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Opeler
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Discussion Starter #1 (Edited)
I've been kicking around building an engine up. My thought is to use these pistons

Keith Black/KB Pistons IC835-STD - Keith Black ICON Premium Forged Pistons - Show All - SummitRacing.com

with stock small block rods. the big ends are 2" not 2.045" but milling the crank will solve that. My math points to it being .018" taller than the stock 1.9 and the pistons are just under 95mm so it wont be 2 liters but close.

compression distance stock 1.776"
new pistons are 1.133"
stock rod is 5.039"
small block chevy is 5.7"

1.776" - 1.133" = .643" + 5.039" = 5.682"

so the 5.7" will be .018" taller

only issue I see with this is balancing the flywheel to match rotating assembly

as for the head planned on doing 1.85 intake and 1.5 exhaust basically using RallyBobs suggestions.

Does this sound like a good build or am I setting my self up for a punch in the wallet.
 

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The stock sbc rod (crank) journal size is 2.0990-2.1000.
The sbc rods are .945 wide on the bigend.
.018 out of the hole aint a bad thing.
 

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Opeler
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Discussion Starter #4
The stock sbc rod (crank) journal size is 2.0990-2.1000.
The sbc rods are .945 wide on the bigend.
.018 out of the hole aint a bad thing.
Yeah sorry blended another idea that didn't pan out. On the small block rod the plan was to use over sized bearings. Its odd how things blur together.
 

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Old Opeler
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5,564 Posts
Large & Small

The later 305/350 etc SB Large rod journals are 2.0990-2.1000" but the earlier 'small' journals are 1.9990-2.0000.

Rods from 283 CI - 327 CI blocks before about 1968ish (?)

I have a set of 2.3L Ford rods that are machined for the smal journal Chevy con rod bearings. It just involves grinding the Opel rod journals about .043" undersize to fit standard Chevy small journal shells.
Each box has two sets for an Opel in it!
 

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Super Moderator
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5,298 Posts
Valves . . .

I've been kicking around building an engine up. My thought is to use these pistons

Keith Black/KB Pistons IC835-STD - Keith Black ICON Premium Forged Pistons - Show All - SummitRacing.com

with stock small block rods. the big ends are 2" not 2.045" but milling the crank will solve that. My math points to it being .018" taller than the stock 1.9 and the pistons are just under 95mm so it wont be 2 liters but close.

compression distance stock 1.776"
new pistons are 1.133"
stock rod is 5.039"
small block chevy is 5.7"

1.776" - 1.133" = .643" + 5.039" = 5.682"

so the 5.7" will be .018" taller

only issue I see with this is balancing the flywheel to match rotating assembly

as for the head planned on doing 1.85 intake and 1.5 exhaust basically using RallyBobs suggestions.

Does this sound like a good build or am I setting my self up for a punch in the wallet.
. . . just curious, but is there any difference between Chevy SB and Opel CIH heads' I/E valves "C-to-C" distance and, if so, what?
 

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. . . just curious, but is there any difference between Chevy SB and Opel CIH heads' I/E valves "C-to-C" distance and, if so, what?
I don't have the numbers in front of me, but yes, they are different locations and C-to-C spacing.
 

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Opeler
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12 Posts
Discussion Starter #11
I found an option to raise compression.
These Pistons:
Keith Black/KB Pistons IC832-STD - Keith Black ICON Premium Forged Pistons - Overview - SummitRacing.com
These Rods:
Eagle Specialty Products 5565B3D - Eagle ESP H-Beam Connecting Rods - Overview - SummitRacing.com

The pistons have a compression height of 1.265 and are flat top valve reliefs so they are +3.2cc piston volume rather than the +10cc of my first post.

The rods are 5.565" length and 2.1" bore so still would have to use an over sized bearing.

This setup is still .015" taller than stock opel. My main worry is getting compression ratio to around 10:1 and clearing the larger 1.85 intake and 1.5 exhaust valves I plan on using. I've never built an engine. So I'm going by mostly what I've read on these forums. The stock setup is usually .004"-.007" below deck this will be around .011"-.008" above deck. The head gasket is .030" compressed thickness. would there be issues with piston to head contact especially since this engine is going in an autocross vehicle (DM class no street service)or would I need a thicker gasket. The stock combustion chamber is around 53cc with the larger valves and hardened seats (was told that was a must for unleaded fuel hoping to use premium) about what would the chamber size be. Would it be smaller around 45cc where i would want it to be or is that a simple matter of machining to what I want. The head is a 73 12-bolt. I would like to keep it simple with stock rockers and lifters maybe a new grind on the cam or a performance cam from ogts, But if there is a affordable alternative I would be interested. Needless to say I don't want to build a turd or buy parts to find out there is no way they'd work.
 

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Living in the past
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2,334 Posts
running pistons up out of the block

I found an option to raise compression.
These Pistons:
Keith Black/KB Pistons IC832-STD - Keith Black ICON Premium Forged Pistons - Overview - SummitRacing.com
These Rods:
Eagle Specialty Products 5565B3D - Eagle ESP H-Beam Connecting Rods - Overview - SummitRacing.com

The pistons have a compression height of 1.265 and are flat top valve reliefs so they are +3.2cc piston volume rather than the +10cc of my first post.

The rods are 5.565" length and 2.1" bore so still would have to use an over sized bearing.

