DUI Distributor issue |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Posted: August-19-2016 at 7:51am |
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Gary, I searched for a picture that would explain it better than I can in words but didn't find any so, I'll try again. The technical description of the distributor gearing is a crossed helical gear set. These gears have straight cut gears so when they mesh, there's only a single point contact. This single point contact can be anywhere on the gear face.so depth of engagement of one gear to the other can be anywhere on that face. IE: the point contact doesn't need to be centered on the face. Where's the new member who's the gear engineer for Chrysler? Maybe he could explain it better than I can? |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Pete I'm not talking about it not meshing correctly. I thought we were discussing the distributor not being fully seated. If it's not fully seated and say only half of each gear were meshing would not the forces on those gear teeth be that much greater? Ken I have only owned 2 Chevy's in my life,none were apart but small Honda motorcycles used the same drive as well as VW and MG. Interesting they all use a similar method |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10680 |
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I did a little looking at Chevy distributor shafts and oil pump intermediate shafts today and from my "simple" measurements there is about 4/10 of an inch of engagement when the distributor shaft is bottomed out in the oil pump shaft
Since all the installation instructions tell how to make sure it's not bottomed out and say nothing about engagement, it's probably because you have plenty of engagement and you use shims where the distributor sits on the manifold to reduce engagement if you're bottoming out in the oil pump shaft. The location of the mounting pin hole in the distributor shaft makes it pretty much impossible to screw up the gear mounting because you can't really drill a new hole anywhere. You can't mount the gear too high and you can't mount the gear too low either The first picture shows the distributor shaft with the gear off and you can see the mounting hole. You can't redrill a hole closer to the distributor body or you'll be drilling thru the gear to put a pin in it. There's no room to drill closer to the oil pump end without breaking off the tang at the end of the shaft. And you can't go 90 degrees without drilling into the tang also. You also can't drill the hole in the gear at a different height and have it fit and mate with the existing hole in the shaft. The second picture shows how much engagement there is when bottomed out against each other. (The piece of wire is just sneaking in to do a little photobombing) I didn't take a picture of the distributor itself with the gear on it but there are a million or so on the internet to look at. So........lot of words to explain at least to myself why nobody seems to worry about lack of engagement on a Chevy distributor. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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The distributor can't move outward from it's axis. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10680 |
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Pete Could you put this into some language that can actually be understood and makes sense too? |
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13511 |
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Am I confused or does the cam gear have nothing to do with distributor seating? Couldn't you just twist it right through completely if there was no distributor shaft shoulder or oil pump?
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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The OD shoulders on the main shank of the distributor body that are in the block maintain the proper gear engagement depth no matter how far the distributor is inserted into the block. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10680 |
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I remember that. Good write up you did about it back then From another simple guy PS When I should have been getting my beauty rest last night I think I thought of a simple way of checking the engagement depth on a Chevy but I'd rather try it first to see if it actually works. |
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Air206
Grand Poobah Joined: September-28-2008 Location: Roanoke, VA Status: Offline Points: 3000 |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10680 |
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It worked for me with a Ford distributor.
I was curious what I had for engagement since I hadn't really thought about it before this thread and I'll guess neither had you. Now I know. what mine is. I didn't have any "instructions" on how to do this, just thought about it logically and started measuring things. The "about" was rounding off a few thousandth's at the most to get the concept across and keep things easy to read. You can take measurements of the new distributor just as easily as you can the old one and figure out how much engagement you have when you know how deep in the engine the top of the oil pump shaft is. You can have faith that DUI or any other outfit did it right or you can measure. You probably did a quick comparison of the new and old before installation right? |
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JPASS
Grand Poobah Joined: June-17-2013 Location: Orlando Status: Offline Points: 2283 |
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Couldn't you measure the gear engagement the same way you would on a rear differential?
I've seen where they use a bright white or yellow paint and brush it on the ring gear, then spin the pinion and see how the teeth mesh by the transfer of the paint. |
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'92 Correctcraft Ski Nautique
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Air206
Grand Poobah Joined: September-28-2008 Location: Roanoke, VA Status: Offline Points: 3000 |
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That's exactly what I am saying - The "checking upon installation process" doesn't assess minimal engagement only bottoming out. The only way to do it is to measure the old dizzy and hope the setup doesn't change (intake manifold change, etc.). In your write up, you give measurements and use the term "about". The DUI install discussion says to seat and wiggle to assess 100ths of inch wiggle. That's my point.... "wiggling to assess 100ths of an inch" is best guess process given what's known. It isn't a process that separates the "hack", as Pete calls, them from the Engine Gurus. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10680 |
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If you go back to page 1 of this thread you can see how I checked a 351 engagement that came out the same as what the broken DUI had (about 1/4 to 5/16 of an inch). This particular engine has been running for 40 years with this distributor so the engagement must be OK.. It would be taking the same basic measurements on a Chevy and doing some math. I think it would be a little harder to get all the measurements on a Chevy but it can be done. |
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Air206
Grand Poobah Joined: September-28-2008 Location: Roanoke, VA Status: Offline Points: 3000 |
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Keno-
His directions are exactly what I did and what I am referring to. You can assess too much engagement (bottoming out) but it is not possible - by the means in that description - to assess too little engagement. Hard to throw anyone under the prop if you can't assess marginal engagement. Using the old dizzy shaft setup would be the only practical way I would see to compare placement... and that assumes proper initial setup. Are there fancy ways to assess marginal engagement, Pete? |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10680 |
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Here's a good Chevy explanation of setting distributor height and the article has input from Steve Davis of DUI. Right now I'm too simple minded to make the link work for whatever reason http://www.hotrod.com/articles/ctrp-0606-proper-distributor-installation-practices/ KenO |
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Air206
Grand Poobah Joined: September-28-2008 Location: Roanoke, VA Status: Offline Points: 3000 |
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So, I replaced the Pro Tec with a DUI in a 454. When I dropped it in place, it is not possible to tell how much of the shaft is engaged. If it bottoms out, you can tell ...... but engaging 1/4 inch vs 3/8 inch vs 1/2 inch.... how would you know? Maybe mine isn't engaged enough...I wouldn't know. I have never heard of anyone measuring the distance prior to install. Is that done? How can you tell during install since you don't see anything and it would "feel" the same. Stupid question from a simple guy.............
