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tips, technology, tools and techniques related to vehicle driveline components

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ddelong1
Doug DeLong

(25 posts)

Registered:
02/06/2011 08:34AM

Main British Car:


Rover Block Crack
Posted by: ddelong1
Date: July 17, 2016 11:00PM

Well, my attempts to get a new engine for my racecar up and running are not going well. I was close (or so I thought) to firing a new 4.0L with new liners, forged pistons, TA heads, etc. When I put water in the cooling system I had leaks into the valley area that I thought was the Cometic MLS gaskets I'm using. Today I got the engine out and the heads off and found a much more dire situation, it appears I have cracks around one of the head bolts between cylinders 2 and 4. I'm certain it wasn't this way when I assembled it, it seems like the torque of the head studs caused the cracks. I used ARP studs and installed per their instructions - torqued to 100 ft-lbs total in an ascending sequence of three steps.

The block was a used take-out unit that was bored and new liners installed by a reputable machine shop (will not be named until I can resolve this issue) that has lots of experience with these engines. Has anyone seen a failure like this before? I don't think I have much alternative but to replace the block, will be calling them tomorrow to discuss.

Rover.jpg


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5689 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Rover Block Crack
Posted by: BlownMGB-V8
Date: July 17, 2016 11:40PM

I think you will find that head bolt torque to be excessive.

Jim


ddelong1
Doug DeLong

(25 posts)

Registered:
02/06/2011 08:34AM

Main British Car:


Re: Rover Block Crack
Posted by: ddelong1
Date: July 17, 2016 11:54PM

Had that thought. A little too late now unfortunately.


Blown v8
Bryan Phipps

(46 posts)

Registered:
03/10/2013 04:52PM

Main British Car:


Re: Rover Block Crack
Posted by: Blown v8
Date: July 18, 2016 01:21AM

I only torque mine to 70lb,


tr8todd
Todd Kishbach

(347 posts)

Registered:
12/04/2009 07:42AM

Main British Car:


Re: Rover Block Crack
Posted by: tr8todd
Date: July 18, 2016 06:43AM

FWIW, my machinist won't use ARP bolts and studs on the Rover engines. His reasoning is that they need to be torqued more than what the block can hold to be more effective than stock bolts. I have a set of used ARPs that was in an engine I sent out to be rebuilt. Didn't even know they were in there until he called me looking for a set of stock bolts. Also have a set of brand new ones that came with an unassembled engine that was part of another project. He wouldn't use those either. He installs time serts?? in the heads before they are needed as well whenever we do roller rockers or stiff valve springs for the same reason.


MGBV8
Carl Floyd
Kingsport, TN
(3561 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Rover Block Crack
Posted by: MGBV8
Date: July 18, 2016 10:30AM

Now you tell us, Todd. ;)

Seriously, I have not heard that. I pulled the threads out of one of 3.9 blocks just torquing an ARP stud to right at 55 lb-ft.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5689 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Rover Block Crack
Posted by: BlownMGB-V8
Date: July 18, 2016 10:39AM

I inserted double stacked helicoils in my Olds 215 block and still had problems with pulling the threads at about 50 ft/lbs of torque. (of course that was with 16 lbs of boost)

Pulling torque on those blocks always felt mushy. Moving to an iron block fixed all that.

Jim



roverman
Art Gertz
Winchester, CA.
(2964 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Rover Block Crack
Posted by: roverman
Date: July 18, 2016 11:13AM

Doug, Perhaps you can post-up, where ARP says to torque a 7/16" stud, in aluminum, to 100 ft/lbs. ? IF you torqued 7/16-14 bolts to 100 ft/lbs, that would have increased by approx. 43%, with the 20 tpi., of the studs ! I suspect you'll find the deck(s), are no longer flat. Good luck. roverman.


ddelong1
Doug DeLong

(25 posts)

Registered:
02/06/2011 08:34AM

Main British Car:


