Refreshing engine

[aeronca65t]

This brutal Winter combined with other projects at work and at home have kept me away from working on #909. But I knew I needed to get back into the engine before the '14 race season started.

For one thing, the 1275 is pushing a bit of oil out of the rear main scroll "seal". I haven't really changed anything in terms of crankcase venting so I've been assuming crankcase pressure has increased for some reason. The engine has about 50 hours on it, so it's due.

It's important to note here that the engine was running OK and still able to pull almost 7000 in 4th gear. But the oil leak spoke to emerging, related problems. I've been decent with maintenance; new oil / filter every event (20W/50 racing). Valves checked/adjusted regularly (although these are stock rockers so they are hardly ever off at all).

Last week, with reasonable temps, I decided to do a leak down test. The test confirmed my guess: 60% leak down in cylinder #3 with others in the 40% range. During the test I also ran about 60 psi directly to each cylinder and used a piece of 3/4" plastic pipe (as a sort of primitive stethoscope) to listen for leaks. Cylinder #3 was allowing a lot of air into the sump (I could hear it via the dipstick hole). And cylinder #2 was allowing a lot of leakage via its intake valve (it was audible from the from carbs).

So, off comes the head.

None of the valves actually looked too bad. Margins are a bit skinny (I ground them 2 years ago) so I will replace all with new ones.

Head gasket looks like it may have been compromised between #2 and #3. I'll have to look at that.

Ring end-gaps were all pretty loose. Cylinder #3 was over 0.035" (it should be around 0.010" or so). One ring came out cracked but that may have been my fault. There was a large built-up of crud at the top of the bore and I may not have cleaned it up as well as I could have before knocking out the piston.
One thing that I always notice is the excess build-up of crud on valves, pistons and the upper cylinder bore. I would guess these are lead deposits because I never see this much gunk on cars running unleaded street gas. I'm also running a slightly rich fuel mix, but this looks more like lead than carbon.

I think the heavy bore deposits may be related to the fact that the 21253 AE pistons place the upper ring pretty low relative to normal pistons. This make the upper part of the piston stronger but leaves a space for deposits to build up

When I had my first MGA back in the '60s, this sort of heavy lead deposit was common (I don't really think it's carbon). Build up of lead on plugs was very noticeable even after 1000 miles. The owner's manual for my old TR-3 used to advise that you should "remove the head and de-coke every 10,000 miles".

Two of the pistons I removed have scuffing on the skirts of the pistons. I'm not sure why; the other two are perfect. So I'll buy two of the 21253 pistons (+.040) and re-ring the old pistons. Then I'll balance the piston/rod assemblies, run a dingleberry hone up and down the bores and hope for the best. These are pretty mild, dished pistons designed for 9.75:1 compression.
Combined with a "fast road" cam (276 Kent), stock carbs and a non-LCB header the engine is overall, pretty mild. I'd guess maybe 75 horsepower.

Rod bearing journals measure good so I'll just replace them with new tri-metal bearings (-.010" in my case).

Right now, I'm waiting for parts from Moss and 7Enterprises. Then the fun part begins.

 

[dougie]

Neils -

I'm freshing the 6-cylinder in # 414 as well. A new cam, valve train, lighter flywheel and Tilton 7.25 light weight twin plate clutch assemble should improve hp and torque a few levels.

Have you seen the latest issue of Octane Magazine? They profile a pretty tick "Tea Pot", made me think of your project.

 

[aeronca65t]

Thanks Dougie....I haven't seen that one!

Will go down to my local bookstore and buy it.

 

[DrEntropy]

Nial, from the pix it appears you had some pressure passing twixt #2 & #3 at the head gasket.

Once ya get the deposits off the cylinder walls, it'll be interesting to see if the pistons with the skirt scoring have tipped long enuff for the rings to have gouged the bores in those two holes. The skirt scoring would indicate those two bores may be a bit too large, or the piston skirts weren't "ovaled" correctly, allowing a bit too much 'tipping.'

 

[aeronca65t]

As near as I can tell, the problem between #2 and #3 is that pressed in brass plug.
You can see it between the two cylinders (above center point).

