'84 1200 engine for a '82 GW

[canuckxxxx]

Got the urge to start butchering up some metal. :builder: Put the cam key in the slot in the cam and scratched a line so I would know how far down to make the offset. Then put the key in the vise with only that part sticking up. Used file to reduce width from 4mm down to slightly less than 3mm. Put it on cam and put the cam wheel on to see if it would give offset. It does but now I am left with a 1mm gap on the cam wheel keyway. Will have to make a 1mm spacer to fill this space.

BTW, This is exactly what Eric describe that he does to offset cam wheels.

Key in vise

offsetting cam wheel key 1

• canuckxxxx
• Jul 21, 2015

Modded key

offsetting cam wheel key 4

• canuckxxxx
• Jul 21, 2015

Cam, key, and wheel together showing offset

offsetting cam wheel key 3

• canuckxxxx
• Jul 21, 2015

 

[dan filipi]

Gees just 1 mm eh?
Can imagine what a belt off by a full tooth does then.

 

[ekvh]

You guys piqued my interest. I went out and added another 3/4 degree or so of advance. Me likes. But the liking part for me may have been that I've been riding a while with an intermittent plug. Fixed it idles like a rock again. The nice thing about doing cam's vs crank, is the ign timing remains the same. If you do the crank, the ignition timing will be moved and you'll need new marks. I am probably four degrees advanced now. I should build a degree wheel, but math is so much more fun.lol

 

[joedrum]

opcorn:

 

[canuckxxxx]

dan filipi » Tue Jul 21, 2015 8:56 am[/url]":1vgm01h3]
Gees just 1 mm eh?
Can imagine what a belt off by a full tooth does then.

Dan, the cam wheels are about 117mm in diameter so 1mm offst at the key gives about 6mm where the belt goes.

 

[ekvh]

Here's what I did and I have far different numbers for how much is needed. This is what it looks like now. You can't see it, but there is a 0.025" thickness piece of blue tempered steel, and a piece of 0.006" piece. The 0.006" piece is to the left of the one in the photo. I'm pretty sure it's now 4.4 degrees because without the shins in place, you can rotate the pulley stop-to-stop and it's about half a tooth on the outer pulley, at the belt.

I shaved the pulley, not the key.

 

[ekvh]

I put the file in the vise and slid the pulley. You have to be somewhat careful. Mine are tap tight in the pulley. They're tighter than stock.

 

[canuckxxxx]

ekvh » Tue Jul 21, 2015 10:56 am[/url]":2wenw91v]
Here's what I did and I have far different numbers for how much is needed. This is what it looks like now. You can't see it, but there is a 0.025" thickness piece of blue tempered steel, and a piece of 0.006" piece. The 0.006" piece is to the left of the one in the photo. I'm pretty sure it's now 4.4 degrees because without the shins in place, you can rotate the pulley stop-to-stop and it's about half a tooth on the outer pulley, at the belt.

I shaved the pulley, not the key.

So Eric, it looks like you offset the cam wheel from the cam by .025" + .006" = .031" or .79mm. With a 20mm diameter cam that would give an angle change of 4.5º at the cam wheel. But because the crank rotates twice as far as the cam there would be a 9º change relative to the crank.

 

[ekvh]

No, the crank is half of the pulley speed, half of pulley diameter, half the number of teeth, so 2.25 degrees at the crank......I tink. The big factor in thinking it's right is the half a tooth measurement.

 

[ekvh]

ekvh » Tue Jul 21, 2015 12:01 pm[/url]":1ts6s6bj]
I put the file in the vise and slid the pulley. You have to be somewhat careful. Mine are tap tight in the pulley. They're tighter than stock.

The pic may make the key look loose, but it's not. I put one shim on top of the key too because it is that loose stock.

 

[canuckxxxx]

Because the crank has half as many teeth as the cam wheel it move twice as far (in degrees) as the can wheel. Cam move half the speed of the crank.

It's is what happened to me: I moved the cam wheel by 1 tooth which I expected would give me 9 degrees advance at the crank but it was 18 degrees.

The degree wheel is good because it shows you what you have done even if it isn't what you expected.

