Mallory Advance Curve Change Kit Question

I have twin SBC 2000 Vortec FWC Crusaders. The LH rotation engine uses a Mallory YLM624AV ,and runs fine. The RH engine had destroyed two mallory Distributors. The downward pressure on the dist. shaft from the reverse rotation caused the dist. plate to grind up the base of the housing cup. Crusader/ Pleasurecraft, provided replacements. The first failed like the original . I sent the Failed distributors to So.Carolina, and the tech sent back a Mallory YLM 619BV .I was told the 619 had a thrust washer or bearing that would correct the problem. The engine has been running for several years with no reoccurrence ,but it never had the same advance curve as the LH rotation engine. I was recently told that a kit Mallory# 9-26804 can be used to change advance curves. My Question is can this kit make the 619 advance like the 624? :rolleyes: I would greatly appreciate any help anyone may offer. Thanks JPM

The YLM's all use the mechanical advance and that is the kit for making any changes to the advance curve.

I'm kinda baffled why they sent you a distributor with the wrong curve....stranger things have happened.

Just make sure you verify the curve after you install the selected components from the kit.

Thanks for the reply. I understand the advance in the 624 is 12 degrees @ 3750 rpm When you say verfy the curve does that mean I should have the distributors checked on a machine? Thanks again , JPM

Jim, whether Crusader, Merc, Volvo, or ??? SBC Marine....., the curve/limit should be pretty close to one another, IMO.

The 619 curve/limit is not same as the 624 according to Mallory. With twins, you should be using the same Advance and Curve on each engine. If you do not, you will have trouble, as I'm sure you know!

Both distributors and oil pumps rotate is the same direction.
And yes, you are correct, there is a down-ward pull on the BV gear set that is NOT realized on the AV!
This is due to the gear cut!
This down-ward force should be countered via a special thrust washer/bearing at the upper end of the distributor shaft, as you also know!

Question:
Are you running excessive oil pressure that would place a greater load on this gear?
As I see it, this would be about the only thing that would create this excessive wear on a BV distributor housing....... if the BV is set up correctly.

Also, regarding your Ignition Timing, if I may:
I do not know what you are shooting for re; a BASE advance.
But if your BASE advance is anywhere near 10*, the mechanical advance will be in the neighborhood of 16*.........., giving you a TA of 26* or so!
A BASE of 10* plus a mechanical of 12*, gives you a TA of only 22*.... and even with full dished pistons, a TA of 22* may not be enough, IMO.

It would behoove you to have your balancers marked off for setting/checking TAT.

NOTE: these are generally Full IN @ approximately 3,200/3,400 rpm or so.


Jim, it is, or can be, very time consuming to play around with the advance curve yourself. Kit or No Kit!
Your engine and marked off balancer becomes your "Distributor Machine", so to speak.
Having these both checked by a pro, and dynamically on a Distributor Machine, is not a bad idea.

He said these are Vortecs, Rick, and he's got an A and a B version distributor so it is highly UNLIKELY that the distributors spin the same way.

What I was getting at by "verifying the curve" can be done as Rick suggested....the trick is getting the curve. I would expect to find it in the service manual (I don't have one covering those engines). It will show the degrees advance vs rpm for the entire RPM band. Usually they only show the advance so you will have to add the initial timing if so spec'ed.

makomark said:

He said these are Vortecs, Rick, and he's got an A and a B version distributor so it is highly UNLIKELY that the distributors spin the same way.....

Click to expand...

Mark, while these may be 2000 Vortec Engines, I'll assume that Jim has these carbureted, and will be using the older style YLM 624 AV "VR" Ignition system...... of which I actually prefer.
BTW....., Good move Jim, IMO.
However, I can assure you that the YLM 624 AV and YLM 624 BV both turn CW.
If these distributors did not both rotate CW, the RH engine would require a Reverse Rotation oil pump.........., and to my knowledge, Mark, I don't think that one is available..... at least I have never seen one!

But as per my Mallory experience here, the difference between the BV and AV is the Helical Cut of the "driven" gear!
While the RH engine camshaft may rotate CCW, the camshaft "drive" gear, and BV's "driven" gear are cut to correct the rotation of the distributor... making it conventional rotation.
It's all done via the direction of Helical gear cut!

I've taken a BV distributor......, replaced the BV gear with an AV gear....., and used it in a Standard LH Rotation application before.

But here's the rub, and what causes the wear issue:
The special Helical cut of the "driven" and "drive" gear, are what causes this "down-ward" thrust on the shaft. If the BV distributor is not equipped with the special thrust bearing/washer at the top of the shaft, then I'm not surprised that he is having issues after a short amount of time.
An oil pump can require quite a bit of power to turn it!


