torquing head with ARP studs

[moTthediesel]

Well, I haven't been on this forum in years, but I have a question for the knowledgeable. I'm going to be installing a new all metal, 19L head gasket on my hydraulic valve 1.6TD. What torquing procedure do you recommend?

I have been running this engine for about 6 years and about 12k miles without incident, but I blew the head gasket a couple of weeks ago while competing in the Targa Newfoundland Rally. I had turned up the boost a bit for competition purposes (max 20 psi) and we were hammering on it pretty good, and then the HG let go on the second day of the 6 day event. Much sadness ensued.

The engine is a Canadian market 1.6TD, it has a Giles pump, a long-runner GTI intake manifold, VNT15 turbo with my own mechanical vane control, and a Porsche 944 intercooler. It was built with all ARP fasteners, including the head bolts, and I used the all-metal 1.9 HG. I guess that 20 psi is kinda pushing it, but damn it -- we were racing!

I plan to dial-back the boost a bit now, but I still want to be sure that this doesn't happen again, what procedure should I follow?

I don't know if any of the old-timers here remember me, but the engine is mounted in the back of an old 356 Porsche, as you see here.

 

Tom

[libbydiesel]

Your car is awesome.

20 psi is really quite moderate.  You really shouldn't have any issues at that pressure provided the head and block are both very flat.  Were both machined flat before install?

Here's how I would approach it at this point.  I would pull the head, buff off the pre-chamber inserts and inspect for the little cracks.  I would replace any that are cracked.  The sadness caused by dropping a pre-chamber insert into the cylinder is magnitudes higher than blowing a headgasket.  If the inserts do not have any cracks, I would remove them (I use a hardwood dowel that is just slightly smaller than the injector hole) in order to flatten the head.  For flattening the head, I have hand lapped it using 120 grit paper from an 8" roll glued to polished granite (sink cutout).  I've used 3M spray adhesive and lubed the paper with plenty of WD40.  It works very well.  You could also have the head planed at a machine shop, but if doing so I would still have the pre-chamber inserts removed.  When inserting the pre-chamber inserts, make sure they protrude above the head surface slightly. 

Clean the block surface meticulously.  Use a very light coat of hylomar spray on both sides of the gasket, on the head, and on the block.  I'm not sure when you got the ARP studs.  If it was long enough ago, they are likely the Ford Cosworth studs.  More recently ARP has come out with turbo-diesel specific studs that are supposedly stronger.  I would use those and torque them to the torque specified by ARP.

[theman53]

I would suspect the block or head surface. I have arp studs and have went to 40 psi ish max but it sees 25psi every time I run the car. If you didn't retorque them that could have been a problem. The process I have used is similar to the Bentley but none of the 1/4 turns. I use the Bentley order and ft/lb recommendations and then when you get to the 66 ft/lbs or whatever is the last step value, then I go to 85 then 100 and then 110...following the same order. Some have gone to 120ft/lbs but I think most around 100 even should be fine.

The stud and metal gasket combo is very good. 20 to 25 psi with studs and a fiber gasket has been ok for most. For it not happening again I would take the head and block to be measured for warpage.

BTW, do you still have that TV video of you on the mileage show?  If so post it again.

[vanbcguy]

How does your vane control work? Have you ever measured exhaust manifold pressure? What about EGTs? 20 PSI is not really that much, wondering if your old HG got cooked. The VNT15 can generate some pretty high exhaust pressure if the vanes are closed down too much...

[moTthediesel]

I did surface the head with emery cloth on a plate when I put it together last time, but I'll do it again. I did not use hylomar last time, but I've ordered some. My studs are surely the old Cosworth items, and I'm surely going to be using them again. 

I did retorque the head after 200 miles or so, but maybe I should have waited till I had a little more time on it? I'd forgotten about that video  -- I wish I still had it, but I don't.

My vane control works by a cam on the shaft that turns to pull the fuel rod. There is also a boost can incorporated that allows the vanes to open when max boost is reached. It works pretty well. I have no way of measuring exhaust pressure, but I do have an EGT, and it seldom even exceeds 1kF (pre-turbo), so I doubt that's my problem.

Re: the 1.9 HG: I read somewhere that those gaskets have extra, small, water passages between the cylinders that are drilled out on the 1.9 block and head. "They" said that these can be drilled out on the 1.6 block and head as well to give additional coolant flow -- anybody know anything about that?

It's a simple matter of Quantum mechanics...



Tom

[vanbcguy]

Yes, the steam holes can be drilled on the 1.6 block, just use the holes in the head gasket as a template.

The Cosworth studs have led to head gasket issues for quite a few folks in the TDI world.

[moTthediesel]

The Cosworth studs have led to head gasket issues for quite a few folks in the TDI world.

I did some research on this and the proper TDI studs do seem to be a worthwhile upgrade, so I've got a set on the way -- thanks!