Need to lightly hone out my block to removes some scratches. Can I reuse my 78K pistons and connecting rods as-is with new rings and bearings or should the rods be reconditioned? I will never be using a power adder.

 

It would be a good idea to have better bolts (ARP) installed in the rods and have them honed back to spec since you have them out.

The pistons might be another story because the scratches in the wall might require some serious metal removal to the point where the clearance between the stock piston cylinder wall is too great. Then you would have to get a oversize piston and most likely bore the blockt to get there.

The first thing is figure out how much needs to be taken out of the walls to remove the scratches. Start with the worst cylinder and if the clearance is too large (over .002" on stock hyper pistons) you might as well go to a aftermarket .010"+ piston.

Bret

 

That being said if I have to replace the pistons I will just get .030" over and bore the block.

Funds are starting to run a bit low (imagine that) so what are some aftermarket high quality pistons that will work well for me?
I will never have juice or other power adders.

It appears that the stock pushrods can be reconditioned for $100.00
Will these be strong enough for 355 using ARP wave lock bolts with no power adders?

 

After spending $100 on reconditioning the rods, and $50 on ARP rod bolts.. might as well spring for a set of Scat forged I-beam's for $50 more.

 

Good advice, please keep it coming.
This is my first shortblock project.

Also can someone please clarify why there are 5.70" rods and 6" rods and what their specific differences are. What do i need for a 355?

 

I can't fully explain the benefits to a 6.0" rod... but, it sets the wrist pin higher in the piston. Both a 5.7" Rod and a 6.0" rod will create a 355 (nothing to do with stroke as the mount point is the difference).

I believe the difference is in piston travel speed?

If reusing stock pistons you'll be using a 5.7" (stock) rod.

My 355 shortblock has 6.0" scat i-beams pushing a set of Mahle power pak forged/coated pistons.

 

Yep, that's always my thought.

Mostly the longer rods reduce the mass of the pistons and therefore load the crank and rods less. There are other things going on in there, but it has little to anything to do with output or power production.

Bret

 

Rods are a handy thing to connect the piston to the crank. Don't worry 'bout side load,speed,"G's",ect. just put in there what fit's with your pistons.

 

Cool, that makes sense. Thanks all.
Who wants to reccomend some nice but not radical forged pistons, what brand and price if you happen to know?

Again no power adder, I just want somthing that is robust and I will swap a few HP to get that at an affordable price.

 

The Mahle's are a great complete bang for the buck.

 

SRP's are pretty cost effective.

 

A longer rod will give you less side loading on the cylinder walls, slower piston speed at TDC and BDC which is supposively a way of tricking the engine to stay at TDC longer allowing for more of the combustion process to happen at a constant volume.

 

I would assume that if there were any gains they would be microscopic. Right?

 

Thats really tough to say, Theroretically there is power to be had... I've never seen anyone ONLY change a rod and test the results.


Can you picture what I mean about reducing piston travel speed at TDC? That is important, or nice rather because you can have a longer time to burn at a constant volume. Something like 75% of the burn usually happens very close to TDC> As that piston moves further away from TDC the change in pressure falls off exponentially. This is all tough for me to put down in a post.

Another advantage to a longer rod is that because average piston speed must remain constant between two different rod lengths (average piston speed is determined by stroke, not rod lenght).. the piston speed at 90 ATDC is higher.. This is a good thing because you can actually induce better volumentric effiencies sometimes with higher piston speeds.

You want most of your burn to happen at constant pressure... This ensures your doing pumping work (row*dvolume/dtime) and if engergy doesn't go into pumping work it goes into heat. A way to do that is to keep the piston at TDC longer, or make the flame travel faster.

Flame travel speed, piston postion, and instantanous change in pressure brings me to another topic I've never really seen anyone go into.. and that is why pistons burn at leaner mixtures and how they can even burn at mixtures leaner than stoich when stoich is the hottest flame temp... I'll save that one for later.

 

BTW.. I dont' think I ever gave my opinion as to what you should do..


If I was you and on a budget I would go with an affordable, reputable fordged 30 over piston, recondition the stock rods with ARP rod bolts and reuse the stock crank.

I did this once for a build. The car ran lots of boost, make mid 500rwhp and is still together today. In fact the valve covers have been on the car for 3 years and the engine has been in the car for almost 4 now.