This setup is still .015" taller than stock Opel. My main worry is getting compression ratio to around 10:1 and clearing the larger 1.85 intake and 1.5 exhaust valves I plan on using. I've never built an engine. So I'm going by mostly what I've read on these forums. The stock setup is usually .004"-.007" below deck this will be around .011"-.008" above deck. The head gasket is .030" compressed thickness. would there be issues with piston to head contact especially since this engine is going in an autocross vehicle (DM class no street service)or would I need a thicker gasket. The stock combustion chamber is around 53cc with the larger valves and hardened seats (was told that was a must for unleaded fuel hoping to use premium) about what would the chamber size be. Would it be smaller around 45cc where i would want it to be or is that a simple matter of machining to what I want. The head is a 73 12-bolt. I would like to keep it simple with stock rockers and lifters maybe a new grind on the cam or a performance cam from ogts, But if there is a affordable alternative I would be interested. Needless to say I don't want to build a turd or buy parts to find out there is no way they'd work.
The determining factors about valve-piston clearance is duration on the cam lobe (how long the valve stays open) and valve lift on the cam lobe (how far the valve opens). Valve reliefs in the top of the piston need to be measured and rotating clearance checked by modeling clay coated with a light oil and placed on the valve reliefs with the motor being rotated with the head and gasket in place (use and old head gasket that has been compressed. Measure the thickness of the clay where the valve made the impression on it to get valve to piston clearance measurement, anything more than .003-.005 up out of the hole can and most times will work on the top ring land and put a lot of heat on the top ring. In other words if you have not built this type motor and it lived, leave it alone and find someone that knows about engines, because you're not talking about a taxicab rebuild here and you are going to spend a lot of money and wind up with a motor that will not live or worse yet fly apart and ruin the whole deal. Just my TCW
 

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The rods are 5.565" length and 2.1" bore so still would have to use an over sized bearing.
I do believe that the late model sbc rods have a 2.2247-2.2252 bore.
The large journal crank is 2.0990-2.1000 on the rod.

A stock Opel crank has the split of 2.0464 +/- .0003 so it can range from
2.0461-2.0467 on the rod journals.

Aint this fun..mixing and matching?
 

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Opeler
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12 Posts
Discussion Starter #14
I do believe that the late model sbc rods have a 2.2247-2.2252 bore.
The large journal crank is 2.0990-2.1000 on the rod.

A stock Opel crank has the split of 2.0464 +/- .0003 so it can range from
2.0461-2.0467 on the rod journals.

Aint this fun..mixing and matching?
Might have phrased it wrong. The 2.1" rod ends are with std. bearings. I was planning on using +0.60 bearings putting them at 2.04" and then polishing crank for fit. I had over sized when I was meaning under. Something seems odd about adding material and implying its smaller.
 

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Opeler
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12 Posts
Discussion Starter #15
The determining factors about valve-piston clearance is duration on the cam lobe (how long the valve stays open) and valve lift on the cam lobe (how far the valve opens). Valve reliefs in the top of the piston need to be measured and rotating clearance checked by modeling clay coated with a light oil and placed on the valve reliefs with the motor being rotated with the head and gasket in place (use and old head gasket that has been compressed. Measure the thickness of the clay where the valve made the impression on it to get valve to piston clearance measurement, anything more than .003-.005 up out of the hole can and most times will work on the top ring land and put a lot of heat on the top ring. In other words if you have not built this type motor and it lived, leave it alone and find someone that knows about engines, because you're not talking about a taxicab rebuild here and you are going to spend a lot of money and wind up with a motor that will not live or worse yet fly apart and ruin the whole deal. Just my TCW
Thus the reason for asking. Would it be unheard of to grind the rod ends and then re-size them to bring the pistons down in the hole? I know they re-size elongated rods to obtain proper bearing clearances. The .008-.011 that I'm estimating doesn't seem like too much to remove from the rods. That would get my deck clearance back so no worries of contact and get the excessive abuse to the upper ring back close to stock pistons. As for combustion chamber size I can angle mill the head to build up compression. Now if all that works when it comes to the valves. Would building the bottom end up and then bolting down the head with old gasket and intended valves in position and measuring from contact to fully closed at top dead center then subtracting the proper clearance to get my lift work well? Figure that method would give me enough clearance that if something did go wrong say timing chain jump then the valves would be non-interference fit. And I think RallyBob mentioned valve lift higher than .45 is a bad thing with the valves I plan on using. Now if only I can get the engine specs to be somewhat plausible. Then I'd have to find a shop willing and able to do it right. Get the feeling the willing will be no problem :p
 

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And I think RallyBob mentioned valve lift higher than .45 is a bad thing with the valves I plan on using.

Overlap is what creates most valve interference issues. So I'd be far more worried about lots of duration and narrower lobe separation angle than valve lift. When the valves are fully opened, the pistons are nowhere near top dead center.

I've run a cam with .482" lift on a stock flat-top block with a head milled .030" and with 2.0 litre valves with no issues. But that cam was only 224 degrees of duration @ .050". Otto from Texas now has this cam in his 2.1 litre Opel engine.

When you start getting into the realm of 245-250 degrees then it's a problem, even with low valve lift!
 

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I've been kicking around building an engine up. My thought is to use these pistons

Keith Black/KB Pistons IC835-STD - Keith Black ICON Premium Forged Pistons - Show All - SummitRacing.com
I'm a little late to the party, but what about using these pistons with 5.7" rods made for the 2.3 Ford? The Ford journals are just .0004" larger than the Opel, so you can use the Ford bearings (better quality available) and you'll have just a tad more clearance which is fine for a performance engine anyway.

You can usually order the Ford rods with a .927" pin end, so that solves that issue.

The Ford rod's big ends just need to be narrowed .013" to fit the Opel crank pins.

The Chevy rods are narrower than stock. With excessive side clearance your oil pressure will drop, something to consider....

You still have to deal with the overall height however.

Bob
 
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