Re: Rover Block Crack
Posted by: ddelong1
Date: July 18, 2016 06:40PM

The ARP kit (157-4301) contains and instruction sheet with torque instructions and pattern. Looks like I can't attach a PDF but you can easily download it off their web site. Here's the key text though:

"7. Lubricate the stud threads, nuts and washers with ARP ULTRA-TORQUE FASTENER ASSEMBLY LUBRICANT.
Then install the washers and the nuts onto the studs and tighten them hand tight. ARP recommends using the
ARP ULTRA-TORQUE FASTENER ASSEMBLY LUBRICANT that is provided with each kit as opposed to
motor oil. This is due to higher friction on the studs as well as inconsistencies in the clamping force of
the fasteners when motor oil or other low quality lubricants are used.
PRELOAD (TORQUE) RECOMMENDATIONS
8. Following the manufacturers recommended torque sequence tighten the nuts in three equal steps to 100 ft lbs
with ARP ULTRA-TORQUE FASTENER ASSEMBLY LUBRICANT. "

I have spoken with ARP today and they are investigating. The gentleman I talked to sounded legitimately concerned and asked for photos, block info, etc. I'll report back when I hear more from them.


MGBV8
Carl Floyd
Kingsport, TN
(3561 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Rover Block Crack
Posted by: MGBV8
Date: July 18, 2016 10:46PM

I think ARP owes you a block.

[arpinstructions.com]


roverman
Art Gertz
Winchester, CA.
(2964 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Rover Block Crack
Posted by: roverman
Date: July 19, 2016 11:53AM

First, hang the "proof-reader", then argue for a new "Coscast" block,(add boot/$ as needed).


ddelong1
Doug DeLong

(25 posts)

Registered:
02/06/2011 08:34AM

Main British Car:


Re: Rover Block Crack
Posted by: ddelong1
Date: July 21, 2016 08:09AM

Well, it still isn't resolved but I have made progress. ARP says that they tested the factory head bolts when designing this kit and the 100 ft-lb torque spec correlates to ~10% increase in clamp load. They have sold around 600 sets of these and say this is the first cracked block they have heard of, though they did seem to acknowledge reports of thread pull-out. They are arguing that they can't be held liable for the full damage because it may be that I just have a weak block. There's another complicating factor - I got the studs through TA Performance and evidently there is some difference between the ones I have and the pure Rover kit, sounded like a slight material change. That didn't make a lot of sense to me and the gentlemen I talked to was sort of vague about it but indicated that TA should really be providing the exact Rover kit. He acknowledged though that the slight difference in stud isn't really the issue, it's the strength of the thread in the block.

They're thinking about changing the value of the torque spec or putting in some kind of warning in the instructions, but also said they might just stop selling the kit. I think that they are thinking that if they acknowledge this is a possible result then they could be liable for cracked blocks or stripped threads when it does happen.

They said they would try to help me out with the repair and I'm waiting on a call with a proposal. We'll see what happens.


mstemp
Mike Stemp
Calgary, Canada
(189 posts)

Registered:
11/25/2009 07:18AM

Main British Car:
1980 MGB Rover 4.6L

Re: Rover Block Crack
Posted by: mstemp
Date: July 21, 2016 08:39AM

Doug,

Sorry to hear of your issue. Got a question. How did ARP come up with a torque value comparison when the stock bolts are torque to yield?


MG four six eight
Bill Jacobson
Wa state
(287 posts)

Registered:
10/23/2007 02:15AM

Main British Car:
73 MGB Buick 215, Eaton/GM supercharger

Re: Rover Block Crack
Posted by: MG four six eight
Date: July 21, 2016 09:34AM

100 ft-lb is a lot! It's been awhile, but if I remember correctly I think that I only went up 5% from the stock torque spec when using ARP head studs. For the bottom row of bolts it was less so that it wouldn't cock the heads.
You may want to contact Mark at D+D for more info, he's the one who gave me the torque specs and I've good luck so far even with running 9.5 to 10 psi of boost.

