before you pull it down you might want to put a leak down tester on her and see if you can pinpoint where the leak might be.

It could be a number of things though. Anything from gasket surfaces that wern't clean enough, impropper torque, bad bolts (did you used new ones?). Maybe your used heads are cracked/dammaged. Perhaps the heads were milled, and your intake is lifting the heads when torqued down, or maybe the intake gaskets didn't seal.

Somtimes its hard to tell by the headgaskets where the leak was. Leak down testers are very handy (and cheap).

Hope you find your problem, keep us posted!

 

Oh yeah.. couple more things... some GT40s use 1/2 bolt holes and lack of a stepped bolt, or reducer bushings can cause the head to slide around. Also, did you check/replace the head alignment dowels?


Lastly, the sealant goes on the lower head bolts only. I like permatex teflon sealant but some use RTV. I've never heard of using Anti-Sieze. I would think that's a very bad idea and may cause bolts to come loose. A very light coating of engine oil is all that is required. I use a tiny bit of assembly lube under the face of bolt head/stud nut to aid in torquing.

 

First, I would check the intake and make sure it is not leaking coolant into the engine.

Did you buy the heads from someone you know? Are they 100% known good?

 

my did that with the temp, i put a steel 3 core radiator from a part store for anout 130 bucks and sloved all my problems. my temp would go up and back down and i had small bubles in the antifreeze but my oil was fine, just a thought

 

When you're done fixing this, make sure your cooling system is completely burped before you go driving it around, sounds like you had air in your system for one.

 

Used the washers or stepped bolt? Still bet could be those gaskets are on wrong.
Let us know what you find. Good-luck.

 

Well, in 4 hours I had the heads back off the car. I can find NO indication of what went wrong. The gaskets appeared intact and they were installed correctly. The heads appear flat. I see no visible cracks. The heads are used, not "known good" because the guy I bought them from, bought them used and hadn't yet used them. It's possible they've been milled but I highly doubt it, although they were machine-shop clean.

I used new ARP head bolts but not stepped-down style, didn't know I was supposed to? You sure?

The alignment dowels were in place in the block when I installed the heads. The head gaskets were installed properly but I didn't use sealer on them...should I have?

The upper intake gasket was wet around #3 port. Also the #3 intake valve was physically wet but I don't know if that's because I loosened the top head bolts first or what.

One thing I forgot to look at last night was the gasket around the EGR passages...there's this goofy little insert that has to be used (NOT the block-off), and even though I used tack & seal on the head side of the lower intake gaskets, I wonder if that's where the problem was.

Like I said...I can see NOTHING wrong, so part of me says get new gaskets and start over again but the rest of me says no f-ing way. I'm running out of *******ed time to waste on this though, that's for sure.

 

Not to say that your heads are the cause of your problem, but, this is the number one reason why I refuse to buy used heads from anyone, especially someone who I do not personally and mechanically know. Good luck man, hope you find the problem soon.

 

why blame the heads??? intake could have been leaking coolant too

don't use anything but a thread sealer (lowers), oil, or arp lube on head bolts/threads

even though you filled the block before the rest of the cooling system, that doesn't rule out the possibility of having air in the system. Next time let it idle until the stat opens up, then top her off...check for leaks at that time as well.

The temp gauge will act exactly as you described when there are large pockets of air trapped in the top end of the motor...especially with an electric temp gauge.

Did you check the compression?

How was the intake isntalled? torqued? Hand tight? When you drop the intake onto the heads/block, get 4 3" studs and place them in each heads "corner" bolt hole. This way you can drop the intake right on, and have the gasket stay exactly in its place. Also put a thin coat of sealant around each water passage on the head-intake surface. install the remainder of your intake bolts hand tight and replace the studs with their respective bolts

Even if those gt40's are for 1/2" bolts, many many people have run them w/o stepped bolts or washers.

 

I did use some home made studs to locate the lower intake when I dropped it on. I torqued it down to about 25 lbs using my highly calibrated white knuckle method...but in retrospect I was surprised how many times I had to go through the torque-down sequence on the lower until they'd stay torqued. Like, at least 4 times. I thought that was odd...does that indicate anything?

 

Yeh, you need the ARP stepped bolts if you are using 302 blk & GT-40 heads. The
bolt holes in the heads are 1/2" & the threaded holes of the blk are 7/16".
(I think). Used thread-sealer, pipe dope on your lower head bolts? NOT rtv.

 

how long did you let it sit before you filled it with coolant? i did an intake swap a couple years ago on my 88 and i could not get that mofoer to seal, i had it on and off like 4 times. i took it to a machine shop and got it checked, finally the guy at the shop where i was buying my gaskets told me to do the trick you are doing with the studs and rtv the coolant passages which i was already doing but he also said that after i put it on and tourqued it down to let it sit over night to let the rtv dry. i did that and no more coolant in the oil. maybe it will work for you too.

 

I did use some home made studs to locate the lower intake when I dropped it on. I torqued it down to about 25 lbs using my highly calibrated white knuckle method...but in retrospect I was surprised how many times I had to go through the torque-down sequence on the lower until they'd stay torqued. Like, at least 4 times. I thought that was odd...does that indicate anything?

