I was told that if I have the 305 heads ported and polished I will have a better compression ratio than what I have now. I know the valves are smaller, so that will build compression, right?would it be worth my money to have these heads ported,polished, with a 3 angle valve job?

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Bright red 87 GTA with 350 tuneport. Basic mods such as K&N filter, Flowmasters, Wells MAF, TPIS air foil, Accel 8.8mm plug wires with Bosch platinum plugs, Accel distributor cap and rotary buttons.Gutted cat. Hope to port runners and plenum in about 2 weeks.

 

This is just my opinion but I have heard that
350 TPI heads off F-cars are very close to exactly the same heads similar years Corvettes use, which are 58cc I believe, the SAME as a 305 head. So if those 305 heads are so good why aren't they on Corvettes and 350 TPI cars? Cause they are not. DON'T DO IT!

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88 IROC the best RS ever made!
well except for the BC4s

 

Actually it's because the chambers are too small and the L98 (or any 350) would have high a high compression ratio. The 305 heads have 58cc and 350 heads (less aluminum "true" L98) have 64cc. I have a pair of L98 (or should I say B2L) cast iron heads, and they are definately 64cc and do not resemble the AL L98. The only concern about using L69 (you said '87 HO, did you mean the carb'ed engine?) heads on an TPI would be the center intake bolt could be at a different angle (canted). Larger valves do not affect compresion ratio in any way. The only aspect of the cylinder head that affects the CR is the chamber volume. I would opt for W/P torque 305 instead. They feature larger ports (which can be ported larger than any OEM 305 head) and all the stuff you would want from an aftermarket head.

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George P. Lara
1994 Z28 LT1 T56
1984 Z28 High Output
Member: SCCA, SCFB, SC3GFB

[This message has been edited by MRZ28HO (edited September 15, 2000).]

 

305 heads have smaller intake valves, and smaller ports too, I think. Get 350 heads. Dont even bother with 305 heads on a 350, its not worth it.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

What Kevin said. They won't perform as well..don't bother. not to mention that would put your CR too high for iron heads.

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
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Whoops, sorry folks. Yes, Kevin is right, use only heads specific for a large bore (ie: 4.00" bore). I just got carried away with the 305 thing.