shim under or above the barrel?

[nicolas]

Ok, maybe a bit of a trivial question, but i am weighing the pros and cons on a solid 1mm shim under the barrel or a copper 1mm shim on top between barrel and head.
which is better, are there benefits doing one or the other?

[Martin S.]

I like having a completely flat head topping the cylinder. No step, no copper gasget, nothing with any kind of edge to start pre-ignition or detonation. It should be as sano a connection between head and cylinder as possible. No tweaking, no distortion, just a completely flat and square join between the two for best results. Put the spacer next to the case. Ideally you would have long cylinders and machine them to the exact length and have no spacers. 

[modnrod]

Well there you go, I was just thinking of this the other day too.
 

Can I add a quick question to this too please?

Has anyone ever noticed any corrosion on the head from using a copper head gasket on a long-term street engine?
(dissimilar metals)

[richie]

Lots of variables but if its a N/A street engine with sensible stroke and rod ratio? then under barrel just as its cheaper  

[nicolas]

Lots of variables but if its a N/A street engine with sensible stroke and rod ratio? then under barrel just as its cheaper  

OK, it was a NA, but will be turbo, hence the slight lowering in CR. but all very modest. engine is a 2276 with porsche length rods. as for the price, i have both options available.

[richie]

Lots of variables but if its a N/A street engine with sensible stroke and rod ratio? then under barrel just as its cheaper  

OK, it was a NA, but will be turbo, hence the slight lowering in CR. but all very modest. engine is a 2276 with porsche length rods. as for the price, i have both options available.

I would put copper on top then to keep as much of piston as possible in cylinder at BDC

cheers Richie

[nicolas]

thanks.

see if i can make this work. 

[Martin S.]

Lots of variables but if its a N/A street engine with sensible stroke and rod ratio? then under barrel just as its cheaper  

OK, it was a NA, but will be turbo, hence the slight lowering in CR. but all very modest. engine is a 2276 with porsche length rods. as for the price, i have both options available.

From John C. : '69-82mm crankshafts can use the VW (5.394″) or Porsche (5.354″) length rod, IF it is made of Chromoly. Once you start using an 84mm crank, you are required to use a 5.5″ or longer connecting rod so you don’t overstress the rod and rod bolts! I recommend a 5.7″ or longer rod for strokes longer than 88mm.'
I agree with John on that one, and you're making a mistake using Porsche length rods. NOBODY does that in the automotive world, and most do the opposite and use as long a rod as possible.

[richie]

Lots of variables but if its a N/A street engine with sensible stroke and rod ratio? then under barrel just as its cheaper  

OK, it was a NA, but will be turbo, hence the slight lowering in CR. but all very modest. engine is a 2276 with porsche length rods. as for the price, i have both options available.

From John C. : '69-82mm crankshafts can use the VW (5.394″) or Porsche (5.354″) length rod, IF it is made of Chromoly. Once you start using an 84mm crank, you are required to use a 5.5″ or longer connecting rod so you don’t overstress the rod and rod bolts! I recommend a 5.7″ or longer rod for strokes longer than 88mm.'
I agree with John on that one, and you're making a mistake using Porsche length rods. NOBODY does that in the automotive world, and most do the opposite and use as long a rod as possible.

Martin

So John C says use Porsche length rods up to 82mm stroke and you agree with him?  and this is 82mm stroke [2276] but you think its a mistake to run Porsche length rods? I am confused which it is?  Porsche length rods have been used with 82mm stroke in 1000s of engines over the years

cheers Richie

[Martin S.]

I'm agreeing with John that it can be done. And I'm agreeing with John with his last statement too. Name one engine builder in the world (besides us bug guys) who uses these short rod lengths, just one

[richie]

I'm agreeing with John that it can be done. And I'm agreeing with John with his last statement too. Name one engine builder in the world (besides us bug guys) who uses these short rod lengths, just one

Nissan

[Martin S.]

What rod length/ratio do they use?

[richie]

What rod length/ratio do they use?

Factory RB26 skyline 4.78inch rod 

[spoolin70]

(Stock Config "Overaquare/Short Stroke" 86mm x 73.7mm & 121.5mm):
OEM RB26DETT Configuration/Stroke.
121.5mm Rod Length & 73.7mm Stroke = 1.65:1 (1.64857530529)
30mm CH/PH Piston Used (Standard).
-----------------------------------------------------------------

I was thinking RB too 

[Martin S.]

OK that's one. Everyone else uses long rods for good reason. Look at listings for rods for V8's. Stock length, or longer.

[Martin S.]

