With or Without some Lube?

[HotRodHudson]

Ok. Keeping this moderately clean......... I'm giving my hemi trucks factory cast iron exhaust manifold an old fashioned DIY milling to straighten the mating surfaces with the aluminum head. (Broken exhaust bolts was the reason for this).

To do so I scored a large piece of scrap granite to use as my flat surface, then used some contact cement to glue the sandpaper to the granite then I can give the manifold a rubbing across the surface. What I'm wondering now is should I sand dry or add some lube & what kind? I'm hoping to use something I already have handy.

 

[zmotorsports]

Ok. Keeping this moderately clean......... I'm giving my hemi trucks factory cast iron exhaust manifold an old fashioned DIY milling to straighten the mating surfaces with the aluminum head. (Broken exhaust bolts was the reason for this).

To do so I scored a large piece of scrap granite to use as my flat surface, then used some contact cement to glue the sandpaper to the granite then I can give the manifold a rubbing across the surface. What I'm wondering now is should I sand dry or add some lube & what kind? I'm hoping to use something I already have handy.

So basically you are doing more of a lapping job than sanding. When I do motorcycle cylinder heads or am lapping components for fitment, I tape my sandpaper down to the granite plate and use some WD40 as a lubricant. Prior to sanding I will spray a light coating of "blueing" on then work in a figure 8 until the blueing is gone. Works great and the WD40 helps to keep the sandpaper from clogging up prematurely and it lasts a bit longer.

Mike.

 

[Stuart in MN]

I once flattened the surfaces on the exhaust manifolds for a 352ci V8 in a 1965 Ford F-100 by simply using my hand held belt sander on them. It only took a few minutes and worked great. If I remember correctly the belt was 150 grit.

I suspect that unless your manifolds are really warped, it will go quickly and a lubricant won't be necessary.

 

[zmotorsports]

In agreement with Stuart above, for exhaust manifolds when I suspect they are warped, I take the table off of my combination disk/belt sander and lie it down horizontally and run the manifold along that until true. I have 120 grit belt on my sander, works great.

For lapping, I use the procedure I mentioned above.

Mike,

 

[HotRodHudson]

I worked on this more tonight & im not seeing much results now. The two center ports are clean but the ends are only half way there. I was using Harbor Freight Emory cloth (China) but I think I was having better luck with the 3M paper backed sandpaper I first used.

 

[HotRodHudson]

Here's the other end:

 

[gungatim]

how much warp or twist is there across the entire length? seems to me after a few heat cycles, it's time to use a gasket...

 

[HotRodHudson]

I didn't see a twist (spiral), but more of a bow at the ends. From one end to the other I had 1/16 of an inch on an accurate (machine shop) straight edge.

Are you thinking that even after lapping, a few heat cycles later & I'll likely see warp, so just gasket it & be done?

 

[406Rich]

I use high temp RTV with Sanderson hedders ( recommended by them and no gaskets) , tried it on chevy ram horn manifolds it worked there as well after doing the same with sandpaper taped to glass...

 

[ilovevocs]

I'm a firm believer in using quality sand paper. It's one of the products that I don't believe I see value in a cheaper product.

When lapping I use 3m wet sand, my surface plate and use soap and water as lubricant. I use a rag to add water and keep the sandpaper from loading up. Once it loads up your not doing yourself any favors.

Never lapped a part that big. Mostly power sports heads and cylinders.

Good luck.


Sent from my iPhone using Tapatalk

 

[rlitman]

How much bow? A little in the right places can be ok, so long as it ends up flat when bolted in.

 

[gungatim]

I didn't see a twist (spiral), but more of a bow at the ends. From one end to the other I had 1/16 of an inch on an accurate (machine shop) straight edge.

Are you thinking that even after lapping, a few heat cycles later & I'll likely see warp, so just gasket it & be done?

if it's not warped and just bowed a bit, then torqueing it center out would straighten it. I say gaskets because a lot of manifolds installed gasket-less at the factory are fine until they get miles on them, warp a bit, and get some corrosion and pitting from little leaks. that's what I see in your pics. it would take a lot of work to clean them up to new specs and not use a gasket, so for the effort, I would just put gaskets on and be done...and use good quality bolts/studs so they don't pop...not sure if hemi's have that problem like the 5.3 chevy's did at one time...

