Not my first rodeo, so I know the cooling system on any car that has been sitting for years needs a thorough going over.
For those just now joining in on my adventure. My '76 XJ12 was lumped in 1993 and then driven all of 2,422 miles and last registered for road use in 1994 before the owner became disabled and unable to drive it - he just left it in his garage for the next 23 years until passing last year. I just recently bought the car and I am bringing it back to life. It didn’t take much at all to get the engine running again, now I’m disassembling the car and going through everything.
I have no idea what mix of water or what kind of coolant was in the cooling system in 1994, but I’m sure it wasn’t put away with the idea that it would sit for so many years.
This is mostly corrosion tinted rust color because the water outlet and water fittings are steel. I’ll remove the intake manifold, water pump, and radiator tomorrow. I may just install a new intake as the water passage appears thin and suspect. I’ll send the radiator out for cleaning, and may install a new water pump. While the intake is off that will give me a chance to inspect part of the engine.
Good idea to pull the manifold, IMO. Over the years I’ve seen some aluminum intakes badly eroded at the manifold-to-cylinder head mating surfaces. Easily repaired with JB Weld…although I’m sure more sophisticated methods exist.
It is a Chevy SBC, a 350. Up close shots may look mysterious, but you can see a little hint of the Chevy orange paint in the second pic and that is a standard Edelbrock Performer intake manifold. It is a 4 bolt main ex police car "CMJ’ code block from 1974. I’m half tempted to really wake up the horsepower by bolting on a set of modern performance cylinder heads and stab in a camshaft with ~ .500 lift 230 duration.
1974 engine would be a low compression engine, 8.5:1 and around 150-160 h.p. all is not lost though. different heads can raise your compression and provide bigger valves. don’t know codes from memory but some modern heads will do both and can be had cheap. depending on your driving habits, rear end ratio and auto trans, you may want to consider less duration. cmj code was also used on 305’s
Wiggles, I’m sure to run some cleaner through it to clean the rust in the block and heads. The radiator has a small hole part way down besides needing cleaning - but instead of fixing it I ordered a new IROC radiator because it was only $72 with free shipping cheaper than fixing the existing radiator. I think I’ll install a new water pump with the improved high flow impeller design, they are cheap too.
I always check the other casting numbers to narrow things down, the block on this one is 3970014 which was used from 1970 to 1976, so then I looked up the CMJ code used during that period. The car did come with some paperwork, including the receipt for the 4 bolt 350 engine from the rebuilder. But you are right that a person shouldn’t just go by the stamping number as those can mean different things depending on the year. What sucked even worse than the low compression in standard 1974 passenger cars was the stock cam had a delayed opening on the exhaust valve to improve emissions. The 1974 Corvette L48 350 was rated at 195hp and the L82 350 had 9:1 compression, a different camshaft and a very mild performance carb/intake upgrade that bumped the rating to 250hp. It really doesn’t take much at all to wake up a smog era 350. For sure its 8.5:1 compression ratio or lower - which is why a set of 62cc or 64cc modern big valve aluminum performance heads will bring the compression up at least one full number, and a cam like a Comp 268XE or 280H along with the existing Performer EPS intake, Carter 625 performance carb, HEI that came with the car will easily bring horsepower into the 320 to 340 range. That would make it a fun driver, but I’ve got plenty of other things to fix on the car before tearing into the engine.
CMJ was a fleet order 350 in 1974, made in both 2 and 4 bolt main versions for use in police cruisers and taxis. it would have been made with all the emissions of 1974 which wasn’t much externally besides air injection into the exhaust and fuel tank charcoal vapor canister. The wimpy camshaft (less than .400 lift) and 76cc cylinder heads doomed it to 165 hp with a 4 barrel carb. There were no laws at the time that required the smog pieces to remain on the car, but most fleet service departments would have left it all in place.
The rebuilder of this engine delivered a standard long block complete with the smog dog heads - I’m sure the rebuilder didn’t care about the engine code or what it originally came out of, just that it had 4 bolt mains for which he charged $50 extra.
The Edelbrock Performer was probably just cheap eye candy costing less than a new cast iron GM intake, and delivered no power benefits with low compression and lame camshaft.
The readings from a compression test do not completely reveal the compression ratio - as the results also depend on the camshaft valve timing events. You can actually have a low compression engine with a wimpy cam show higher cranking pressure than a high compression engine with a performance cam - but then we get into dynamic compression and other details that don’t matter when all you are looking for is to confirm fairly uniform cranking pressure on all cylinders.
The heads will be coming off as I can see that a couple of rocker studs have pulled out: the part of the stud near the boss was inside the boss, and now a couple of valves have sloppy action. Who knows how many times these heads have been rebuilt (the same can be said of the block). In my book when press in studs on a low performance engine start pulling out, then it is time to retire those heads or thread them for screw in studs. I’m just going to use it as an excuse to replace the heads with new modern heads rather than spending money on these heads.
that is a good price on those. at 72cc, it wont add much on compression though. 64 cc vortech heads would be the best bang for the buck. had a '77 vette with a similar engine. did the upgrades 1 at a time. the performer intake made a noticeable improvement, headers helped but not as much as the intake and the 650 double pumper gave crisp throttle response. adding a comp cams 292 made huge h.p. gains but was best at/above 3500 r.p.m’s. I eventually removed engine and went with 11:1, 2.02 valve and smaller 268 cam. less top end power but MUCH better all around drivability. what I lost at redline was more than worth what I gained off idle. I would of liked to try the 280 cam but the 268 ran so well that I never did. 11:1 is too much compression for todays fuel so yet another variable for my 2 extremes but given what I know, I would pic the 268 before the 280 if my compression was less.
Wiggles, Jrinam has it right that 72cc wouldn’t be much of a compression change. 62cc to 64cc should be just about right, I’ll know better when I have a head off to see which pistons were used and how far down in the hole they might be - rebuilders sometimes even used dished pistons which made the compression equation worse!
cheaper than fixing the existing radiator. I think I’ll install a new water pump with the improved high flow impeller design, they are cheap too.