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Opeler
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Discussion Starter #1
I really try to search for an answer before asking as there is so much information already available on this site I figure someone has asked it before. But, it seems this has been asked in various threads but I can't find an answer and I want to be sure I have accurate information before taking my parts to the machine shop. I also searched the FSM.

What should the size of the big end of the connecting rods be when reconditioning them?

And while we're at it what should the size of the main bearing shells be when having the block line bored?
 

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boomerang opeler
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5,629 Posts
things like how long is a piece of string come to mind


big ends should have the crank measured and inspected for wear then if the crank is ok a standard bearing in the rod or if the crank needs to be ground down , a bearing to match the grind ( 10,20 or 30 thou under size )

the block would need measuring to find out what size it is over bored to when line bored and this would be to a standard over size shell back (again 10.20 or 30 thou oversize )
the bearing surface of the mains should be inspected at the same time and ground if needed to get the right finish (yet again 10,20 or 30 thou under size)
so you can have an oversize and undersize bearing on the outside and inside of the same shell
make sure you can get bearings to do this before you start as they may not be available or you may end up with a block that is only good as a boat anchor
 

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Heres how I would handle this problem.
Take all your parts to a good machine shop and have them inspect and advise.
If they pass the visual, hot tank the parts get them real clean.
If they don't pass they might want to pull out the mics and measure then advise.
Next step assy. rods and main caps torque then measure and you guessed it advise.
What kind of condition is the crank in any way?
I've got the specs for the rods and mains at the shop but not at home.
Second thought any good machine shop WILL have the specs!!!!!
 

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Old Opeler
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5,564 Posts
Big End Bore Size

I am sure it is the size of the big end of the conrod that is being looked for - the diameter that the outside of the rod bearing shells fit into. Likewise the diameter that the main bearing tunnels are linebored to.

Unfortunately, I have been unable to find an accurate specification for this size in any of my Opel documentation. Even the very comprehensive Holden 1900cc Engine Manual does not list this information.

This is extremely importany information that determines the correct "crush" that holds the bearing shells into place and makes them 'round'

Must be available somewhere!
 

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I just went through all this recently.
If there is a dimension specified anywhere for con rod big end size or the main diameter it is top secret.
We gave up.
Measure your mains and look for out of roundness. That's all you can do.
We were lucky, it was nearly perfect, close enough.
A reground crank spun beautifully in our block after torqueing down the mains. That is good, we went with it...
As for the rods, well, let's just say we didn't care what the stock Opel specs are. We knew the spec for the rods we used!
 

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The old paper books has the dia. (ie clevite) of both main and rods
I'll post the specs in the AM if it would help.
 

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Old Opeler
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Con Rod Big End Bore

Found this spec in the Mahle/Clevite con rod bearing catalogue 2005

Connecting Rod Housing Bore: 2.1653"/2.1658"

So now just the Main Bearing Housing Bore to find.
 

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crankshaft
main 2.2830-2.22835
rod 2.0460-2.0467

block
main bore dia 2.4409-2.4415

rod
big end 2.1653-2.1658
 

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Opeler
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886 Posts
Discussion Starter #9
Awesome!!!

Thanks so much for the replys. I don't have extra parts and I want to avoid mistakes when taking them to the machine shop. I think most of you can appreciate that. :veryhappy:veryhappy:veryhappy
 

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Cam-in-head?
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238 Posts
crankshaft
main 2.2830-2.22835
rod 2.0460-2.0467

block
main bore dia 2.4409-2.4415

rod
big end 2.1653-2.1658
Great information. I sure could use the bore diameters for the 1.1 liter as well (I have the crankshaft journal dimensions).

-Kurt
 

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Opeler
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41 Posts
So, here's my quandry....

I'm rebuilding a 72, with flat-tops that were in the "goodie box" when I bought the cars. Unfortunately, the caps were not kept with the pistons/rods. Random selection doesn't work. If I tighten the caps on more than 1, the crank can't be moved.

Any idea how to match the caps with the rods?
 

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Non Civilian
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2,085 Posts
Sound like wrong side bearings.
 

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Cam-in-head?
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238 Posts
I'm rebuilding a 72, with flat-tops that were in the "goodie box" when I bought the cars. Unfortunately, the caps were not kept with the pistons/rods. Random selection doesn't work. If I tighten the caps on more than 1, the crank can't be moved.

Any idea how to match the caps with the rods?
There are usually machining marks inside the the rod and cap where the bearings sit. Sometimes you can match them up that way...

-Kurt
 

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Old Opeler
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5,564 Posts
Con Rod Big End Bore

P.O.s can be a real pain in the butt!
I take it you have four con rods and four loose caps ... but do not know which caps fit which rods because the dreaded P.O. threw them into a box without bolting them together ... :banghead:

Some rods do have numbers 1;2;3;4 stamped each side of the part line at the Factory - so check that first. Sometimes P.O.s do manage to mark the rods with centre dot marks in the same place - so check carefully.
Failing that - know that the notches which the bent out tangs on the bearing shells fit in too go together on the same side of the hole - but staggered - so that they do not line up but one forward/one aft. I guess you just have to selectively assemble the caps/rods till you get the best fit with minimal misalignment ... and then have the rod resized to make sure the hole is round and the correct size. Connecting Rod Housing Bore: 2.1653"/2.1658"
Use new con rod bolts, if at all possible, and torque them up 2 or 3 times before getting the rods resized.

BTW: The notches DO NOT hold the bearing shells from spinning - it is the friction due to the clamp (or "crush") of the correct sized housing bore and the back of the bearing shells which holds them in place - that is why they are installed DRY - NO OIL between the back of the bearing shell and the con rod housing bore. The little bent-out tags just align the shells fore and aft in the con rod.
 

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Opeler
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41 Posts
Problem solved

Well, thanks to OpelKurt and GTJim. Matching the hone marks was all it took. No, that's not totally true. The caps had to be oriented correctly. It is strange that the retainer notches are on the same side. Also strange is that the notch on the outside of the cap faces to the rear of the engine, as opposed to the ones on the pistons.

Anyway, she spins freely. On to the head...
 

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Cam-in-head?
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238 Posts
It is strange that the retainer notches are on the same side.

Anyway, she spins freely. On to the head...
Note that the retainer notch rule applies to the main bearings as well....

-Kurt
 

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Old Opeler
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5,564 Posts
1.1L Bearing Bores

Great information. I sure could use the bore diameters for the 1.1 liter as well (I have the crankshaft journal dimensions).

-Kurt
Found the Specs!


Connecting Rod Big End: 48.001/48.011mm ~ 1.8898"/1.8902"

Main Bearing Tunnel Bore: 58.001/58.014mm ~ 2.2835"/2.2840"

Very tight specifications.

Thank You - King Engine Bearings. Looks like they supply many Opel Bearings including the hard to find 2.4L con rod bearings which differ from the 1.5L/2.2L shells. If you flick through the panels in the link below there are also the specs for a wide range of Ope motors from the 1959-62 Olympic to the later model European motors. King Engine Bearings has a US Corprate HQ - click 'Home' in the Link below.

http://www.king-bearings.com/cat/panel/pan190.htm

Here are some more 1.1L Specs - put them here so they are all in one place ...

Block Deck height (crankshaft centre to head face) 191.0mm
Connecting Rod centre-to-centre length 122.50mm
Connecting Rod Big End width (also pin end) 22.95/23.00mm
Piston Pin Height (centre of pin to top of piston) 38.0mm
Piston Pin diameter 20mm - well 19.98-19.99mm

I measured these from a 1969 GT1100 motor - please correct any errors!
 
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