: Head bolts & time-serts?



botboy
02-15-05, 08:02 PM
I'm curious about this -

On a stock northstar, no time serts, I understand the necessity of new head bolts because of the special coating that serves as a lubricant (for torquing) and later as a thread-lock to keep the heads from pulling away from the block.

Now what I'm curious about is that I've time-serted all 20 head bolt locations in my block, but the factory manual doesn't address time-serts, and the time-sert manual doesn't address what head bolts need to be used..

So...when I put this engine back together, do I need to buy all new head bolts in spite of the time-serted head bolt holes, or can I reuse the old ones?

JimD
02-15-05, 09:18 PM
New bolts included with head gasket package I believe.

haymaker
02-15-05, 09:51 PM
I'm curious about this -

On a stock northstar, no time serts, I understand the necessity of new head bolts because of the special coating that serves as a lubricant (for torquing) and later as a thread-lock to keep the heads from pulling away from the block.

Now what I'm curious about is that I've time-serted all 20 head bolt locations in my block, but the factory manual doesn't address time-serts, and the time-sert manual doesn't address what head bolts need to be used..

So...when I put this engine back together, do I need to buy all new head bolts in spite of the time-serted head bolt holes, or can I reuse the old ones?
I can give you an opinion based on installing the time-serts and head gaskets in one N*. I can also give you an opinion based on a little testing of the old head-bolts for stretch at torque and their resiliency or ability to return to their relaxed, resting length or dimension. I completely cleaned and ran a thread cutting die on three of the old head-bolts. I then applied a liberal coating of the loctite 266 and allowed it to dry for 18 hrs. I checked the bolts relaxed lengths with a micrometer. I then fabricated a bolt-testing fixture from one-inch mild steel bar, which I drilled and tapped for the head-bolts. I did the testing to find the difference in final torque between the different head-bolt torque specs (22 lb/ft-60-60-60 degrees and 30 lb/ft-70-60-60 degrees). Anyway to get to the point, I tested these three head-bolts all the way up to 30 lb/ft and then an additional 240+ degrees, which worked out to 105-110 lb/ft of total torque. I then removed the head-bolts. All three head-bolts in their relaxed state came back to within one thousand of the pre over torque length.

If I were preparing to time-sert and replace the head gaskets on another N* would I use the old head-bolts in the garage? No. If you buy from Gmpartsdirect the head gaskets come in a kit with the new head-bolts. When I order from my local supplier I can order just the head gasket, just the head-bolts or both but for the price of the head-bolts I would still replace them. If I was installing the head gaskets along with the new head-bolts and found one of the new head-bolts was bent or somehow unusable I would clean, loctite and use one of my old head-bolts without any concerns whatsoever.

BTW there is loctite or sealer between the bolt head and washer also. IMHO I do believe you still need the head-bolt loctite (sealer) when installing into the time-serts. When I dissembled my N* to replace the head gaskets two of the head-bolts were loose, one on each cylinder head so the loctite must have failed. This was the first time the engines cylinder heads had been removed so the loose head-bolts canít be blamed on sloppy work. I think the new head-bolts with the new loctite or sealer is the your best chance of keeping the bolts tight and the new head gaskets clamped in place.

BeelzeBob
02-16-05, 12:51 AM
Use new head bolts with the timesert repaired holes just as if the timeserts were not even there. Whether the head bolt holes are timeserted or not...new head bolts need to be used when the engine is reassembled.

zonie77
02-16-05, 01:46 AM
Botboy,

You must use new head bolts.The bolts are "torque to yield" which means they can only be used once.

If you have a problem with installation you can retorque them but once they've been run they can't be reused. They will not hold the torque setting again. They'll work for awhile, then lose tension.