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Forums->Hot Heads Tech Talk->Intermediate shaft length

Hurricane
Intermediate shaft length


Doing final assembly on a rebuilt 331 Marine hemi. I used a HH intermediate shaft and purchased a marine Prestolite distributor for a small block Chrysler. In doing my mock up I confirmed the int shaft is dropping in and engaging the oil pump well. My question is how much should the distributor shaft engage the intermediate shaft. I blued the dist shaft and measured and I am only getting .165 engagement. Seems like it could engage about twice tha much so I don't want to proceed if I need a longer int shaft. Thanks.
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on: Sat 11 of Mar, 2017 [19:35 UTC] reads: 3259

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billm
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Re: Intermediate shaft length
on: Tue 21 of Mar, 2017 [18:09 UTC] score: 0.00
I think you're getting some bogus information. The camshaft drives the intermediate shaft in a way that forces the intermediate shaft and gear towards the bushing in the block. The only way the intermediate shaft could "lift" is if the engine was running backwards, or if the oil pump was spinning faster than the camshaft. Neither is plausible. Decelerating is not the same as running backwards, and the oil pump cannot run faster that the shaft driving it.
That said, I agree with your concern about having only .165" engagement of the distributor tang and intermediate shaft slot. There are several ways to correct this, but I've been modifying small block Chrysler distributor housings by machining-off the existing mounting flange and replacing it with a "slip collar" I've designed. The slip collar allows moving the distributor up or down to ensure full engagement with the intermediate shaft. I can provide pictures, information, or parts if you are interested.
Bill

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Hurricane
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Re: Re: Intermediate shaft length
on: Tue 21 of Mar, 2017 [21:57 UTC] score: 0.00
> I think you're getting some bogus information. The camshaft drives the intermediate shaft in a way that forces the intermediate shaft and gear towards the bushing in the block. The only way the intermediate shaft could "lift" is if the engine was running backwards, or if the oil pump was spinning faster than the camshaft. Neither is plausible. Decelerating is not the same as running backwards, and the oil pump cannot run faster that the shaft driving it.
> That said, I agree with your concern about having only .165" engagement of the distributor tang and intermediate shaft slot. There are several ways to correct this, but I've been modifying small block Chrysler distributor housings by machining-off the existing mounting flange and replacing it with a "slip collar" I've designed. The slip collar allows moving the distributor up or down to ensure full engagement with the intermediate shaft. I can provide pictures, information, or parts if you are interested.
> Bill

Thank You Bill for your reply. I talked to my engine builder and he agrees with your first statement 100% so the fear of the shaft climbing is gone. Now I do need to address the short engagement, my builder states he has placed shims between the Int shaft and busing to raise it up .100 on other builds with similar issues. No one I've talked to likes cutting the shaft and adding the collar/splice to lengthen it. I would really like to see what you've been doing with your dist mods, if you could send a few pictures to sales@actionscreen.com i'd love to see what you're doing. Thanks Again

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George
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Re: Re: Re: Intermediate shaft length
on: Thu 23 of Mar, 2017 [15:23 UTC] score: 0.00
No one I've talked to likes cutting the shaft and adding the collar/splice to lengthen it.

I did that on one of mine. There's no real stress on the shaft so it works. The only problem is if the dizzy goes away on the road an off the self replacement won't work, or any other moded dizzy for that matter. Better off getting the extended int shaft. I had one made for my current engine.

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Hurricane
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Re: Re: Re: Re: Intermediate shaft length
on: Fri 24 of Mar, 2017 [13:59 UTC] score: 0.00
> No one I've talked to likes cutting the shaft and adding the collar/splice to lengthen it.
>
> I did that on one of mine. There's no real stress on the shaft so it works. The only problem is if the dizzy goes away on the road an off the self replacement won't work, or any other moded dizzy for that matter. Better off getting the extended int shaft. I had one made for my current engine.