Great now I'm googling this like everyone else
Here's an article where they are trying longer rods on a Nissan motor (gee I wonder why ...

Building the Long Rod Nissan SR20VE Engine
'We researched economical ways to do this by perusing the rod dimensions from other motors. We did not want to order custom rods for cost and timing reasons so we figured we could find a rod/bearing combo that was close and work with that. We ended up settling on the rods from a Honda H22 Prelude motor. The H22 rod is 5.630” long vs the stock SR20’s length of 5.365”. This would give a stroke to rod length ratio of 1.66:1 vs the stock 1.58:1. Not a huge difference but one that we could probably find measurable results from.'
http://www.motoiq.com/MagazineArticles/ID/2135/Building-the-Long-Rod-Nissan-SR20VE-Engine.aspx

[richie]

Name one engine builder in the world (besides us bug guys) who uses these short rod lengths, just one

 

OK that's one. Everyone else uses long rods for good reason. Look at listings for rods for V8's. Stock length, or longer.

Later OS30 engine uses 86mm stroke[ so relevant  to our scene agreed ? ] with a 5.45 rod  , Now given what they were doing with these engines I am guessing they thought about it for quite a while before doing that.

Here's another one off top of my head[ yes I did check this before writing as its not something I am really familiar with, BMW 2002 M10 has 80mm stroke and 5.31 rod ratio, not as short as Nissan but still similar to our VW topic so I am guessing there are dozens, maybe 100s more out there.

All I am saying is there is more than one way to do things

cheers Richie

[Martin S.]

I want some of what you're on if you think short rods are the way to go in a bug engine, har har 

[richie]

I want some of what you're on if you think short rods are the way to go in a bug engine, har har 

PG tips Tea  Yes you should try it and that's not actually what I said is it?  I said there is more than just one way to do it, and there is in my opinion, we all have different ideas and aims for our engines and what we want to achieve in performance and reliability

cheers Richie

[Jim Ratto]

1956 Ferrari 750 Monza: 90mm stroke, 142mm rod = 1.57
1959 Maserati T61: 92mm stroke, 143mm rod =  1.59
1967 BMW Apfelbeck M10: 80mm stroke, 135mm rod = 1.68

[Martin S.]

Maybe check your weed wacker engine too! 

[spoolin70]

To#¤ta - 1JZ Bore x Stroke: 86.0mm x 71.5mm
To#¤ta - 2JZ Bore x Stroke: 86.0mm x 86.0mm

1JZ Rod Length: 125.25mm
2JZ Rod Length: 142mm

That makes a 1JZ a 1.75 rod to stroke ratio 

[Martin S.]

To#¤ta - 1JZ Bore x Stroke: 86.0mm x 71.5mm
To#¤ta - 2JZ Bore x Stroke: 86.0mm x 86.0mm

1JZ Rod Length: 125.25mm
2JZ Rod Length: 142mm

That makes a 1JZ a 1.75 rod to stroke ratio 

 

[Taylor]

Virtually all of Honda's B,D,H and K motors have a rod ratio shorter than an 82/Porsche rod vw. Subaru 2.5 STI is 1.66
Unless your talking under 1.4 or over 2.2 who cares?!?

[Martin S.]

Virtually all of Honda's B,D,H and K motors have a rod ratio shorter than an 82/Porsche rod vw. Subaru 2.5 STI is 1.66
Unless your talking under 1.4 or over 2.2 who cares?!?

B16A1, A2, A3 - 1.74:1

http://www.superstreetonline.com/how-to/engine/0506-ht-rod-stroke-ratio/

[Martin S.]

The only 'good' reason to use a short rod is to stuff your big motor into an oval. (and that's good reason!)

[Jim Ratto]

Ok, maybe a bit of a trivial question, but i am weighing the pros and cons on a solid 1mm shim under the barrel or a copper 1mm shim on top between barrel and head.
which is better, are there benefits doing one or the other?

Nicolas, one thing I learned about 20 yr ago was to machine the chamfer off the top of the cylinders, to increase seating area. No matter copper gasket or not.

[Martin S.]

Berg use to offer the service of honing your cylinders straight on a honing machine. More recently I had mine done locally and they said the new AA cylinders were wonky from new so it's well worth doing.

[Eddie DVK]

I want some of what you're on if you think short rods are the way to go in a bug engine, har har 

TYPE 4 engines. 
Not big strokes but short rods for torque to push heavy buses.

[modnrod]

Cool! Back to "discussing" rod lengths again.
Good fun, keep at it, I'll get the munchies.
LOL!