77 Lightweight engine overhaul

[benji77]

So,
I have owned my lightweight since early april '14 and have managed to do a few things with it. before i get into my questions i will tell you a bit-
2.25 petrol
RHD
weber 34 ich
ducellier distr with pertronix ignition

I put on parabolics, new brake cylinders, new carb, and multiple ignition parts. as i worked on the ignition, i noticed, it didn't make much difference to the idle if the 4th cylinder had spark or not. so, after running through some checks i have determined that a valve job is in order. i plan on having the head overhauled, but my uncertainty comes from the pistons. do i need to replace pistons? number 4 looks worse than the others but honestly they all look pretty rough. this is my first time to break one apart so any information is appreciated.

i wasn't planning on any other engine changes/repairs but if i end up replacing pistons i might think about installing the 2.5 cam as well.

the vehicle had very poor performance due to many factors. it seems that running lean for too long has caused the issues i am facing now. i have been trying to find a rochester b carb to replace the weber but haven't found one yet. the weber is new, the old weber had many issues and i replaced it before doing my homework.

thanks for any/all the help!



here is a picture of my lightweight

[SafeAirOne]

First off, nice air-portable! Boy, I love those...

Next, How did you determine that you needed a valve job, as opposed to, say...just a simple spark plug, plug wire or distributor cap? By the looks of it, and as you noticed, there wasn't a whole lot of combustion taking place in #4, though it does seem like fuel/air was getting into the cylinder.

Now that you have the head off, is there something grossly and obviously wrong with the #4 valves or valve seats? Presuming it's not an ignition issue, I figure it'd have to be pretty bad in order for NO ignition/combustion to take place in that particular cylinder.

As for pistons, I don't think we can really tell much by the pics--you might need to take closer pics or describe what you're seeing. For instance, is the #2 piston all dinged up, as if some foreign object got crunched in there, or are those just surface discolorations on the top of the piston? Are there any cracks or damage on the #1 and #4 pistons, or is that just some simple glazing and discoloration? If there's no damage I wouldn't do anything to them except maybe try to clean the piston tops off with acetone so they can be inspected, being careful not to get any acetone on the cylinder walls (you don't want to clean the piston ring contact area on the cylinder walls if you can help it, assuming you don't plan on replacing the piston rings).

What were the cylinder compression numbers for each one when you did the compression test during troubleshooting?

[jac04]

Benji- Where are you located? I have a complete head that I removed from my Lightweight. The previous owner had it refurbished a while back, and I think I actually have the receipts for the work done. I have no use for it if you are interested.

[I Leak Oil]

To add to what Mark said, it also looks darker between #3 and #4 on the deck surface and slightly darker inside the #3 bore just below it. Perhaps it's just the light in the picture though.

[benji77]

I am in Texas. I have a machine shop that'll do the work for $250-300 but can't source parts, so I will most likely be ordering from RN. How much would you need to take yours off your hands?

Thanks,
Ben

[benji77]

Mark,

I have a newer set of plug wires that have good spark out of all four. The dist cap was also relatively new and looks to be in good condition. I tried 3 different brand new spark plugs just to make sure they weren't faulty. Checked the gaps, etc.

The plug in 4 was wet and very black/sooty. The others had some black/soot but less than 4. The valves look really nasty.

[bugeye88]

Well.... The valves certainly look worse than the pistons. that intake valve on #4 looks particularly bad. Still odd that #4 wasn't firing though. So you'll certainly need some head work, hard to tell on the pistons/block, but with the use this engine has had, it wouldn't be a bad idea to pull it and take a look at the whole shebang.

Luck to Ya,

Rob
Bugeye88

[benji77]

Well, I have my head at the machine shop getting cleaned up properly and have begun removing the pistons. I had planned on fitting new rings since I had gone this far and found a new problem. These deep scratches in the 4th cylinder. I don't believe it was burning much oil, but also seemed to not really be doing much of anything with the valves in the shape they were. Forgive my newbie question but is having my block bore enlarged now a necessity?



Thanks for all of the help so far.

[SafeAirOne]

Can you feel any surface imperfection when you rub your finger over those lines or are they just stains? They look like the points where the ring gaps are riding, with the gunk from the top of the piston staining the cylinder wall and not being scraped off because of the gap.

If it is actual damage, the answer may well be "yes, you'll need to do something more than just honing the cylinder to make everything right."

However, pretending to be an optimist, I'll say that you need to measure how much you'll need to take off the cylinder wall to make it undamaged and round and verify the cylinder-to-piston gap will be within tolerance as listed in the bible. This, of course, presumes that the piston is still a cylindrical, round shape and not oval.

Edit: On second look, the one line runs up the cylinder above the height of the piston rings, so I'm going to guess that it's not stained as I described above.

[o2batsea]

Hindsight being 20/20, I would have done a compression test and a cylinder leak down test to determine overall health before ripping into it.
Without putting my own eyeballs on it, I'd say from my remote vantage point that the engine should go to the shop for a .030 over bore. With a new set of pistons, the redone head and a 2.5 cam, you will be getting about all you can expect to out of it.

[benji77]

Yes, I have come to the realization that a compression test was in order. I had incorrectly come to the conclusion that it only needed a valve job.
The scrapes seem pretty deep, but I couldn't find the culprit. There wasn't anything broken or loose when I pulled the piston. Took quite a bit of time with a ridge reamer to get the piston out.

Just so I do it correctly, what is the proper way to pull the block out? I have a haynes manual and green book but there still is a lot of reading between the lines and this is my first foray into engine removal. I can undo all the bolts, hoses, and such but what do I connect my lift to exactly? Please excuse my inexperience.

Ben