T4 Tear Down / Rebuild in Jax FL

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wreck
Posts: 146
Joined: Thu Aug 14, 2014 2:07 am
Location: Brisbane Australia

Re: T4 Tear Down / Rebuild in Jax FL

Post by wreck » Fri Nov 03, 2017 4:56 pm

I went through this recently , the case spigots may not be flat and as Ray and Pile have mentioned any burrs or differences in rod length /crank stroke show up . I ended up taking .003 of the top off 2 pistons to get the deck with in .001 . In a relatively standard engine I would not of gone to the trouble .
something worth doing is to put some sealant on the base of the cylinders ,torque the heads down ,then after the sealant has cured ,carefully remove the heads and check the cylinders are even ,use a small 6inch straight edge and slide it across the top of the cylinders .They should be dead flat . this is more important than getting the decks dead even .
No matter where you go , there you are !

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Clatter
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Location: Santa Cruz

Re: T4 Tear Down / Rebuild in Jax FL

Post by Clatter » Sat Nov 04, 2017 9:09 am

Has the case been decked?

There's a bit about this buried in my build thread.

After 40 hard years pushing a bus, most cases need decked;
Best by a guy who counts how many thou it takes to clean them up.

You hope for only a couple thou to clean up,
And toss the case in the bin if it takes .004 or .005"..

Look real real careful like at a straightedge across the tops of two cylinders, in the case, on the deck.
You will typically see the area right between them a bit 'high',
Indicating a spread center main.

They all have it, the question is how much.
Unless it just got decked, of course.. ;-)
"Oh, You don't need to do all that... The valve seats are just going to fall out of it anyway!"
- Doug Ellsworth

Beginners' how-to Type 4 build thread ---> viewtopic.php?f=1&t=145853

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Clatter
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Location: Santa Cruz

Re: T4 Tear Down / Rebuild in Jax FL

Post by Clatter » Sat Nov 04, 2017 9:21 am

Oh, and those cylinders suck for how different they are in length.
They should all be dead nuts, or at least within .001".

Are you _sure_ there's that much variation? Calipers aren't always the best for pulling tight measurements.

Those are maybe the Mahles with the AA cylinders?
Look for the little flat spot cast into the fin area near the cylinder base.
It's at the bottom of the flat area where the cylinder fins are clearanced for the other cylinder..
A little flat area about 1/2 cm square, where they cast in AA if it's an AA, or not, if it's to be packaged as a Mahle.

Alas, just because it says Mahle on the box, doesn't mean it's a Mahle cylinder (or that it's made correctly).
If you have that much variation, anyone half-way decent with an old manual lathe can make them right.

Metallurgy with AA stuff is hit-or-miss, but most often good.
Bad machining can often be corrected.

So chin up! :D
Think of how so many people just throw these things together straight out of the box,
Thinking it's still the old days,
And the inevitable results that follow..

You have had some real poop luck so far, but are still on track to success no doubt..
"Oh, You don't need to do all that... The valve seats are just going to fall out of it anyway!"
- Doug Ellsworth

Beginners' how-to Type 4 build thread ---> viewtopic.php?f=1&t=145853

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analogtherapy
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Re: T4 Tear Down / Rebuild in Jax FL

Post by analogtherapy » Sat Nov 04, 2017 11:37 am

Clatter wrote:
Sat Nov 04, 2017 9:21 am
Those are maybe the Mahles with the AA cylinders?
Well...about those Mahles...

The Mahle set that I got looked great upon visual inspection. Forward 5 months-ish later, and one was bent ever so slightly at the lower circumference of the cylinder, enough that you could just baaarely see it, but also enough that the piston wouldn't fit into the cylinder at all. A second was just off enough to be a snug fit when sliding the piston in. The remaining 2 had no issue at all. And you know what? You can't buy the Mahle's without the pistons. Since I didn't need a full complete set, I opted to go with a set of AA's, just the cylinders, since they sell them that way. The only other cylinders sold by themselves like that are no-name brands that I didn't want to gamble with. Sucks, but, I'm at the end of my budget and that's just how it is.
Clatter wrote:
Sat Nov 04, 2017 9:21 am
You have had some real poop luck so far, but are still on track to success no doubt..
Thanks man. It has been frustrating for sure. I'm still hopeful that I can finish this before the end of the year.

OK...so I switched the #2 and #4 rods since it seemed that they were the opposite. One being high, and the other a bit low. Got everything tightened up again, and here are my latest measurements:

#3

Piston/Cylinder DH = .010 (.25mm)
Total DH = 1.05mm

CR: 7.8

#4

Piston/Cylinder DH = .014 (.35mm)
Total DH = 1.15

CR: 7.8

#1

Piston/Cylinder DH = .011 (.28mm)
Total DH = 1.08mm

CR: 7.8

#2

Piston/Cylinder DH = .010 (.25mm)
Total DH = 1.05

CR: 7.8

HAM Heads step + .8mm to DH
Bore = 94
Stroke = 71
CC's 64.5 (15cc piston dish + 49.5cc head)



So....can I get excited yet?! :D

The only thing is, is that I'm aiming for between 7.5 - 7.75 CR, so I'm a tad high for the Web 142...

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analogtherapy
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Re: T4 Tear Down / Rebuild in Jax FL

Post by analogtherapy » Sat Nov 04, 2017 11:44 am

Looking over my numbers, am I right in thinking that if I switch out the cylinder gasket with an .010 spacer, that will get me to 7.6 CR?

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Clatter
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Location: Santa Cruz

Re: T4 Tear Down / Rebuild in Jax FL

Post by Clatter » Wed Nov 08, 2017 3:38 pm

7.75.. 7.8.. Same difference.

A smidge more compression sounds about perfect.
As long as you tune it well, you'll be fine.

Just make sure to run premium fuel,
At least until it get 20-30K miles on the clock, and loosens up anyways..
"Oh, You don't need to do all that... The valve seats are just going to fall out of it anyway!"
- Doug Ellsworth

Beginners' how-to Type 4 build thread ---> viewtopic.php?f=1&t=145853

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