Front cylinder low compression + blow-by in rocker cover + pushrod tubes

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Ratedspeed
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#76

Post by Ratedspeed »

Can you post a photo of the timing marks? If the builder said he used two right wheels I wouldn't think the timing marks would look factory, so maybe he found a left wheel.
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#77

Post by panama86 »

With my valve timing so off I wonder if something is indeed up with the stroke if that's really enough to set it off to the degree that it is. I'm baffled.

Yeah I'm at work at the moment I'll take a photo when I get home of the marks.
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#78

Post by Ratedspeed »

Try retarding the cam two teeth ( clockwise ) but check crank endplay first.

1) check crank endplay
2) install cam, cover and pushrods
3) adjust tappets
4) turn crank slowly for two revolutions to make sure there's no piston / valve interference.
5) check valve timing as before:
Intake on ramp ( no lash ) - how close to TDC ?
Intake full lift - How close to 9 o'clock
Intake closed ( lash ) - How close to 4:30
Exh on ramp - How close to 9 o'clock
Exh full lift - How close to 3 o'clock
Exh closed - How far after TDC

Mike
panama86
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#79

Post by panama86 »

I just went down and measured the end play. Measured from the end of the pinion shaft with cam cover removed. Measurement was .041". Probably slightly more than that realistically. So way out of spec 3x the max given in the manual. Here are a couple of photos of the flywheel timing marks also.
PXL_20221219_074606057~3.jpg
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PXL_20221219_074529126~2.jpg
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Raytag
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#80

Post by Raytag »

I find it impossible to check the runout of the crank with the engine still installed.
Because whatever you do the frame and the dial is shaking.

The closest reading with engine installed was with cylinders removed, a steel plate bolted onto the case, attached a magnetic flexible dial holder to it.
Then I pushed the crank in, zeroed it, turned the engine over 1 revolution, pulled the crank and pushed it back in.
While I was doing this the bike was strapped firmly to a bike stand.
I repeated this several times and still I was having slightly different readings

Then I pulled out the engine.
Put the crank into the vise so that the crank is vertical
Then zeroing a dial onto the case , I pulled the case and let it drop again and repeated this several times.
The reading was always identical and it differed from the reading with the engine in the frame.
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#81

Post by Ratedspeed »

Raytag wrote: Mon Dec 19, 2022 11:06 am I find it impossible to check the runout of the crank with the engine still installed.
Because whatever you do the frame and the dial is shaking.

The closest reading with engine installed was with cylinders removed, a steel plate bolted onto the case, attached a magnetic flexible dial holder to it.
Then I pushed the crank in, zeroed it, turned the engine over 1 revolution, pulled the crank and pushed it back in.
While I was doing this the bike was strapped firmly to a bike stand.
I repeated this several times and still I was having slightly different readings

Then I pulled out the engine.
Put the crank into the vise so that the crank is vertical
Then zeroing a dial onto the case , I pulled the case and let it drop again and repeated this several times.
The reading was always identical and it differed from the reading with the engine in the frame.
True, but if Panama is seeing anywhere near .040, nuff said, bike has to come off the road.
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#82

Post by Ratedspeed »

panama86 wrote: Mon Dec 19, 2022 8:57 am I just went down and measured the end play. Measured from the end of the pinion shaft with cam cover removed. Measurement was .041". Probably slightly more than that realistically. So way out of spec 3x the max given in the manual. Here are a couple of photos of the flywheel timing marks also.

PXL_20221219_074606057~3.jpgPXL_20221219_074529126~2.jpg
Those timing marks look factory to me, so there must be a left wheel in there.
If you want to continue with the valve timing check, so you can build some kind of baseline for things to tell another shop or for your own knowledge, do so, but it's time for disassembly. But as Raytag said, once cylinders are removed get a better reading of the endplay and record.
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#83

Post by RooDog »

The view through the timing hole tells me that is not a right side flywheel.
I know this because I built a Panhead in 1968 with two RS, 74, wheels. And when viewed through the timing hole the rim of the wheel is about a 1/2 inch to 3/4 inches recess away from that viewing port. You most defiantly have a left hand wheel in there.
Once you pull the jugs you will see that the left is wider than the right.

Two Right Side 74 Wheels.
DSC02365.JPG
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Here you can just barely see the edge of the left wheel inside of the cylinder spigot bore.... RooDog....
DSC02001.JPG
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panama86
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#84

Post by panama86 »

Thanks everyone for your input on this saga.

It's clear I am going to need to pull the the motor and go over all of this properly. I would like to figure out before I pull it though exactly what was causing the valve timing issues. I can't wrap my head around how the stroke of my wheels would be affecting that valve timing so dramatically. I keep coming back to the cam but it does seem to be as it should.
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#85

Post by awander »

Stroke should not affect the valve timing.

TDC is TDC and 30 degrees BTDC is 30 degrees BTDC, no matter what the stroke is.
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#86

Post by RooDog »

Absolutely, Andy....

For a awful long time in hot rod history cams have typically been installed "straight up", that is zero advance or retard. This is easily verified by what had been called "split overlap" That is @ TDC at the end of the exhaust stroke and the beginning of the intake stroke both valves are equally open. This is the center of the over lap faze. Got that? Many cams today are ground and installed slightly advanced, 4-6 degrees. But split overlap, straight up, usually will work, and work well.....
You can use this information to check if your cam is installed and timed properly....
....RooDog....
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#87

Post by Ratedspeed »

awander wrote: Tue Dec 20, 2022 5:17 am Stroke should not affect the valve timing.

TDC is TDC and 30 degrees BTDC is 30 degrees BTDC, no matter what the stroke is.
FL ( 3 31/32" ) vs EL ( 3 1/2" ) at 1,000 rpm ( Idle )

FL. ( 3.96875 stroke x 2 x 1,000 ) / 12 = 666.6 fpm
EL ( 3.5 stroke x 2 x 1,000 ) / 12 = 583.3 fpm

Yes, piston travel does change when the stroke is altered.
Cam timing doesn't because it's running off the pinion gear.

So, yes I believe a big part of Panama's issue has to do with the altered stroke along with a higher lift cam that has more duration.

Mike
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#88

Post by Robbo »

Really interesting thread. It is great to see the expertise on this forum on show. Rather than individual thanks, I really want to say thanks to everyone, especially the regulars who always provide answers to questions.
Great work folks.
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#89

Post by Ratedspeed »

panama86 wrote: Fri Dec 16, 2022 9:44 am Losing my mind trying to figure this out, the stroke has got me baffled too. I measured again and I'm sure i was able to get a straight shot this time. Piston travel is definitely coming in at 3 13/16". As far as i am aware that's the stroke of 45". It's definitely not coming in at 3 1/2" which would be EL stroke and not 3 31/32". A straight shot measuring piston travel should give me exact stroke right? These are the exact flywheels that are in this motor before they were cleaned up. IMG_0570.JPG
Panama,
The rods in this picture appear to be the shorter ( 7.440" ) 24290-74 & 24294-74 1974 & Later rods, The earlier rods XA-705 & XA-706 are a little longer @ 7.470"
Just an FYI,

Mike
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Re: Front cylinder low compression + blow-by in rocker cover + pushrod tubes

#90

Post by awander »

Rod length has nothing to do with stroke length, guys.
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