Boring out an F4R (2.2L)?

[Andyman]

Can go to 84mm bore from 82.7mm. Done loads of them. Seems to be around 5bhp difference between stock size bores on high comp and oversized. Worth boring out if you're already buying forged pistons, but not otherwise

Only 5 bhp difference on average going high comp and oversize ?

 

[Chip-mk1]

Only 5 bhp difference on average going high comp and oversize ?

He obviously means both as high comp mate, he just didnt write it very clearly.
Quite a difficult thing to put a figure to in the case of the F4R though when seemingly very similar engines make different power outputs anyway.

 

[ben_r1]

Makes for an interesting read at 6am Saturday morning lol.

 

[Andyman]

He obviously means both as high comp mate, he just didnt write it very clearly.
Quite a difficult thing to put a figure to in the case of the F4R though when seemingly very similar engines make different power outputs anyway.

Reading fail on my part, it was late haha

What kind of average gains would you expect going high compression on stock sized pistons?

 

[Chip-mk1]

Reading fail on my part, it was late haha

What kind of average gains would you expect going high compression on stock sized pistons?

That depends on the cams you are running, the hotter the cams the larger the gains that you will see.

Take a totally standard car and fit high comps and remap and the gains will be relatively modest, but if you have really lairy cams and are revving to 8K then you could easily see upwards of a dozen horses.

In fact I bet if you took one of the 240bhp engines that Fred@BTM mentioned earlier in this thread and dropped the CR back to standard I bet it wouldnt even make 220bhp but obviously no one ever builds an engine to that spec on standard pistons as it would be so pointless so I doubt you'll find an exact figure from anywhere.

 

[Andyman]

What high comp bore size would you opt for given piston prices are the same between bores:

83 or 84mm ?

 

[Chip-mk1]

Even at 84mm the blocks are still not prone to cracking, so unless its for absolutely ridiculous turbo power, I'd go straight to that.

 

[Andyman]

Thanks Chip - The only other mods are really cams and headwork so won't be big power. Loosing oil so just rebuilding a whole bottom end.

Would you recommend ACL bearings throughout or stick with Renault stock shells ?

 

[Jonny1*2]

ACL big end would be a good idea. ARP bolts etc. Do you need a block. My old 182 one would be ideal for it. Needs a rebore.

 

[Andyman]

Yeah was going to go ACL on the big ends but not sure about the mains whether its a bit overkill? Yeah ARP essential on the rods

Did you get your Wossners fitted Jonny? Read elsewhere on here you were in the process of getting them done

 

[Chip-mk1]

Thanks Chip - The only other mods are really cams and headwork so won't be big power. Loosing oil so just rebuilding a whole bottom end.

Would you recommend ACL bearings throughout or stick with Renault stock shells ?

I think you will have no problem with either of those bearings, just avoid cheap auto factor ones.

 

[Jonny1*2]

Yeah was going to go ACL on the big ends but not sure about the mains whether its a bit overkill? Yeah ARP essential on the rods

Did you get your Wossners fitted Jonny? Read elsewhere on here you were in the process of getting them done

Iirc it's only my big end which is acl. Standards will be fine for the main ones. Yes Wosners fitted mate

 

[Dan519]

FYI, ACL are a good quality manufacturer of standard parts of course you may be referring to their RACE brand

 

[Jonny1*2]

True Danny. Do forget that

 

[Andyman]

FYI, ACL are a good quality manufacturer of standard parts of course you may be referring to their RACE brand

Do you mean the stock Renault ones are unbranded ACL items in the way that Gates make Renault belts?

 

[Jonny1*2]

i think he means that ACL supply OE spec ones, an alternative option to renault.

 

[Chip-mk1]

ACL sell decent quality replacement bearings, these would be a good idea for most people on here building a clio engine, or mahle, or genuine renault, but ACL also sell a "race" range, the race range generally are best avoided for road cars IMHO, they arent as durable as the top layer is very thin and the barrier layer beneath it is not a low friction material so once the top layer gets marked they can quite quickly damage the crank, although on the plus side they are capable of withstanding a much higher load in the first place without deforming hence their suitability to race engines.
So basically like most "race" products they are suitable for high load short duration use rather than for thousands of cold starts etc. Also if your crank is slightly deformed the race bearings are less able to cope with wider tolerances.

F4rs dont typically suffer from bearing failure unless there is some significant oil pressure problem on the engine, so there is no need to "upgrade" the bearing material in the first place unless you are building a really monster spec motor that isnt planning on doing many miles.

Good quality standard spec bearings are generally the answer for 99% of engines that people on here are likely to build IMHO

 

[Andyman]

Yeah i wasn't wanting to go down the race version route. Stock Renault or standard replacement will do me fine.

One of the mains bearings had a substantial groove marked in it but luckily the crank its self escaped damage.