What Timing Is This??

D

DRC21

Member
I got a open flathead that i bought. Had a stock 5hp flywheel on it with a #7 advance key. Can anyone help me out on what timing that is? Thanks
 
Could be anywhere from 34 to 37 or so because the offset keys have a good bit of movement when installed on a crank. One thing for sure is you really need to get a billet flywheel for it , a stock flywheel on an open is a risky proposition. You need to keep the rpm's down well below what an open is capable of doing. The reason billet wheels were mandated for the Limited Mod class is because they where known to fail ( explode) even on a Limited. That's kinda like playing with a snake, sooner or later your gonna get bit. Jon
 
Yah i have a billet flywheel for it. Was just wondering on the timming. Cause i bought the motor and it had that on there and i guess i set timming wrong and the piston collapsed. Guess i burnt it up or the piston was weak. Is a really older motor
 
i dont use keys for timing i simply put some grinding compound on the crank rub the flywheel until it gets that good texture to it then i set timing between 28-31 then torque it to 80 ft pounds.
 
Timing being so important, I'm surprised you would want to leave it to chance. Even if you're just moderately into racing, timing is so important, you should get the tools and make sure it's where you think it is. Or get somebody to do it. It can't cost that much to check the timing.

I doubt the piston was weak. It's more likely that you had the air/fuel mixture wrong. And of course, if the timing was wrong, (too advanced) that would just make things worse.

Do you know how many cc's in the combustion chamber? Is it possible that the engine might have been modified? Too much compression, with all the other problems, could cause the piston meltdown.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Im not sure out of the cc's. Its a limited modified motor. Running a Tilly Alky Carb. So ik it ran good and rich. so more than likely the timing was to far advanced. Was running a jrracecar pvl flywheel
 
Al, you can't build too much compression into a Limited Mod, it's not gonna happen. Even though you gain some going with minimum deck height, you then have to cut some deep valve relief's into the head to clearance for a modern big limited cam. I wish we could get too much , then we could back it up to just right. DRC, put your timing at 36 to 37 degrees, you'll be fine with that. Jon
 
Listen to what Jon said, he knows his stuff, and whatever you do , don't even think of running that stock flywheel on any modified engine, it's like a time bomb, it will explode, and you'll be darn lucky if you don't get injured. Plus, it's illegal at any track worth running at.
 
Right now my block is decked zero. and my head had been milled down. Has deep Valve reliefs milled in it. and thats how i got it
 
As Jon said, you can't have too small of CCs on a limited flathead. Big lift cam and cutting spring reliefs in the head make sure of that! ;)

If it is an older engine (as you have suggested) it is quite likely that the piston was an older design (H'man, Wiseco, etc.) that were very weak (especially at the rpm we turn limiteds.) We routinely yanked the wrist pin bosses out of those old design pistons (hence the newer and improved designs that have come out since.)

Does JR Racecar have a PVL flywheel? I thought the JR wheel was designed for use with a stock coil?
If indeed it is a PVL compatible flywheel, I'd back the timing down considerably -- thinking 32-34*. Keep in mind that the PVL doesn't lose timing as rpm increases like the standard coils do.

-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com
Celebrating 25 years of service to the karting industry
765-339-4407
bcarlson@CarlsonMotorsports.com
 
10420110.jpg


Here is a pic if it works. Its a non pvl my bad.

And i blew a whole in it. Made it indented on the piston.

Also i can key this flywheel cause it isnt a keyway for a flathead
 
You must log in or register to reply here.
Back
Top