[AIR RAM]

Just curious what people are using for the Outer main bolts on the splayed mains. I have Program Engineering Mains and not sure if I should use the supplied bolts or if there is a part number for ARP 8740 outer bolts...

SPEED SAFE, NICK

[GTOGEORGE]

Originally Posted by AIR RAM

Just curious what people are using for the Outer main bolts on the splayed mains. I have Program Engineering Mains and not sure if I should use the supplied bolts or if there is a part number for ARP 8740 outer bolts...

SPEED SAFE, NICK

ARP studs.



GTO George

[AIR RAM]

Originally Posted by GTOGEORGE

ARP studs.



GTO George

Unfortunately ARP does not advertise a stud kit for "Splayed Mains"

So I use the center 2 bolt kit.... and what ARP kit is everyone using for the outer studs? I cant seem to find an outer bolt kit for the Splayed mains.

The traditional 4 bolt kit from ARP wont work because the outer studs in that kit are to thick and way to short.

Does anyone have a length that should be used?

SPEED SAFE, NICK

[shaker455]

I got mine from Butler and they supplied the outer bolts.

[Dragncar]

Are they 7/16 or 1/2" ? I have some Program Splayed mains and have grade 8 bolts. The guy that originally did the fit work (Dan Whittmore) made sure the bolts were made in USA (LE) Its hard to find grade 8 bolts that are not made in China these days. Plenty have been found out to be grade 5 with the grade 8 6 lines on the head. The military even bought some and have them fail on their M1A2 Abrams main battle tanks.
I originally sent him some main caps that had 1/2" outer bolts and he would not use them in the stock block.

[Skip Fix]

My machinist used Allen head bolts as they are Grade 8, I had the 4 bolt stud kit but it is really made for straight not splayed.

[GTOGEORGE]

I have splayed main caps, no problem with studs I install caps, screw in studs and torque. ARP have all kinds of different length stud.


GTO George

[Scott Stoneburg]

I think the outter bolts on my current stock block are 7/16 Allen head bolts.
I will check my IAII block that is still on the stand. But I believe it has 1/2 studs on the outside splayed bolts. Studs on the center.

[Skip Fix]

Scott I think you are right my IA has studs on the outside also. I'll have to look a pictures.

[GTOGEORGE]

Originally Posted by GTOGEORGE

I have splayed main caps, no problem with studs I install caps, screw in studs and torque. ARP have all kinds of different length stud.


GTO George

my KRE block have all 1/2" studs.


GTO George

[Skip Fix]

I think the splayed caps on the 400 block I have came with just 7/16 holes also.

[Murf]

I don’t want to derail this thread but,
At what level of build should a person consider this mod and are there other mods to the bottom end a person should consider doing?

Thanks
Murf


Sent from my iPhone using Tapatalk Pro

[Scott Stoneburg]

Originally Posted by Murf

I don’t want to derail this thread but,
At what level of build should a person consider this mod and are there other mods to the bottom end a person should consider doing?

Thanks
Murf


Sent from my iPhone using Tapatalk Pro

My previous 461 had 2 bolt main. ARP studs with longer dowel pins. It was around 650hp. I ran it for years, had it apart 1 time and had no visible signs of bearing issues. Spun it to 6800 running 10.20s at 130. Finally had a rod( stock rods) let loose.

[AIR RAM]

You guys are correct that they are 7/16th outer bolts. I just need to know what length to order... I have looked all over and just cant seem to find anything talking about the outer studs for a Splayed main for Pontiac Specific application. I dont trust the bolts that came with the caps and really want to run an ARP stud on the outer bolts. It would be nice to have specifics as to thread length/pitch + shank width + thread length/pitch.

Im sure we can spec them out... I was just hoping to save some time and get them ordered.

Thanks for all the assistance!!!

SPEED SAFE, NICK

[Scott Stoneburg]

Checked my IA block, I have 1/2" bolts in the outside holes. ARP marked on the head.

[AIR RAM]

Originally Posted by Scott Stoneburg

Checked my IA block, I have 1/2" bolts in the outside holes. ARP marked on the head.

Thank you for taking the time to look at yours.

Are those for SPLAYED mains or traditional vertical mains? Those look awfully short for splayed...

So I called Butler and they are sending be the correct 7/16 bolts for the Program mains. My mains came with 1/2 bolts however the outer holes are 7/16ths.

I was looking into adding studs to the outside however they made a good point. If the outer splayed main bolt gets stuck for what ever reason... you're going to have a heck of a time getting the main cap off. They recommend using bolts on the outer splayed mains for that reason. Makes a ton of sense once you think about it. They also suggested that the grade 8 bolts that come with the Program mains are more than strong enough and they did NOT recommend upgrading to an ARP bolt. They said the block would crack before that bolt became a problem. I wanted to go with the ARP for the increased clamping force... but they said they use those bolts all the time without issue.

So I think my search has been concluded.

Thank you to everyone who offered advice and tried to help.

NICK

[Scott Stoneburg]

They are splayed mains on my IAII block.
My stock block has 7/16" bolts on the splayed putters.