On a Standard LH Rotation engine, the Helical cut of both "drive" and "driven" gears cause a normal "up-lift" on the shaft. This "up-lift" is taken care of via the thrust washer directly above the driven gear. It has worked for years and years in all GM cars.
Now days, the washer is nothing but a plane looking washer. (in the old days, they were bronze, and they had a "tang" on them)

Anyway........, I hope that makes sense, Mark!

makomark said:

................
What I was getting at by "verifying the curve" can be done as Rick suggested.... the trick is getting the curve. I would expect to find it in the service manual (I don't have one covering those engines). It will show the degrees advance vs rpm for the entire RPM band. Usually they only show the advance so you will have to add the initial timing if so spec'ed.

Click to expand...

Mark, we fully agree here!

Jim, IMO, best to see the OEM advance curve, but a curve for these can be fairly linear.
Just be sure that it does not come on too soon. The dished pistons don't much care for lots of advance too early.

.

Thanks for keeping me honest.....that's what I get for not checking on things I don't get to touch frequently.

You can also change the limit, in the distributor, if needed, to get the span the advance works over. The springs control the rate, which pretty much represents the slope of the advance curve, when plotted.

Hey Mark, I know that you are honest, and I was not trying to do anything other than explain this! This is an easy one to be confused on when it comes to LH -vs- RH rotation.

I still think that he'd be better off to have both of these tested on a machine. Any adjustments can be made right then and there.

.

First let me Thank both MakoMark and Rick @Ricardo Marine for your help. It pleases me to know there are people who are unselfishly willing to help a fellow traveler.
I found what I believe to be the original Mallory distributor in my shed. Apparently I only sent back the second distributor to South Carolina. I measured 1/8 inch play between top of gear and the shaft with a thin washer in between. It is interesting to see the part number is ylm 624 bv. I popped out the pin on the helical gear. The Allen heads of the four screws in the base of cup were almost completely worn away and no sign of any thrust washer or bearing of any kind. I spent most of Friday past trying to find a shop with a distributor machine. It is impossible. The performance shops I contacted didn't do work on distributors and none knew of anyone with a distributor machine.
I checked the base timing on both engines and found a base of 10 degrees at 750 rpm. The info I got from the Mallory tech (12 degrees additional @ 3750 rpm doesn't seem reasonable to me as Rick noted, I will call them again. I wonder Rick, when you pulled the gear off the 624 bv did you notice a thrust washer at the base of the cup under the adjustment plate. The 619 may be a short production run made for Crusader to corrrect the downward pressure problem, just a theory. I have 3 Crusader/Pleasurecraft Manuals, all have little or no info in these areas. The oil pressure on both engines has always been consistent about 60 bls. PSI is my best recollection and thats off the gauges at cruse with the correct oil level.
Regarding the curve, the secondaries on these Holly carbs cut in at about 3000 RPM with fuel costs as they are I try to keep my cruise just below. The RH rotation engine uses 4 gallons per hour more @ 300 RPM. Can this be attributed to the different advance curves?
I noted the concerns about changing the curve in the 619 bv without proper testing befoe installing. I don't like the idea of dropping $272.00 for a new distributor. (Summit Racing sells the YLM 624 bv at discount). This doesn't appearl to me but it may be a way to go. Thanks again for any guidance you may provide. Jim

Jim:

Thanks for the positive words!

Does your manual(s) give you the timing curve for your engine? If so, I'd be inclined to use it.

Also, you've said a couple times that the Mallory tech said there was "12 degrees" additional; did he say if this was additional advance, default - out of the box, in the distributor or total? I'm thinking that is the measure in the distributor so you should see double that on the crank.

Not finding a machine locally is getting more of the norm. If you want the advance checked on a distributor, there are many shops you can send it to.

I'd get a couple "timing tapes" from your local performance shop and go D-I-Y. Only tricky part is you need to put the tape on the reverse rotation engine's balancer "backwards". If you aren't positive about orientations, just use some chalk or whiteout and mark the balancer and get the directions straightened out.

Jim and Mark,
Mark, the distributor advance is usually calculated at crankshaft degrees.
It would make little sense if this were actual degrees at the distributor, let alone confusing to the average Joe!

But let's run with that idea:
If you were to have a BASE of 10, and an actual distributor advance of 12, your high rpm advance @ crankshaft (10 B + 12 dist X's 2) would be 34* TA.
34* TA may be OK @ 3,700+ rpm.........., but certainly NOT OK @ 3,200 rpm.
And 3,200 rpm is where the YLM 624 is generally FULL IN... unless Mallory has changed this.

Once again, best to have both of these tested on a Distributor Machine.
Check with some old Hot Rod enthusiasts. They may know who has one.



