1g studs in 7 bolt block

[fast95turbo]

So my question is, has anyone used 6-bolt (M12) studs in a 7 bolt (M11) block?

I understand there will be some machine work but I'm wondering about the head lifting at high boost (30psi) and would like the benefit of the extra 1mm...

 

[lilsam]

the head wont fit on so you will have to make the holes where the head studs slide through the head bigger

 

[ArmyGSX]

You would have to have both the head and block bored out. Then the block would have to be taped.

I would just go with some 7 bolt L19 headstuds if you plan on running that much boost.

Would cost less then all the machine work and then having to buy 1g L19 headstuds.

 

[fast95turbo]

this will be with a 1g head.

 

[ArmyGSX]

I don't think I have ever heard someone putting a 6 bolt head on a 7 bolt block.

Can I ask why you want to do that?

 

[fast95turbo]

the ports are much larger on the intake side, the intake is already ported for a 60mm throttlebody.

 

[RadDsm]

7 bolt bottom end and a 1G head is like having the worst of both worlds.

If you are worried about the head lifting, buy L19s.

 

[fast95turbo]

the 7 bolt bottom in question is a fully built 2.4, arp mains and everything.

 

[RadDsm]

The combo makes more sense then, L19s or H11s are still your best bet.

 

[fast95turbo]

UGHH, my previous understanding before tonight was the head diameter was the 11-12mm difference so i ordered the 1g ARP's until i could afford the L19's.

Guess I just needed someone to tell me to suck it up and get em now...

 

[RadDsm]

See if you can cancel the order if it isn't too late. Many have ran higher boost than that on standard ARPs and an OEM HG.

 

[99gst_racer]

How much airflow (lbs/min) do you plan on pushing?

The 11mm L19/H11 studs are good for 75 lbs/min no problem, maybe more. So, unless you're going to be exceeding that amount, I wouldn't bother with the machine work.

With that being said, I will be drilling and tapping my 7-bolt block to run a larger stud sometime this winter. I haven't yet decided if I'm going to run 12mm studs or 1/2" studs. I'm going to drill and tap a junk block and head over at SIM sometime soon to test to see if a 1/2" nut will clear the valve springs. I'll be sure to post my findings.

 

[BogusSVO]

99gst_Racer... you may end up having to spot face the head some around the head bolt holes so the nut flange will seat flat on the head casting.

 

[donniekak]

I don't think a head will actually lift with the h11/l19 fasteners. It's more likely for it to flex in between fasteners. What usually happens is the area where the fire ring seals the combustion pressure in has a water passage under it, making a thin area. Drilling these areas and then welding more material can help. It's a common fix for the 6g72 heads.

 

[phunny]

How much airflow (lbs/min) do you plan on pushing?

The 11mm L19/H11 studs are good for 75 lbs/min no problem, maybe more. So, unless you're going to be exceeding that amount, I wouldn't bother with the machine work.

With that being said, I will be drilling and tapping my 7-bolt block to run a larger stud sometime this winter. I haven't yet decided if I'm going to run 12mm studs or 1/2" studs. I'm going to drill and tap a junk block and head over at SIM sometime soon to test to see if a 1/2" nut will clear the valve springs. I'll be sure to post my findings.

I actually just had this come up. I have a 7-bolt with 12mm studs. The problem is that the 12mm studs are 3/8" shorter, so I'm hoping that isn't an issue as the stud may not be able to go all the down in the block but the threads do go pretty far down in.

 

[99gst_racer]

I actually just had this come up. I have a 7-bolt with 12mm studs. The problem is that the 12mm studs are 3/8" shorter, so I'm hoping that isn't an issue as the stud may not be able to go all the down in the block but the threads do go pretty far down in.

Is that block something new to you. So, you drilled and tapped them larger?

 

[phunny]

Is that block something new to you. So, you drilled and tapped them larger?

No I didn't. Pina Motorsports did the short block for Jeff Bush and did him a favor by changing them to 12mm. It was then realized that the 12mm are a 3/8" shorter so a custom set of Arp's were made ($900 for standard arp's).

I sent a few messages out and it looks like you can just countersink the 12mm about 1/4" down in the block and it should work fine. If it doesn't, the only option is to have some made.

 

[99gst_racer]

Why can't you just run regular ARPs (or regular L19s)?

 

[delta448]

That's what I want to know as well Paul. Studs should not bottom out anyway in order to prevent twist and stretch in the shaft. If they bottom out, they're not really any better than a bolt with a fixed head.

 

[phunny]

Why can't you just run regular ARPs (or regular L19s)?

I believe I can and, after speaking with Arp, the difference between the 11 and 12mm is only .2 inches.