[53Chev]

I have a 350 with vortec heads and after recently replacing the valve covers, I checked the head bolts and found that they were at about 55-60 ft lbs. Is this normal? Will they need to be retorqued? If nothing is done will they still loosen? Will this have any effect on engine performance?

Anyone got any suggestions?

 

[BlueSS454]

Cylinder heads get torqued once, that's it. Intake bolts should be checked from time to time though.

 

[53Chev]

Well as I mentioned in my first post mine are not torqued at the reg specs for vortec heads. They are about 15-20 ft lbs under what they should be.

The machine shop said that some of them loosen up.

What should I do?

 

[charbilly2001]

FWIW its been my experience over the years that properly installed head bolts do NOT loosen up.

That said, if yours are too loose then retorque them using the proper pattern and do it in small steps so that you don't warp the head.

 

[bluechevelless]

Mainly if new bolts are used that sometimes they will strech, Had this happen on my supra, bought new ARP head studs torqued to 75 ft-lbs and a new headgasket. 500 miles later the headgasket blew and the head bolts were loose. I torqued them at 100 and it lasted 1500 miles.
DONT BUY A TOYOTA SUPRA THEY ARE CURSED

 

[onovakind67]

I have a 350 with vortec heads and after recently replacing the valve covers, I checked the head bolts and found that they were at about 55-60 ft lbs. Is this normal? Will they need to be retorqued? If nothing is done will they still loosen? Will this have any effect on engine performance?

Anyone got any suggestions?

The actual clamping of the bolt is just a small part of the torque picture. A change in the CF of the threads or bolt face will change the torque reading considerably.

 

[Rich-L79]

Seasoned bolts should be good to go if they are properly torqued. New bolts should be torqed, loosened and retorqued at least 3-4 times. Once this is done they should be good to go once the engine is running assuming they are all torqued correctly.

During the rebuild, the bolts should all be torqued at least three times to insure none have loosened while the surrounding bolts have been torqued and that none have been missed. Always follow the appropriate torquing sequence even when simply retorquing already tightened bolts. I usually run through each set of head bolts with 4 tighten-loosen cycles and then run through the torque pattern 5 times. This may be overkill, but it provides a decent upper body workout and leaves less to chance. I find it helpful to count the bolts as I torque them so I know I've hit them all.

 

[Bill Pritchard]

I find it helpful to count the bolts as I torque them so I know I've hit them all.

Ditto. Very good advice.

 

[meb]

Rich,

Is your advice specific to the types of bolts we see today -vs- the bolts of yesterday (say pre-80's)? In other words stretch bolts -vs- non-stretch bolts. I've never heard of a torque loosen re-torque cycle.

 

[HemiTCoupe]

A wet bolt (lubed, silicone, Loctite, or...) torqued to number will be tighter then a dry bolt torqued to the same number.

Pat

 

[charbilly2001]

Rich,

Is your advice specific to the types of bolts we see today -vs- the bolts of yesterday (say pre-80's)? In other words stretch bolts -vs- non-stretch bolts. I've never heard of a torque loosen re-torque cycle.

With respect to the average seasoned bolt out of the average small or big block found in the average Chevelle you only need to torque them once. That said, you torque them in three or four steps. IE: if the final torque of the bolt is 80 lbs then torque each bolt in 20 ft/lb steps, going completely through the entire pattern before increasing to the next ft/lb step.

If you are running a 13 to 1 compression ratio and 800 HP I'd be inclined to do what Rich-L79 said.

The only head gasket I have ever blown was on my present 383 after a vicious overheat. Both head gaskets blew several months after the overheat event and I had to have my heads milled before I could reuse them.

 

[Rich-L79]

Rich,

Is your advice specific to the types of bolts we see today -vs- the bolts of yesterday (say pre-80's)? In other words stretch bolts -vs- non-stretch bolts. I've never heard of a torque loosen re-torque cycle.

The torque-loosen-torque cycles stretch the bolts and in effect, "season" them so they will provide more consistant clamping for a given torque. The bolts should be lubed for all torque-loosen cycles.

 

[53Chev]

Although I appreciate all the help thus far....I am still awaiting some answers to my last couple of questions in my first post. Anyone willing to step up to the plate?

thanks!

 

[charbilly2001]

Although I appreciate all the help thus far....I am still awaiting some answers to my last couple of questions in my first post. Anyone willing to step up to the plate?

thanks!

Generally speaking a blown head gasket will have an effect on your engines performance. You may take that as gospel from the fingers of one who knows these things.

With respect to your specific problem I would retorque your headbolts to factory specs. Since I have never worked on a Vortec engine I do not know the torque spec so I'll have to leave that up to you. If your heads are torqued anywhere near the factory spec then I would retorque them in one step following the recommended sequence. If they are ,say, 30 lbs lite then I'd do them in 2 steps of 15 ft/lbs each.

Under no circumstances would I leave them at anything less than factory spec.

There, does that answer your remaining questions?

 

[Hi-po SS 454]

More info on your head bolt question:
http://67-72chevytrucks.com/vboard/showthread.php?t=91816
Seems the question is what head bolt are you using will depend on how that bolt gets torqued..

 

[Junkyard Dawg]

DONT BUY A TOYOTA SUPRA THEY ARE CURSED

Funny you should mention that....those cars are well loved by many....