Replacing crank gear

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Model T Ford Forum: Forum 2014: Replacing crank gear
Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth from NC on Friday, April 11, 2014 - 07:34 am:

Howdy everybody - so, hopefully someone is going to chime in here and say "Hey! Don't pull the whole engine, just _________________________" and you can install the new crank without messing up all those nice fresh seals you just did a few months ago!

Yeah, right. (big heavy sigh and rolling my eyes) I'm psyching myself up for pulling the engine this weekend. I got some beautiful, brand new Dan McEachern gears and tragically still have too much play between the new bronze timing gear and the old crank gear. I went ahead and ordered a new crank gear the same time I ordered the timing gear but was really hoping I wouldn't need it. Oh well.

I'm not 100% certain, but it sure looks like the old gear will just pull off and the new gear press right on . . . once I get the pan off. Anything in particular I should watch out for or make sure I definitely do/don't do?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Georgetown TX on Friday, April 11, 2014 - 07:38 am:

OK I give up - why would the engine need to be removed to change timing gears?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Friday, April 11, 2014 - 08:17 am:

To change the timing gear on the crank shaft you'll have to pull the engine, I think, and that's the best way to do it if the crank gear is original and worn.

For situations when the main bearing babbitt isn't machined in the correct relation to the cam (100 millimeters) there are oversize large timing gears made, I think. They're not supposed to be used with a worn crank gear, but it's likely there are a few who tries to get by with that and does for while - most T's doesn't get driven lots of miles. A nylon timing gear may be soft enough to adjust to the irregularities of a worn crank gear and may work for quite a while?
Fiber timing gears were common on cars in the 50's and 60's and were made for T's too, but with the added strain of a generator they often fail prematurely. Maybe the quality of the later ones is inferior compared to OEM fiber gears for other old cars


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth from NC on Friday, April 11, 2014 - 10:43 am:

Royce - the timing gear on the cam isn't the problem. I've already taken the old one off and tried it with the new one. The problem is the smaller crankshaft gear. I'm going to have to pull the engine in order to get the oil pan off and replace that gear.

Roger - I haven't measured it specifically but it's enough that with the new valve springs and cam shaft I get this bump/knock/clink noise when I turn the engine over. Originally I thought maybe my connecting rods were lightly contacting the new cam shaft. It took me messing and feeling around for quite a while to finally determine the real source: Every 180* the force from the valve springs on the down-ramp of one of cam lobes is making the cam and timing gear spin forward and take up the lash between the cam gear and crank gear.

I'm mainly wondering if there's anything I should definitely do or avoid doing when I pull off the old crank gear and install the new one.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd on Friday, April 11, 2014 - 10:57 am:

According to the Ford service manual, parargaph 458, w/the engine in the car, it is possible to unbolt the engine from the crankcase, remove the timing gear cover, etc, raise the engine for enough clearance to R&R the crankshaft gear.
Of course if the crankcase to block gaskets have been installed w/gasket goo or some other gasket sealer then you're SOL and will have to R&R the engine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth from NC on Friday, April 11, 2014 - 11:06 am:

Yeah yeah Ken that's what I was afraid of. Like I said I'm psyching myself up for the engine R&R part. When I felt the lash was still there despite the new timing gear my heart just sank. I thought "Maaaannnnnnnnnnnnnnnn . . . "


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Friday, April 11, 2014 - 11:44 am:

Seth

I think Roger's giving great advice and asking pertinent questions, the most important of which is: "how much backlash do you have?"

Our primary tour car has a pretty pooped engine which has a jingling/clinking sound coming from the timing gear. At idle or loafing along, will jingle. It also has great compression and runs like I stole it, so I don't care. FWIW, if you've correctly identified the problem, and the idea of the effort to replace the gear is distastefull to you, (and I think from your post, you do...) then I'd run it and not worry about it. There are a lot of undiagnosed loose timing gears out there and no one's the wiser.

Best of luck what ever you decide.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth from NC on Friday, April 11, 2014 - 01:35 pm:

Well, money sometimes constrains me from doing what I want to do, but in general I want to whatever is really the best/right thing to do. In this case the only thing inbetween having good gears is time and effort. I might not care much right now if I just put the timing gear in and leave the crank gear, but I'll know and think about it everytime I crank the speedster up. I'm just whining about doing it. Lol, I'm going to just bite the bullet instead of letting it gnaw at me.

For the question: I honestly don't know how much backlash I have. Feels like a lot to me. What's the best way to measure that? With both of the old gears it was probably at least a quarter the thickness of a tooth at the fat part. Now with one new gear it's probably about an 1/8.


Top of pagePrevious messageNext messageBottom of page Link to this message  By ROBERT BERGSTADT on Friday, April 11, 2014 - 04:06 pm:

I have a oversize cam gear in fiber if you want to go that route, Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Friday, April 11, 2014 - 05:03 pm:

Seth -- The oversize timing gear from Bob might be a way to get you by until you need to pull the engine for some other reason.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Friday, April 11, 2014 - 05:15 pm:

It could be the spacing of the crank and cam are a touch off and when you have the new gear on you will have the same situation.


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