 

[ekvh]

When you're talking advancing the cam's, the number used is the number of degrees the cam moves, I think. I guess we're talking different things. When I advance the cam's, I keep the crank in same position at tdc. It's only the cam that gets rotated some. I was thinking that the timing wouldn't move on my 1000 cam's with the advance but it probably has. Since its on the other end of the cam, it has advanced some too. Probably why idle was better.

 

[dan filipi]

You guys are putting a lot more time and effort into this than I ever could. Great thread, keep it going!

 

[slabghost]

ekvh » Tue Jul 21, 2015 3:47 pm[/url]":3a1bus4m]
When you're talking advancing the cam's, the number used is the number of degrees the cam moves, I think. I guess we're talking different things. When I advance the cam's, I keep the crank in same position at tdc. It's only the cam that gets rotated some. I was thinking that the timing wouldn't move on my 1000 cam's with the advance but it probably has. Since its on the other end of the cam, it has advanced some too. Probably why idle was better.

That is the advantage of cam driven ignition. Advance the cam you advance ignition just as much.

 

[slabghost]

canuckxxxx » Mon Jul 20, 2015 11:09 pm[/url]":9tmq2139]
At the front of the 1200 service manual there are some specs.: Intake opens 10º BTDC, closes 40º ABDC. Exhaust opens 40º BBDC, closes 10º ATDC all at 1mm lift. So the cams are advanced as compared to the 1100.

My 1100 cams only have 48º duration vs 50º for the 1200. So with my setup, maybe I should shoot for Intake opens 9º BTDC, closes 39º ABDC. Exhaust opens 39º BBDC, closes 9º ATDC.

Joe and Eric, you guys are putting different cams and heads on 1200s all the time. What do you do about valve timing?

Brian

1100 cams are set to open intake at 5 btdc and exhaust at 45 bbdc so the spacing is the same. 1100 cams in the 1200 are already advanced 5 degrees as compared to the 1100. Although they are set as the 1200 cams. It seems stock is stock regardless of which motor the cams are in. This is giving me a headache.

 

[ekvh]

T1 is T1 in both engines. The 1100 cams at T1 in a 1200 would have the valve open at 5 atdc. That is set in the keyway in relation to T1. It would need to be advanced with either a spacer or offset or a new keyway cut. I talked to a machinist about broaching a keyway 180 degrees on the other side less the four degrees. Too expensive for my cheap blood. Sorry about the headache. I've been wrong before.

 

[slabghost]

T1 on 1100 has the intake opening at 5 degrees btdc. T1 on the 1200 has the intake opening at 10 degrees btdc . So yes T1 is T1 on both motors but on the 1200 its 5 degrees advanced over the 1100.

 

[canuckxxxx]

I agree that T-1 is TDC on both engines. But my experience with the 1100 cams in the 1200 showed me that it does not give the right timing if you go by the marks on the cam wheels. Installed accurately according to the markers I had intake opening at 3 degrees after TDC, not 5 degrees before TDC like I was expecting.

The teeth spacing is the same for the belts but the length is different because of the 1200 being wider.

Brian

 

[slabghost]

going by the marks on the cam wheels the timing of the cams is where it's supposed to be on either the 1200 or 1100 regardless which cams are used. 1200 is supposed to open the intake at 10 btdc and it will using the cam pulley timing marks.There is no difference in size, number of teeth or timing marks on cam pullies. from 1000cc to 1200cc they all interchange. And again the length of the timing belt is completely irrelevant. One full turn at the crank will still be one half turn at the cam.

 

[ekvh]

With 1000 or 1100 cams and heads on a 1200 block the intakes open 5 degrees btdc. The cam profile dictates when it commences in reference to the keyway......me thinks. Brian, I would venture to guess something was awry in your measuring tools, because all pulleys are interchangeable 1000-1100-1200. Advancing the cams will help bottom end, but piston clearance must be checked.

Took mine for my first highway ride last night. Mostly 60-80mph, two ways so no wind aiding, then 30 miles city, but behaving. Got 38mpg. My best on the highbrid. I think it'll break 40 with the 18" rear.