Poor life choices - C4 content

Day-60(2-hours):

Thanks to Opti the sensor is in the correct place, but I'm still not sure about the hole in the block. None of the galley plugs fit(I kept the old ones), but it's threaded so I don't think it's one of the drive-in type either. Any ideas?

I cleaned off the valve covers a bit, and was surprised to see how pitted they were under the finish.

What I'd thought was just the paint releasing from the metal was actually the filler underneath.

Next I installed the water pump, pulley, and heater pipe.

Then started pondering how to reinstall the accessories, find a way to mount the alternator without the air pump present, and hopefully still keep the reverse-rotation water pump.

Crackers wrote: I'm pretty sure that boss/hole are for the old style mechanical clutch linkage that went between the chassis and the block, and was probably unused in this application.

That wasn't my first guess but I do believe you are correct. The angle of the photo makes it look a lot like a dipstick boss. But the hole is horizontal, on further inspection. Ball stud hole!

ClemSparks wrote:

Crackers wrote: I'm pretty sure that boss/hole are for the old style mechanical clutch linkage that went between the chassis and the block, and was probably unused in this application.

That wasn't my first guess but I do believe you are correct. The angle of the photo makes it look a lot like a dipstick boss. But the hole is horizontal, on further inspection. Ball stud hole!

I'll have to shine my LED flashlight down it(the free one from Harbor Freight ) and double-check, but it looked like it opened into a coolant passage.

is that the original water pump? I have to replace mine and am wondering about stock versus an aftermarket. I'd like to stay close to original but after all the work involved, I wonder if the other would be a better choice.

In reply to Iusedtobefast:

It's a new(not reman) Gates pump from Rockauto. Mine looked like it was still the original pump, so after 32-years I wasn't going to chance it.

That threaded hole is absolutely for earlier mechanical clutch linkage. It's a blind hole.

Day-61(4-hours):

I got a late start today due to errands, and replying to a Craigslist ad for 2 C4 Vettes/parts for sale. It was mostly a bust, as he's more interested in clearing his yard than parting them out. I neither have the room, money, or time to deal with parting them myself. However, he also had this...thing.

It's an 84, but with a C5-ish body kit.

By the time I left he'd said he'll take $2500 for all 3, including a supposedly running L82/700r4 combo he pulled from the other 84, an 85 with a long block of unknown(probably bad) condition & 700r4, and the yellow mess above. My gut says he'd take less if you start counting out $100's.

One other stop was Harbor Freight to pick up a dial indicator & mount so I could check valve lift.

Granted, I'm no machinist, and I'm using the cheapest tools possible, but my measurements weren't anywhere close to the specs. I checked cylinders 1 & 2 and got the following measurements:

Cyl-1 intake .452 Cyl-1 exhaust .256 Cyl-2 intake .273 Cyl-2 exhaust .233

The cam specs are supposed to be .488/.509 at the valves.

I made sure the indicator was as parallel to the valve stem as possible, but I think the curvature of the rocker, and possibly the triangle stamped inside the end, were skewing my readings.

I also continued hanging the accessories & plotting the alternator mounting/belt routing. You can see in the pic below the stock locations, including the space where the air pump would have been, and the resulting problem with the belt route.

Moving the alternator upward seems logical, but then the valve cover will be in the way.

So I'll need to do a bit more research on my options.

In reply to Cousin_Eddie:

Thanks! I checked with a flashlight tonight too and it's definitely a blind hole.

Everytime I see an update I feel a need to search Craigslist for Corvettes. Must resist.

Where does the knock sensor go? Could that be what that hole is for?

You will likely get a false reading for lift with it all together - the hydraulic lifter isn't going to have any oil inside, locking it and preventing it from collapsing.

Maybe take a rocker off, and check the lift off the pushrod? ie: no spring pressure on the lifter.

Measuring valve lift should be done on the valve spring retainer. You will never get accurate readings as shown in your picture.

In reply to Stampie:

I can send you the link to the ad if you want?

In reply to vwcorvette:

Actually, I'm not sure which sensor is which, and forgoing the stock fuel injection for a carb I'm not sure which sensors I'll still be using, although the knock sensor won't be needed. I installed them all anyway though - if nothing else I know they'll plug the hole they came out of.