Using a couple studs to locate the intake is a good idea to insure it goes down flat. I do this myself. It is not uncommon to have to repeat the intake torque sequence multiple times. In fact, I would be a skeptical if it only took 4 passes as I find it usually takes 7 or 8. I go by feel and do not stop until every single bolt feels exactly the same. It could very well be that the intake manifold was still not properly seated and after a few heat cycles allowed coolant to enter the engine through the lifter valley. After you get the engine back together and everything checks out it may not be a bad idea to pull the upper off and go through the lower sequence again for peace of mind. I would not be surprised if you found a bolt or two loose.

As far as torquing the head bolts; if you are using ARP bolts follow ARP's torque recommendations, period. These fastners require a different torque specification for proper bolt stretch vs. the factory head bolts which is what Haynes, Chiltons and other service manuals base their torque values on. All five of the lower head bolts go into the water jackets while the 5 upper bolts are dry holes. I use Permatex Ultra Copper on the lower bolts as not only is it a high temperature sealer, Ultra Copper also has anti-sieze in it which will make for easier teardown should there be a need in the future. Always run a tap or thread cleaner through the lower holes before reassembly. If you are using engine oil as a thread lubricant on the upper bolts be careful that you use the recommended viscosity as the difference in friction between higher/lower viscosity oils will give false torque. I use 5w30.

Lastly, never install used cylinder heads without having a reputable machine shop bless them first. And, even if they do check out a-okay I would still have a couple thousanths taken off for a fresh sealing surface.

 

25ft/lbs can be a little too much especially if the heads are milled you could well be lifting the heads slightly off the block check the geometery of the intake to head gaps when you get it back together. Keep the torque around 15-18 ft/lbs.

I have a feeling anti-size on teh upper bolts may be an ussue too... clean all that crud off and out of the holes.

Lastly esure the holes in the heads and see if they are 1/2" or 7/16. If you done have stepped bolts or the bushings you really should get em. I ran my gt40 heads without bushings not realizing they were 1/2 for a couple months but I did eventually blow a headgasket from the head shifting. Granted that was under boost though. Its really just a case of doing it right the 1st time.

 

If the heads bolt holes are 1/2" and your using 7/16" thats your problem.

You can do one of two things. You can either use the Edelbrock Bushings for the heads or buy the step down bolts.

In my opinion, take the heads to a machine shop and get them checked for cracks, otherwise you might be going through the same thing again.

 

While you have them off, take them over to Day Automotive in Independence and have the heads and intake checked for cracks that you can't see. It's cheap insurance and will tell you if they are right or not. They'll also be able to help you out if you haven't found the leak.

 

One thing you can do is put a bead of RTV around the four water ports on the intake and heads, on each side.

 

25 ft lbs on the lower intake is too much. I know that the haynes manual says that, but I personally only go to 15 ft lbs and I'm turbocharged.

There was a guy on here a couple years ago with a dart block and coolant problems.....turned out he was overtorquing the lower intake(25 ft lbs) and it was lifting the upper part of the heads.

Did you torque your upper row of head bolts more than the lower? (you are supposed to)

 

No, I torqued them all the same, didn't know they had different specs.

 

Most people on here torque the upper row of head bolts 5 or 10 ft lbs more than the lowers. This is to offset the intake bolts that will be pulling up on the head when you torque the intake down

 

A coolant pressure tester is a great tool to have to. You can rent them at Autozone (free after return).

You take the radiator cap off and screw the pressure tester on like a regular radiator cap. Then pump it up to the rating that is on your radiator cap ( I think 16 lbs is the rating on a mustang)

Watch the pressure guage to see if it leaks off. If it does, you have a leak and sometimes can hear where it is coming from.

 

Once you do like 94cobra2615 said you can then pull your plugs and then turn over the engine and see if yu get any antifreeze coming out one of the holes, this will help tell you if it is the head gasket or not. I did this on my winter beater and let it sit for about an hour and low and behold number seven had about a cup come out. I'm still having a hard time believing that an intake will lift a head, come on the heads are on with 7/16 bolts and 100 foot pounds torque, I would think you would strip the intake bolt or even break it before it lifted the head. Oh and check the spring pockets on the head, I've seen the spring ware into water jacket which caused coolant to go into the engine (that guy wasn't none to happy).
Len

 

25 ft lbs on the lower intake is too much. I know that the haynes manual says that, but I personally only go to 15 ft lbs and I'm turbocharged.

There was a guy on here a couple years ago with a dart block and coolant problems.....turned out he was overtorquing the lower intake(25 ft lbs) and it was lifting the upper part of the heads.

Did you torque your upper row of head bolts more than the lower? (you are supposed to)

Ding, Ding, Ding. This would be my guess too. 25 ft lbs is much too high. I know you're using iron heads but since I've been dealing with aluminum heads you only snug those intake bolts down. You may have lifted the heads off the block.

Also, you do need the stepped bolts or at least those APR hardened washers
when bolting on GT-40 heads on a 5.0.

 

Also, you do need the stepped bolts or at least those APR hardened washers
when bolting on GT-40 heads on a 5.0.

I run the Edelbrock spacer bushings to neck the hole down to 7/16". If you get the spacer bushings you are gonna crap when you price them. They are about $50.00

 

$45 at summit...on top of the $38 I already spent on bolts...but the stepped bolts are something like $95. Christ.

I'm looking at close to a $200 bill just to put this thing back together again, never mind any machine shop charges for checking things over, assuming my $65 worth of head gaskets are junk now that they've been torqued down and leaked upon.