Whats involved in installing larger valves?
 

I have a set of 781 large oval port heads. What exactly is involved in putting larger valves, and how much should one expect to pay? I already have enough money in these heads, I could have purchased a new set of Edelbrocks. :eek:
(EBAY learning experience :mad: – bolt on ready to go..)

I put these on a 496 stroker I built last year. Also are these intake runners (230?) way to small? Or should I be thinking about going to rectangular heads?
Thank for you input
JIM

Re: Whats involved in installing larger valves?
 

496 and what is your max RPM? The large oval ports make pretty good heads with larger valves and a little work depending on how much HP your goal is. Sell em and go with new heads might be the better route.

These would work nice also. http://www.cpperformance.com/detail.aspx?ID=6791

Machine work will likely cost you 500+$ depending on who you know. Tyler is quoting $600 to install larger valves - new 11/32 guides and deck them .020 for his kit. Does not include parts but does include asseembly and checking for cracks. Valves will cost 500 or so depending on mfg of valve.

Re: Whats involved in installing larger valves?
 

Its a 496. Max RPM is 5,500. I only have about 50 hours on this set of heads. All new guides, valves, springs, etc.
I would be happy with 475HP :D

Re: Whats involved in installing larger valves?
 

I would try Jim V here on the boards. I would think 475 is with in reach but not if they still have small valves. :(

Re: Whats involved in installing larger valves?
 

TTT
Anyone, tell me what needs to be done besides the valves.

Do you need all new valve seats?
I hear you need to cut the throats(explanation).

Re: Whats involved in installing larger valves?
 

Jim,
The throat/venturi is the most critical area in the cylinder head and requires the most experience to modify successfully. This choke point just under the seat/valve interface is the area of greatest restriction in the port. The venturi area sets up the transition from the port/valve/combustion chamber and can kill an otherwise efficient head. Depending on the cylinder head the throat area should be 87%-90% of the valve diameter.
Rule of thumb:
Intake valve 50% - 52% Bore size
Bob

Re: Whats involved in installing larger valves?
 

For the money your fixing to spend I would look at a new set of rectangle port heads

Re: Whats involved in installing larger valves?
 

That is exacty what I am thinking. I hate to tear apart a good set of heads with 40 hours on them :D

Anyone have thoughts on what size of intake runners I should look at? Its a stroked 496 with 9:1 compression ratio, with IMCO Powerflow exhaust. Cam is a mild comp [email protected]

Re: Whats involved in installing larger valves?
 

I have a fresh set of 188s 4-sale in the swap shop..

Re: Whats involved in installing larger valves?
 

BIRDOG, could you shoot me a PM and tell me more about the heads. What size of valves, intake runner size, who ported the heads or anything else.
And most important the $$$ :D
Thanks
JIM