blower motor cam recommendation

K

khschs

Member
I just fired up my 276" blower motor and it ran great, for about 20 minutes. Lost power,shut it down, cam flat.
Need a recommendation for a cam for 276" blower motor that will be used primarily on the street. The car is a 32 cabriolet with a C4 and a 8" ford differential with 3.00-1 gears and 31" tires.
The cam must have good road manners as the wife will be driving it from time to time.
Thanks Keith
 
Wow, did you have brake in lube on the lobes and lifters? What brand cam was that?
Most blower cams are not that wild because the blower forces fuel/air into the chamber, and flatheads don't like overlap anyway.
 
You will get many opinions from many sources - I happen to like my Schneider 270F bcam which is employed in my 284ci S.C.o.T blown flathead - has a strong flat power band that pulls better and better as my rpm increases. I did not prioritize a rumpy idle - I prioritized pure performance 270 gross duration 230 at .050 with 365 lift. I encourage you to call Schneider and discuss your exact engine specs and power needs.
 
I'm also running the 270F but with 114 lobe seperating for the blower. They did a custom grind for me. I would recommend and use them again!

hopefully you used the ZDDP in your oil. I added an extra bottle to my first break in.
 
I used ZDDP paste on the cam and lifters and added 2 bottles of liquid ZDDP to the oil. The valve springs are Reds LZ on Chevy 1.6 ss valves with one 0.035" shim.
Keith
 
That .035 shim don't tell us what your installed spring pressure is, valve length, keeper grooves, all make a difference, if you wiped a cam out in short time sounds like a lot of pressure. Walt
 
When I put the valve assembly together along time ago I used a valve spring tester at the machine shop. The installed height was 2.120. I don't remember the pressure. The valves are Chevy 1.6 single groove stock keepers
Keith
 
khschs said:
When I put the valve assembly together along time ago I used a valve spring tester at the machine shop. The installed height was 2.120. I don't remember the pressure. The valves are Chevy 1.6 single groove stock keepers
Keith
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I don't any Red's LZ springs in my shop right now or I would check pressure at 2.120--- may be someone here on the Barn has and can check pressure. Walt
 
Yep, the plan is to completely disassemble the engine clean, inspect and reassemble. Will still need a new cam. Sure hope I find something obvious.
Keith
 
Find someone that knows how to measure installed height, then have the springs tested at that length. On a stock valve assy, a.060" shim will usually do it to a stock spring.
 
khschs said:
I just fired up my 276" blower motor and it ran great, for about 20 minutes. Lost power,shut it down, cam flat.
Need a recommendation for a cam for 276" blower motor that will be used primarily on the street. The car is a 32 cabriolet with a C4 and a 8" ford differential with 3.00-1 gears and 31" tires.
The cam must have good road manners as the wife will be driving it from time to time.
Thanks Keith
Click to expand...

Did you run it at a higher RPM for the break-in period? Hopefully you didn't let it idle.
 
Bored&Stroked said:
Did you run it at a higher RPM for the break-in period? Hopefully you didn't let it idle.
Click to expand...

That was my thought as well! You see all these videos of people firing up engines (new rebuilds) and having them idle for extended periods of time. Bad idea, very bad idea.
 
I haven't found the cause of the failure yet so I don't think it would be fair to start nameing names until I'm sure of the cause.
Keith
 
khschs said:
I haven't found the cause of the failure yet so I don't think it would be fair to start nameing names until I'm sure of the cause.
Keith
Click to expand...

Hi Keith, you should always try to use the older "Moly" lube on the lobes and lifter bottoms. It's getting tougher to find, we're fortunate enough to have an ample supply on hand at all times. We actually supply it to other local shops.

Having said that, you MUST know the accurate spring pressure's you have, both closed and open. You also need to follow the "old-school" rule about keeping the RPM's around 1500/2000 for the first 15/20 minutes!

Thanks, Gary in N.Y.

P.S. General "rule-of-thumb" with blown units, you need a "few" extra pounds spring pressure on the intake valves. Doesn't hurt on the exhaust's either but the intakes "feel" the add'l blower pressure on the backside of the valves.
 
One of the big questions is how was the cam break-in performed? Almost any idling with high spring pressure can spell the death of a cam in short order.

And I don't like to keep the RPMs constant, I adjust it up and down every few minutes.
 
Re: break in,
Started engine,checked timing at 700 rpm and then moved it up to 1200 rpm. I changed engine speed from time to time never going over 1500 rpm and never letting it idle very long. The engine temp ran 185+- oil pressure never below 50 psi. The plan was to run it for 20 minutes, shut it down, drain the oil and change the filter. I almost made it.
Keith
 
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