 

[rsanter]

Use the black ADHEASIVE silicone and stick it on there.
Been using a smear of that on exhaust manifolds for years with no gaskets and that stuff is great

If you use a gasket use the soft copper ones. None of the composit to paper gaskets I have ever used have lasted more than a short time.
I still use a smear black ADHEASIVE silicone on the copper, just a thin smear

Bob

 

[bgarrett]

I use a table mounted belt sander

 

[HotRodHudson]

For as much as this was bowed from one end to another (1/16 of an inch), I have definitely learned the hard way this go around. The cheap sandpaper is junk, went back to 3M & it cuts much better, not like cutting aluminum but better. I wasted way too much time lapping this cast iron piece by hand. I need to figure out a good power tool for future items or just belly up & pay the machinist.

I'm almost done lapping it & will add a couple photos a little later after I run kids around!

 

[HotRodHudson]

Thank you all very much for your feedback, it has helped a great deal! I've decided I'm done lapping the exhaust manifold. Switching to quality sandpaper helped so much, my sore back is very greatful I'm done. I definitely will put some anti seize on all the bolts which I am a huge believer of doing when & where I can. I picked up some of the liquid gasket material & while I do have a felpro gasket, I think I will use the two together due to the irregularities still present on both surfaces.

I wasn't sure what bolts to use since the factory 10.9 grade ones failed, but I did buy the Dorman replacement kit of 10.9 grade bolts along with a couple stainless steel bolts. With as much corrosion as the old bolts had it makes me think that played a role in their failure, but it's just a guess. Hopefully the y-head pipe isn't putting torque on the manifold but I will know in a little bit when I go to reassemble.

A couple other questions: 1) the aluminum head surface: cleaning suggestions? I've used a gasket scraper & razor very gently but still have built up corrosion I'd like to get off. 2) coating to exhaust manifold: has anyone heard of Slip Plate? I was thinking of some high temp paint but without a blasting cabinet it's probably useless to paint the rusty outside of it.

Since I am about to start in on restoration of the yellow coupe in my avitar, I'd love to see photos & details on bgarrett's table mounted belt sander!

Again, many thanks!
Brian

 

[HotRodHudson]

Here's a photo of the aluminum head exhaust surface. (The scratches are my doing but look worse than they are, bc I can't feel them with my fingernail)
This is the worst of all 4.

 

[LXCam]

Oh **** all this time I thought we were talking ole school mopar. Then when you mentioned the metric rating and obviously the pics were a dead give away realized you have a 5.7. Those logs are bad to begins with. But only use the stock mopar gaskets and use a high temp thread locker on the bolts or stage 8 bolts. Everything else will come loose on you. Do not stack the gaskets, that will fail.

 

[APEowner]

In applications that don't have gaskets from the factory you really shouldn't put gaskets in when you re-install them. If you do use a gasket use a copper one. The reason is that the manifold relies on intimate contact with the head for cooling. If you use anything other than a copper gasket your repair won't last long.

 

[575cat]

Dont get too carried away they will break again .

 

[LXCam]

I'm not sure how dedicated you are to staying with those cast logs but I would highly suggest you change to the 6.1 headers. But if you have already purchased mids or are running cats, you'll need to change those out as well. If you do decide to go that route get the stock 6.1 header bolts, those never have an issue.

 

[HotRodHudson]

Top gasket is two pieces of metal. Bottom is the FelPro.

 

[HotRodHudson]

Hold on.... Are you saying I can use the 6.1 factory manifolds? I haven't done anything with headers but am looking at options. How do those 6.1's compair?

 

[LXCam]

Yes. The 6.1 is a D port but does not create a ledge on the 5.7 port. And you can still use the stock 6.1 gaskets. For what it's worth trust me on the gasket selection. I've built more modern hemis then I can remember at this point. Sounds like you might be another mopar nut and if you happen to get mopar action, I built the challenger on the cover of last july's issue.

They're worth a solid 15/20 across the board, the factory 5.7 stuff is that bad.

 

[HotRodHudson]

This is what I really want a nice hemi in!

37 Hudson 2 door business coupe - 1 of 3 known left in existance per the 37 Hudson guru Robbie Williams with the Hudson club.

We will definitely need to talk!

 

[LXCam]

Now that's going to be very cool. I'll pm you.

 

[blindley]

This is what I really want a nice hemi in!

37 Hudson 2 door business coupe - 1 of 3 known left in existance per the 37 Hudson guru Robbie Williams with the Hudson club.

We will definitely need to talk!

Guys, please don't talk too long. We want to see pictures of a hemi going in this beauty!