Heads Heads Heads
04-23-2003, 04:32 AM
#1
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Heads Heads Heads
I'm going to get 58cc heads (for my 305) and I KNOW that They have 1.94/1.5 valves... BUT I'm getting the exhaust cut to 1.6... I'm getting a set from a guy I know.. THEY already freshly rebuilt (0 miles) have a slight bowl blend and 3 angle valve job... WHAT SHOULD I GET DONE FOR POWER... I'm looking for the most amount of power I can get out of a set of GM casting heads... that will still be streetable.. I have a guy who will do the port work for me, BUT I DONT WANNA PAY FOR SOMETHING THAT WONT HELP ME ... OR KILL ME (for mileage, or drivability) With ALL the mods done to a set of heads like this.. what sort of power increase should I be expecting on a 305 ???
Thanks in advance
Thanks in advance
04-23-2003, 04:57 AM
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Car: 89rs (previous 2.8)
Engine: 406
Transmission: 700r4 (for now)
The head gurus here suggest keeping the exhaust valves at 1.5 on a 305...check out these posts by Sitting Bull
https://www.thirdgen.org/techbb2/sho...hreadid=117410
https://www.thirdgen.org/techbb2/sho...hreadid=117410
04-23-2003, 08:04 PM
#3
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Stock GM 305 heads never came stock with intakes larger than 1.85" but since you're sure about these heads I won't go there.
Larger valves don't necessarily equal more flow, especially on a small bore 305 block. Especially if they are just "cut in" with little attention paid to the ports and valve seats. It's quite possible that the results can be worse than with the stock valve size.
Remember that many 350s ran for YEARS with a 1.94/1.50 combo and they made good power and had decent intake/exhaust flow numbers. Even the very popular Vortec heads still only use 1.94/1.50 valves. Just suggesting that there might be better places to spend money than a valve size "upgrade."
Larger valves don't necessarily equal more flow, especially on a small bore 305 block. Especially if they are just "cut in" with little attention paid to the ports and valve seats. It's quite possible that the results can be worse than with the stock valve size.
Remember that many 350s ran for YEARS with a 1.94/1.50 combo and they made good power and had decent intake/exhaust flow numbers. Even the very popular Vortec heads still only use 1.94/1.50 valves. Just suggesting that there might be better places to spend money than a valve size "upgrade."
04-23-2003, 08:25 PM
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Car: 89rs (previous 2.8)
Engine: 406
Transmission: 700r4 (for now)
another..they have been machined for screwin studs and guideplates...I will be porting them soon...
04-23-2003, 10:15 PM
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Well, who said they were STOCK castings ??? I didn't... they are GM performance castings... With 1.94/1.5 valves AND 58cc chambers... I'm probably getting 1.6 exhaust ... and thats what I'm asking... What can I do that makes the best power... in terms of porting and blending ... thanks though ... with 1.6 valves and a 3 angle/pro port on the valves... It will flow better on the exhaust side..
04-23-2003, 11:55 PM
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Car: 1986 Sport Coupé
Engine: 305-4v
Transmission: 700R4 and TransGo2
Sounds like you have some L98 heads. Almost identical to the 305 heads. Anyway, follow the instructions at the end of my sig. Will work fine for you.
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