"New" engine saga

[aermotor]

I recently purchased a "running" chassis that didn't quite run and began building a sportster while sorting out the engine. The verbal history stopped with a deceased owner.
What I found with the engine was interesting:
1. The serial number boss was machined clear
2. The head is supposedly high compression
3. The head bolts all have small hex screw slots on the top and have exactly2 threads showing and the piston tops indicated that the engine was never run.
4. Further inspection revealed: new pistons, rods, bearing inserts, adjustable lifters, new oil pump, rear main and center main bearings between .001 and .0015, new exhaust and 2bbl Weber intake machined flat with new studs, new leakless water pump. The crankshaft looked different than my original 28 Tudor crank, but I wouldn't know a c'balanced shaft if it was laying on my desk. The crank flange run-out and all run-outs aft were spot on.
5. So far so good, but now things get amateurish. Ring gear on backwards, busted ear on the starter, mangled bendix, Mallory distributor in the hole with what was a center tab bent to fit the off set drive shaft slot, 180 degrees out on timing, old engine mount pads and front engine mount a mess.
I dropped in an original distributor, installed new ring gear and bendix. Installed a Weber 2 bbl (don't know the designation) and it fired right up and is the smoothest and quietest model A engine I ever heard. It's a keeper - so what is the problem? I need a centrifugal or vacuum advance as it can't handle things when that 2 nd barrel kicks in. Which do I want?

John

[aermotor]

Just went to the "save for later" box and found the Mallory distributor. The drive tab was not bent, it appears to be made centered. The corners were banged up and the collar was missing. The shaft was beat up and there were marks on the housing where a screw or bolt was really torqued down, I do recall that the distributor was not seated on the head, but slightly engaged. It is a centrifugal advance so I may just have a new shaft made with a center slot on one end and off set the other end if new ones are are not available. I found all this when I was checking the timing and found it 180 out. What say the experts?

John

[40 Deluxe]

Sounds like an inexperienced do-it-yourselfer bought a high dollar reman engine and installed (butchered) it himself. Any reason you can't use the Mallory that came with it?

by "it can't handle things....", do you mean it misfires under load? Maybe weak coil or condenser, or grunge in the carb?

[aermotor]

Originally Posted by 40 Deluxe

Sounds like an inexperienced do-it-yourselfer bought a high dollar reman engine and installed (butchered) it himself. Any reason you can't use the Mallory that came with it?

I agree with the above.


by "it can't handle things....", do you mean it misfires under load? Maybe weak coil or condenser, or grunge in the carb?

When the 2 nd bbl kicks in there doesn't seem to be enough advance quick enough to keep from " backfiring". See my second post about the Mallory

Thanks, John

[Tom Wesenberg]

Backfiring could be fuel related.

[40 Deluxe]

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I don't think there's a way (or a need) to suddenly have extra advance when the 2nd bbl. opens. It sounds more like a lean backfire. Maybe the 2nd bbl. is opening too soon or too quick. If engine speed is too slow to use the extra airflow, the speed of flow drops and the mixture goes lean, thus the backfire.

[Jim Brierley]

Your head studs are made by ARP, the best money can buy. I agree no need for quicker advance, more likely a lean mixture. If it indeed has higher compression than stock you will likely need less total advance than stock. A compression check will give you an idea of the existing ratio. I've never run a Weber carb but hear they are not jetted correctly for the A as they come when new.

[Dave in MN]

From your initial post, I assume you have insert main bearings. If the insert main bearings are as you state .001" to .0015", they are too tight. The minimum clearance is .00165". The clearance on the rear main with inserts should not be less than this amount. I set the rear at .002" min. to avoid "melt-down". If the rear main is at .001", you very well may experience bearing failure when you bring the engine up to operating temp. at full load. I have done lots of Dyno testing with inserts...I have proved this to be true!
Have fun with your new project.
Good Day!

www.durableperformance.net

[johnneilson]

not saying this is the cause of backfire when secondary opens, but have seen this before.
there should be a restrictor of some type to keep the secondary from opening too fast.
on holley carbs it it a checkball in the vacuum diaphragm assy.
what happens is the secondary plate opens too fast and the vac signal to the main and idle circuits is lost thus causing a lean condition. then the secondary slams shut and it takes time for the jets/emulsion tubes to start metering correctly again.

do not ask me how i know this, when correct you should never feel the secondary open only a consistent acceleration.

j

[40 Deluxe]

Originally Posted by johnneilson

not saying this is the cause of backfire when secondary opens, but have seen this before.
there should be a restrictor of some type to keep the secondary from opening too fast.
on holley carbs it it a checkball in the vacuum diaphragm assy.
what happens is the secondary plate opens too fast and the vac signal to the main and idle circuits is lost thus causing a lean condition. then the secondary slams shut and it takes time for the jets/emulsion tubes to start metering correctly again.

do not ask me how i know this, when correct you should never feel the secondary open only a consistent acceleration.

j

I may be mistaken but the Weber may be mechanical secondary operation, whereby the timing, rate and amount of secondary opening Is dependent on the driver's right foot.

[Kahuna]

Secondary opening with a mis/backfire is caused by too lean a mixture or a vacuum leak. Has nothing to do with the advance.

[denniskliesen]

The Weber 32/36 is manual progressive secondary. Most of the current Weber kits use this type of carburetor.

[CarlG]

Originally Posted by Jim Brierley

Your head studs are made by ARP, the best money can buy. ...

What Jim said!

[mike657894]

an unbalanced stock crank will have steel circles and the balanced will be pear shaped. sounds like you have a nice set up there.

[johnneilson]

Originally Posted by denniskliesen

The Weber 32/36 is manual progressive secondary. Most of the current Weber kits use this type of carburetor.

I stand corrected, it is not vac sec. sounds like jet/emulsion tube issue.

John

[aermotor]

Thanks for the answers, the backfiring/hesitation was do to the mixture and operators fast foot, the carb is a 32/36 mechanical progressive, the rear and center clearances are closer to Dave in MN recommendations than my original hasty check, the cam gear is aluminum, the crank is counterbalanced and there are no leaks. Would be nice to know who built it (I purchased it in the hills of western NC) and wish it was in my Tudor - where it may end up. Should I continue to try and deal with Mallory/MSD/Holly or whoever it is for a distributor cap and get a shaft machined with a centered slot on one end and offset on the other to use the centrifugal advance or keep the original distributor?

John

[Railcarmover]

Fix the Mallory, enjoy the engine longer.