Type 4 Aero Conversion (Con Rods)

[T4Flyer]

Let’s talk “Con Rods”

I think most of us know how to balance pistons (they must all weigh the same, right) but from talking to various people, it seems a lot of us don’t understand that Con Rods need to be balanced a little differently

If you just grind a little away from the heaviest rods until they all weigh the same (very easy) you may in fact be putting your rods more out of balance than they were before you started (“say what”) no really!

With rods, you need to do what is commonly known as “end to end” balancing. With this method, you are basically going to match the weight of each of the small ends and each of the big ends separately

Why, because of something called reciprocal mass and rotating mass. The big end is going round and round, while the small end is going up and down. (Wow I made that sound simple!)

Look at this simple and exaggerated example

You have two rods, one weighs 610 grams and the other 600 grams you grind 10 grams from the first rod (let’s say it has a balance pad on the small end) and they are now balanced, yes?

Well no, if the first rod had a small end weight of 205 and a big end of 405 (610) and if the second rod had a small end of 200 and a big end of 400 (600) what you now have is one rod 195 – 405 and one rod 200 and 400. Although they are both now 600 grams they are in fact still out of balance.

Look at the pics of the balancing rig I had made up to do my rods (a picture is better than a thousand words)





Of course, this is not a complete explanation and I have plenty more pics, but it should get the ball rolling

Cheers

[ZeroAxe]

Hmmm, interesting Rig you got there!!! Mine was much more primitive, but did the same job. Got to make me one of those rigs now

[T4Flyer]

Hi Zero,

I searched the net for quite some time looking at all the pictures I could find before I settled on a design for my rod balancing rig and Yeh, the guys made a nice job of my rig.

It actually covers for three jobs. It started out as a very old magnetic dial gauge stand! I needed to make a stand for my pipette to do my cylinder heads so I got the guys to make a new longer upright shaft to attach to the magnetic base and a new longer secondary arm with an attachment to clamp the pipette into, that way I could use the original swivel clamp (would have been the hardest bit to make). It worked like a dream (see pic in my previous post).

For the rod balancer, we taped the other end of the new upright post to accept a counter sink cap head screw, counter sunk a row of holes into a 10mm aluminium plate, screwed the two together and once again attached the original swivel clamp.
We then made up another new secondary arm, aluminium square bar dropper arm (with needle roller bearings) and a solid transfer arm. The dropper arm slides on to the secondary arm.
Two bushes, also with needle roller bearing, were made up, one for the big end and one for the small end.
Lastly, a smaller aluminium stand to hold the “being weighed end” of the rod was made up.




The whole balancing rig works a treat, very accurate, and very consistent readings. (By the way, I used the spite level to ensure that the angle and placement on the scale was always consistant)

I am very pleased with the results, maximum total variance 0.2 grams.

Cheers

[AirPower]

Hi T4Flyer.

That is well thought out. What rod bolts are you using?

[T4Flyer]

Hi Airpower,

I thought of using ATP but with the current exchange rate they came out at about R2,000. For 8 nuts and bolts!.... bit to rich for me. I am only going to rev to +-3500rpm (in Climb) and maintain 3000rpm (in cruise) and have not heard of any bolt failures in aero engines I will reuse the original bolts with new nuts. (although this does go against the grain and I'm still not happy)

If anyone knows of a better option I would be glad to know. I have read that some T4, 2000cc rods have been modified for SB chevy ATP bolts (much cheaper option) but I don't know anyone in SA who has or can do the machining work.

Any body.... Before I build my engine ????? Pleeeease....

Cheers.

[Tony Z]

CB has decently prices bolts... conrods too

[T4Flyer]

Hi Tony Z

Oh Oh, Very interested... But new to this site, CB? who, where and how do I get hold of him/them.

Cheers.

[Tony Z]

clearanced new conrods $140
http://www.cbperformance.com/catalog.asp?ProductID=1513

new replacement stock rods
http://www.cbperformance.com/catalog.asp?ProductID=1179

ARP 2000 conrod bolts $7 ea
http://www.cbperformance.com/catalog.asp?ProductID=1229

[Tony Z]

Bugger bought a set of rods based on my suggestion. They look pretty good and I think he is fairly happy with them

[T4Flyer]

Tony Z,

The bolts don't appear to be for the type 4 rods and the rods also look more like type 1.

Cheers

[Tony Z]

tis true but I have a feeling that the dif betw T1 and T4 rods is that T1 is 1mm longer and has a different gudgeon pin size which can easily be reamed out from 22 to 24mm

look into it cause I am not sure

Write to CB, maybe they do have some T4 rod bolts

[AirPower]

http://www.conrod.co.za - might be worth a try.

Thundersport in pinetown might also be able to help - they also stock ARP bolts. I've dealt with them before, although vw are not stock items so they will also need to import.

This from the ARP catalog - if you need the part No. - you probably need the Porsche type 4 ones.



From what I read the rod bolts are a problem for high revving motors, but as you say - 3500rpm is not high and they might be fine. I believe IMPI uses standard bolts in his motors - IMPI any comments?

Then again - what is your life worth to you? less than R2000.00?
Mario

[T4Flyer]

Hi Guys,

Thees dam rod bolts have been bothering me for a long time.

I have not found anyone here in SA who has changed from the standard bolts and every one I have spoken to assures me they are fine, in-fact these rods are the same ones I pulled out of my old engine and I had no problems with that motor. However, I have not built my engine solely to a budget and want piece of mind (I'm a perfectionist who worries a lot!)

I have found a supplier in the USA (No Limit Motorsport) who advertise ARP 104-6006 at $122.75. This is their highly discounted price. I want to go for it (well I don't actually, but those who know me, know I will )

Can anyone please confirm they are the right bolts for the VW Type 4, 2000cc rods? I just want to be very sure before I place an order. (I can't really afford them in the first place, defiantly can't afford to throw them away!)

Cheers

[calooker]

T4 rods and bolts are bullet proof, your RPM is 3500 max, I would use the standard bolts that came on the rods you have, I have yet to see a broken T4 rod due to bolt faliure. I know of several T4 big CC with plenty HP motors running stock rods.
T4 specific H-beam rods are extremely expensive, T1 rods will not work as there are too many differences, ie: length, width, small & big end size.

[Bugger]

Bugger bought a set of rods based on my suggestion. They look pretty good and I think he is fairly happy with them

The bigend size is smaller on the T4 2L and the lenth is shorter
I have once broken a T4 Rod and is the only Person to date that I have heard of to break a Type 4 rod , but that was from serious overboost and high RPM and the rod broke with the big end side still attatced to the crank and spinning
I do understand how you feel T4 it is your life at the end of the string after all but moet nie worry nie alles sal oraait wees

No serious these rodbolts are very tough