Replace head gasket, compression test

Sounds like the replacement M12 bolts you were supplied are too long... as I've never heard of a standard (not severely skimmed) head, standard gaskets and standard bolts bottoming out in the threaded holes...

Do you still have the original bolts to compare your replacements against?

SteveC
 
If they are original FIAT head bolts with 19MM heads, then these are "conventional" head bolts that are torqued to an end value in several progressive stages, then must be retorqued after a certain amount of time/miles/heat-and-cool cycles have elapsed. These can be reused as long as they are within spec measurements.

If they are original FIAT head bolts with 17MM heads, then these are the more modern TTY aka "stretch" head bolts that are torqued to a lower value then tightend by angle (90 degrees) twice, and then left alone, NO retorque. [The FSM is mum on whether or not these bolts can be reused. Typical, current/modern practice is to not re-use these bolts.]

The above procedure is covered in the factory shop manual (as posted below by Mike Hynes).

If you want to play it safe and not re-use the original 17MM "stretch" bolts, the problem is that they are pretty much NLA (no longer available), at least here in the USA. What can be used are 15MM head, integrated washer stretch bolts from slightly newer FIAT SOHC cars, these are available from Euro suppliers such as EuroSport, for reasonable prices. On my 10-bolt early '86 car, I did not like that these bolts had the integrated washer, plus if used without the additional hardened washer these bolts are generally 2-4 threads shorter than the originals, resulting in slightly less thread engagement, not ideal IMO. So I reused the hardened washer that came with the original head bolts and had my auto machinist buddy mill down the cylinder head's "landing pads" for the head bolts to a depth that would allow for the added thickness of the washer plus a little more to recover the several more thread engagements lost to the slightly shorter bolts. And as Steve C (FiatFactory) noted, you have to factor in how much if any material was taken off the block surface of the head if it was resurfaced.

Video here: https://1drv.ms/v/s!AkvLg2jkzcHLgZNB5kaqtzye3DkHtA
 
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TTY? Why?



I hate to hijack this thread but I can find no reference to TTY bolts in the manual.

None.

The Fiat manual is very comprehensive. It does not state that the 17mm head bolts should not be reused.

I don't have any interest in starting a controversy, or to be contrary. But it seems to me that misinformation, based on conjecture, is being disseminated. Have you found any authoritative reference, anywhere, that specifies the 17mm head bolts are TTY and shouldn't be re-used?
 
Once again TTY is a SYSTEM, that works only in conjunction with the correct type of cylinder head gasket. Torque and angle method of tightening implies they are TTY, or else a regular three/four stage and retorque method would be specified

If used in the TTY method then if bolts are re-used you run the risk of the bolts going out of their 'elastic' range and into their 'plastic' range and deforming (stretching beyond their design limit) and therefore not providing sufficient clamping force.

The only engine w/shop manual I have for the sohc that mentions all this is in German, and it quite clearly states (several times) that the head gasket needs to be an 'Astadur' (polymer composite construction)

If you use the 17mm head bolts with a non polymer conmposite gasket, then the best method would be several stages and 61.5lb/ft final torque.

SteveC
 
Point Taken

I will edit my post to reflect what you pointed out, that the FSM does not specifically state that the TTY aka "stretch" head bolts supplied as OEM cannot be reused.

While it does not say not to reuse them, OTOH, it does not say you can reuse them :)

The aftermarket bolts I used on my cyl head had it specifically stated on the package that they were not to be reused. [Of course that could have been their way of selling more bolts, too :whistle:]

Hanging out with a good friend who has been an automotive machinist and has run his own shop for over 30 years, I often have occasion to look at industry reference material (manufacturer FSMs as well as Mitchell, All-Data, etc) for a wide variety of engines, American, European, and Asian. It's been my observation that the more modern the engine, the more the reference material stresses that many engine fasteners should not be reused...head bolts the most common, but sometimes you see that caution for cam gear to camshaft bolts, main cap bolts, conrod bolts, etc.

Based on all of that, my suggestion would be that with the 17MM bolts, for "best results", either acquire a new replacement aftermarket set of stretch bolts, or perhaps convert to aftermarket non-TTY conventional bolts such as those available from ARP.
 
Method to approximate bolt stretch

Steve, I have to disagree. There are many different ways to try to approximate the amount of clamping force a bolt is supplying. The torque turn method is but one of them. Recommending the torque turn method does not imply that the bolts are torqued to yield. It's just another way to estimate the clamping force. You simply can't imply that the recommendation of the torque turn method means the bolts are TTY. Recommending that the bolts can not be reused, on the other hand, might.

I suppose someone who knows a lot more than I about bolts could tell you by looking at the bolt (material, heat treat, design, torque applied, etc.) whether the recommend torque would stress the bolt to it's yield strength. But for most of us I think it can't hurt to not reuse them. I don't know what they cost, but it's got to be cheaper than replacing a blown head gasket!
 
