I have a 1998 ls1 and doing hci.
i bought arp head bolts and the last 2 dont fit anyone ran into this problem before arp # 3609

 

Where did you put the 2 shorter large bolts? I just used this kit on my 99.

 

9 and 10 are shorter

 

Just checked the part#; he got the right kit. Thought at first he got the late kit with all same size bolts.

 

Yeah, I could see that happening. I'm thinking he put them in without realizing there were a couple short ones in each head.

5.3 - the kit comes with 4 shorter bolts. Look at what you have left to determine how many you have used already and start taking bolts out until you find them. Then start over with your torque procedure.

 

Tomorrow I’ll go to the shop and check
but if I am not mistaken the mechanic told me the treads are bigger

 

If you got the right kit for the engine you have the threads will be JUST RIGHT!
You will have 8 long bolts, 2 short bolts, and 5 smaller bolts for the top row. ARP does not mess things like that up. Your mechanic might have mixed the bolts up. He must not work on many LS engines.

 

☝️☝️ Completly correct. ARP is my most trusted fastener manufacturer. Out of all the LS kits and other import cars I've worked on, I've never experienced a single issue with them. There head fasteners and main cap studs are unmatched in quality. I seriously doubt they put the kit together incorrectly. I'm sure machinist is screwing up order of bolts.