Flathead Refresh Cycle

Stig77

New member
I have a newbe question. My son has been racing road course for a few years and does very well. He's going to race oval next year as a second class. My animal engines have been ultra reliable and only need one to two refreshes per year. I hear flathead engines need to be refreshed more often. Is that true? How often should I plan on refreshing the engine? My son is 9 and will race in a restricted alcohol oval class.
 

JPMKarting

Premium User
Flatheads take more abuse to the valve train then an OHV engine, so theoretically yes, they do need to be rebuilt more often.

I cant speak for a restricted engine, but our unrestricted adult flatheads, we have redone every 8-10 weekends....since your running a restrictor and not turning as many RPM, you may get a little more out of it then you would an unrestricted
 

alvin l nunley

Premium User
One way to determine the timing on a “refresh” cycle is to do a regular leak down test and a compression test. Compression is the Holy Grail.
But still, all the bearings in a single cylinder engine take a lot of abuse. The main bearings in particular. It would be nice to figure out some way of determining their replacement cycle.
Comments, Compliments, Criticisms and Questions always welcome.
 

JPMKarting

Premium User
One way to determine the timing on a “refresh” cycle is to do a regular leak down test and a compression test. Compression is the Holy Grail.
But still, all the bearings in a single cylinder engine take a lot of abuse. The main bearings in particular. It would be nice to figure out some way of determining their replacement cycle.
Comments, Compliments, Criticisms and Questions always welcome.

The problem is, there is no way to determine a certain time period...different forms of racing, different weight classes, dirt vs. asphalt, all will have an effect on how long an engine will last.

I wont get nearly as many races out of an engine on a dusty dirt track turning 7200 RPM as I will on a clean pavement track turning 6200 RPM
 

flattop1

Dawg 89
as stated the valve train is what gets abused the most and I think a good restricted is going to be similar to a unrestricted in as much as you are floating the valves albeit at a lower rpm.
competiton level will have some effect on this ,as if you are racing the best they are gonna be up too snuff every time, where as a local racer is likely to run them a little longer before attention.
 
For purple or blue plate flathead, you can easily get 10 races out of your son's engine before rebuilding. Of course that's assuming a good maintenance program (oil changes, clean air fitlers, etc.)
Valve train isn't as much of a problem on small plate engines as it is on unrestricted engines. Valve springs will be good for 12-15 races. I suggest to our customers that we see the engine for a simple freshen-up after 8-10 race days. The first place that you lose power is in valve seal. A leak-down test will show you very accurately where you are losing power. Seldom is it past the rings that costs power on a plate engine. In fact some of the strongest plate engines I've seen have the cylinder and rings pretty much worn out. We already build them with undersized and low tension rings. The reduction of friction and drag outweighs sealing up the cylinder perfectly. Free is fast when it comes to small restrictor plate engines.

Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com
765-339-4407
bcarlson@CarlsonMotorsports.com
 
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