I will be replacing on my 79 the cast iron heads with a set of aluminum heads from a ZZ4 engine. Are the torque specs for the heads the same as a cast iron head.
Also how thick of a head gasket should I use?

Thanks for all responses.

David

 

You should be safe with your stock gasket/torque specs especially if using bolts. Sometimes aluminum heads will need to be retorqued after the first heat cycle!

KM

 

Thanks for the info 88-406.

I read about different thickness of head gaskets used. What determines which thickness you should use?

Thanks
David

 

I don't think that the aluminum head has any inflence on gasket thickness. The desired thickness would be more a matter of squish distance. You do, however; want a gasket intended for a bi-metal application.

 

make sure you use hardened washers under the bolt heads to prevent them from cutting into the aluminum. use a small amount of engine oil under the bolt heads when torquing up the bolts. :chevy

 

You might want to choose your gasket thickness pretty carefully. The ZZ4 heads have a 58cc chamber which I think is going to raise your compression considerably from the 10:1 you've got now.

When used on the ZZ4, these heads use a .051 thick gasket. You could go thinner, but you're going to be flirting with a 11:1 CR if you do.

 

Thanks for all the responses.
The heads are 58cc chambers.
If I did end up with 11:1 compression with the Aluminum heads will 92 octane pump gas be enough or should I find the .051" thick gasket to keep the 10:1 ratio.

Thanks

David

 

There is a "rule of thumb" that an aluminum headed engine "needs" one addition point of compression due to the thermal effeciency of the aluminum. I would chance it, especially if the thinner head gasket provides a tight squish clearence.

 

Going from a .040 or so head gasket to a .051 is only .011 greater thickness and won't lower your CR from 11.0 to 10.0:1

To drop CR one whole point calls for about 9 ccs or about .040 more gasket thickness.

Jake

 

Hey, CFI, I've always heard and read the same thing too, but did you read the latest dyno testing on just this point?

Theory got all shot to "he**". the aluminum heads made more power all the way across the band and the heads were equal in CR too. I believe the heads used were World Products and were as close to identical as they could get them with the major difference being the casting material, CI Vs aliminum.

Back to the drawing board, huh?

Jake

 

Are the heads used? If they are, you may need to look at them closely to make sure the old gasket didn't leave indentations. I installed Felpro shims that are rubber coated when I installed my Darts.
I chose them because I wanted a tight quench area, & they don't brinnel the heads (cause indenttations)
Once the heads are brinneled, you need to stay with that brand & model of gasket.

Also, I called Felpro about retorquing procedures. They recommended retorquing after the intial install/torque. Once you get them all up to the proper torque, go back to the first one you started with and loosen it to zero torque. After you have it backed off, smoothly bring it back up to full torque. Do this to each of the bolts, one at a time. I did this & have had no problems.




[Modified by 71coupe2, 1:27 AM 3/24/2002]

 

David, MoorTyme sorta led you astray with his post. The gasket thickness has
a minor impact, at best, on compression. You're choosing the gasket for your
quench hgt, and component material composition. You will not only need to cc
your original heads, (which btw, I expect to be larger than 58 cc) but I would
also cc the new heads. Don't care what 'they say' the heads are. (Would
expect them to be closer to 60 cc)

As for the comment on power production with alum. vs. iron; I'll believe the
results AFTER I see the 'contestants' in person. Otherwise, I'd consider the
test another flawed experiment. There have been similar such tests in the past.
When the details eventually came out, you say to yourself, no wonder!

 

The heads are used but with only 800 miles on them. But after reading all the post I have decided to use the Felpro 1010 gasket which was also the gasket used on the previous install. This gasket claims it does not brinell the heads but better safe than sorry.

I have heard that you should retorque the heads after 1st engine warm up cycle but i did not know I should also loosen and retorque them after going through the initial 3 stage (30,50,70ft-lb.)torque process.
Is this really wise?

I also am going to install the XE268H cam while I have the engine apart.

Hopefully all the part changes will produce a strong street performer. Watch out Mustangs!

 

Many times, advice and recommendations given are, infact, overkill.

What happens, I think, is that there is a combination of trying to sell more parts and the absolute BEST way to do something. We racers often find and use what I call "work-arounds". Some are good and never cause a problem, others are prone to cause disaster.

Take one example of using a 5 pound hammer to knock on the harmonic damper; definitely frought with the possibly of catastrophic failure. Other things, like retorquing may be the absolute best thing to do, but most often NOT retorquing (if using a non retorquing required head gasket) won't cause a problem at all.

In the case of retorquing, I follow the gasket maker's recommendation. Most of the Fel Pros that we use, 1010, 1014, etc, don't require retorquing, but if you choose to retorque, the correct (BEST) was is to loosen the bolts/nuts and retorque them.

Of course many folks don't go to that trouble and have no torque related problem. The trick is to recognize those things that you surely MUST do and those that are simply over-kill and really unnecessary.

If you're gonna run an artifical power adder like nitrous or a blower, or run a lot of RPMS and make a lot of cylinder pressure, sure I'd do it. But for a street engine with pump gas compatible compression, I NEVER do.
In fact, all the 8 second 1/4 mile BB engines I've built never had a head gasket retorque and we never had a headgasket failure because of this.

But like all other things, different folks will have different views.

If you follow some of the recommendations you'll find in the mags or catalogs you'll end up doing a lot of really unnecessary stuff. For example, some cam companies recommend that you install new pushrods when you change rocker arms. Well, unless they're too short or too long, I skip that recommendation.

Just my views.

Jake

 

Don't think so, re-read the post. My point was the following:
- with all other things being equal, changing from a 64cc chamber to a 58cc chamber head is going to raise his compression .73 to 10.73:1.
- a change of .012 on his gasket thickness from say .051 to .039 will further increase CR by .34 to 11.07:1
Thats all I'm saying.

Just trying to alert him to the fact that given the gain in CR he's getting with the smaller chamber, he might want to consider gasket selection carefully or end up with a higher CR than he wants. I don't know what thickness he's currently using, but he should look at all the variables.

 

As far as retorquing, Felpro recomends the method I described above (As well as gkull)
Overkill? Maybe. But why not. the engine is on the stand, get another beer & go over the bolts one more time - no big deal.

 

I have decided to use the Felpro 1010 head gasket with the aluminum heads and have bought a set of ARP head bolts and a Comp Cam XE268H cam and lifters set. I am going to install them all this weekend with time permitting with the Holiday.

Thanks for all the opinions on the gasket and Torque recomendations.

I sure hope the combination of parts work out.

By the way the Beer idea may have to come into the process several times.

David

 

I recommend checking the ARP web site and go with their specs for the bolts you are using.