SMALL VALVE TO LARGE VALVE UPDATE
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Instructor
Joined: Jun 2001
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From: nova scotia canada
SMALL VALVE TO LARGE VALVE UPDATE
In my previous post on this topic i guess i didn't convey what my intensions
were in regards to changing valve size.First of all my intent was to not just change valves but to change heads to the large valve type.I believe my current setup will support this change.I have a 350 vette with small valve 462's (camelhump) heads(64cc chambers) ,these heads have a 3 angle valve job and are coupled with flattop pistons giving aprox. 10.25:1 cr. My intake is the '70 LT1 high rise al. duel plane with a holley 750cfm duel feed carb.My cam is a crane 278 h10 with 1.6 full roller rockers giving a lift of .498 on intake & exhaust with 225 duration.I am running the complete msd system ( 6al box,blaster 2 coil & pro billet distributor recurved to 36deg. all in at 2800 ) My exhaust is true duels 2.5 in. The car works great with 4speed and 4:11 rear but i am changing rear to 3:36 for highway sake. Once again, if i change out my heads to the large valve type (202/160) with 3 angle valve job and some bowl work & port matching what will i see for performance increases?I will be using the older style camelhump heads similar to my present ones except for the valve size and they will be 64cc chambers.
thanx very much
wade
were in regards to changing valve size.First of all my intent was to not just change valves but to change heads to the large valve type.I believe my current setup will support this change.I have a 350 vette with small valve 462's (camelhump) heads(64cc chambers) ,these heads have a 3 angle valve job and are coupled with flattop pistons giving aprox. 10.25:1 cr. My intake is the '70 LT1 high rise al. duel plane with a holley 750cfm duel feed carb.My cam is a crane 278 h10 with 1.6 full roller rockers giving a lift of .498 on intake & exhaust with 225 duration.I am running the complete msd system ( 6al box,blaster 2 coil & pro billet distributor recurved to 36deg. all in at 2800 ) My exhaust is true duels 2.5 in. The car works great with 4speed and 4:11 rear but i am changing rear to 3:36 for highway sake. Once again, if i change out my heads to the large valve type (202/160) with 3 angle valve job and some bowl work & port matching what will i see for performance increases?I will be using the older style camelhump heads similar to my present ones except for the valve size and they will be 64cc chambers.
thanx very much
wade
Drifting
Joined: Jul 2001
Posts: 1,418
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Re: SMALL VALVE TO LARGE VALVE UPDATE (wadey)
I must have missed your other post.....anyway just a guess you will pick up 20 hp which is not much but!....... if done properly the low lift cylinder fill and resulting power will be felt in the seat you are driving in and probably worth the effort.
The difference in 2.02 and 1.94 valves in GM castings is little to none though as long as the intakes are back-cut and the porter does not ruin the flow .
The 1.94's will tend to work better with the 3.36's as well--still do some bowl work though
Glad to see someone running a Crane Cam--sometimes I think this is the Competition Cam Corvette Forum
;) :p:
[Modified by mountainmotor, 6:25 AM 8/31/2003]
The difference in 2.02 and 1.94 valves in GM castings is little to none though as long as the intakes are back-cut and the porter does not ruin the flow .
The 1.94's will tend to work better with the 3.36's as well--still do some bowl work though
Glad to see someone running a Crane Cam--sometimes I think this is the Competition Cam Corvette Forum
;) :p:
[Modified by mountainmotor, 6:25 AM 8/31/2003]