I agree, no real stress on the diz shaft especially electronic so I'm just going to lengthen it. HH kit won't work because this is an aftermarket prestolite marine and the shaft diameter is larger but I have a buddy at a machine shop that is willing to make a collar and do it for me. I always carry an extra module for the electronic dist anyway since they are notorious for leaving you stranded on the lake. I really don't quite understand though why the shaft HH sells as a drop in to be used with an LA distributor isn't just made longer to begin with. Not to knock HH because they have been a great resource but reading all the forums I am certainly not the first one to question this. Anyhow, thank you for all the advice and direction.

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billm
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Re: Intermediate shaft length
on: Fri 17 of Mar, 2017 [21:08 UTC] score: 0.00
Oop's, I misread your question. Sorry about that!
Distributor shaft length engagement with the intermediate shaft isn't nearly as critical as oil pump shaft length engagement with the intermediate shaft. There is very little power required to drive the distributor, so minimal engagement is okay if there is not too much clearance between the slot and tang. More engagement is good- but not necessary.
Bill

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billm
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Re: Intermediate shaft length
on: Tue 14 of Mar, 2017 [22:38 UTC] score: 0.00
I hate to say it, but I disagree with Hot Heads about the .140" engagement being adequate or normal. Every Hemi I've disassembled had about 3/8" engagement of the tang and slot. I've done some research on this, and cannot support the .140" dimension.
It's a good thing you measured this. I would suggest that you do what you can to get more engagement.
If you still have the original intermediate shaft, compare the length below the gear to the new shaft. They should be the same. If not, contact Hot Heads.
You didn't mention what oil pump you are using. If you are using the stock pump, it cannot not be the problem. If you are using a Hot Heads "modified 340" pump for the 331/354, that may be the issue. I had a similar problem on my 331 when using their 331/354 pump. After much of time and expense I found that using the Hot Heads "modified 340" pump for the 392- when fitted it with the adapter plate and pick-up from their 331/354 version- works perfectly.
Don't run your engine as it is. You need to get more shaft engagement. Please let us know what you find.
Bill

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Hurricane
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Re: Re: Intermediate shaft length
on: Thu 16 of Mar, 2017 [17:29 UTC] score: 0.00
> I hate to say it, but I disagree with Hot Heads about the .140" engagement being adequate or normal. Every Hemi I've disassembled had about 3/8" engagement of the tang and slot. I've done some research on this, and cannot support the .140" dimension.
> It's a good thing you measured this. I would suggest that you do what you can to get more engagement.
> If you still have the original intermediate shaft, compare the length below the gear to the new shaft. They should be the same. If not, contact Hot Heads.
> You didn't mention what oil pump you are using. If you are using the stock pump, it cannot not be the problem. If you are using a Hot Heads "modified 340" pump for the 331/354, that may be the issue. I had a similar problem on my 331 when using their 331/354 pump. After much of time and expense I found that using the Hot Heads "modified 340" pump for the 392- when fitted it with the adapter plate and pick-up from their 331/354 version- works perfectly.
> Don't run your engine as it is. You need to get more shaft engagement. Please let us know what you find.
> Bill

Hmmm, Ok Billm Thank you for the reply. I guess I'm not done with this yet. I am using a stock oil pump, I did check the HH intermediate shaft against the stock Int shaft and the length below the gear is the same so I'm comfortable the oil pump is being engaged properly. I also had to turn the engine over by hand to get the shaft to engage the oil pump shaft and when ti did it dropped in very solidly.

