Seriously, just as the title says. Why do the tabs on my intake keep cracking off?

Offenhauser DP.

This is the FOURTH tab that's busted while I'm torquing it down.

Ultra clean, ultra straight, everything perfect. I take my time, I check with a straight edge. New gasket. Lined up right. Everything everything, and then POP. A tab breaks.


I've probably put over $200 into this darn intake getting it repaired!!

I walk on pins and needles and am scared to death to ever torque it down, and here we go again.

Any words of advice? This is insane.

I can't deal with this anymore.

 

Oh man! What a pain. That is odd. Could it be that remflex gasket--as in 'flex'?
Did you torque in stages? Center out? (I know you did.)

I torque those dry, no lube. Lube changes the torque, I was told. Was the manifold new or used when you got it? Used would mean untold temp. cycles.

What a bummer. If you find out the cause, pls post it.

*Just a thought: What was the temp of the intake when you installed it? Was it early morning or night, when the temp was cool/cold? Could the thermal properties of the aluminum be the culprit? I'm reaching here. Also, looking at your photo, I would put a caliper on both tabs (either side of the stud) and check their thickness, to confirm they are the same or not.

 

I don't think it was the gasket. Honestly, I was only up to around 5 - 10 ft/lbs and it was on the very first bolt.

When I get it back, I'm going to see if it was hanging up on something. It's the only thing I can think of.

The intake was used when I got it, so I don't know the history behind it. But I've had it about 8 years now.

The tabs on the exhaust are a hair thicker, which I think it due to having the intake repaired and then sanded down, but it's very minimal. I don't *think* it'd be enough to cause an issue, but who knows?

It was about 70° when I was installing it. Beautiful day, I might add.

 

Crazy that you keep breaking them.

I have a clifford intake and when I install mine, I torque them from the center out. It's a hassle to get a few bolts with the shorty headers as well, but I torque mine down very tight without issues. The intake tabs are quite thick, thicker that the header tabs anyway...

 

Since I have a tendancy to drop/lose my bolts and washers, some of mine have large washers and they mishape themselves a bit as I torque them down since my intake and exhaust aren't even. On the rest of them I use the origninal washers with the curved out side towards the engine and the curved in side against the bolt. The washer adjusts itself and settles against both the exhaust and intake.

Perhaps those thick washers are to solid and "crude" against the intake. Just thinking out loud.

 

Alright, well, I figured out what it was, and it's my own stupid fault (at least this time).

I should always triple check.

I mated the intake against the head to check it and it was nice and flush, but then I installed the alignment pin and did not check it again afterward.

It never even occurred to me that the alignment pin hole doesn't go through all the way!








I shortened it by about 1/4" and now it properly aligns the intake AND allows it to sit flush against the head.

Intake is welded and fixed, and I'm back in the garage and back in business.

Going to go torque it down now. I'm still nervous about it, but at least this time I know what the problem was and was able to address it.

As for the washers, that's a good thought. I do like the idea of being able to put the more "round" side against the intake/exhaust instead of a sharper edge.

 

I'd get everything lined up, snug one or two bolt in the center and check everything with a flashlight to make sure it's all tight against the head. Maybe a very small feeler gauge will help make sure there's no gap?

 

Here's how mines done


second ones a little blurry. The washer isn't that thick and just shapes itself against both the intake and header. If I used thick washers I bet they'd bottom out on the intake and have little clamping force on the header. The washer with the curve out sorta does the same thing.

 

Interesting thought. I originally had thinner washers that bent, but I swapped them out for thicker ones so that they wouldn't.

Either way, after I sorted out what caused the issue, they installed without an issue, and even though I was a nervous wreck (my heart was literally pounding and my imagination kept hearing another tab break) they torqued down without an issue.

 

Good to hear you found the "why" and fixed it.


Question? Did the stock intake also use a pin like that?
I ask because I did not know of this till now so never looked for it.
Dave ----

 

I believe so. This is a 78 head and it had the pin. It's something to hang it from while you're installing. Yours might have just been pulled out at some point.

 

Thanks for the info. I just went out and looked at mine which is yet to be assembled ('88 head and used Offy C). The alignment hole in head & Offy at the front, and rear is supported by a stand alone bolt. I will watch that when I put it together!

I got the intake manifold and some used efi exhaust for $100 partly because one of the tabs was broken off on the intake. He didn't have it. I took the Offy and a stock efi intake lower to my local NAPA auto machine shop and they welded it back up. I don't recall now which tab it was, but don't think it was the first one.