OEM Main Bearings vs Race Main Bearings

[TheCAB]

Hi,

Just building a high spec n/a F4R 172 engine for sprint competition use.

In then past I have followed the school of thought of using race standard big end bearings and Renault OEM tanged main bearings which have always been fine with no issues arising.

Race mains give a bigger crank to bearing surface clearance so can adversely affect oil pressure, Clio oil pressure not brilliant to begin with. Bigger mains clearance will give less frictional forces so a plus maybe. Race mains are a stronger bearing but is deformation on main bearings in Clio block such an issue?

Not a question of cost at all, more fitment for purpose as average sprint runs are circa 60 seconds so engine not under as much load (period of time wise) as a circuit racing one, although I appreciate mains are subject to both rotational under inertia forces, oscillating forces and associated heat cycling.

Thoughts from you competition engine builders out there as to what bearings you use much appreciated.

Cheers

 

[NorthloopCup]

My personal preference is to run with a good quality standard bearing, such as Mahle.

Reason being that they’re a bit more forgiving than a full on race bearing.

Also, clios suffer with piss poor oil pressure, so here’s a few things that in my opinion, are a must have/do:

Oil pump tolerances closed up to improve efficiency.
Oil squirt jets replaced with new or deleted - they’re not that important anyway. Oil haemorrahe
Block checked for straightness - line bore if required.
Restrictor in the block oil feed to the cylinder head.
Camshaft journals checked - they haemorrhage oil pressure in this area as well.
Delete the vvt solenoid if you’re going that high on the build spec.

Also important - fully warm the engine and transmission before a spanking.

 

[TheCAB]

Thanks for the swift reply.

Have used oil pump that I modified the pressure relief valve on in the past with good results pressure wise, will strip and check tolerances as well.
Oil squirt jets have been removed / binned and I will fit new ones.
Block was honed and checked out ok for straightness by machine shop. I just need to alter block to accept tanged mains.
Any info on oil feed restrictor for block much appreciated.
Cylinder head is a brand new modified 197 one so bearing journals are all good.
VVT delete cams being fitted as part of build, I also have a machined up "plug" with o rings fitted ready for the solenoid in head socket

Once again many thanks for the benefit of your experience, I find it always good to seek advice when necessary from people "in the know" as costly errors can help be avoided and also confirm or otherwise the build path I am going down is ok.


Cheers.

 

[NorthloopCup]

Thanks for the swift reply.

Have used oil pump that I modified the pressure relief valve on in the past with good results pressure wise, will strip and check tolerances as well.
Oil squirt jets have been removed / binned and I will fit new ones.
Block was honed and checked out ok for straightness by machine shop. I just need to alter block to accept tanged mains.
Any info on oil feed restrictor for block much appreciated.
Cylinder head is a brand new modified 197 one so bearing journals are all good.
VVT delete cams being fitted as part of build, I also have a machined up "plug" with o rings fitted ready for the solenoid in head socket

Once again many thanks for the benefit of your experience, I find it always good to seek advice when necessary from people "in the know" as costly errors can help be avoided and also confirm or otherwise the build path I am going down is ok.


Cheers.

No problem.

If you’re running a 197 head, you won’t need a restrictor as the vvt oil feeds are different to the 1*2 head.

 

[TheCAB]

No problem.

If you’re running a 197 head, you won’t need a restrictor as the vvt oil feeds are different to the 1*2 head.

Cheers

 

[fordy51]

Hi all

So im building a 172 block based turbo engine for my 5 gt turbo so i can retain the jb/jc gearbox for now and doing research on the block build

northloop,
how are you tightening oil pump tolerances?
Pressure relief valve..do you shim them? We used 1mm shims in the 5 gtt pumps
Is the renault oil pump the only good one to get or will a marelli pump suit/same

Will be using mahle or renault bearings had good luck with them in current forge build