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LS2 accessory bolt size

Old May 1, 2017 | 07:34 PM
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Default LS2 accessory bolt size

Hey all,
Yes I have searched and found the entire bolt kit for a LS but I am specifically looking for the bolt size and pitch for the accessories to the heads. I have Mammo 235 heads and Tony thinks they are a 10mm x 1.50 and I called AFR and they guy I spoke to was a complete tool and said they use stock casting which helps me 0 Anyone else have issues with the OE bolts not fitting?
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Old May 1, 2017 | 09:00 PM
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I don't know if I will e much help . But for what it's worth I have TFS heads with holley accessory drive . All there bolts look like OE to me .
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Old May 2, 2017 | 12:03 PM
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Originally Posted by Sick LS2
Hey all,
Yes I have searched and found the entire bolt kit for a LS but I am specifically looking for the bolt size and pitch for the accessories to the heads. I have Mammo 235 heads and Tony thinks they are a 10mm x 1.50 and I called AFR and they guy I spoke to was a complete tool and said they use stock casting which helps me 0 Anyone else have issues with the OE bolts not fitting?
I have Tony's MMS 235 heads and the stock GM bolts are indeed what they are tapped for. 10mm x 1.5 is what I used without any problem. I just installed Gen 1 CTSV front accessories with 10.9 grade 10mm X 1.5 bolts. They seemed slightly undersized (likely just micro burs) but are fine after one pass through with a bolt. You will need GM's head plug 11610259 for the hole in the head that doesn't get a water temp sensor (passenger side head). It is not an NPT thread as I originally thought.
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Old May 2, 2017 | 07:30 PM
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So I have a GTO is there any chance the LS2 in these cars have different accessory bolt sizes(Im aware this is unlikely but wanted to throw it out there)? My bolts are either to small; to the point they dont grab or they are too big. I will go to the hardware store tomorrow and get a 10mm x 1.5 and see what happens. I appreciate the input though
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Old May 2, 2017 | 07:54 PM
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That is a M10 with a 1.5 thread pitch. You will still need to know length of the bolt .
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Old May 2, 2017 | 08:04 PM
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Originally Posted by Sick LS2
So I have a GTO is there any chance the LS2 in these cars have different accessory bolt sizes(Im aware this is unlikely but wanted to throw it out there)? My bolts are either to small; to the point they dont grab or they are too big. I will go to the hardware store tomorrow and get a 10mm x 1.5 and see what happens. I appreciate the input though

No difference. The CTSV came with both the LS6 and LS2, both having 243 heads. Likewise, your GTO will have both the same heads and front accessories.

These are the GM bolts for the GTO/CTSV accessories sans AC.
  • (2) Bolt, Transaxle Br p/n 809-11515768
  • (3) Bolt - Hvy HX Acorn Flg Hd p/n 809-11518637
  • (2) Bolt - Hvy HX Acorn Flg Hd p/n 809-11518630
  • (3) Bolt - Hex Flg HD p/n 809-11518075
  • (3) Bolt, Gen p/n 809-11518633
  • (2) Bolt Hvy Hex Flg p/n 809-11515760
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Old May 3, 2017 | 06:36 PM
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Found them!! It was a tight fit and I think thats why I thought they were wrong. Once I started threading it got better. I appreciate the assistance
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Old Sep 15, 2023 | 02:35 AM
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Originally Posted by Sick LS2
Found them!! It was a tight fit and I think thats why I thought they were wrong. Once I started threading it got better. I appreciate the assistance
If you can remember what was actually size of those bolts
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