blue66

A few years ago I had my 66 327/300 rebuilt and I'm sure I've put over 500 miles on it since then. It is necessary/recommended to recheck the head bolt torque? I haven't had any issues so far.

Powershift

I would...............for peace of mind.

Larry

Easy Rhino

Why?

Do you believe that you have "retorque head bolts after 500 mile" head gaskets?

Or perhaps your head bolts have undergone creep stretching, or have loosened?

While it's not hard at all to do on a mid-60s engine, there was no requirement or need to do it back in the day.

Powershift

Rhino:

I disagree..........but maybe I am just older. Back in the day, we surely did retorque after a short run time. Later (late 60's maybe early 70's) the head gasket companies were coming out with gaskets that they said you only torqued once. But I never bought the story........again, maybe just too old to learn new stuff.

Today, a production shop should not have to do anything more than once. But for a hour or less of easy work, why not just do it. Maybe you find some other issue to fix as well.

Larry

Greg

I was a heavy line tech for GM and assembled hundreds of engines. We never retorqued and never had a head gasket fail.
Retorquing head bolts was more common in the vintage days of poor gaskets. They've come a long way since the 30's/40's.

Powershift

I'm not THAT old.................

Larry

Greg

Sorry Larry!
I didn't mean to infer you were.

pop23235

If you re-torque, you risk a coolant leak by the threads into the water jacket. Pick your poison.

Powershift

Pop:

A good point. My early cars did not have the threads going into water as I recall. But it has been many years.

But breakaway torque of a fastener is greater than the final torque when the bolt is still moving. So if the final torque is good, the bolt should not move under re-torque. If it does, then you know you have some bolt stretch or other issue.

Based on what everyone is saying, and considering todays improved head gaskets, OP should probably go and find something else on his car to fiddle with. I will concede (i.e. I give up).

Larry

Westlotorn

Fel-Pro advertized the No Retorque Head Gaskets and made a strong name in the market and this technology was one of the building blocks that made them famous.
The part numbers ended with a PT, the PT stands for Perma-Torque IE: 7733PT-1, standard 4" bore GM small block head gasket.
I know several of Fel-Pro's engineer's. They all will tell you point blank it is always better to retorque after the first heat cycle.
If you are running stock engines, low horsepower you can get away with no retorqe every time.
When the power goes up Re Torque is highly recommended by Fel-Pro engineering staff. This is also in print in the Fel-Pro performance catalogs.
An L79 327 is rated at 350 HP. That is 100-140 HP more than a stock passenger car engine. Good reason to re torque if building a L79 or any engine with similar upgrades.
It is well known that MOST people today never re torque and most people have no problem because of this.
I am just sharing what I know to be recommended even today by Fel-Pro and they do have great people in the labs.
Heads will run hotter than the block below it. The heat in the head will make the heads grow a little. When the head grows the gasket gets crushed a little.
This is why a retorque is recommended after a heat cycle. A gasket does not bounce back, once it crushes it stays crushed. A retorque can compensate for any crush that happened on the first heat cycle.
I have seen many blown head gaskets caused by short term overheat, normally the gasket will blow out within one or two weeks of use after the overheat. This conversation makes me wonder, if the owner took time to retorque after the overheat if the gasket would hold rather than blow out? In tear down after an over heat head gasket failure you find loose bolts around the crushed area.
Hope this helps.
Mark

ChattanoogaJSB

Fascinating thread, truly. I’d never considered retorquing at all and now I am.

That said- was there any precedent for a factory assembled L79, L84 etc coming back in for commonplace check of torque or were those engines retorqued in the plant after a test run?

Again- good topic.

Benton

Frankie the Fink

A classic case of, "...if it ain't broke, don't fix it" IMO...

Vettegeezer

"Original", factory assembly used a sheet metal gasket and gasket "shellac" - completely different from composite gaskets used today. Back in the day you rarely heard of gasket leaks, and same goes for needing re-torquing of head bolts. I think this issue (retighteneing of head bolts), is probably more common when aluminum/iron material combination is part of the equation that is, iron block/aluminum heads due to different heat expansion ratios, especially as noted previously, if excessive heat cycling is involved.

Greg

If head bolt retorque was really necessary, GM (and the others) would have made it part of the service schedule for new cars. But none of them do.
Perhaps the time/cost for this service alone was enough to have them all invest in better gasket technology.

blue66

Thanks all for responding. I asked this question because when I picked up the engine the builder said to re-torque after 500 miles. This was like and after thought on his part as we talked about the rebuild. I did not do any re-torque after the first few heat cycles as Westlotorn asked.