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TedR
Groupie Joined: June-26-2016 Location: Clear Lake, IA Status: Offline Points: 55 |
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BTW the new 3 blade prop creates a much less turbulent wake than the 4 blade. Smoother hole shot too.
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TedR
Groupie Joined: June-26-2016 Location: Clear Lake, IA Status: Offline Points: 55 |
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May be too late too ask but how much is slightly higher? Just curious because Ford has some pretty tight tolerances on the distance from the bottom of the seating flange to the bottom of the gear, see the link below dist gear installation Sounds like a DUI screwup on the original shaft KenO[/QUOTE] KenO, not sure how much higher ~1/16" to 1/8" at max... I did not get a good enough picture, that "Ford Racing" guide had some good info, thanks. I have not called DUI yet to give them a constructive debrief. I'm so dang happy that my boat works. I put on the new 3 blade Acme 540 and i ran it up to almost WOT. 44 mph (not GPS certified) @ ~ 3900-4000 RPM. The only hitch is that there is a new "whine" when the boat is engaged in forward. It does not happen in reverse. The alignment still looks ok. I pulled it out of the water and ran it, and no whine... no binding, all sounds and looks ok. Again, so thankful to no longer be "boat-free" |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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But if not fully seated the gears would be running out farther on their tips instead of the full width of the teeth? The pressures would have to be that much greater
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Gary,
There wouldn't be any wear on the gear since they are straight cut bevels. |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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I understand that but we have know way of knowing if it was fully seated or not do we, we were not there. If it was not fully seated would there not be unusual wear on the gear too? Remember it's that gear that turns the distributor first, any forces that sheared the oil pump drive would also be concentrated on those gear teeth first, the OP never mentioned the gear being damaged.
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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The "harshness" was directed to whoever installed the distributor not noticing it wasn't seated and not to DUI's gear placement possible mistake |
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halfnelly
Senior Member Joined: January-14-2013 Location: Maitland, FL Status: Offline Points: 253 |
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I've always been taught not to run a high volume pump in a Windsor, simply because they don't really need one. The rationale I was always given was "It ain't a small block Chevy, don't build it like one!"
They can pump the pan dry at high RPM and cause a lot of wear on the distributor gear or twist the pump driveshaft, plus they cost more HP to run. I've seen a lot of guys use a blueprinted stock pump instead of HV in their Windsor builds. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10680 |
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May be too late too ask but how much is slightly higher? Just curious because Ford has some pretty tight tolerances on the distance from the bottom of the seating flange to the bottom of the gear, see the link below dist gear installation Sounds like a DUI screwup on the original shaft KenO |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21116 |
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Hv pumps are definitely harder on dizzy shafts and therefore cam gears. The Windsor oil pump drive and smallish dizzy shaft diameter can be problematic with HV/HP pumps, apparently. Bow tie stuff is much larger and not an issue per the folks I spoke with from Milidon and Melling... I just went through this on my BBC.
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Duane in Indy
Platinum Member Joined: October-26-2015 Location: Indiana Status: Offline Points: 1578 |
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re: sheared drive, I would venture to say that 90 + % of the drag racers are running high volume, high pressure pumps in their Fords. Never heard any complaints. Interesting thought though.
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Keep it as original as YOU want it
1978 Mustang (modified) |
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Gary S
Grand Poobah Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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I think that's pretty harsh especially if DUI determined that the gear mounting was questionable. I'm sure Robert Yates has lost an engine or two over the years would you fire him too? Joe had 408 troubles,I would not hesitate for him to touch any of my engines.
I'll never know,but my dad had his Ski Supreme's 351 rebuilt and right after that it split the distributor drive. I wonder now if a high volume pump had been put in. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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TedR
Groupie Joined: June-26-2016 Location: Clear Lake, IA Status: Offline Points: 55 |
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Hey Folks, thanks again for the help and insight. The problem is solved! The remounted dizzy shaft came back with the drive gear mounted slightly higher than before, so that the hex engages more of the oil pump drive shaft (length does matter)
just idling the engine, with a some powerful magnets on the oil filter trying to capture any ferrous fillings that might be left after using cleaning out the "dizzy hole". Then oil change and try out on the water. Thanks again Gentle Correct Craft Fans. Very Respectfully, Ted |
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