Long rod 4A or how to destroke a 7A

[bermy]

In all honesty guys it could be worst than the stocker... all the piston assembly (piston, pin, rings (gapped), snap rings) were all within 0.2g of each other... I was pretty proud of toyota that day... the nissan rods : 3 were within 4 or 5g of each other but the 4th one was a whopping 27g too fat... on 482.2g that's way over 5% :S

[trdee]

Depends on what you're after. "Better" or "worse" depends on the application. For racing categories with capacity restrictions I can see this as a way of keeping the engine at 1600cc but hopefully with more longevity and power when doing bulk revs. Where capacity isn't a restriction you would almost certainly go for more cubes though and just not rev the engine as hard.

[bermy]

Depends on what you're after. "Better" or "worse" depends on the application. For racing categories with capacity restrictions I can see this as a way of keeping the engine at 1600cc but hopefully with more longevity and power when doing bulk revs. Where capacity isn't a restriction you would almost certainly go for more cubes though and just not rev the engine as hard.

Or you can just reengineer the bottom end so the small engine rev high enough to make the torque difference of the cubes disappear while still having the internals under less load than the slow revving big engine...

In an engine where displacement is limited by bore size, that is always an option... just an other case where less is more...

[Adsport]

I was wondering if there has been any thought put in to how the dynamics of this combination would affect camshaft choice ? Will you be able to retain the same ramp and lift characteristics of conventional 4age camshafts?

[rolleraction]

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[PrettyCoolWagon]

I know first hand 3 different people who have used spool 4age rods off the shelf and where right on spec ready to be used for the engine

Another forum member on here and myself have reported the same issue.
When you open the Spool packaging it even advises that the big and small ends aren't honed to spec.

Perhaps they initially honed to spec and later stopped as a cost effective exercise. I can only guess.

[bermy]

I was wondering if there has been any thought put in to how the dynamics of this combination would affect camshaft choice ? Will you be able to retain the same ramp and lift characteristics of conventional 4age camshafts?

Honestly, I don't know for sure. The longer dwell time at TDC does reduce cylinder scavenging but a little higher lift cam could help in that department. The thing I'm sure though is that I'll need to dial in cam center line and overlap because that will certainly not have the same effect as a standard 4A-G.

For the rod honing, I always increase ID a little anyway to increase oil clearance. In the case of a high revving engine, I also hone the rods oval, with the ID at the parting line a little bigger than the vertical ID. So even if the rods would be honed "to specs" they are never honed to "my specs"... that wouldn't stop me form buying those...

Oh and BTW nissan GA16 rods are also direct drop in on the bluetop crank but are 3mm longer. If that engine proves reliable, I'll probably drop a bigger budget to build an other one going with H beam GA16 rods and order custom high comp pistons with the pin moved 3mm higher up and drilled for 19mm pin to save on machining cost and weight . That would be even better!

*edit*

Pauter also has the 137.4mm E16 rods and 140.5mm GA16 ones... around 900$ for a set

http://www.nolimitmotorsport.com/pau...ps-Nissan.html

[Celica RA45]

argo engineering in morpath will make any rod combo you like they are a bit dearer than overseas ,but are easy to talk to
im using a 3sge rod that is 8mm longer than std 138mm =146mm better rod ratio and another 1300 rpm over std

[Sam_Q]

Oh and please report back on the harmonics calculation method, I'm really interested

here you go:

http://www.ae86drivingclub.com.au/fo...cer-discussion

post #22

"an oscillioscope coupled to a particular accelerometer"

makes sense

[Sam_Q]

argo engineering in morpath will make any rod combo you like they are a bit dearer than overseas ,but are easy to talk to
im using a 3sge rod that is 8mm longer than std 138mm =146mm better rod ratio and another 1300 rpm over std

as in a 3sge rod in a 4age?

[trdee]

I assume he would be talking about his 3S BEAMS in his RA40 race car.

[bermy]

Yeah, 3S rod journal are 48mm... will never work on any 4A crank... plus 137.4mm rod in my destroked 7A is as much as you can go without ordering custom pistons, 146mm is way too long to work. Might get some 1NZ or GA16 140.5mm to work with custom pistons but cramming a 148mm rod in there would put the piston pin deep inside the oil ring territory... probably way to close for comfort to the 2nd compression ring.

[Celica RA45]

yes talikng about my 3sge beams motor ,but any one in the states might be able to help you with longer rods for a 4age motor

[bermy]

yes talikng about my 3sge beams motor ,but any one in the states might be able to help you with longer rods for a 4age motor

Sure enough. I just like the facts that I can just go and grab over-the-counter rods to fit my application... It's faster and way cheaper than having custom rods build to my specs. That was mainly the point of this whole thread : destroking a 7A block using cheap, readily available parts.

[oldeskewltoy]

the early 40mm rod journal crank is safe to about 8500 rpm as long as it has a real crank pulley on the end.....

even if it is "only 8500 rpm"... The local race shop near me can twist their "tall blocks" to about 9000 rpm and make about 270hp and 170#/ft

What Nissan car did these rods come in? USA models??