Distributor end float

[bigjones]

To yank out the starter motor, it was necessary to remove the distributor. Seemed like a good idea to remove it completely from the block - that way the timing is not lost (provided you remember where the rotor is pointing).
On re-install it did not look like there was a gasket there - either that or it decomposed in an oily mess. This looked like a good place for it to leak oil so I made a gasket up from proper gasket paper.

Anyhoo, I was looking through Haynes and there is a procedure for determining the thickness that this gasket should be to give an end-float of 3 to 7 thou.

Basically, you place a washer of known thickness on the shaft and re-install distributor. Measure the resulting gap between distributor flange and the block with some feeler gauges. You can then determine the necessary thickness of the gasket to give the end-float gap spec.

OK, fair enough - however, big problem. Knowing my luck, that washer can easily fall off the shaft, into one of the holes and into the inside of the engine. You can't stuff a bit of rag down there to block the holes because the shaft is high up inside the distributor body - ie. the rag would prevent the dist. from seating properly.

Any thoughts?

PS. I don't think this applies to the 1275 series just the 1500 engine (why not, I wonder?)

 

[dklawson]

The dizzy shim issue came up recently on the NASS list regarding all versions of the Triumph engines. No one had a definitive answer on the shims. If I remember correctly, they are supposed to go underneath the dizzy mounting casting that bolts to the block. The dizzy itself may (or may not) have an o-ring around its shank to seal it to the inside of that casting. No one on the NASS list said they really worried about the endfloat. As you noted, it's not really discussed on the A-series engines and they can use the same Lucas distributors.

As for removing the dizzy w/out affecting the timing, if you unbolted the dizzy mounting casting and removed it from the block with the dizzy clamp still secured, the timing will be pretty close when you put it back together. Only a little bit of angular play is present around the mounting bolts. if you still have a dizzy with points you can always static time it. If you need a timing light just let me know and you can use one of mine.

 

[bigjones]

Doug,

Thanks for the post, info and your kind offer on the timing light. Like you say, I think there is only a very small amount of play re the mounting studs. Someday I would like to fine tune the timing. I think I had set it to 12 deg BTDC with my timing light and it runs fine but I would like to experiment with slightly more advance.

I think I'll replace the homemade gasket (31 thou) with another one (7 thou) (made from a Lowes Food grocery bag, ha!), smeared with a tiny bit of Hylomar Racing.

Thanks again - its put my mind at rest.

Cheers!

 

[Guest]

I don't think it's a big deal either. I didn't sweat it on my 1500.

 

[bigjones]

While waiting for the starter motor, I re-visited this end-float thing again and followed the directions in Haynes, using the washer technique.
Unfortunately, the results don't make much sense to me.

With a 93 thou washer under the skew gear the distributor was raised enough to give a whopping 224 thou gap between the dist and the block. If this washer is removed, the gap would be reduced to (224 - 93) = 131 thou. Add to that the desired end-float of 5 thou and I would need a gasket of 136 thou.

That's a pretty thick gasket. The gasket that was originally there was only 12 thou. Just to give you some idea - of the gasket sheets from FLAPS - the cork is 83 thou and the black, rubbery-smelling one is 27 thou.

To check this result, I removed the washer and replaced the dist - sure enough, there is a gap there - 90 thou (To measure this, I had to snug the dist down with the securing nuts because there was a bit of back-to-front rocking).

(Side note: I then removed the skew gear and re-installed the dist (leaving off the securing nuts). I could rock it back to front - I could slide a 8 thou feeler gauge in there. I'm thinking that is acceptable)

What worries me is that this car has been running with 131 thou of pre-load which doesn't sound good.

Not quite sure what to do - just put in the black gasket and to heck with it or make up a really thick gasket of the proper thickness.

 

[bigjones]

OK, y'all gonna kill me.

This is kind of embarassing but, when I was doing all this measuring, #1 was not at TDC. Doh!

This time I read all the directions and everything turned out well.

 

[jlaird]

LOL, happens to all of us.

 

[dklawson]

This is kind of embarassing but, when I was doing all this measuring, #1 was not at TDC. Doh!

Are you saying that the extra thickness you measured was the height of the tang on the dizzy drive dog? If the dizzy is fully down against the pedestal casting on the 1500, and the drive dog on the dizzy is in the slots of the drive gear run by the cam, your measurement method makes sense to me.

In fact, my younger son helped me lower the 1500 in the Spit this morning and I decided to use your method to check the end float. I ended up needing a gasket around 0.008" thick to get the endfloat. I measured what was left of the old gasket (tore during removal) and it was 0.010" so it all seemed to be in the right ballpark. BTW, I made a new gasket out of a 3x5 card. I think manila colored office folders are 0.010" or there abouts.

 

[bigjones]

Doug,

Good job on the engine installation!

Where's all my sons?

This is my understanding, someone please jump in if it's not correct:

The skew gear is driven off the camshaft. Not only does this skew gear spin around but it also goes up and down. As a reference point, Haynes says to get #1 piston at TDC - I believe this is where the skew gear will be at it's lowest.