In reply to SkinnyG:

When I followed the valve adjustment procedure, it had me snug the rockers so the pushrods have no slop. I'll need to readjust them once it's running and the lifters have pressurized, but regardless of whether the lifters are pumped up or fully collapsed the total lift is dependent completely on the cam, correct?

In reply to Don49:

Ah...thanks! I'd searched for step-by-step instructions on measuring lift, but didn't find any that explained either simply enough, or with pictures, so I could understand it.

I would rock that yellow car so hard.

In reply to mazdeuce:

It's a basket case, and there's lots of small areas on the body that need reworked, but it honestly didn't look too bad in execution. When I first walked up to it from behind I questioned him whether it truly was a C4.

Adjusting the rockers is usually: with the valve NOT opening, rotate the pushrod while tightening the rocker nut until you feel resistance, then go half-turn more.

BUT,

There is a spring inside the lifter itself, which is taking up any slack right now. When the engine is running, oil pressure fills a cavity inside the lifter, and when the lifter is raised, that oil is "locked" inside, acting pretty much solid, and the valve et al is opened. When the lifter comes down, oil again is pumped into the cavity, taking up any new slack from things wearing, and repeat.

With the engine NOT running, you don't have the lifter locked solid. The lifter will likely be fully bottomed inside before you start opening the valve, and give you a false reading.

Usually for checking valve lift, you measure at the valve itself, using VERY weak valve springs that won't work against the wee spring inside the lifter body.

Most SBC heads can't do much more than 0.470" or 0.480", and you have a cam that is 0.510 at the largest.

You could get some 0.050" offset keepers and some 0.050" valve spring shims to be able to handle 0.520" lift.

If you want to hit the simple button on the accessory belt there are air pump delete pulleys that bolt in place of the air pump. Up to you to decide whether the price of the delete pulley and bracket (try the CF classifieds for a used one maybe) outweighs the hassle of finding the right belt. You may have already checked out this option, though.

In reply to SkinnyG:

Thanks! Following some directions I found online I disassembled one of the old lifters, installed shims to lock it in place, and used it to check the valve lift again. I did 3 readings on the intake & exhaust, making sure I was zeroed after each full rotation...

Exhaust .443-.445/Intake .562-.570

Published lift is .488/.509. I'm not sure why I'm so far under on the exhaust, but over on the intake?

Regardless, it sounds like this cam is too large.

Are you setting the lash with a feeler gauge with your "solid" lifter and accounting for that? That could explain the low reading, tight lash, dunno on the high one though. Regardless, too big without machining the heads or some special parts.

What ratio rockers are you using?

Them are stock rockers. 1.5:1

In reply to SkinnyG:

At this point am I better off dropping another ~$50 on a better cam vs. trying to use this one by going to different keepers?

Not to be overly pedantic, but every time I read basic cam lift specs, they're always given in Intake then Exhaust, so .488/.509 would be a slightly greater amount of exhaust valve lift vs. the intake lift. Are you reading the cam card properly?

I'd guess you'd be better off with a more mild cam that will work with the stock converter (i.e. actually idle), compression ratio, etc. versus making this big one physically fit in a mostly stock rebuild.

I think something like this is what you're after, but I don't know much about cams. https://www.summitracing.com/parts/sum-1103/overview/make/chevrolet

Well,

A set of shims (Like this individual one) and a set of .050" keepers (Like these) will give you enough clearance to run the cam.

That's a pretty snotty cam. With those heads (look like 76cc) and those pistons (flat top), you're probably close to 9:1, assuming a THIN head gasket. That cam would be much happier with 10:1 or better. A smaller cam might be wiser.

The choice is 1) Re & Re a different cam, or 2) Re & Re the valve springs to install shims and offset keepers (which can be done with the heads on), or 3) pulling the heads and doing the shims and keepers.

You haven't fired the engine, so you can likely re-use the head gaskets without an issue.

BrokenYugo's cam suggestion would be GOOD.

Cheaper than trying to make what you have actually work. And he's right - gears, converter, mucking with the holley to idle at 8", recurving the timing to maximize low cylinder pressure. Big cams need a LOT more to make awesome.

(but golly I love the sound - I call it "potato therapy")