdi/Sunnen VGS....have the valve guides replaced with some that don't have the fail prone reputation of the original GM guides....I know of more than one valve guide failure in those old GM aluminum cylinder heads and can still remeber pulling the spark plug on my buddies L-89 Nova 396 at the drag strip and being burnt by hot coolant from a cylinder head failure. Those retainers look like they are aluminum...loose them for some lightweight tool steel retainers.

 

In the late 1970's I assembled a L88 engine for GM piece parts. I think the engine came with 12.5:1 compression. I had 0.1 inches milled off of the piston domes. I think that got me down to 11.5:1 compression. At the time I started on this project, you could buy 104 octane pump gas. By the time the engine was in the car, his high octane gas was no longer sold. The pump gas sold would not really work even with my 11.5:1(?) engine. I bought high octane Av Gas from the Torrance airport to drive the car without knocking. At first they pumped the gas into Jerry cans..when they got to know me, they just pumped Av Gas directly into the car...highly illegal!!

If you're worried about octane ratings, you can buy racing gas for about $10 a gallon (110 octane, alcohol free). It comes in 5 or 55 gallon containers. It's a lot more expensive then pump gas, but if you don't drive the car that much, it's not really not a problem.

 

I actually have 110 octane race fuel available in my town at $7/gal because of a local race track. But running race fuel means I can't go on a spur of the moment cruise. Gas stops would have to be thought out.

 

I could make round trips to Las Vegas....it's 300 miles one way, 600 round trip. With my exact rebuilt L88 engine (OK piston domes milled 0.1 inch), a 3.08:1 rear end, stock Muncie 4 speed, and hooker header sidepipes (basically no mufflers), I could drive to Las Vegas on approximately 3/4 of a tank of gasoline. With my gear ratios, I was turning really low rpm's at 70 mph (1800 rpm?) and not burning that much gas...got fantastic gas mileage for a high performance car!!

I would leave LA with a full tank of high octane Av gas. I would drive the car and burn out perhaps 1/3 of a tank, and then pull over and fill up with normal pump gas. This would dilute my octane, but still plenty high enough. Similarly I'd top up after another partial fuel burn downs. Another dilution of octane. No problem getting to Las Vegas. This was a PITA of course. By the time I was on my last legs on the homeward bound trip approaching my LA home, I was running on pretty much on pump gas octane. On pump gas, I had to really baby the car. No more AC (yes I had AC! with my L88) . Any kind of acceleration would get pinging.

One final comment...when I built up my L88 clone, I could not get the L88 aluminum heads..I had to buy the rectangular port cast iron heads. I did subsequently did buy the L88 aluminum heads when they finally became once more available, but by this time the entire car was stolen. My motive is to build up my 70, still in progress, is to replace my stolen 69.

 

If you have 93 octane available and will run aluminum heads, I would keep the compression up at 11:1. Part of the "Bark" in the exhaust is compression related.

 

Got over and grabbed the casting numbers of everything I could find to help document what I have on this engine.

Transmission tag. I believe the first number is covered by the bolt and should be a 3. 3950318 looks to be an M22 off a Camaro, Chevelle or Impala.


3904351 engine casting means it was cast in 1967. Engine stamp pad is blank, so it was either a crate engine or was decked at one point. I haven't dug into the engine but I would bet money that it is a 4 bolt main.


3933163 aluminum intake manifold


3975928 aluminum water pump

 

Got out to the garage to begin the engine tear down. Had some fun.

Intake and first head removed. Some built up gunk and rust. Hopefully not too much rust damage...


The bottom of the head from that side.


Disassembled on the counter


2/10/67 and 2/11/67 casting dates. Looks like an original matched pair of early L88 heads



March 7, 67 block casting date. I'm wondering if this could have been paired with the heads originally as a crate engine.


Parts removed



Cylinder degradation. Hopefully not too bad. I need to get back together with 63mako who I have talked to about rebuilding the engine.

 

Good thing u didnt wait any longer. I dont think the head that was over #1 cyl will pass a pressure test.

Thx for all the pix. Interesting to see this and then to hear what your machine shop says. Hope you find a shop that respects collectors hardware.

 

If you havent found out already. From that picture alone you can tell its a 4 bolt main block. The 1/2 in pipe thread plug above the oil cooler is a giveaway

 

I hadn't posted about that yet, but I did actually figure that out yesterday based on that plug. Nice catch

 

those pics bring tears to my eyes....hope you can un-seize those without too much damage to the cylinder walls, I think you can go all the way to .070 over if you have to but obviously machine shop will know...hope those heads can be saved, they can tig about anything on the aluminum heads if you find a good weldor...

 

We will see... Three little letters, std, on the pistons are giving me hope. Looks like the cylinders were never machined so hopefully I have plenty of metal there to clean up any issues.