Based on the opinions given I'm going with the 'if it ain't broke...' solution. Problems have an easy time finding me without my trying to find them.

Robert61

I can tell you in the late 80s we built about 6000 engines with only fel pro blue gaskets never retorqued never an issue. GM built millions I would guess with no retorqued.

dplotkin

Me too.
Consider that the engineering behind that gasket intended it be torqued one time. Doing so a second time was not a consideration in its design or manufacture, so why not follow instructions. Do you cook one minute oatmeal in 5 minutes because that was how it was done in the 40's? Or do you ruin your breakfast?

Dan

Westlotorn

Fel-Pro offers a two page read in the Fel-Pro Performance catalog on this subject. Page 154 and 155, 2010 Performance catalog specifically.

They offer many tips on head gasket installation and a couple paragraphs on proper torque.
Nice information and easy read. One of the performance concerns was that Performance engines make their max power up to 2,000 RPM higher than a stock engine like the 327/250 HP.
This increases the stress on the head gaskets.

My choice would be if your engine is stock tune, like the 250 or even 300 HP bolt it up and forget it. If you run more horsepower you might consider what the manufacturer tells you to do.
Probaly 95% of engines on the road are stock but most Corvette engines are considered Performance engines.

Robert61

Chevrolet is probably around 130-140 million SBCs now. None of them were retorqued. Many were performance Vettes. Far as I know they don't retorque new vettes which are eons away in performance. Their tech guys, FP, on their own web site say no retorque is required even on performance gaskets. One even said when asked about studs and MLS gaskets with ARP studs that FP didn't say to retorque but to follow the stud manufacturers suggestions. How do you retorque tty bolts?

Westlotorn

Robert, as you know, TTY or Torque to yeild bolts changed the game as we know it. They strech till a certain known amount of torque is applied and hold that amount of torque, they are not reuseable. So you are correct, no TTY retorque will ever be applied the bolts would break.

All I did was offer what Fel Pro Engineers, say and put in print, do you really think the guy on the tech line knows more than they do. If you do, OK I will leave it at that. I should have exculded TTY bolts in the discussion and we should exclude stock engines in the discussion as those are built every day with no re torque. The Tech Phone guys are usually hired out of the aftermarket after working in shops, some have many years of experience and can answer most questions off the top of their heads because they do it everyday. They are expected to know and anwer parts about Spark Plugs, valve Train, Piston Rings, Gaskets, Chassis Parts, Engine Parts, Wheel Hubs, Windshield wipers, Seals, Bearings, Engine Bearings, Timing sets, Pistons, etc. I knew several of the Tech Line guys, they are great guys and most are very knowlegable but you take experience to another level when you work with the guys that design, manufacture, invent the materials and test the final products first on dyno's in the labs and then on real vehicles before releasing the products to the market. They write the Patents, are real engineers by schooling and vocation. They have knowledge few of us will ever be exposed to and you should see the toys they get to play with to develop this stuff. They have a nuclear powered gun that can shoot any material and quickly tell them exactly what the metal make up is in any part after it has been manufactured. This gun is regulated by the Atomic Energy Commission and they visit the plant to check and verify this gun frequently. I say gun, but it is more like a High Tech Temperature sensor.
And I know GM built a lot of engines, one GM plant built thousands of 350's a day in the hey day but Fel-Pro holds over 90% of the gasket market in the USA today. They sell a lot of gaskets and have a fair amount of knowledge, they have the reputaion of being a problem solver for the industry.
Do you think GM makes gaskets, nope. GM buys from Victor Reintz or McCord ( Since 1998 McCord is owned by Fel-Pro/Federal-Mogul/Tenneco) These are the two major OEM gasket suppliers. To supply OEM you need production equipment machines designed to kick out the exact same part 10,000 times per day.
The after market does not build in those quantities and they use different equipment for smaller run gaskets.

Like, you I know of Thousands of engines that rolled out every month and I can't say I ever had even one fail because of lack of re torque, not one. I had one customer that did 1,500 engines per month and several that were in the 50-400 engines per month.
That is a lot of engines and all failures were looked at because someone wanted a warranty. Head gasket failures were always Detonation induced or Over Heat induced and each of those were easy to read on a head gasket, there were no secrets.
I don't get a paycheck anymore from Fel-Pro but I do think they make good products and have good knowledge, if they tell me a re torque is better on a performance engine I will do it but each to their own.

Mark