Crate 350 HEI conversion --- what plug, what gap?
Thread Starter
Burning Brakes
Joined: Dec 2005
Posts: 1,153
Likes: 341
Crate 350 HEI conversion --- what plug, what gap?
Sorry to keep begging for help, but...
Crate 350, nothing fancy or high compression. Mild cam. I can get a block # if that would help...
Just take the stock plug (1969 350 motor) and gap it out to .055-.060 ?
Any suggestions?
Crate 350, nothing fancy or high compression. Mild cam. I can get a block # if that would help...
Just take the stock plug (1969 350 motor) and gap it out to .055-.060 ?
Any suggestions?
Race Director
Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
Many argue on the correct plug gap for a HEI. distributor setup. Standard plug for a 76 350 should be perfect. And gap with which HEI? most will say .045. If running a very Hot HEI as a DUI. yes. Most I would gap to .040
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
NGK plugs. 5 heat range. I run my gap at .045. Side gap the plugs. Maybe it helps to do that? It doesn't hurt.
https://www.google.com/search?q=side...id:3OYe7pV0SpI
https://www.researchgate.net/publica...e_and_Emission
https://www.google.com/search?q=side...id:3OYe7pV0SpI
https://www.researchgate.net/publica...e_and_Emission
Last edited by REELAV8R; Jul 7, 2023 at 09:29 AM.
Race Director
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A modern crate 350, 5/8" tapered seat plug wont use the same as a 69 350. 3/4" gasket seat plug. The gap will be .045 but the type of plug depends on the type of heads.
Race Director
Joined: Nov 2006
Posts: 13,199
Likes: 7,796
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
Good answer. I didn't even think about that. My Aluminium heads use different plugs than my original iron heads. You need to know if you need tapered seat or gasketed plugs. And the reach length your heads require.
