Torque Intake With Heads?

[TurboGN]

Christmas day. I was killling a mustang at about half throttle and ka-blewee! Sounded like a cannon going off. Fortunately, it was out the bottom outside on #4 and was only a couple of blocks from home. Some recommend torquing the intake while torquing the heads. Does this really help? If so, whats the sequence and torque stepup amounts, i.e., procedure? Did the factory do this? I hope not to repeat this scenario. The mustang guy drove by and looked like he didn't hear or see anything. I think he knew I could still take him, even with a blown HG! Thanks, Joel:

 

[TurboGN]

Anybody?

 

[blackbuick87]

Well I dont know about the factory, but I just finished torquing my head bolts without the manifold on. When I retorque the heads the manifold will be on. I realize they are not the same thing, but it sounds like your heads were never retourqued.

How do you know that is what caused the gasket to go? Was the engine just built? What type of head bolts?

 

[TurboGN]

Originally posted by blackbuick87
Well I dont know about the factory, but I just finished torquing my head bolts without the manifold on. When I retorque the heads the manifold will be on. I realize they are not the same thing, but it sounds like your heads were never retourqued.

How do you know that is what caused the gasket to go? Was the engine just built? What type of head bolts?

Blackbuick87, it could be several factors that caused it to blow. Mainly, no scan numbers except from Scanmaster. At half throttle I may not have adequate injector duty cycle. Scanmaster gave no timing retard or minimum O2s due to the lack of throttle position. The heads were torqued to 85#, heat cycled, and retorqued. The engine is original, the fasteners are ARP, and gaskets are GM Victor #25528486. The block has never overheated and the heads are from Champion. I'll check deck/head flatness when I get the new gaskets in (leaving heads/intake in tac until then). I'm starting to envision larger injectors and Direct Scan. Thanks for your interest and I wish you better luck. Joel

 

[JDEstill]

What I believe I've heard recommended before, and what I did is:
- lay the heads down on the block
- get the head bolts started, maybe get them finger tight (if that much)
- install an old intake manifold gasket and the intake
- get the intake bolts started
- tighten up the head bolts a little to take out the slack
- torque the intake bolts
- torque the head bolts down
- remove intake and gasket
- retorque the head bolts

The aim is to get everything all lined up and perfect between the heads and intake and get it all bolted down in that manner. When you put the intake on for good it will bolt down in the perfect spot and get the best sealing and alignment.

On mine, when I removed the intake, my head bolts were considerably looser than what I had torqued them down to with the intake on. My heads are an unknown quantity, no idea if they have ever been decked or anything. Wonder if that was a sign that I've got a bit of intake to head misalignment? I did have a water leak between the intake and head once, but seem to have that good and sealed up now. AFAIK anyway.

John

 

[TurboGN]

Thanks, that makes good sense to me.

 

[ijames]

What John posted is what FelPro recommends on their website, but hey, what do they know?

Also, torque in steps and sequence and then completely loosen the head bolts five times before doing the final torquing, to burnish in the threads and make sure that the friction has reached a low and stable value. Yes it's boring but it's good exercise. If you are doing stock tty bolts take them to about 5 ft-lbs less than the max value before the angle step - you don't want to stretch them, just break in the threads. ARP recommends this on their website, and so do bolt textbooks.

 

[TurboGN]

Thanks Carl. Five times? I'll do it! I greatly appreciate your input. Hopefully, this will be the last time on this car. Joel

 

[ijames]

I've done this a couple of times and there was a noticeable difference between the first and second torquings but I really couldn't tell any difference between the 3rd, 4th, and 5th. I guess ARP just wants to make really, really sure.