While LSG and I have a different opinion on that, there are some good ideas in that thread. One way is to mill the head to intake surface on the heads to account for the machine work done to the head and/or block surfaces.

I’ve done the intake mod many times and have never had a problem with it, but I also keep parts a while.

Personally, I’d ditch that intake anyway and get a RPM, Stealth or the like. Maybe talk to a machine shop and see what they would recommend.

 

Mahalo for all the replies! Here's the latest....

Just to be clear, the intake doesn't leak until the bolts loosen up.

After my car cooled down, went back out to the garage and tried re-torquing all the intake manifold bolts. I turned every bolt about 1/4 of a rotation before the torque wrench clicked (set at 20 ft-lbs per Edelbrock instructions). So, they indeed had started to come loose. Started the car and checked for leaks using carb cleaner spray, and yes there are still leaks at the intake manifold to head surface, so another intake manifold gasket replacement is now on the to-do list.

First question is: what gaskets should I use? @Kelly_H @macstang and @Dan Babb recommended thicker Fel-Pro steel core gaskets, but a search of the Fel Pro website only turned up these two for a '68 289.

https://www.oreillyauto.com/detail/c/fel-pro/engine-parts---mounts/gaskets/intake-manifold-gasket/edcfe482705b/fel-pro-intake-manifold-gasket/fel0/ms901031 (Felpro site says "Except High Performance"

https://www.oreillyauto.com/detail/c/fel-pro/fel-pro-intake-manifold-gasket/fel0/ms901161/v/a/15193/automotive-car-1968-ford-mustang?q=90116&pos=1 (FelPro site says "High Performance")

Do I need to search for gaskets for a later year 302? Or, is there a different brand that would be better than the Fel Pros? (And yes, I do use silicone instead of the cork end gaskets)

Personally, I’d ditch that intake anyway and get a RPM, Stealth or the like. Maybe talk to a machine shop and see what they would recommend.

I understand that the Performer 289 is not the best intake, when I purchased it 24 years ago it seemed like the best match for the very mild cam and my ported cast iron heads. Not sure I would benefit from a Performer RPM or similar manifold, and I'm not confident it would fit since the machinist felt that it was necessary to trim the intake manifold.

If you ran an actual THREADING TAP and not a thread chasing tap down the holes in the cylinder heads you could have damaged the threads (cut away material) to where the fasteners will not stay tight. Also, cheap fasteners often have imperfect threads. If the fasteners ARE coming loose you could drill the holes and install TimeSerts or use a strong threadlocker on studs.

As for checking there are a couple methods... a protractor using the China Wall as as horizontal plane against the cylinder head sealing surface should yield a 45* angle on either bank. Next would be a check of the distance between opposing sides of the intake, at the bottom of the ports versus the distance between cylinder heads at the same point, accounting for the compressed thickness of the intake gaskets.

When reinstalling the intake, use four 5/16 x 5+" bolts with the heads cut off and ends rounded as alignment studs, one at each corner bolt position, to keep the gaskets and intake aligned.

I've used a tap before, and it took VERY little twisting force by hand using a tee handle to run it down the threads. Only resistance was felt when I got deep enough in the holes to encounter whatever oily residue built up below the bottom of the manifold bolts. Also, no metallic shavings were seen.

What sort of tool would be used to measure the distances across the intake? I don't think my tape measure would be accurate enough.

My SS ARP intake bolts kept loosing up. I called Loctite and they recommended using 243. They said to make sure it is fully dry before running the engine. I also use Nord-Lock serrated washers. It worked.

Good to know that Loctite has helped someone else. Somewhere on the internet, I read that you should never use Loctite on intake manifold bolts, so I have been hesitant to do this.

Why did you add the NordLock washers? Overkill? Or did the Loctite not work on its own? (BTW, the Nord Lock washers are pretty interesting. I've never heard of them before).

Harry Z, I prefer to mill the face of the heads, rather than the intake, because if the heads are heavily milled, the heads then are ALREADY not stock sized. Cutting the intake faces lets you run a NORMAL intake. If one mills the intake sides, then you have an undersized intake that ONLY fits your bastard combination, or requires special order thicker intake gaskets. And on the Fords, its SUPER EASY with the 90* intake faces. LSG

Makes sense. Now I'm worried that if I decide to try another intake, it might not fit! Unfortunately, I have no idea how much the head surface got milled. I do remember asking the machinist about this at the time to see if there was a specific amount of material removed from the head where he decided it he needed to trim the intake, and it sounded like he just winged it.

And if I end up having to pull the heads to trim them so another manifold will fit, I might as well buy new aluminum heads, and as long as the heads are off I'll upgrade to a roller cam etc., etc.

Again, mahalo for all the replies.

Harry Z

 

If you ran an actual THREADING TAP and not a thread chasing tap down the holes in the cylinder heads you could have damaged the threads (cut away material) to where the fasteners will not stay tight. Also, cheap fasteners often have imperfect threads. If the fasteners ARE coming loose you could drill the holes and install TimeSerts or use a strong threadlocker on studs.

