Which supplier has the correct APR connecting rod bolts of 2.0 rods?

AirCooled doesn't carry them.

CB Performace has APR bolts but I don't know if these the correct/best ones.

Paul

APR directly $140 or Summit $110. Summit racing item #APR-104-6006 Don't know why aircooled wouldn't have them, same bolts for the 1.7 . Tough call, CB says the 2000 bolts are stronger. Summit lists them as being for watercooled. I'd give Summit or APR a call and ask them to compare the two.

Yea

Get the p/n from ARPs' website, then order them from summit

CB has them for $6.95 each.
http://www.cbperformance.com/catalog.asp?P...?ProductID=1229

Seems like a best buy to me.

These bolts require more torque and also require a resizing of the big end of the rod. You can't just install them...

OH... so what to do?

Is it a matter of taking the rods and bolts to a machine shop and having them ream the hole 'till they fit?


Paul

Well, if you're gonna do that, you could have them ream the hole off-center, stretch the rods, and bump up the compression some....

(Spoken by a man without a running 914... so beware! )

-Rusty

Damn.....
Looks like he has rod ratio and CR confused.

Yes Paul, have a machine shop resize them with the proper specified torque from the bolt MFR

Me?

Hmmm... Somewhere along the line (maybe it was for 911 motors only?), I heard that if you stretched the rods, you could get a slight bump in compression.

Am I incorrect for a T-4 motor, Jake?

-Rusty

At high revs, the stock rods do stretch some... If they do you get higher CR due to a tighter deck height.

If they stretch too much they become two pieces.

Does the engine have that much more power so that you'd need the stronger bolts? If your concerned about the cost of the bolts, why wouldn't you use stock bolts and skip the machining? I'd ask APR if they're that much better.

Okay... my terminology must be off.

Stretching = putting undersized (ID) bushings into a rod, drilling them offset so the effective rod length is longer.

Slightly longer rod length pushes the piston closer to the head, in effect, increasing CR.

Now I remember where I heard about this... Waynes book.

The only way to change CR is to change swept volume!

a longer rod doesn't change CR because it is ALWAYS LONG. If the rod was short at BDC and long at TDC that would be a different story.

The stock bolts are IMHO not even good enough for a stock engine. The stock rod weighs 700+ grams and the weight tries iots best at higher RPM to separate the cap from the beam just after TDC on the way back down. Since the beam is so damn heavy the RPM really works on it with inertia.

The ARP bolts are abot 3 times less elastic than stockers

So, the ARP2000 bolts are three times stronger than the ARP600 bolts? Is the model # also the strength rating?

Due to my piston's pin location, I can only use stock or Carillo$$$ rods. So I'll be using APR bolts and taking about 50 grams off of each rod.

To lighten them I'll be cleaning up the ends and the sides with my grinder/beltsander. Than get them all balanced.

Jake have you ever drilled holes in the web of the rod???

Paul

Like this...

Ahh, I was going to argue, but now I understand. Modifying the rod will change the uncompressed volume and the compressed volume by the same amount. i.e. A smaller amount of air/fuel is being compressed into a smaller space. To bump CR you need a larger (or same) amount of air/fuel being compressed in to a smaller space.


I suppose one could argue that there is a miniscule CR increase because the % of volume lost at BDC does not equal the % of volume lost at TDC. But I'm splitting hairs.

4 in^3 / 2 in^3 = 2:1 ratio
3.998 in^3 / 1.998in^3 = 2.001:1 ratio

It's been 30yrs. since I rebuilt a Type lV, lots of changes. I love this stuff.