Hi, guys,
Currently I am working on VL 1200 motor. Building stroker using Truett and Osborne flywheels. My concern is that there is no any threaded holes for securing bolts holding securing rings for crankpin and main shaft nuts.
Should I drill them and install or just use Loctite to secure the nuts? As I know newer OEM flywheels e.g. on EVO motors don't have securing rings. Personally I have never found any nuts loose but maybe it was just a good luck?
Also please advise proper torque for these nuts as there is no any info in the only book I have by Steve Slocombe
Thanks
drilling and tapping would remove metal and adding screws and locking rings would add back ,thus would have to rebalance yes a few grams I know ,but they have been balanced as you received them no? just a thought
The torque specs are the same as Knucklehead and early Panhead. The crankpin nuts should be upgraded to the flanged type. The retaining rings are not needed if everything is torqued properly.
The pin is 1.000", are flanged nuts available?
Is 150 lbs. still correct?
Std. VL bore is 3.421875" (3-27/64"), same as 1937-41 UH, ULH. VL & UH replica pistons are 3.4375" (3-7/16"), or +.0155" larger.
I assume (in the absence of stroker pistons) that you're using stroker plates and shortening the skirts where needed?
Truett shows the VL stroke to be 3.96875" (3-31/32", same as 1941-* FL), not "4 in." as shown in older literature.
The new stroke is 4.25", yes? Therefore, the plate thickness to retain piston to head clearance is .1406": (new - old) / 2. I strongly recommend a thinner plate even if you have to make one. The original clearance was much greater than optimum (frequently .060"), and reducing the plate to 1/8" (or less)* (VL has same bolt pattern and center hole as 1936-83 knucklehead, panhead, shovelhead cylinders) will improve combustion through increased turbulence, increase static CR slightly, and most important improve quench (increase anti-knock protection).
* Measure carefully, you want .035" (including compressed base and head gasket thicknesses) minimum. A gasket between the plate and cylinder flange is probably not needed since there is no oil transfer through the joint.
kitabel wrote: ↑Sun Nov 20, 2022 6:11 pm
The pin is 1.000", are flanged nuts available?
Is 150 lbs. still correct?
Std. VL bore is 3.421875" (3-27/64"), same as 1937-41 UH, ULH. VL & UH replica pistons are 3.4375" (3-7/16"), or +.0155" larger.
I assume (in the absence of stroker pistons) that you're using stroker plates and shortening the skirts where needed?
Truett shows the VL stroke to be 3.96875" (3-31/32", same as 1941-* FL), not "4 in." as shown in older literature.
The new stroke is 4.25", yes? Therefore, the plate thickness to retain piston to head clearance is .1406": (new - old) / 2. I strongly recommend a thinner plate even if you have to make one. The original clearance was much greater than optimum (frequently .060"), and reducing the plate to 1/8" (or less)* (VL has same bolt pattern and center hole as 1936-83 knucklehead, panhead, shovelhead cylinders) will improve combustion through increased turbulence, increase static CR slightly, and most important improve quench (increase anti-knock protection).
* Measure carefully, you want .035" (including compressed base and head gasket thicknesses) minimum. A gasket between the plate and cylinder flange is probably not needed since there is no oil transfer through the joint.
Thanks for your reply and advise. Yes I shortened the pistons at the bottom skirts and using stroker plates.
I fabricated them already with aluminum. Steve Slocombe, VL guru, also suggests to use thinner plates to rise the compression so I made 0.10 thick. Then I can check and adjust if necessary. Will try to get 0.035 between piston and heads as you suggested.
I have no personal experience with the VL engine (except for riding a borrowed 31V!), but the factory specification for valve-to-guide for its descendant, the "U" series is .0035", with .0055" listed as acceptable.
This distance would be very loose (compared to an OHV), but the angularity (non-concentric alignment) is effectively reduced by the extreme guide length. A .0035" clearance in a 2" guide allows a greater misalignment than the same clearance in a 3" guide.
The danger of tighter clearance is, of course, seizure, especially since the flathead engines have temperature problems.
In a flathead with return oil (1937-*) I would divert some of the return oil to the upper valve covers via a steel brake line (like Triumph did to supply the rocker boxes on the "B" range twins, using about 18% of the return volume)). I'm not comfortable with reducing the VL's system pressure by using the supply circuit (not to mention where to interrupt it).
Does anyone have an opinion as to whether the late 45's vented tappet guides connected to the crankcase interior puts oil mist inside the cover assembly? If yes, that can certainly be added to the V (and R), without disturbing the original appearance. Then, perhaps slightly tighter guide clearance would be safe.
Last edited by kitabel on Tue Nov 22, 2022 12:26 am, edited 1 time in total.
.035" appears to be the low limit for a very wide range of engines, including automotive. It's the smallest distance that (almost) guarantees NO P-H contact at full operating temperature, load, and RPM.
Some engines with very small bores (50mm) can tolerate down to .025", but this was discovered by experiment, and resulted in some loud noises and red faces.
Figures slightly above this (.040"-.050") are less effective in all the virtues, but .060" is where the anti-knock efficiency decays (depending on variables such as spark advance, mixture strength, rod ratio, static CR, temperature, load, atmospheric pressure), and is effectively gone before .090".
"Squish" still remains: as the piston approaches TDC on compression the volume in the contact area is violently expelled into the major chamber volume and adds turbulence (but not anti-knock).
