Matt75

Hey Mate,

3.820" bore size is 97mm so don't think it would fit would it?  I think the max is around 93mm for a pinto isn't it?

Look good though.

Woz, Let me see if I get this right.  The longer rod length of 5.7 would really only be suited to a screaming race engine with a port job to match the rod length and cam to match?

Cheers

Matt

 
Not that simple.  It's very hard to explain, so I'll try and be as simple as possible.
 
On my engines I use rods from std length to around 133mm.  I only use the std length rods in milder engines (up to 7000rpm constant), on "fast road/club race" style engines I use a 128.5 (cosworth) length rod, mainly because the are very cheap and very relaible, and on a "race/track only" engine I use up to 133mm.
 
The Pinto suffers from an inlet port that is already too big which makes it hard to maintain air speed.  By changing the rod length you alter the piston acceration rate which effects how the air is drawn into the cylinder.  Depending on how your cylinder head flows, and your cam profile works directly relates to piston acceration.  Decrease piston acceration you also decrease air speed at a given point.  A big port may require more piston acceleration to maintain air speed, and vice versa.  The valve lift required at a given piston position also comes into play.  You will get varied opinions on what works and what doesn't, but the key is matching the variables.  You could get varied combinations on all of the above with a similar result in power.  I am not an expert on every combination, but I know what works in my engines.
 
My advise to you would be that if you don't want to spend many hours and many dollars on developement work, machining, testing and trying different combinations to stick with a formula that works, the KISS theory (Keep It Simple Stupid!) 
From you postings you're not wanting to build an all out racer, just a reliable package that makes half decent power, which means you don't need to do developement work or try new things.  A package with cossy length rods, forged pistons, decent head and off the shelf cam, 45's and extractors with the time and money spent in the right areas will make 190+hp done properly.  Nothing special, just off the shelf items.
 
I have seen a number of Pinto stroker engines done and none of them have really grabbed my attention to be much, if any better than a standard stroke one done properly.  You're still stuck with the same size valves and head regardless of how many cubes you put underneath it.
 
Cheers
Woz

Matt75

Thanks for the in depth explanation.   That makes things a lot easier to understand

As you say, i don't want to reinvent the wheel but just get some ideas and opinions on what others have done and what has worked for them.

There are so many components that need to be matched to get the most of the whole package it is very hard for the untrained "backyarder" to sift through what is good info vs bad.

So, a YB length rod mated to some flat top forged pistons flush with the block is a good place to start and then go from there?

We really need to change the name of this thread to something more appropriate. 

Cheers

Matt


I like the sound of 190hp though!  

 
Cossy length rods and some forgies is a perfect place to start, simple to fit and excellent bang for buck
 
Woz

 
Matt
 
That is exactly what mine, Peter R and a few others have. The rods we used are SPOOL brand which you can buy complete with ARP bolts for around $600 online.  Pistons, get Woz to organise you a forged set which will no doubt be the same as ours. Whack a steel flywheel on the back and away you go. A strong reliable bottom end and then its over to the cylinder head to generate some HP.
 
G

Steel flywheel? Both!  You can machine weight out of a standard flywheel and in a straight road car will probably get away with it. The one in my yellow RS weighs only 5.5kg and has had pretty much all of the counter weight machined off the back but it doesnt get revved hard so the risk is low. In race applications a steel flywheel is much safer

Matt
 
Have you seen these on ebay?
 
http://www.ebay.com.au/it...mp;hash=item2ebe4c0dc0
 

Gdub

You can machine weight out of a standard flywheel and in a straight road car will probably get away with it. The one in my yellow RS weighs only 5.5kg and has had pretty much all of the counter weight machined off the back but it doesnt get revved hard so the risk is low.

With the counterweight machined off, the standard flywheel must be much stronger & safer than an original non lightened one. With the counterweright removed, there is less mass & thus less centrifugal force acting on the 'web' of the flywheel. Reducing the thickness of the web would be a worry though.
 
Cheers Gregg