flathead head milling question

[MB165]

How much can I mill off the head on the 5hp flathead before it starts to become hard to pull start?
Top of the exhaust valve is .300" off the deck, intake slightly less. I have .018" clearance between the ex valve and head before adding a head gasket. how much clearance is needed ?
Forgot to add.... I can mill reliefs for the valves if needed.

 

[RobK]

Honestly, the compression on a flat head is so low I think you'd have valve interference problems before it became hard to pull start.

 

[roccosbike]

Honestly, the compression on a flat head is so low I think you'd have valve interference problems before it became hard to pull start.

If this is a Briggs 5HP were talking about,you would be surprised how much compression they make with just the easy spin ground off the cam.

 

[65ShelbyClone]

General consensus on 4cycle is that milling the head hurts flow more than it helps compression and that it's better to get either a 4hp head or something aftermarket.

 

[MB165]

These heads arent much. There are some spots which are very thin, so I took .030" off. Someday ill get a ARC head for it.

 

[funky ole]

General consensus on 4cycle is that milling the head hurts flow more than it helps compression and that it's better to get either a 4hp head or something aftermarket.

what he said. your best bet is removing material from the deck to aid in flow between the intake and piston,piston to exhaust. there's just too many crazy curves in the flow path.

 

[GraveBugger]

how would one go about griding the easy spin off?

 

[roccosbike]

Contact... Tim, Isky Cams.

 

[GraveBugger]

and this will provide net gains as far as compressin goes?

 

[loampey]

no.