'84 1200 engine for a '82 GW

[slabghost]

ekvh » Wed Jul 22, 2015 7:07 pm[/url]":3vkr8f2c]
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.

Have you verified that statement with a degree wheel? You may be right but the 1200 states it opens at 10btdc. Lobe spread is virtually the same on all the cams. The pullies interchange. The marks are all the same position. If you are right advancing the cams 5 degrees will put the valve opening in the 1200 as designed for the 1200.

 

[canuckxxxx]

But having said all of that, I've been absolutely sure I was right in the past and was full of sh*t. :shock: My mind is on the verge of being boggled with this stuff so big errors are possible. oh2:

Thanks for your indulgence.
Brian

 

[ekvh]

I should make or buy a degree wheel to know for sure. I am just going by the books and what I understand of them. If the pulley marks are the same, how would the 1100 cam get pushed to 10 degrees btdc? The marks on the covers appear to be the same also.

My head is spinning too. The one factor I haven't considered is the extra tooth in the belt. It makes the belt longer on the top and the bottom, so half of nine degrees would be close to the five degrees difference. It's due to the increased stroke.

If you shave the heads or block, you retard cam timing, so it stands to reason that spacing the head further away advances cam timing.

If this is true, mine are now at 14 degrees advanced. Yikes!!

 

[slabghost]

the length of the belt could be a flippin mile if you could keep it tight the motor would run just the same. Ten teeth moving at the crank is still five at the cam.

 

[canuckxxxx]

This valve timing thing is very interesting because it makes such a big difference in performance. It's worth spending some time on.

I made some one-piece offset keys just with my vice, a file and using a cam and cam wheels from the 1200 heads that I am not using yet to test fit. They worked pretty good but now I have intake opening at 5 at BTDC on the right side and 6 degrees at BTDC on the left. :head bang: So I will have to make another offset key. I will try for 6 degrees (but will settle for 5).

Brian

 

[slabghost]

ekvh » Wed Jul 22, 2015 10:07 pm[/url]":25h9bb6r]
I should make or buy a degree wheel to know for sure. I am just going by the books and what I understand of them. If the pulley marks are the same, how would the 1100 cam get pushed to 10 degrees btdc? The marks on the covers appear to be the same also.

My head is spinning too. The one factor I haven't considered is the extra tooth in the belt. It makes the belt longer on the top and the bottom, so half of nine degrees would be close to the five degrees difference. It's due to the increased stroke.

If you shave the heads or block, you retard cam timing, so it stands to reason that spacing the head further away advances cam timing.

If this is true, mine are now at 14 degrees advanced. Yikes!!

How do you figure that shaving the heads retards timing?
If anything the valves are closer to the pistons so even with stock timing I would guess the valves would open slightly earlier.

 

[slabghost]

canuckxxxx » Wed Jul 22, 2015 10:21 pm[/url]":37egcgvg]
This valve timing thing is very interesting because it makes such a big difference in performance. It's worth spending some time on.

I made some one-piece offset keys just with my vice, a file and using a cam and cam wheels from the 1200 heads that I am not using yet to test fit. They worked pretty good but now I have intake opening at 5 at BTDC on the right side and 6 degrees at BTDC on the left. :head bang: So I will have to make another offset key. I will try for 6 degrees (but will settle for 5).

Brian

Why would you do that if the ignition timing is for the 1200 which opens the valves at 10 btdc? :headscratch:

 

[canuckxxxx]

slabghost » Wed Jul 22, 2015 8:29 pm[/url]":2ai3zkrz]

canuckxxxx » Wed Jul 22, 2015 10:21 pm[/url]":2ai3zkrz]
This valve timing thing is very interesting because it makes such a big difference in performance. It's worth spending some time on.

I made some one-piece offset keys just with my vice, a file and using a cam and cam wheels from the 1200 heads that I am not using yet to test fit. They worked pretty good but now I have intake opening at 5 at BTDC on the right side and 6 degrees at BTDC on the left. :head bang: So I will have to make another offset key. I will try for 6 degrees (but will settle for 5).

Brian

Why would you do that if the ignition timing is for the 1200 which opens the valves at 10 btdc? :headscratch:

Because the intake valves were not opening at 10 BTDC...they were opening at 3 ATDC :shock: when I installed the belts according to the marks . For 1100 cams it should be 5 BTDC so that is what I was trying to get it to with the offset keys.

Brian

 

[slabghost]

Did you turn the crank through another 360 to see where it opens? Something isn't right.

 

[canuckxxxx]

Here is the stuff I use to check my valve timing. It's not pretty like they show in Hotrod Magazine but it works

Degree wheel on the front of the crank with TDC and BDC marked.
Note the pointer.

degree wheel

• canuckxxxx
• Jul 22, 2015

A steel plate bolted to the head via the 2 middle bolts of the rocker rack bolts.

dial indicator mount

• canuckxxxx
• Jul 22, 2015

To which is attached a magnetic mount for the dial indicator which checks movement of the valve.

dial indicator on valve spring top

• canuckxxxx
• Jul 22, 2015

So I turn the engine over via the crank bolt and watch for the valve to start moving. When it starts I let it go .039" (1mm) and then check the degrees from TDC on the degree wheel.
etc, etc

 

[canuckxxxx]

slabghost » Wed Jul 22, 2015 8:56 pm[/url]":2hd8hcj9]
Did you turn the crank through another 360 to see where it opens? Something isn't right.

