Bounty

as above, want more compression but if i got s/h 302 heads do i realy need to put in inserts and hardend seats etc.? been told both ways and dont wanna spend money on the heads if i have to spend another 500 on just getting it ready for gas.

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XF Ute. 351. LSD 9" 4wdics. Manual. Lowered. Tinted. All Elec. 16" mags. Huge "doof doof".

JG33

Yes you will have to put hardened valve seats in the heads unless you find one that already has it.

302 heads on a 351? compression will be too high unless you fit smaller height pistons.

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Rhett

I run a straight gas 351 with 302 heads and flat top ACL's with no detonation problems. The most important consideration is to have the distributor recurved to suit the burning characteristics of LPG and disconnect the vacuum advance.

You don't have to have stellite valve inserts, but your heads won't last very long, because the exhaust valves will start receding into the heads. The combustion temperature for gas is much higher then petrol.

Regards Rhett

russxr67

use the inserts.should cost around 35 dollars each or around 280 for both heads.

Bounty

it is already on straight gas so the dizzy should be right. the ACL pistons u have, what did u pay and how diffrent to standard are they? did u notice a big diffrence with the 302 heads? thanks

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XF Ute. 351. LSD 9" 4wdics. Manual. Lowered. Tinted. All Elec. 16" mags. Huge "doof doof".

Rhett

Dont presume the dissy has been done.
Full mechanical advance should be in no later then 2800-3000 rpm.
I used 30 thou flat top ACL Duralites, (which also come with pre-fitted and pre-sized rings), nice and easy for me since it was my first V8 build. From memory they cost me about $250. That was back in March 2001.

QUOTE FROM ACL ONLINE CATALOGUE

ACL Duratech® pistons are designed to provide enhanced performance characteristics compared to the OEM pistons they replace. These pistons are all solid skirt design which provides up to 30% greater strength than pistons which have a sawn or cast oil return slot in or below the oil ring groove. Oil drain back is via cast slots below the oil ring. High silicon material: ACL Duratech® pistons are made from a high silicon aluminium alloy which is the same as used in most high performance original equipment pistons around the world. This alloy combines excellent scuff and wear properties with maximum strength and minimum expansion.

Benefits . . .
• Stronger than the original equipment pistons they replace.
• Lighter than the original equipment pistons they replace hence less mechanical losses and maximum power and less vibration.
• Highly wear and scuff resistant in extreme situations due to high silicon alloy.
• Able to operate quietly and reliably at low clearance due to low expansion coefficient of the high silicon material and also due to sophisticated computer generated 3 dimensional diamond turned skirt profiles.

Hope this helps. There may be better value pistons around. If you are planning on using NOS, then I'd use Hypers instead.

Regards Rhett