As for the YLM 619..... if that's what it takes to get the Downward Thrust protection, then that's what you may need to go with.
Just have it Re-Curved as per your OEM specs, and as to match the LH YLM 624 AV.
You should see an improvement and equal performance from both engines (baring no other issues).


OH, btw, when I was chaning the BV to an AV gear, these Ignitions were being installed in LH engines, so I did not experience the issues that you are having. I just happened to get a great deal on some BV's.
My specialty is Volvo Penta AQ series. In the Volvo Penta twin V-8 I/O applications, there is no such thing as a RH rotation engine. So a BV would never be used.
Like said, Up-Lift only on the AV distributor, and the washer takes care of this.


Why on earth is Mallory selling a BV if it does NOT have downward thrust protection? Errrrh!
Ya know, I've got a couple of them here that have been converted to AV's. Maybe one of these days I'll pull one apart and take a peek.

.

A friend of mine bought a set for his Chryslers, and the supplied distributors were the same! Not only wouldn't it fit his reverse rotator, the bearings would have gone away quick if it had. It took a bunch of phone calls with their "tech rep" (who apparently never owned a boat--a drag car, maybe, but not a boat) to straighten it out.

Jeff

I have made what I think is some progress on my Crusader 5.7 timing issue. I ordered the Mallory#9-26804 which I presumed was the correct kit for both the YLM624AV and the YLM619BV. I followed the instructions (1000 RPM bracket) and got nowhere. The 9-26804 kit is for YT type distributor. I figured my season is wasting away and decided to buy a new YLM624BV. I called Mallory and told the tech about the 9-26804 misinformation and in conversation discovered the YLM624BV does not contain a downthrust bearing, but assured me that the YLY619BV does. I was directed to the Mallory on-site mechanic who told me to use the auto distributor kit #29014 which is designed for the YH type distributor assembly. He said if I used the silver and orange springs and left the plate adjustment at 28 degress, I would be OK.

I ordered the Mallory part #29014. When it arrived I discovered it didn't have a silver spring. I read the literature and chose a pair of springs I thought might do. I chose gray and orange for both distributors. The results were:
RH Rotation Engine LH Rotation
750 = 10 degrees 750 = 10 degrees
1000 = 10 degrees 1000 = 10 degrees
1500 = 13 degrees 1500 = 11 degrees
2000 = 17 degrees 2000 = 18 degrees
2500 = 26 degrees 2500 = 27 degrees
3000 = 32 degrees 3000 = 34 degrees

WOT was a bit over 34 degrees. The boat seemed to run a little better (18kts @ 3000 RPM 22 GPH). Both engines accelerated evenly and the fuel burn was identical at 11 gallons per hour each.

In all the literature I have, there is no information about the advance curve for year 2000 Vortec 5.7 Crusader. Any advice/opinion on all this as always would be appreciated. Thanks. Jim

The fuel burn sounds about right to me, but that 34 degrees advance seems like a LOT of timing for a marine engine. My old Vortec SBChevy used only 26 degrees, total advance.

Jeff

Jim Munley said:

RH Rotation Engine LH Rotation
750 = 10 degrees 750 = 10 degrees
1000 = 10 degrees 1000 = 10 degrees
1500 = 13 degrees 1500 = 11 degrees
2000 = 17 degrees 2000 = 18 degrees
2500 = 26 degrees 2500 = 27 degrees
3000 = 32 degrees 3000 = 34 degrees

WOT was a bit over 34 degrees. The boat seemed to run a little better (18kts @ 3000 RPM 22 GPH). Both engines accelerated evenly and the fuel burn was identical at 11 gallons per hour each.

**In all the literature I have, there is no information about the advance curve for year 2000 Vortec 5.7 Crusader. Any advice/opinion on all this as always would be appreciated. Thanks. Jim

Click to expand...

** and that, IMO, is risky for you!

Jim, just an FYI and a comment for you:

I am in full agreement with Jeff.
A TA (total advance) of 32* @ 3k rpm is very liberal if the engines are NOT using a Q/E piston/head configuration, IMO.
And if these are factory GM engines (2000 Vortec 5.7), I can tell you that they are NOT!

I'd be very careful...... especially on that Port side engine that is getting 34* @ 3k rpm! ........... Yikes!

I'd be lowering the limit, or I'd be re-setting the curve as to NOT be Full In until around 3.4K rpm or so! ....... IMO, that is!

I don't have any issues with what BASE you choose to set these at..... but remeber that any change to BASE (with this type of mechanical advance) affects TA.
You can lower TA by lowering BASE.... but now your BASE may be off!
Best to have these set up on a distributor machine once you establish a decent curve to use.
The person operating the machine can set both up identically.

NOTE; It looks like you are aware of the issue with the BV distributors AND the different curve between the 624 and 619.
Hopefully Mallory will step up to the plate for you.