Now the thickness of the gasket can be determined to give the spec endfloat (5 thou, +/- 2). The skew gear is taken out of the block. A washer (with a 1/2" hole) is carefully placed where this skew gear normally sits. The skew gear is then re-installed on top of this washer and twisted to seat. The distributor is then placed back on the block. (Actually, all you need to use here is the lower half of the dizzie that is bolted to the block because it is the lower half that contacts the skew gear. ie the tang in the upper dizzie does not normally bottom out on installation)

Because of the presence of the washer, the dizzie will be raised up from the block. If this gap is measured, and the thickness of the washer is known, it is a simple matter to determine the thickness of the gasket to give the proper endfloat (gap).

In my case, the washer was 92.5 thou thick and the gap was 93.5 thou. Therefore, I needed a gasket of thickness (93.5 - 92.5) + 5 = 6 thou. The grocery bag gasket I made was 7 thou, so I used that.

Hope that makes sense - this is all down in Haynes - I'll be more than happy to email the relevant pages - I sure Haynes will not mind 2 pages.

Cheers

 

[Hap Waldrop]

Ok, another thought, the face of the distributor mounting sleeve can be faced on a lathe on the side nearest the block to tighten the end float of the dizzy drive to the bottom of the sleeve to insure a more steady ignition.

 

[bigjones]

Hap,

Thanks for the input.

I put the sleeve on a piece of plate glass - there was zero gap or rocking. Of course, that doesn't mean that it is at right angles to the vertical axis.

In more news, when I tried starting the car, the action loosened the dizzie body from the sleeve! I could spin the dizzie around.

I replaced the 7 thou gasket with the 27 thou gasket and tried again. Same thing happened.

More later.

 

[jlaird]

How could it spin, it is locked down with a bolt that tightenes a clamp around the base of the dizzy.

 

[bigjones]

How could it spin, it is locked down with a bolt that tightenes a clamp around the base of the dizzy.

That's right, but it it did come loose, twice.

Since then I've tried something else. Bear in mind, as Jack points out, the 1500 appears to have a different clamping system than the 1275. In the 1500, the clamp is bolted to the back of the sleeve (base). In the 1275, the clamp is bolted directly to the block. Anyway, this time I undone the clamp from the back of the sleeve, then secured the clamp to the dizzie body and sleeve, at a mark I had made a while ago. Then I secured the clamp to the back of the sleeve.

That seemed to have cured that problem. However, the poxy car still won't start, despite trying this procedure sent to me by a kind Spitfire owner:

"For timing to work properly, the slot on top of the gear that receives and drives the distributor shaft must be aligned properly with the crankshaft and camshaft.

#1 can be at TDC in either the top of the compression stroke OR the top of the exhaust stroke. You need to have it at TDC at the top of the compression stroke. The easiet way to determine that its is at TDC on the compression stroke is to remove the rocker cover and check that both the #1 valves are closed (i.e. both #1 rockers are not pressing down on the valves).

When this is correct, insert the drive gear down into the engine. If you have the Haynes manual, it will show you a picture in the engine-rebuild section on what the drive slot on the top of the gear should look like when you're looking down at it. I'm assuming you previously had the Lucas electronic ignition. If so, when you're looking top-down at the top of the gear, the drive slot that engages the distributor should be pointing directly towards the engine, with the smaller half of the gear slot on your left-hand side.

If the gear won't drop in and engage properly in that position, it may be because the tang on the bottom of the shaft is not engaging properly with the oil pump drive below. Pull the gear and shaft again and look down the hole. If needed, take a flat screwdriver and poke it down the hole into the top of the oil pump shaft, and turn it manually so it will align with the tang. The oil pump shaft can be turned as much as you like, it is not subject to any timing, it just turns. But the dizzy drive-gear alignment is critical.

When the oil pump shaft is aligned, drop the gear and shaft back in, fully seating it and make sure the slot on top is pointing to the engine as in the Haynes photo. Put the dizzy housing back on (with your new gasket installed).

Now when you put the distributor back in, the rotor should be pointing towards the #1 plug on the distributor cap. The Pertronix won't make any difference.

This should allow you to start. Once running, you will need to check the timing with a scope, it could easily be out by a few degrees but at least should start and run. "

I'm still trying out things - just taking a break now. There's plenty of fuel in the fuel filter and the coil is getting current. I'll work from there.

Phew!

Breaking news:
OK, I swapped the leads and all is fine. ( 1 with 4, and 2 with 3)

 

[jlaird]

And just look how much more you now know about this system.

Grats.

 

[bigjones]

You're absolutely right, Jack!

Plus I found out that my spare electronics in the glove box needs some wiring, the spare dizzie in the trunk doesn't fit and the spare plug leads in the trunk have vanished.

Also, I need to put more tools in the car tool box if I'm to do an off road repair.

Cheers!

Oh yeah, and my theory that the skew gear goes up and down is bogus. Ha!