question for head porters

my replacement valves are straight stem diameter. the valves I took out were smaller diameter near the head than the stem diameter. will this have a big difference on flow? Manley told me the straight stem should be used with the alky.

Larry Williams wrote:my replacement valves are straight stem diameter. the valves I took out were smaller diameter near the head than the stem diameter. will this have a big difference on flow? Manley told me the straight stem should be used with the alky.

No sir, very little difference imo. Flow testing shows some improvement if you were running FE heads (for example) with a 3/8" stem valve and dropping down to 11/32" stem valve. However, if your stems are 11/32" and then reduced to 5/16" diameter there's not that of a percentage of reduction in cross sectional area, and nothing to worry about unless you are NHRA Pro Stock racing.

Hope this helps,

Charlie

thanks charlie. i was assembling them with the straight stems. nice to know no big loss of power

The main reason the prostock and nascar engines have 5/16" or 7mm stems is to reduce wt. .....more rpm.