Agreed

It can't hurt to replace old used bolts with new - know to be good bolts.:grin:

Bolts have a very tough job. They must be tightened enough to stretch - just enough - to apply the necessary clamping load. If you don't stretch them enough, they don't apply enough clamping force and the joint may fail. If you stretch them too much, they become deformed to the point they can't provide the clamping force they should causing the joint to fail. And while the bolts act a lot like a spring (that can be over stretched), they don't stretch much. It's a delicate balancing job to get enough stretch, but not too much stretch, in a bolt. For most of the bolts we deal with we're talking thousands of an inch. That's why many methods of estimating the clamping force a bolt supplies have been developed. It's also why it's very important to make sure the threads are in good condition, and that the proper method of lubricating the threads, and bolt underhead, (determined by torque estimating method) is employed. If parts fall of of your car you probably didn't take as much care "stretching the bolts" as you should have. :eek:mg:
 
Trying to narrow down my possible approaches to the head torque / retorque, given the materials I'm using.

The "TTY" bolts and procedure - since none of the domestic gaskets appear to be "Astadur" or Polymer, Following the TTY procedure doesn't seem to make any sense for me. (Steve - the Astadur gasket was not in a sealed bag - I was going to buy it...)

The bolts themselves, on closer inspection, are NOT true TTY bolts - they don not have the tapered shank of every other TTY bolt I have ever used on a Volvo. So, maybe they are not really TTY?

I don't understand how a retorque procedure can be applied to any true TTY bolt. Obert told me that the Fiat TTY bolts (only described as 17mm head in the shop manual) should be retorqued. The gasket I have coming from him appears to be no different than any other aftermarket, based on my conversation with him yesterday.

Looking in the shop manual, there is zero mention of a retorque (page 10-51) for the 17mm bolt head angle-torque procedure) I cannot find any reference in the manual to a retorque procedure for either style bolt, btw.

Is it in a service bulletin to be found elsewhere? If I am going to use the TTY bolts, with whatever composite the gasket from Obert is, or even with the VR gasket from Dom, I need to know exactly how one is supposed to retorque the TTY bolts.

Failing that, I can go back to the larger straight bolts I have from MWB & retorque them, which I was told was simply mark each bolt head relative to the head/cambox, loosen one at a time in original sequence & retorque to final torque in one step. I did that on the 2nd to last gasket, and got an extra 60degrees on each bolt.

If I'm using the "TTY" bolts I really need to know the procedure. Again, it's not referenced in the manual in the engine section anywhere I can find it...
 
Not a fan of TTY on performance motors. TTY head screws work when highly controlled conditions and parts are used. It is dependent on had gasket material, cylinder head material, friction involved with threads, under screw head and actual twisting force applied. The concept behind TTY is to put the threaded fastener into the material just at the yield area of the curve turning it into an effective spring that in theory compensate for expansion and contraction of parts involved over time and temperature cycling.

Just too many variables to control for a performance engine build.

IMO, use ARP studs for the cylinder heads and re-torque. It is just not that difficult. Studs and nuts tend to apply more even clamp force due to reduced twisting of the long threaded fastener involved. Torque applied to the fastener head must travel down the length of the fastener before that twisting force can move the threads involved. This distance is much shorter when studs with threads on both ends are involved. This significantly reduces the twisting of the threaded fasteners shank-grip length.

Curious, what brand of cylinder head gasket failed? Does appear to be a fire ring extrusion failure on more than one cylinder.


Bernice
 
For performance engines, using the original M12 cylinder head set up with M12 ARP studs. Torque the whole thing up to 60 ft/lb and re-torque after the first hour of running, then again after about 10 hours or running.

Fiat OEM for the M10 threaded fasteners appear to be angle torque based on an initial torque wrench setting then applying an additional 90 degrees and another 90 degrees making a total of 180 degrees of added fastener rotation post initial torque value. Proper fastener pre-loading depends again on cylinder head gasket material (how much will it compress under load) thread friction and the degree of compression of other materials involved. Deviate from any of these initial design elements, the resulting preloading will be different.


Simply do not like M10 cylinder hardware. The idea was to gain threaded fastener elasticity to compensate for parts movement. The original Lampredi M12 threaded cylinder head fastener design went for rigidity by old school over design.



Bernice
 
New bolts

New bolts. Even with extra washers there is stil exhaust gasses in the rad. Not much though. Everytime i stow the roof, i bleed the rad. The car drives perfect. Maybe i have a small crack in the head. I will have a look later. I have a new projext X with uno turbo engine.
 
Rupunzell said:
Not a fan of TTY on performance motors. TTY head screws work when highly controlled conditions and parts are used. It is dependent on had gasket material, cylinder head material....

Curious, what brand of cylinder head gasket failed? Does appear to be a fire ring extrusion failure on more than one cylinder.
Bernice
Click to expand...

Hello Bernice

I don't recall the brand, it's whatever MWB carries.

The Volvo TTY setup worked fine for me running over 500whp. I find it hard to believe it can't work on such a relatively low output setup. That said, the bolts dont appear to be true TTY, so I don't know what's up with that. Maybe the manufacturer just doesn't follow the usual tapered shank I've always seen with TTY hardware.

