# Ranger exhaust manifolds, gage block sin committed?



## FliesLikeABrick (Apr 19, 2021)

Today I was working on installation of the engine into my '95 Ranger, and had a moment of pause before reinstalling the old exhaust manifolds. I don't have a great "before" picture of the worse manifold, but one is shown below.  The mating faces were rusted to the old gasket badly enough that you could not tell when the gasket stopped and the pitted machined surface began - I couldn't be sure when to stop scraping to remove old gasket, because in some places the texture of the gasket was reflected in the rust pattern of the manifold itself.

I used my insert-based face mill, roughly .010 DOC per pass until the gasket surface was sufficiently flat and clean.  The first manifold was just mounted to the table with 123 blocks, trusting that the original machining on the back of the fastener bosses was a sufficient reference.




I swept with an indicator prior to starting any cuts - the first two ports (further from the camera, above) measured approximately .005" between them.  The 3rd port measured another .020", I believe the manifold may have been warped.  However, this did cause me to question whether the back of the fastener bosses were sufficiently coplanar to use them as a reference for fixturing the next manifold.

Here is the finished first manifold, alongside the second:





For the second manifold, I decided to machine the back of the fastener bosses with the work clamped face-down to the table first.  This would give me a known reference plane that should, on average, be parallel to the unfinished gasket plane:



My longest end mill is my 1" roughing end mill, which I needed in order to reach past the manifold features and clamping.  On this manifold, 3 of the mounting flanges are approximately 0.5" thick, while the rear is approximately 2.5".  I figured as long as I took these down to the same thickness on each side, and knew what the delta was between them - I can mount it face-up on the table later and trust the reference.

Here is where I may have committed a sin of sorts.  I don't have any adjustable parallels or machinist jacks short enough to let me build up the ~1.368 inches I needed to support one side of the manifold above the table.  I ended up using a stack-up of gage blocks to get the exact spacing needed since the far side was on the 3" side of 123 blocks.  I did make sure they were clean, and did not over-tighten them - to minimize the chance of creating raised dimpling in the blocks.  These blocks are a used, old, cheap set from ebay - but I do try to show them respect despite what is shown here.




With this more-careful prep and fixturing, and bearing in mind that the first manifold may have been warped -- I was happy to see only .010" material removal (approximately - I don't know that I started at the highest point) needed to clean this side up. This was done in one pass with the same cheap indexable face mill.

Very happy with the result.  This is a Rockwell 21-100 with no power feed, so exact surface finish was a bit of a crapshoot.  However, it's clean and flat -- and that is all I needed in this case.









Thanks for reading


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## Lo-Fi (Apr 19, 2021)

Lovely having the kit available to do jobs like that, isn't it!


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## RandyWilson (Apr 19, 2021)

Ford exhaust manifolds of that era came pre-warped from the factory.


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## Packard V8 (Apr 19, 2021)

You did good work.

After being subjected to hundreds/thousands of heat cycles above 1000 degrees, most any exhaust manifold will be found to be warped.

In an automotive machine shop, jigging up an exdhaust manifold to flatten it is a least favorite task.  As you've found it is very labor-intensive.

Some engines, Ford FEs come to mind, also warp the exhaust mounting surfaces on the head.  The FEs are almost impossible to remove all the exhaust manifold bolts without twisting off one or more.  Having to EDM out the broken bolts, flatten the exhaust side of the head and the manifold can double the cost of a top end repair.

A FWIW, milling the head surfaces and both exhaust manifold surfaces will make vee-type engine "shorter/narrower" to the point one-piece Y-pipe exhaust downpipes no longer fit between the outlets - BTDT.

jack vines


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## FliesLikeABrick (Apr 19, 2021)

Packard V8 said:


> A FWIW, milling the head surfaces and both exhaust manifold surfaces will make the engine "shorter/narrower" to the point one-piece Y-pipe exhaust downpipes no longer fit between the outlets - BTDT.


I was wondering how much I will be able to get away with, thanks. I'm putting a reman long block in, so depending on the history of those heads I'll keep this in mind. If the y pipe no longer fits, any preferred fixes to suggest? Or just give 'er a little squeeze?


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## benmychree (Apr 19, 2021)

Of course misusing gage blocks in that manner is a no no, and deserves a slap on the wrist with at least a wet noodle.


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## macardoso (Apr 19, 2021)

They include the "wear" blocks in the set for a reason right?


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## darkzero (Apr 19, 2021)

Yup, using gage blocks for workholding setups is a no no but if ya gotta do what ya gotta do, just don't get caught!  

I bought me a set of Mitutoyo gage blocks to keep as my "good" set. I then bought me a cheap China set to use as beaters. I wouldn't regret using my China ones for workholding setup if I really needed to someday but I would try to think of other alternatives first.

I guess it's time for you to shop for some machinists jacks.  Heck I just have cheap Starrett copies & they do the job just fine. They're also easy to make with just about anything laying around in the shop.


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## westerner (Apr 19, 2021)

Very nice! I have always used a file, with my best technique for holding flat and square

Then, I would trust the gasket and Permatex Ultra Copper to make up for my haste and hack.

I would think your work will be at least as good as the factory's was


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## FliesLikeABrick (Apr 19, 2021)

darkzero said:


> I guess it's time for you to shop for some machinists jacks.  Heck I just have cheap Starrett copies & they do the job just fine. They're also easy to make just about anything laying around in the shop.


Yeah I already made a larger set - Need to make some that are small enough to fit under something like this


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## pontiac428 (Apr 20, 2021)

Your eBay set of inexpensive far east gauge blocks is practically made for that purpose!  Cylinder heads and castings with jacking bosses just don't bolt straight to the table or perfectly fit a set of 1-2-3 blocks.  Screw jacks are too tall.  That leaves gauge blocks.  I don't think anyone who uses them this way would do it with a $4000 set, so I'm not going to chide anybody for doing something that makes sense.


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## FliesLikeABrick (Apr 20, 2021)

pontiac428 said:


> Your eBay set of inexpensive far east gauge blocks is practically made for that purpose!  Cylinder heads and castings with jacking bosses just don't bolt straight to the table or perfectly fit a set of 1-2-3 blocks.  Screw jacks are too tall.  That leaves gauge blocks.  I don't think anyone who uses them this way would do it with a $4000 set, so I'm not going to chide anybody for doing something that makes sense.


I guess I could or should pick up a cheaper set for this purpose -- the set I have is not import, it's from the '50s but has a mixed set of different manufacturers in it, and a label from it's last certification in '93 with a laundry list of which blocks are out-of-tolerance.  Thanks for the input


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## westerner (Apr 21, 2021)

If I had a suspect Chinese set, or a GOOD set from the auction, I would still use them in the application.
Just me, and my outlook on tools in general. 
If a guy has the tool for the job, but deems it too delicate or inappropriate, then I wonder why he has the tool to begin with.  
Can we afford a different set for every situation that arises?


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## Illinoyance (Apr 23, 2021)

In a pinch you could measure the height needed and machine a piece of bar stock in the lathe to fit.
Chinese adjustable parallels sre cheap.  You should get a set or two.
A shaper or planer gauge works beautifully for adjustable height.


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