I tried it many times. I agree something isn't right.

 

[ekvh]

Shave the heads, valve is closer, but belt spacing is the same, so the cam is forced to be rotated further away, retarding timing of the valves. The math on mine with 0.025" shaved was about 3/4 degree if I recall correctly.

 

[joedrum]

ok if i am following everything ...brian is saying that when all timed right the 1100 cam is 3 degrees ATDC ....this cam is suppose to operate at 5degrees BTDC ....thats 8 degrees difference if all things are right in brians test ......ok it dosnt matter what the 1200 cam dose in specs ..its not part of the build ...another way to look at it is ..the 1200 motor dosnt rule where the 1100 cam goes ...the cam dose.....

so if the brian figures are right we are saying the 1200 is retarded 8 degrees machaniclly when set at T1 with 1100 cam in it ........hmmmm ok ..now were back to that one tooth on the belt and the longer stroke deal .....so if you advace the belt one tooth that should put you right at 5degrees BTDC ......this seems logical to me and makes up the 1/4" difference in the stroke ... but it also makes it seem that when belt is put on and timed that all the difference seems to be on tension side of belt ....

im having a hard time figuring out why moving one tooth would not make it closer as oppose to further away ......crank is still at TDC ....when other cam is done and moved to match the other all things should remain the same .... there is no doutb id like to get the 1100 cam to its closest spot on 1200 motor ...

ok i suggest that you put motor at TDC... this is a unchangeable spot ...crank pully goes on and belts fit groove ... teeth are spaced the same ... all these things cant change ...even with keyway out of cam you are still bound by tooth spacing ......seems the only way to really move cam is on the tension side of belt ....if you could adjust length of belt to cam pully on the tension side with another pully you raise tension belt up some you get adjustable cam setting ....hmmmm wishful thinking

 

[ekvh]

Could be one tooth off. The other factor here could be the backplates, the ones the marks line up with. But Brian's bolted right on because it was an 84???? Joe's and mine the backplates had to be modified to fit. I could be off a little on that. My marks are spot on, but I do have 10-15lbs more compression one side to the other. There's a good chance my backplate on the left side is not perfect. A degree wheel is needed for me to check where I really am. Mine is much less than machine shop quality work, just guessed and reamed out holes to hold the backplates on. I need to examine that closer.

I think the extra tooth on the belt is a red herring. It doesn't matter how many teeth it has, the crank turns one revolution and turns 20 teeth, the cam moves 20 teeth, half a turn. The position of the keyway could be huge, but since they all interchange, I thought they were the same, but it's possible people have swapped them without realizing they're different. If I can find mine, I'll compare them.

 

[canuckxxxx]

joedrum » Thu Jul 23, 2015 5:42 am[/url]":3mn1f0h6]
ok if i am following everything ...brian is saying that when all timed right the 1100 cam is 3 degrees ATDC ....this cam is suppose to operate at 5degrees BTDC ....thats 8 degrees difference if all things are right in brians test ......ok it dosnt matter what the 1200 cam dose in specs ..its not part of the build ...another way to look at it is ..the 1200 motor dosnt rule where the 1100 cam goes ...the cam dose.....

so if the brian figures are right we are saying the 1200 is retarded 8 degrees machaniclly when set at T1 with 1100 cam in it ........hmmmm ok ..now were back to that one tooth on the belt and the longer stroke deal .....so if you advace the belt one tooth that should put you right at 5degrees BTDC ......this seems logical to me and makes up the 1/4" difference in the stroke ... but it also makes it seem that when belt is put on and timed that all the difference seems to be on tension side of belt ....

im having a hard time figuring out why moving one tooth would not make it closer as oppose to further away ......crank is still at TDC ....when other cam is done and moved to match the other all things should remain the same .... there is no doutb id like to get the 1100 cam to its closest spot on 1200 motor ...

ok i suggest that you put motor at TDC... this is a unchangeable spot ...crank pully goes on and belts fit groove ... teeth are spaced the same ... all these things cant change ...even with keyway out of cam you are still bound by tooth spacing ......seems the only way to really move cam is on the tension side of belt ....if you could adjust length of belt to cam pully on the tension side with another pully you raise tension belt up some you get adjustable cam setting ....hmmmm wishful thinking

The trouble is that from the start of one valley on the belt to the start of the next valley is about 9mm which moves the cam wheel about 9 degrees.

closeup of belt

• canuckxxxx
• Jul 23, 2015

But for the crank to move the cam wheel 9 degrees it has to move 18 degrees which is way too much. That is why, when I moved the cam wheel by 1 tooth it changed my opening from 3 ATDC to 15 BTDC. So to get a smaller change you have to go to the offset keys.

 

[slabghost]

I wonder if there is a difference in head height from the gasket to the cam journals?

 

[ekvh]

Aha!! Pulleys are different. When key watts are lined up, teeth are about 1/2 tooth off. Pics soon. Maybe someone else could compare and confirm. I have 1000 vs 1200 pulleys. So Mother Honda increase can advance to ten degrees with a slight difference in keyways.

 

[ekvh]

I need a shaft long enough to accommodate both pulleys and a piece of key-stock to confirm. I just have a drill bit in right now and lining up with the eyeball. I might be seeing things.

 

[ekvh]

I think I'm wrong. I used a belt to hold the pulleys together lining up the teeth and the keys look the same. Sorry.

 

[slabghost]

pullies are designed to work on either side too. So when matching them up it matters which way they face.