Maxpeeding rods

[5tox]

I decided that i was going to have to either buy a bloody expensive set of rods or the cheap ones as i was skeptical that all of the mid range priced rods were the chinese ones under a different name.

Well they arrived and i was extremely impressed with the quality and happy with my purchase until i tried the wrist pin which i was able to slide in easily by hand.... the only thing different is the bronze bush, do you reckon they are perhaps the 2.5 rods which have a bigger wrist pin??

Cheers steve

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[Graham]

sorry im lost, whats the issue? the pin should NOT be tight in the bush

[Forest_rallying]

I have a set of Pec 2.5 rods and Wossner pistons for the Duratec in the cupboard here. At the moment I can't measure the pins as my digital verniers are broken. If I can find someway of measuring them I'll let you know the size Steve.

After typing the above I have noticed Grahams comments, how loose are the pins in the bushes, are they sloppy or a nice slide in fit?

[Graham]

yes i should of qualified what i said, the pin should be able to slide in easily but not be really loose. you should have about half a thou clearance 0.0005" which to be honest will be really difficult for you to meassure. if you like you can always pop down with a rod and pin for me to "feel"

i assume your using pistons with circlips to retain the pins, steel rods are not manufactured for interference fit rods.

[5tox]

I see what ive done here, im trying to use bushed after market rods with original pistons.

I think what i need are aftermarket pistons with circlips.

The original dura pin is an interference fit in the rod

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[Graham]

I see what ive done here, im trying to use bushed after market rods with original pistons.

I think what i need are aftermarket pistons with circlips.

The original dura pin is an interference fit in the rod

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correct, possibly you could shorten the pins and modify the pistons to run circlips, TBH it would be far better just to get pistons to suit the rods which will fix the valve/piston clearance issues you will have if you fit cams

[5tox]

Yeah your right, using the 2.0 pistons is going to be more bother than its worth

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[Forest_rallying]

Why are you wanting to use std pistons with steel rods Stox?

The Duratec Wossner pistons I have here are Part no. P4 Dupec- HO160-89 bore 89mm, the weight is 319 grams and the pins are 21mm if that's any help.

[5tox]

I thought that the standard 2.0 pistons on a 2.3 engine would be a cheap way of raising the cr.
The original 2.3 pistons are domed to lower cr a bit like turbo pistons.
Ill take a look later when im home and see what you have

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[katana]

I thought that the standard 2.0 pistons on a 2.3 engine would be a cheap way of raising the cr.
The original 2.3 pistons are domed to lower cr a bit like turbo pistons.
Ill take a look later when im home and see what you have

How can a domed piston lower the CR - it intrudes into the chamber therefore raising the CR!

[Forest_rallying]

How can a domed piston lower the CR - it intrudes into the chamber therefore raising the CR!

Surely he means dished.

[5tox]

Yeah sorry wrong use of words, dished 😁

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[5tox]

Why are you wanting to use std pistons with steel rods Stox?

The Duratec Wossner pistons I have here are Part no. P4 Dupec- HO160-89 bore 89mm, the weight is 319 grams and the pins are 21mm if that's any help.

Whats the web address mate, i should know this but i have a memory like a sieve

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[Forest_rallying]

performanceenginecomponents.com

[3.5cologne]

If you really want to run the stock pistons, an option is to machine up some teflon buttons to fit into the gudgeons to retain them in place. Cheap and easy to do.

[5tox]

If you really want to run the stock pistons, an option is to machine up some teflon buttons to fit into the gudgeons to retain them in place. Cheap and easy to do.

Sounds very interesting, not something i had considered was even an option.
Im also weighting up the option of getting grooves machined into the pistons for circlips.

On one hand id love a proper set of aftermarket pistons but its a lot of money when the standard 2.0 pistons will give similar results for a fraction of the cost.

I think i need to do more research

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[Forest_rallying]

If you really want to run the stock pistons, an option is to machine up some teflon buttons to fit into the gudgeons to retain them in place. Cheap and easy to do.

We tried that method 30 years ago, the teflon buttons hold oil in the gudgeon pins and they also polish grooves in the bores so the piston rings don't bed in.

[Forest_rallying]

Sounds very interesting, not something i had considered was even an option.
Im also weighting up the option of getting grooves machined into the pistons for circlips.

On one hand id love a proper set of aftermarket pistons but its a lot of money when the standard 2.0 pistons will give similar results for a fraction of the cost.

I think i need to do more research

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How do you intend to machine pockets into std pistons for high overlap cams unless you intend to run stock ones?

[5tox]

Currently have the cosworth yd0859 and yd0860 so would deffinitely need valve cut outs.
Later looking to upgrade the the piper 285's which have even more lift

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[katana]

We tried that method 30 years ago, the teflon buttons hold oil in the gudgeon pins and they also polish grooves in the bores so the piston rings don't bed in.

That's a new one on me as teflon buttons are widely used for race bike engines - no one (that i've heard of) has reported grooving of bores from button use. Bikes mainly use fully floating pins and double the rpm's of most auto engines - the buttons have to be sized for the bore size and allow 0.5 - 1mm pin float so again not sure how oil is trapped?

[3.5cologne]

We tried that method 30 years ago, the teflon buttons hold oil in the gudgeon pins and they also polish grooves in the bores so the piston rings don't bed in.

LOL Yes it was about 30 years I last used that method. I had no issues with them that you describe. IIRC We put some slots into the side of the button that inserted into the gudgeon to relieve pressure and oil retention.

[Forest_rallying]

That's a new one on me as teflon buttons are widely used for race bike engines - no one (that i've heard of) has reported grooving of bores from button use. Bikes mainly use fully floating pins and double the rpm's of most auto engines - the buttons have to be sized for the bore size and allow 0.5 - 1mm pin float so again not sure how oil is trapped?

I am only informing people about our experiences and no one elses. The Buttons at the time were supplied by Dave Brookes Engines of Crewe.

[katana]

I am only informing people about our experiences and no one elses. The Buttons at the time were supplied by Dave Brookes Engines of Crewe.

And mine was to provide a balanced view. I don't doubt DBE expertise but as you say 30 yrs ago! Obviously with more modern 'slipper' type pistons buttons can't be used anyway.

We put some slots into the side of the button that inserted into the gudgeon to relieve pressure and oil retention.

Thats interesting about inserting into the pins - bike buttons don't, they sit between the pin and the bore and float independent of the pin. Approx 6 - 10mm long, I guess is why no oil is trapped

[Forest_rallying]

I recall the buttons were a taper fit into a tapered pin, once oil found its way into the pin the tapers would make a seal with expansion and hold oil in the pin. The pins would have to have been ground down on the pistons we used to have a straight button without the taper fitted. The pistons we were using were 93mm Cosworth Pinto forged ones that could only be bought via a Gentleman called Mr Reid in Ireland.