It moved "in" a bit (maybe 0.030" or so). *Just* enough to breach and allow some crossover of gases.
Yesterday I pulled it out and drilled and tapped the hole to 3/8-NPT. This is a pretty common problem. Unfortunately, I couldn't find a solid, threaded 3/8 brass plug so I had to make one last night. Just another chore in a long list. Today, I'll screw it in, cut off most of the part sticking out and then flycut the entire head.

The bores are pretty round as measured with a telescoping gage. And they are within spec size for +.040" . The reason for the bruised pistons is sort of a mystery.
I talked to ~Mike Kusch~ yesterday about this (he's sort of a guru in our area). He said he hates the oil ring design on these pistons. That may be related to the problem. Or not.

The lucky thing is these engines don't have to be perfect to run OK. It actually ran fine the way it was pulling well past redline in 4th. The real problem was the moderate blow-by causing a big oil leak out via the rear main bearing scroll. More than anything else, I took it apart to chase the oil leak.

Crossing my fingers...........

 

[DrEntropy]

Those scroll seals are the bane of many an LBC engine builder. As for the piston scoring, it likely comes from a lack-o-lube if all else is within spec. Only thing I can think of is the galleys in the con rods or crank being constricted in some way.

 

[SaxMan]

What's scary is that having just replaced the head gasket on my Sprite...I completely "get" everything I'm seeing in the pictures. That wouldn't have been possible even six months ago. I guess its a bit more than just a coincidence that you're having the blanking plug issue with your 1275 as well.

I see you're running the lever shocks...are they any different than the stock ones? Did you move the battery to the trunk? I know some people do that to get better balance.

Out of curiosity is there any significance to the number "909" -- I know there was a famous B-17 that had the same name as "Nine-O-Nine", and the Collings Foundation has done up their B-17 to represent the original one.

 

[aeronca65t]

Flycutter needed new cutter inserts. Finally found them but too late to proceed. Today is busy day (watching grandkids). So may not get to this until tomorrow.

I've done these plugs on two 1275 heads.

I am running front tube shocks but they are disabled and just serve at upper control arm for suspension. I have add-on gas tube shocks. No lever shocks on rear....running same gas tube shocks on rear. I have info about it ~Here~.

This is somewhat controversial and everyone seems to have an opinion on whether it's a good idea (or not). About half the guys I race with run some version of add-on tube shocks and the rest run the levers.
One of the reason I like the gas tube shocks is resistance to overheating. I ran my cars in club-race enduros for many years (some events were 4 hours), and the gas shocks never faded. For a street car or vintage racer only running 20 minute sessions, I doubt this is an advantage.
These days there are decent, adjustable lever arm rebuilds available that I was not aware when I originally built this car (late 90s).
I'm currently building another car with Spridget suspension and right now I'm not quite sure if I'll run the gas shocks or use the improved lever arms shocks.
My street Midget has (leaky) front levers but I'll probably just hunt down a set of decent, used lever arms and refill them with clean oil (20W motor oil or motorcycle fork oil works). I feel the levers are fine for street use.

When I first started club racing in the early 1970s, I used "11" because it was easy to make with tape. I kept that number until around 2006 when I moved into more vintage racing.
In vintage, my race class has many more cars with several other "11"s and things got confusing.
So I decided to switch to a number that was less likely to be seen. I'm a big Beatles fan so "909" came to mind. This is one of the first songs the Beatles did when they first performed in The Cavern in Liverpool.

You see the song around 11:00 in ~This Clip~

 

[SaxMan]

Wow. Never heard that song before, and I thought I knew the Beatles catalog pretty well.

Interesting thread on the gas tube shocks, too. I'd one day like to get a second Spridget and build it up as a vintage racer...but that's likely to be quite a bit down the road. It's like the "If You Give a Mouse a Cookie" book. If you build a vintage racer, you're going to need a trailer to take it to the race track. If you get a trailer, you're going to need a vehicle to tow the trailer. If you get the vehicle to tow the trailer, you're going to have to widen your driveway so it can be parked. If you widen your driveway....well, you get the point.