As for checking there are a couple methods... a protractor using the China Wall as as horizontal plane against the cylinder head sealing surface should yield a 45* angle on either bank. Next would be a check of the distance between opposing sides of the intake, at the bottom of the ports versus the distance between cylinder heads at the same point, accounting for the compressed thickness of the intake gaskets.

When reinstalling the intake, use four 5/16 x 5+" bolts with the heads cut off and ends rounded as alignment studs, one at each corner bolt position, to keep the gaskets and intake aligned.

 

I have one set of angle milled heads and the intake did not have to be touched. Well, I did touch the intake but that was to port match it to the heads. The heads were angle milled because I needed more taken off than you can do with a flat mill.

I run a thicker intake gasket. That might fix your issue as well if the intake is leaking. It is true technically that you should never need to reface the intake. You may however need a bottom cut if the head and block work put the intake down onto the China rails. Even then, try the thicker gaskets first.

 

My SS ARP intake bolts kept loosing up. I called Loctite and they recommended using 243. They said to make sure it is fully dry before running the engine. I also use Nord-Lock serrated washers. It worked.

 

On top of the tips above, use the felpro steel core gaskets. Pretty much the same price and a much better gasket than those crappy print-o-seal black ones.


Sent from my iPhone using Tapatalk

 

I would keep the ARP bolts but try using a basic threadlocker with them first. And as Dan noted, a good set of intake gaskets is important - the printoseals really only work on perfect matches because they are thin and prone to blowout. The Felpro steel core ones have never given me issue.

Another thing I have seen myself is a warped intake, end-to-end (like a banana). That was a pretty interesting one. The ports still seemed true (straight edge laid across them was flat), but it was low in the center and high on the ends. Couldn't get the intake to seal right on the ends, and it eventually cracked pretty catastrophically.

If the basic application of threadlocker and a better gasket doesn't keep that intake down, I would look into putting a different intake on it entirely in case yours is done.

 

Harry Z, I prefer to mill the face of the heads, rather than the intake, because if the heads are heavily milled, the heads then are ALREADY not stock sized. Cutting the intake faces lets you run a NORMAL intake. If one mills the intake sides, then you have an undersized intake that ONLY fits your bastard combination, or requires special order thicker intake gaskets. And on the Fords, its SUPER EASY with the 90* intake faces. LSG

 

What sort of tool would be used to measure the distances across the intake? I don't think my tape measure would be accurate

Digital Caliper.

FWIW, I use Victor-Reinz (Mahle) gaskets with corks and no RTV.

What I'd recommend, this time, after you torque all the intake bolts, is to paint a reference line on the head of each bolt from the center of the bolt forward on each bolt so you can see if the bolts are actually loosening or if the gasket is simply compressing/shrinking. If they are loosening, perhaps replacing the bolts with studs, using hi-strength LocTite between the head and stud.

 

Aloha @Woodchuck! Great idea about painting the witness marks on the bolt. I've done that before, should have remembered it! A couple more questions:

1) Do intake manifold gaskets normally compress? Should you have to re-torque intake manifold bolts after initial run of the engine after installing new intake manifold gaskets?

2) It looks like the only place here on Oahu that carries Victor Reinz gaskets is Auto Zone. They list two part number for a '68 289:

1. Part number 11-10376-01 for "high performance"
   
   
2. Part number 11-10140-01 which is "except high performance"

There is no other description provided to guide me on which one would be best for my car. Which one would you recommend for my very mild 289?

Mahalo

 

Harry, If I were working on your 289, I would use the 11-10140-01. The other number is a 351W intake gasket, which has an extra bolt hole in the waterport that you don't need. LSG

 

Mahalo @LSG . Any info you can share on whether or not intake manifold gaskets compress?

 

Wood, why is the 10376 a better gasket ? other than it has the material for a bolt hole that our man doesn't have ? Full disclosure- I put my engine together with Fel Pro Permatorques, so I have never handled to gaskets we are looking at. Should he cut out the portion of the gasket that his heads bolt have a bolt for ? LSG

I've had good luck with the FelPro 1250 S-3. What gasket did you have that failed you ?

 

The 10376 is a composite gasket, the 10140 is plain fiber. I've always used Victor-Reinz gaskets, unless they don't make one. Why mess with something that works?

 

Harry, I'm looking in the smaller Fel Pro performance catalog. The 1250 S3 is a nice gasket with a steel reinforcement sandwhiched inbetween two layers of gasket material. This helps it retain its shape. I put Fel Pro gaskets on almost EVERYTHING. Not because they're better ( although they are good gaskets ) but because the warehouse my employer uses stocks almost every gasket I've ever needed. See if you can get that, or if you can get the V-R faster. They're both good stuff. LSG

 

Aloha @Woodchuck and @LSG . We pulled the manifold and took a look at it. We could see where the machinist re-set the milling machine when working on the intake to head surface. It's obvious to the naked eye, and you CAN feel it with your fingertip. I cannot catch a fingernail on it though. I had another, new, in-the-box Performer 289 so we installed that one with the Felpro 1250 gaskets that were available at my local Oreilly. So far, no leaks! Mahalo for your advice and guidance!



Harry Z