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oil pump drive angle not quite 47-49 degrees
- Thread starter mightyohm
- Start date
Jeff, I think you have assured that the timing chain is on correctly. And your explanation of why your drive slot angle does not match the WSM certainly matches your experience and may make sense. The remaining mystery is why my 1725 engine and two other 1725's I've worked on DO match the WSM. I'm not so sure that others have had the experience you are having. The good news is that, as long as the timing is correct, the angle of the slot is not important as you can always orient the dizzy (and wires) in several different ways that achieve proper spark timing. Maybe someone else with experience on 1725's can confirm your experience and explanation, but at this point the issue is moot. I am pretty confident that many who have worked on their Alpine engines would have easily accepted a 32 deg angle as "close enough" to the WSM instruction, without taking any great pains to measure more precisely. But I know I looked very carefully at mine and found it to be at the WSM angle. I have also seen Jumpin Jan refer to the angle as 48 deg. It's a mystery!
Tom
Tom
RootesRacer
Donation Time
Perhaps put it down to incorrectly indexed camshaft gear or incorrectly indexed pump distributor drive in manufacturing.
mightyohm
Donation Time
I was concerned about the cam gear, since mine is a replacement gear I purchased relatively recently. However the alignment issue happens with two totally different gears, one of them looks original, so I don't think it's the gear.
The pump might be suspect and I am quick to judge the quality of most "new" sunbeam parts, but strangely all of the "old" used pumps I have yield the 32 degree angle. If anyone has a "known good" pump with the proper slot angle I'd be happy to try it.
mightyohm
Donation Time
Tom, I agree, many folks wouldn't notice the difference between the angles if they were judging it by eye.
I'm hoping I can convince someone to measure their motor using the templates I created.
For convenience here are both templates in one file:
https://www.dropbox.com/s/xkrk0dlzo91r00q/oil_pump_drive_template_20190602.pdf?dl=0
Thanks for all of the suggestions and help. I'm still not sure why I am the first person to notice this issue, but I don't have much choice but to push onward and see if the motor runs when I am done.
mightyohm
Donation Time
Quick update on this. First, thanks again for all of your help and patience, particularly Tom and 65beam.
I realize there are a lot of ways to solve the problems I was having. My primary interest (aside from getting the car running) was to understand why what I was seeing didn't match the factory manuals. That's usually a bad sign, but in this case there was more to the story.
After I triple checked the cam timing and scratched my head for a while, I ordered a couple more oil pumps from the usual suspects.
Guess what? When installed, the drive slot orientations were different for both of them (and different from all of the other pumps on the shelf). And if I take a close look at the distributor drive I can see that the slot rotation with regards to the gear varies quite a lot from pump to pump.
It turns out that only one pump out of half a dozen had a slot that matched the factory spec. It was one of the new pumps I just ordered recently.
Fast forward a few weeks and the car fired right up and timed correctly using this pump, and that the distributor vacuum canister doesn't run into the dipstick.
I think the big takeaways are:
1. The 1725 oil pumps available today (at least the ones I've come across) display a significant variation in slot rotation. So depending on which oil pump you are using, your results may or may not agree with the angle in the WSM or with my results.
2. Trying to measure the angle precisely to check against the 47-49 degree spec is an exercise in frustration. It's more important that cam timing is correct, the motor is rotated one revolution after installing the cam gears and before installing the distributor (to set TDC #1), and that the distributor doesn't run into the engine block or the dipstick when the motor is properly timed (setting the static timing will give you a pretty good preview of where the distributor will wind up.)
2. At least in my experience, "most" old oil pumps from used engines will result in the distributor vacuum canister being much closer to the dipstick than it should be given Rootes 47-49 degree spec. From what I've seen on the forums, this is pretty typical. As long as you're confident in the cam timing and you're set to TDC #1 when you install the distributor you should be fine.
65beam - Thanks for suggesting rotating the distributor 180 - this is a great idea and avoids the dipstick problem entirely.
Thanks again to all who helped solve this mystery.
I realize there are a lot of ways to solve the problems I was having. My primary interest (aside from getting the car running) was to understand why what I was seeing didn't match the factory manuals. That's usually a bad sign, but in this case there was more to the story.
After I triple checked the cam timing and scratched my head for a while, I ordered a couple more oil pumps from the usual suspects.
Guess what? When installed, the drive slot orientations were different for both of them (and different from all of the other pumps on the shelf). And if I take a close look at the distributor drive I can see that the slot rotation with regards to the gear varies quite a lot from pump to pump.
It turns out that only one pump out of half a dozen had a slot that matched the factory spec. It was one of the new pumps I just ordered recently.
Fast forward a few weeks and the car fired right up and timed correctly using this pump, and that the distributor vacuum canister doesn't run into the dipstick.
I think the big takeaways are:
1. The 1725 oil pumps available today (at least the ones I've come across) display a significant variation in slot rotation. So depending on which oil pump you are using, your results may or may not agree with the angle in the WSM or with my results.
2. Trying to measure the angle precisely to check against the 47-49 degree spec is an exercise in frustration. It's more important that cam timing is correct, the motor is rotated one revolution after installing the cam gears and before installing the distributor (to set TDC #1), and that the distributor doesn't run into the engine block or the dipstick when the motor is properly timed (setting the static timing will give you a pretty good preview of where the distributor will wind up.)
2. At least in my experience, "most" old oil pumps from used engines will result in the distributor vacuum canister being much closer to the dipstick than it should be given Rootes 47-49 degree spec. From what I've seen on the forums, this is pretty typical. As long as you're confident in the cam timing and you're set to TDC #1 when you install the distributor you should be fine.
65beam - Thanks for suggesting rotating the distributor 180 - this is a great idea and avoids the dipstick problem entirely.
Thanks again to all who helped solve this mystery.
jumpinjan
Bronze Level Sponsor
These "new" 1725 oil pumps that you purchased, have the cam gear installed? I have never seen that before. Where are you getting them from?
Jan
mightyohm
Donation Time
Hi Jan!
Yes. I've ordered pumps from Sunbeam Specialties, Speedy Spares (UK), and Victoria British and they all came with the gear already installed.