Bill


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1039 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Rover Block Crack
Posted by: ex-tyke
Date: July 21, 2016 09:42AM

When one considers that the torque spec for the original BOP head bolts was 45-55 ft-lbs, 100 ft-lbs for studs does seem high!



BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5689 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Rover Block Crack
Posted by: BlownMGB-V8
Date: July 21, 2016 05:40PM

Considering that the object of torquing the studs is to stretch them (minutely), it's really a good idea to consider the end fasteners. Top end, no problem, similar material, suitable length of thread engagement. But on the far end, that's where it gets troublesome. IIRC, typical thread engagement into aluminum is 2-1/2 times the thread diameter, minimum. But for high tensile hardened fasteners that number will have to go up, perhaps quite a lot. Maybe even double in some cases. You could need 2"+ of thread engagement before you are able to stretch the fastener. But what does that do to the deck? Even if there is enough depth of thread, is there the internal reinforcement required to prevent warpage and cracking? Apparently not in this case.

When a company sells studs without regard to the construction of the engine they go into and simply specs the diameter, length, and torque necessary to stretch the stud rather than referencing it to the original design in some way there is likely to be trouble. Were it an iron engine it would not be a problem, but aluminum has different requirements.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3561 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Rover Block Crack
Posted by: MGBV8
Date: July 21, 2016 09:38PM

I would think a "weak block" would have pulled threads. The strong, sound block over-torqued? Well,,,,it cracked. Cased closed, pay the plantiff! ;)


minorv8
Jukka Harkola

(134 posts)

Registered:
04/08/2009 06:50AM

Main British Car:
Morris Minor Rover V8

Re: Rover Block Crack
Posted by: minorv8
Date: July 22, 2016 01:59AM

Interesting, the ARP Buick 215 kit 124-4003 "only" has a torque setting of 80 ft-lbs, why would the 10 bolt kit need to be specīd at 100 ft-lbs ?

I think I torqued the Merlin head bolts to 68 ft-lbs. And these are long bolts. The feeling when doing the last round is very scary, it feels like the threads will let go any minute :-)


mstemp
Mike Stemp
Calgary, Canada
(189 posts)

Registered:
11/25/2009 07:18AM

Main British Car:
1980 MGB Rover 4.6L

Re: Rover Block Crack
Posted by: mstemp
Date: July 22, 2016 08:06AM

Jukka,

Felt the same way doing the stock head bolts. 20 mm (14.7 ft lb) followed by 90 and then another 90 deg! Guess those at least stretch more easily than the ARP studs so less chance of pulling out the threads from the block. If we can calculate what the stock bolts torque number would be, Doug would have more ammunition for his battle with ARP. I have seen reports that you get around 65ft lb when turning the stock stretch bolts the final 90 deg if that helps.



Edited 1 time(s). Last edit at 07/22/2016 11:45AM by mstemp.


DiDueColpi
Fred Key
West coast - Canada
(1259 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: Rover Block Crack
Posted by: DiDueColpi
Date: July 22, 2016 01:00PM

Yep, I think ARP has a problem there.
I was checking last night on an old 4.6.
Correctly angle torqued the bolts show 72 ft,lbs consistently.
Measuring the thread engagement into the block shows 1.100" of engagement depth. The block is actually threaded 1.700" so lots more room for stud length
I've got 2 sets of ARP head studs in hand.
Interestingly the literature in one box says 80 ft.lbs. not 100 that other kit advertises.
Measuring the thread engagement into the block shows 0.900" which is roughly 20 percent less than the factory bolt. And far shy of the 250 percent engagement rule.
Due to the fine thread end of the stud being the torquing surface it increases the tensile force on the stud by a rough factor of 2 compared to the coarse thread of the stocker.
This means that even at the lower 80 ft,lb figure, the force pulling the threads out of the block has increased by another 130 percent.
No wonder these things pull out!
I don't think that the machine shop has any liability here at all. It would seem to rest squarely on ARP.
I use ARP stuff almost daily and have never had an issue.
But I am going to check more carefully from now on.

Live like you mean it.
Fred



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