That leads me back to the distributor only sitting into the HH Int shaft .165. It doesn't look like enough to me. I'll talk to my engine builder next and see what he says and I'll have to spend some more time measuring the original distributor and int shaft lengths and see how they engage.
Thank you

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Hurricane
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Re: Re: Re: Intermediate shaft length
on: Mon 20 of Mar, 2017 [15:37 UTC] score: 0.00
> > I hate to say it, but I disagree with Hot Heads about the .140" engagement being adequate or normal. Every Hemi I've disassembled had about 3/8" engagement of the tang and slot. I've done some research on this, and cannot support the .140" dimension.
> > It's a good thing you measured this. I would suggest that you do what you can to get more engagement.
> > If you still have the original intermediate shaft, compare the length below the gear to the new shaft. They should be the same. If not, contact Hot Heads.
> > You didn't mention what oil pump you are using. If you are using the stock pump, it cannot not be the problem. If you are using a Hot Heads "modified 340" pump for the 331/354, that may be the issue. I had a similar problem on my 331 when using their 331/354 pump. After much of time and expense I found that using the Hot Heads "modified 340" pump for the 392- when fitted it with the adapter plate and pick-up from their 331/354 version- works perfectly.
> > Don't run your engine as it is. You need to get more shaft engagement. Please let us know what you find.
> > Bill
>
> Hmmm, Ok Billm Thank you for the reply. I guess I'm not done with this yet. I am using a stock oil pump, I did check the HH intermediate shaft against the stock Int shaft and the length below the gear is the same so I'm comfortable the oil pump is being engaged properly. I also had to turn the engine over by hand to get the shaft to engage the oil pump shaft and when ti did it dropped in very solidly.
>
> That leads me back to the distributor only sitting into the HH Int shaft .165. It doesn't look like enough to me. I'll talk to my engine builder next and see what he says and I'll have to spend some more time measuring the original distributor and int shaft lengths and see how they engage.
> Thank you


I'd like to pose another question on this same issue then. I've talked to several people that tell me the intermediate gear will actually climb up on deceleration of the engine. Question is how much will it climb? Are we talking a few thousanths or are we talking as much as the distributor will allow? My concern is does the distributor shaft ever act as a stop so that the intermediate gear can not climb up enough to disengage with the oil pump, maybe not even fully disengage but a partial disengagement could still be enough to break the tangs. If it is acting as stop then the .165 engagement I measured will allow for a lot of movement of the intermediate shaft.

This is a real concern as I lost this motor last spring. the motor has been rebuilt and I am using the same HH int shaft and LA distributer I had in it last year. Last year the bottom of the intermediate shaft failed, I lost oil pressure and ultimately the engine had to come apart for a rebuild. I just can't move forward without some more information so I appreciate what anyone has to offer. Thanks

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Hurricane
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Re: Intermediate shaft length
on: Tue 14 of Mar, 2017 [13:54 UTC] score: 0.00
> Doing final assembly on a rebuilt 331 Marine hemi. I used a HH intermediate shaft and purchased a marine Prestolite distributor for a small block Chrysler. In doing my mock up I confirmed the int shaft is dropping in and engaging the oil pump well. My question is how much should the distributor shaft engage the intermediate shaft. I blued the dist shaft and measured and I am only getting .165 engagement. Seems like it could engage about twice tha much so I don't want to proceed if I need a longer int shaft. Thanks.

To close this out, after talking to Eric it seems my .165 is more than adequate as .140 is the norm.

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moparruss
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Re: Intermediate shaft length
on: Sun 12 of Mar, 2017 [14:29 UTC] score: 0.00
Which HH intermediate shaft did you purchase? They have a stock replacement shaft for the 331 which is their part number 21945 and they also make a shaft especially make for using a small block distributor which is their part number 21936. If you have the correct one you should check with Bob at HH.

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Hurricane
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Re: Re: Intermediate shaft length
on: Sun 12 of Mar, 2017 [15:10 UTC] score: 0.00
> Which HH intermediate shaft did you purchase? They have a stock replacement shaft for the 331 which is their part number 21945 and they also make a shaft especially make for using a small block distributor which is their part number 21936. If you have the correct one you should check with Bob at HH.


Yes I bought the 21936 for a small block distributor so I should be good but I am going to call Bob in the morning. Just doesn't look like it right to me. Thanks


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