12 replies to this topic

[edjohnson]

When i get a rebore, which pistons shall i go for, on a reasonably tight budget, but dont want to buy some poo and replace it later

so id rather buy better ones now if you think i should

any one got an opinion on the best piston and ring set?

gonna be used with a stage 3 head, 276 cam

cheers

ed

[fikus01]

hmm, if a standard piston copes with 100bhp@the flywheel (which it will) even standard rover ones will be fine, have no doubt omega ones or better may have better materials, may be lighter but with a 276 cam @ stg 3 head you're not pushing the capabilities of the engine too far so the piston cataloge is your oyster really!! powermax arent too expensive. have a search thru minispares and see what they have

[Guess-Works.com]

depends on your eventual aim and application.

For a budget build and a fairly adequate motor 21251's are perfectly acceptable, yes they are know as chocolate pistons, but that's because they are not being used for the right application.... They are basically a std piston, nothing special so won't do anything special...

Then you have 21250's which are just a higher cr version of the 21251...

21253's are the best of the series, and coupled with a good head and decent engine will serve you well...

I've ran all three of the above pistons in the same engine, and never had a problem with any of them, but as the performance requirement has gone up, so has the piston price...

Never used the Powermax piston (thought they were only available in 73.5mm)... maybe you mean the Minispares MEGA piston... never used them either.. but @ 60 quid a piston, total you're only a few quid off omega's

which are next on my shopping list.

[fikus01]

hmm, well they came in my engine from <swear word> mini"monkey"speed. its since been rebuilt by a knowledgable person! was a fair few years ago tho!! maybe 5 years!!

[edjohnson]

now i know this may sound dat, but how do i know if i want high or low comp pistons??

My intention is to have a fun, quick, hopefuly reliable engine, that can cope with me doing some long distance drives, and playing about too

cheers

ed

[Jordie]

high comp (actual compression ratio will depend on head chamber, bore size, piston dish etc)

low comp for turbo engines

These should be fine - http://www.minispare....aspx?pid=37864

Ive got the same pistons in +60thou in my 1330 build.

Edited by Jordie, 20 January 2007 - 11:16 PM.

[edjohnson]

oh cool

they look like he ones id want then

take it the price includes rings?

and id use my old standard rods?

cheers

ed

[Jordie]

Price inc rings and guideon pin.

Remove your old piston from the rod. Put the new one's on.

Theres a guide in the FAQ Section for fitting new pistons to the rods >>>> http://www.theminifo...?showtopic=9199

Not sure whats the best way to remove tho, one of the mini docs will know.

[Guess-Works.com]

The compression also affects the type of fuel you need to some extent... The higher the compression the higher the octane fuel required to prevent pre-detonation ( aka pinking )

[Jordie]

Aha. Just the man. Can you lend some of your worldly wisdom to ed on how to remove a old piston from a conrod? I think it would make a good FAQ too

[edjohnson]

ill get the my old man on the job when it comes to doing the changeover, he's pretty good at that kinda stuff, but neitehr of us really have a clue which bits are best, he's more into his tractors, classic renaults, and lotus escorts.

Im probably gonna run the car on shell optimax or whatever they call it now.

Or proper four star, theres a bloke down the road that sells it.

The Other thing is, i dunno if the will require having any thing being taken off, its flat, but i dunno if the CR could do with being raised, whats the best way to look at this?

ed

[fikus01]

this is also in the part of piston selection, you really need to work out the cc of the head chambers, and pistons and then work out your compression ratio, for a road car really dont go above 10.5:1 if what u have now is below that (9.75:1 or so) then by all means skim off 20 thou or so and see how it comes up after that!

Edited by fikus01, 22 January 2007 - 02:20 AM.

[edjohnson]

I have no idea what cc my chambers are

its a second hand "stage 3" head from a very nice chap on here

any easy calculation?
or shall i just take it to a tuning specialist and ask them what they reckon to the head?

ed