In any event, it certainly looks like the cause of failure was detonation, not a torque/ lack of retorque issue. All the fire rings are evenly hammered around their entire circumference, just 1&2 let go first.
 
Hussein,

why not just go for the ARP M10 option for the head fasteners?

Then you can use whatever gasket you like, and run thru a regular torque/ retorque procedure.

Pics look like detonation did the gasket again...

SteveC
 
fiatfactory said:
Hussein,

why not just go for the ARP M10 option for the head fasteners?

Then you can use whatever gasket you like, and run thru a regular torque/ retorque procedure.

Pics look like detonation did the gasket again...

SteveC
Click to expand...

I don't want to use studs - with the header setup it will be a royal PITA to put together - as it is I angle the head in place so the studs align with the header flange, then drop the rear to seat on the two locators.

I got the correct follow up torque procedure for the TTY bolts that is from a Fiat service bulletin for the PDI inspection. TTY bolts are retorqued WITHOUT loosening in two stages - marking the head/bolt first then

1) 60º
2) 30º

So, I'll follow that after a couple warm up cycles.

My main concern right now is getting appropriate timing mapping before I run it on the road at all.
 
+10.

Flat refuse to use anything other than studs for performance engine cylinder heads. Too many technical reasons to use high quality studs, nuts, flat ground hardened washers, very very few good reasons to use cap screws-aka bolts that can be questionable.

Ease to work on stuff is simply not enough justification for applying what is technically correct.

I'm simply NOT going to tolerate a problem if it can occur even it the technically correct method requires a LOT more effort and resources in every way.

-This is the difference between an endurance race car that runs problem free hour after hour, lap after lap finishes and does well or the vehicle that goes half a lap, rolls over and catches on fire.

It is all about the details and not allowing stuff that can go wrong to go wrong. Even the tinniest seemingly irrelevant detail can result in very serious problems.


Bernice



fiatfactory said:
Hussein,

why not just go for the ARP M10 option for the head fasteners?

Then you can use whatever gasket you like, and run thru a regular torque/ retorque procedure.

Pics look like detonation did the gasket again...

SteveC
Click to expand...
 
lookforjoe said:
I got the correct follow up torque procedure for the TTY bolts that is from a Fiat service bulletin for the PDI inspection. TTY bolts are retorqued WITHOUT loosening in two stages - marking the head/bolt first then

1) 60º
2) 30º

So, I'll follow that after a couple warm up cycles.
Click to expand...

Wait.....what?

[Assume PDI=pre-delivery inspection.]

So do I interpret that tech bulletin as saying that before giving the car to the customer, the mechanic is to add ANOTHER 90 degrees (in two stages of 60 + 30) of turn to the head bolts that were supposed to have already been turned to 30 lbs + 90 degrees +90 degrees at factory engine assembly?

OR, is the tech bulletin meant to correct an assembly line error that can be nailed down to engines built to certain conditions: say a date range, a serial number range, a specific manufacturer's part being used, the week that they put the drunk, cross-eyed janitor on the engine line and he forgot half of the head bolt tightening procedure, etc

My head is getting ready to detonate.:sigh:
 
Yeah. Me too. This would be applicable to any/all cars delivered with 17mm bolts -presumably any engine with the 14 bolt setup? Why it was never added to the shop manual I don't get - it's pertinent info for anyone installing/ using new head bolts, since the procedure differs from the straight bolt torque process. Since listed item#2 is not on this page, I did ask Chris for clarification that this (PDI) step would take place following the torque procedure for HG replacement during a field service replacement (outside normal service requirements).


 
I am guessing that is from Service Letter 100-18, dated 12-10-81? I found a copy here.

It is interesting that the procedure for the Pre-Delivery Inspection (PDI) calls for turning first 60°, then 30° for a total of 90°, while the torque procedure after the head has been removed and reinstalled is torque to 14.5 fl-lb, then to 29 ft-lb, followed by turning 90°, followed by another 90° for a total of 180°.

Perhaps the PDI torque requirement is to correct for incorrect torquing at the factory?
 
Read this short on Torque Control vs. Angle Control.

http://www.assemblymag.com/articles/87404-fastening-threads-torque-control-vs-angle-control

Once non Fiat original head gasket that was specifically designed and tested for the published procedure and threaded fasteners involved used along with many variables that are controlled at the Fiat engine production facility back in the day when that service note was published, it would be extremely difficult to know precisely what the designed clamping forced really is using anything less than precise-identical bits.

Many years ago when during the first encounter with this cylinder head screw issue, it was followed using Fiat OEM parts that were available over the counter at the Bertone/Fiat parts dealer. Procedure worked OK on a stock engine.

Since then most if not all has changed including modified engines for higher output and using non-orginal Fiat head gaskets and more has essentially resulted in ditching that Fiat service bible based on the realities of what has changed.

Reverting back to the original Lampredi design specifications and parameters made more sense along with using the highest quality studs and re-torquing early on in the engine's run time. What is important is proper clamp force uniformity on the cylinder head to block interface. If this can be assured by re-torque and high quality stud/washers/nuts there is little reason to avoid this proven practice.


Bernice
 
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