Discussion in 'Fuel System & Electrics' started by Gordon D, May 7, 2018.
Throttle bit = foot flat to the floor......
Sorty should have been more clear. You want no restrictions on the inflow of the air into the engine to make sure you get an accurate reading.
Got a box of carnie parts here, may have what you need in there ?
Ahh, OK, so throttle full open (even though no firing) so the airflow through the carbs into the compression chamber is open the whole way? Stupid question but will that then put fuel into the cylinders that I don't want there ... or is that not an issue?
Presuming you don't mean you have been keeping circus workers in bits in the freezer Mike, I would really appreciate finding a pair of those little brass (I presume they're brass) accelerator jet pipes
Just red noses and horns haha
Will have a look, remind me if I forget
Or this one
Ooh, I think that's the type ... comes out of the accelerator jet and pumps into the airflow below the butterfly valve?
Yes, they are just little extension pipes to move the fuel into the centre of the flow. More efficient than dribbling it out from the side but not going to make a lot of difference in actual running.
Dont worry about the fuel going in for a compression test. You aren't talking litres and a few mins later most will have evaporated. Most important is to allow the engine to draw a full charge of air before compressing it. With the butterflies in the carbs shut it cant draw as much of air so the compression will be less.
Ahh, OK - will do one more test before I drop the motor this weekend so I have a more accurate base to work from
Most likely a strip down is warranted but if you want more info in top end then a leak down test will do that.
Oil pressure test and end float check along with checking cam and followers plus piston / rod play will give some idea of bottom end.
Real mechanics may offer some more substantial checks.
Most top end rebuilds are temporary due to insufficient check of bottom end but there's a long shot that you might have a bad test on compression and couple if broken rings or oil scrapers.
Given evidence so far its likely a full build but worth amassing the evidence.
OK, just for completeness I redid the CT before dropping the motor tomorrow. Warmed her up, throttle full open and double checked the “bad head” first. #1 reread at 40psi (up by 5psi) and #2 went up by, well, nothing - still 0 on the gauge. Figured that I couldn’t have stuffed it up twice so will accept that #2 is really not well and didn’t bother redoing the “better” head.
Out she comes
May you enjoy the learning curve. Cheers
Something wrong there. Good luck with a rebuild, you wont know yourself.
If it is 0 psi then there would be absolutely no resistance in turning the motor over by hand
... which would explain why I found it so easy to find TDC when checking the timing
No comp on a cylinder , must have been running pretty bad ?
Oh yes - yes it was
I feel pretty bad for not having spotted it sooner ... but I suspect it was a rapid degradation
In think I found one of the accelerator jet outlets ... or what remains of it ... welded to the inlet valve on Cyl #4
I gather some of it is stopping the valves from closing, hence no compression
Separate names with a comma.