non-hemi rod question

#1
Hey yall. Ive got a non hemi 212 on my mini bike and Im getting parts up, dont want to go real crazy but ive got billet fly wheel, mod2 cam, 26lb springs, jetted carb, cone filter, and a nice header. What rod from ARC should i use the standard or plus 20? not planning on doing any head work or anything major still want it to be fairly reliable as a swap meet scoot.
 
#2
You need to measure how far down the bore the piston is from the deck to know what length rod to get. Also if you decide to use a hemi flat top piston then it has a .02 shorter compression height so you would need at least a .020 longer rod. First step measure your piston depth at TDC. You need to keep at least .025-030 clearance from the flat area of the head to the top of the piston with the head gasket installed.
 
#3
All the non Hemi engines I have built used the .04 over rod..especially if using the Hemi piston... using thin head gasket
Even the Hemi engine I use the .04 over rod with a thick gasket...

Now if putting a Predator crank in a Honda... I use the .02 over rod...

This is what I have found works.... but every motor is different...
 
#4
I would measure how far in the hole it is but if your unsure and just want to order the rod before taring the motor apart than just get the stock length rod.
 
#5
Most if not all non Hemi engines are a minimum .040-.050 in the hole... they have a taller deck height than Hemi or clones...
That is why ARC came out with the 2 different rods... .020 for Hemi, .040 for non-Hemi...
 

SAS289

Well-Known Member
#6
My first thought was a question. Has anyone seen under .020 in the hole on any of these clones? You would think to get .020 rod minimum if you want more compression.
 
#7
I vote with Ole, since you have 26# springs to swap in just pull the head and measure the in the hole measurement while you swap springs. Get the rod that puts you closest to 0 deck height. On a predator there is not a "typical" in the hole number, they are all over the board. I, myself, have not seen under .020 in the hole. This mod will increase your compression overall and create more power, take the time to measure it. Putting those 26# springs on would be fun without pulling the head.
 

Latent

Active Member
#9
check how far your in the hole now. i got a +20 rod with a hemi flat top and still in the hole a good amount, if i had a time machine i would of went with the +40 rod, but regardless the +20 and flat top piston will still will put a smile on ur face :laugh:
 
#10
By going a .020 over rod and a Hemi piston puts you at the same place as the beginning...
If you use a .020 over rod and the stock dished piston would move you up .020...

In the Non Hemi I always use a .040 rod and a Hemi piston... ends up right around .020-.015 in the hole... then adjust the head gasket according...

One combo I like using is a Honda crank in the Non Hemi with a Honda 3.403 long rod to bring it upto .005 pop up and a .045 gasket...
Revs quick and hauls the mail...
 
#11
By going a .020 over rod and a Hemi piston puts you at the same place as the beginning...
If you use a .020 over rod and the stock dished piston would move you up .020...

In the Non Hemi I always use a .040 rod and a Hemi piston... ends up right around .020-.015 in the hole... then adjust the head gasket according...

One combo I like using is a Honda crank in the Non Hemi with a Honda 3.403 long rod to bring it upto .005 pop up and a .045 gasket...
Revs quick and hauls the mail...
Prowler, I have read you list this build before. What piston do you use? Is the wrist pin the same size on the predator and Honda?
 
#12
Because I use the Honda crank you use a Honda Rod... yes the wrist pin in the Predators is the same as a Honda...
The reason I mix and match parts is because I do a lot of Kart racing, and the engines blow up on a regular basis...
So what ever left over parts are in the bin I use to build another engine...

Also a lot of the same parts are used in the Champion 208cc engine... but that engine uses a different crank, and the wrist pin on the piston is larger... so I swap over my Clone/Honda parts in the block to make a race engine...
 
#13
Prowler, I have read you list this build before. What piston do you use? Is the wrist pin the same size on the predator and Honda?
Yep I am building an large bore honda clone using an old predator dished piston and honda crank and rod. Makes a 208cc motor. Wrist pins are the same size.
 
Top