Exotic Piston/Rod Upgrade

[chimpvalet]

With build up of a Lotus 4V 4 cylinder in mind how would one wisely approach choosing pistons and rods? Looking at N/A street and track day usage, quite firm on parts remaining suitable for stock dimension crank. Details are: 3.75 inch bore, 5.5 inch rod length, 1.00 big end width and pin diameter, 2.00 pin diameter.

Thanks
Steve

[chimpvalet]

Correction: crankpin diameter 1.995 - 1.9985, bore size 3.751

[Mark O'Neal]

You either run the factory offering, which is probably reasonable sophisticated, or pick a custom manufacturer and send them a sample.

[englertracing]

With build up of a Lotus 4V 4 cylinder in mind how would one wisely approach choosing pistons and rods? Looking at N/A street and track day usage, quite firm on parts remaining suitable for stock dimension crank. Details are: 3.75 inch bore, 5.5 inch rod length, 1.00 big end width and pin diameter, 2.00 pin diameter.

Thanks
Steve

What are you trying to achieve?
Are you trying to spin it faster and feel good about it?
Adding compression?
Are there any known issues you are trying to resolve?

[chimpvalet]

Have to build an engine from 2 oldies, both with issues in need of repair, 1 a turbo w/ 7.5 CR and the other an N/A with 8.4 CR. Don't care to reuse the pistons/rings from either though the iron liner bores are expected to be in very good shape. The stock rods are stout but weigh something like 900 grams, bolts included.

I think CP-Cariilo have done pistons for at least 1 specialist in the UK, and I like to support the business but tough to swallow the cost after they go round trip - USA - UK - Canada. Also like what Autotec offer. So per Mark's suggestion would the piston guys take up the challenge of sourcing rods to match?

[Cubic_Cleveland]

Not sure what the engine application or even budget is, but have you looked at Arrow rods and Omega pistons?

[chimpvalet]

Street toy with occasional track day runs. Long trip reliability of course. We have 94 octane fuel readily available at pump throughout the region, looking at 11- 1 CR, max. Power peak 6500 - 7000.
Omega is likely a very good solution but may be near 1200 USD per set of 4. Similar high cost of rods out of UK where prices seem to match numerically, Pound - dollar.

[frnkeore]

I'm a old Formula Atlantic racer. In my day ('70's-'80's), we used Mahle pistons. I did have Arias make a custom set, for one of my engines. I'd think Mahle would have a spec piston, for your application.

Regarding the rods, for your rpm, I wouldn't worry to much about the rod weight but, you could take them to a machine shop and have them remove some weight from the beam area, leaving the WP and crank pin alone.

[KnightEngines]

I got a set of pistons for a lotus 907 from Ross years ago.

Stock rods are fine, fit ARP bolts, beam polish, shot peen & resize, good to go.

[Mark O'Neal]

Have to build an engine from 2 oldies, both with issues in need of repair, 1 a turbo w/ 7.5 CR and the other an N/A with 8.4 CR. Don't care to reuse the pistons/rings from either though the iron liner bores are expected to be in very good shape. The stock rods are stout but weigh something like 900 grams, bolts included.

I think CP-Cariilo have done pistons for at least 1 specialist in the UK, and I like to support the business but tough to swallow the cost after they go round trip - USA - UK - Canada. Also like what Autotec offer. So per Mark's suggestion would the piston guys take up the challenge of sourcing rods to match?

The ones that have rod companies also might. Mostly that's for idiots like me that specialize in doing this kind of stuff.

[englertracing]

most little engines dont use a rod that wide.
luckily for you a ford 2.3 does, and it used to be almost sort of common to grind the journal to form 2.047 to 2"
there are pre made rods that you can use and pretty cheap 400-500usd
the 5.7 length are particularly cheap if your piston guys can set you up with a tight ring package.
https://www.raceeng.com/p-24960-race-en ... 127-4.aspx
https://www.raceeng.com/p-25101-race-xl ... pecia.aspx
https://www.raceeng.com/c-6-race-engine ... -rods.aspx

your next cheapest option is to use customs from sanez

[chimpvalet]

Thanks, all
Looks like some leads I can follow up on as the program rolls ahead. Used to be we had machinists readily found for shot peening work though when I inquired a couple of years back the view was that cheap aftermarket rods had made the business redundant.