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[email protected] Samba Member

Joined: June 24, 2015 Posts: 850 Location: Rialto. CA
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Posted: Wed Jul 16, 2025 1:42 pm Post subject: Re: What about an emphasis on the 1200cc/40 hp motor. |
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dames wrote: |
Can I use any 3 rivet type camshaft in my 40hp? Looking to buy a nos one but none i have seen have the same part number as the one I have removed. |
If it's a stock 1500/ 1600cc 3rivet flat camshaft yes you can use it on the 40hp but match it with the 1500cc/1600cc rocker arms and compression it will help give little bit of power .... but if you have a 1600cc and want to use a 40hp camshaft no not a good choice 40hp cam has a lower profile your engine will be lower in power ...40hp had 7 .0:1 compression to 7.3.1 ...the 1600cc flat cam had 7.5.1 the 1600cc deep dish camshaft was for a 7.2.1 or even lower compression ...just make sure you put/ have the correct compression when you build it make sure you know what cam you have ...40hp and 1600cc the gears are interchangeable it's the same gears you can use new 1600cc aluminum bolt on gear ..just grind off the rivets on the camshaft drill/ tap the rivet camshaft so you can bolt the new gear to the cam and if you do plan on a new camshaft if your case doesn't have cam bearings get your case machined for camshaft bearings . |
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dames Samba Member
Joined: May 09, 2012 Posts: 94 Location: uk
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Posted: Thu Jul 17, 2025 3:30 am Post subject: Re: What about an emphasis on the 1200cc/40 hp motor. |
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[email protected] wrote: |
dames wrote: |
Can I use any 3 rivet type camshaft in my 40hp? Looking to buy a nos one but none i have seen have the same part number as the one I have removed. |
If it's a stock 1500/ 1600cc 3rivet flat camshaft yes you can use it on the 40hp but match it with the 1500cc/1600cc rocker arms and compression it will help give little bit of power .... but if you have a 1600cc and want to use a 40hp camshaft no not a good choice 40hp cam has a lower profile your engine will be lower in power ...40hp had 7 .0:1 compression to 7.3.1 ...the 1600cc flat cam had 7.5.1 the 1600cc deep dish camshaft was for a 7.2.1 or even lower compression ...just make sure you put/ have the correct compression when you build it make sure you know what cam you have ...40hp and 1600cc the gears are interchangeable it's the same gears you can use new 1600cc aluminum bolt on gear ..just grind off the rivets on the camshaft drill/ tap the rivet camshaft so you can bolt the new gear to the cam and if you do plan on a new camshaft if your case doesn't have cam bearings get your case machined for camshaft bearings . |
Thanks for the reply Jerry. The case does have cam bearings. I'm not doing the build but have been collecting the parts for the chap that is. My confusion comes from new camshafts listed say they are suitable for all but as I would like to use nos parts where I can I'm seeing lots of part numbers and really want to get this right first time. I need barrels and pistons too and am still undecided on 1200 or the big bore kit. Rather than looking for new rockers I think I will bide my time and try to find the correct 1200 camshaft. Again thanks for the advice. |
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SilverThing Samba Member

Joined: July 19, 2004 Posts: 841 Location: Everett
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Posted: Thu Jul 17, 2025 5:36 pm Post subject: Re: What about an emphasis on the 1200cc/40 hp motor. |
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The early 40hp engines (34PS by the German system) have a camshaft with the following specs (measured at 1mm lift at the valve):
Intake Opens: 4 degrees BTDC (Before Top Dead Center)
Intake Closes: 32 degrees ABDC (After Bottom Dead Center)
Exhaust Opens: 41 degrees BBDC (Before Bottom Dead Center)
Exhaust Closes: 1 degree ATDC (After Top Dead Center)
The later 40hp engines have the following specs:
Intake Opens: 6 degrees BTDC (Before Top Dead Center)
Intake Closes: 35 degrees 30 minutes ABDC (After Bottom Dead Center)
Exhaust Opens: 42 degrees 30 minutes BBDC (Before Bottom Dead Center)
Exhaust Closes: 3 degree ATDC (After Top Dead Center)
1300-1600 engines have the following specs (likely only due to the slightly higher rocker ratio):
Intake Opens: 7 degrees 30 minutes BTDC (Before Top Dead Center)
Intake Closes: 37 degrees ABDC (After Bottom Dead Center)
Exhaust Opens: 44 degrees 30 minutes BBDC (Before Bottom Dead Center)
Exhaust Closes: 4 degree ATDC (After Top Dead Center)
I have seen some slightly different specs online that appear to be due to the events being taken at 0.050" valve lift instead of 1mm.
I don't know when the early camshaft was phased out for the later one. I do know that the compression ratio increased from 7.0:1 to 7.3:1 in August of 1972 (by using domed pistons) at the same time that the 1600cc engine decreased compression from 7.5:1 to 7.3:1 (via slightly dished pistons). Camshafts changed from 3-bolt/rivet "flat" style to 4-rivet "dished" in August of 1971. _________________ "I like how everyone likes talking about Zeke's Thing yet he's the only one that's ever seen it." - Katie
"I've seen pictures..." - Jeremy |
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[email protected] Samba Member

Joined: June 24, 2015 Posts: 850 Location: Rialto. CA
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Posted: Thu Jul 17, 2025 7:03 pm Post subject: Re: What about an emphasis on the 1200cc/40 hp motor. |
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SilverThing wrote: |
The early 40hp engines (34PS by the German system) have a camshaft with the following specs (measured at 1mm lift at the valve):
Intake Opens: 4 degrees BTDC (Before Top Dead Center)
Intake Closes: 32 degrees ABDC (After Bottom Dead Center)
Exhaust Opens: 41 degrees BBDC (Before Bottom Dead Center)
Exhaust Closes: 1 degree ATDC (After Top Dead Center)
The later 40hp engines have the following specs:
Intake Opens: 6 degrees BTDC (Before Top Dead Center)
Intake Closes: 35 degrees 30 minutes ABDC (After Bottom Dead Center)
Exhaust Opens: 42 degrees 30 minutes BBDC (Before Bottom Dead Center)
Exhaust Closes: 3 degree ATDC (After Top Dead Center)
1300-1600 engines have the following specs (likely only due to the slightly higher rocker ratio):
Intake Opens: 7 degrees 30 minutes BTDC (Before Top Dead Center)
Intake Closes: 37 degrees ABDC (After Bottom Dead Center)
Exhaust Opens: 44 degrees 30 minutes BBDC (Before Bottom Dead Center)
Exhaust Closes: 4 degree ATDC (After Top Dead Center)
I have seen some slightly different specs online that appear to be due to the events being taken at 0.050" valve lift instead of 1mm.
I don't know when the early camshaft was phased out for the later one. I do know that the compression ratio increased from 7.0:1 to 7.3:1 in August of 1972 (by using domed pistons) at the same time that the 1600cc engine decreased compression from 7.5:1 to 7.3:1 (via slightly dished pistons). Camshafts changed from 3-bolt/rivet "flat" style to 4-rivet "dished" in August of 1971. |
The 1600cc decreased 4 rivet camshafts from 7.5:1 to 7.3:1 do to emissions it had to pass at that time ..... |
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