hi all

just wondering if im going to rebulid my 20 with forged pistons is it worth while doing the rods too?

how much power can they handle?

my power goal is round as much as i can get lol

Cheers

standard rods can cope with around 400hp as so the crank.

oh so its worth doing then... wat can be done to the crank to strenthen it?

Cheers

You might aswell got pistsons and GTR crank/rods and spend a fortune on the head to get it flowing...

(or get an RB25 and do that, better base, less issues)

If your going past the "limit" of stock rods or pushing above 300rwkw your going into big turbo land... which on the RB20 isnt friendly for driving at all, even racing with it would be interesting given it will do nothing in 1st and 2nd at all

Yeh alot of people have said that they will handle 400 to 450HP, I don't know how much true experiences are out their. I'd like to know if the Bathurst units ran STOCK rods, if so thats a 475HP engine.

To me, if they are prepared well they should be able to handle 90HP each, just not sure how long for . They are a great shaped conrod, a better shape than larger capacity RB sixes.

Same with the crankshaft. It will handle more horsepower than you could breathe through an RB20. I think even the main journal sizes are all the same for RB20,25,26,30. Tough stuff.

Cheers

look at it this way 400hp is like 300kw which in my mind is a decent amound of hp for an rb20, but u also gota remember at it not all about power, u'd want sumthin that is suitable to drive daily, that has a good tourqe an power curve through the rev range, nice an responsive, thats pulls up well handles well etc..

Edited June 25, 200620 yr by HR32_GTS-T

400hp is more like 300 kw not 500

What a crock. The RB bottom end is no stronger in an RB25...in fact the RB20 has a stronger block. The crank is the same strength and the rods are stronger in the 20 than the 25. Why does everyone think the RB25 is such a special animal. Just because the head flows shiteloads more.

You can expect the rods and crank to go AWOL at around 450-500rwkw. As long as everything else is setup well enough. As I say to everyone who asks me this same question, a chain is only as strong as it's weakest link....for ALL RB's, this is fuel delivery and oil control. Make sure your fuel system is an overkill and read SydneyKid's writeup on oil control in the Forced Induction section.

You can expect the rods and crank to go AWOL at around 450-500rwkw. As long as everything else is setup well enough.

I dont doubt that a std RB20 bottom end is a good thing, and on merit the crank, rods and big end bearings etc should be more durable then the R35/26/30 etc. But to say the rods are ok for 400rwkws...i would be very worried about the boost and revs needed to make that power.

Word is the Grp A R31s and their RB20s used std prepped rods. I asked a guy that has two genuine GMS engines, one recently rebuilt and he said for my RB20 i would be wasting my money if i went for aftermarked rods. So im still not positive they ran std rods, but most likely did...as my RB20 is making about 400hp and not that far behind in out right numbers then his engine...

The only reason why i got rods for my new engine is according to the scales they are lighter, and im hoping they cant be any weaker, adn they come with good rod bolts...Things im hoping to make the little girl that little bit more reliable at 8,600rpm

There have not been too many ppl to even crack 300rwkws with an RB20, and i have never heard from anyone that has done it for over 6 months and 10,000kms of real use. So not saying they can or cant, just wondering how you came up with those numbers.

My thoughts on the strength of the bottom end, keep boost under 20psi, revs under 7,800rpm and whatever power your thing is making, i think it will do so pretty reliably.

Can you tell me the difference in pin height of the RB20 piston and RB26? There are plenty of cheap R32 GTR cranks around due to their being no love for their oil drive. I wonder how running thre std RB20 bore with the longer stroke crank and GTR rods would go in a little RB20?

I dont doubt that a std RB20 bottom end is a good thing, and on merit the crank, rods and big end bearings etc should be more durable then the R35/26/30 etc. But to say the rods are ok for 400rwkws...i would be very worried about the boost and revs needed to make that power.

Word is the Grp A R31s and their RB20s used std prepped rods. I asked a guy that has two genuine GMS engines, one recently rebuilt and he said for my RB20 i would be wasting my money if i went for aftermarked rods. So im still not positive they ran std rods, but most likely did...as my RB20 is making about 400hp and not that far behind in out right numbers then his engine...

The only reason why i got rods for my new engine is according to the scales they are lighter, and im hoping they cant be any weaker, adn they come with good rod bolts...Things im hoping to make the little girl that little bit more reliable at 8,600rpm

There have not been too many ppl to even crack 300rwkws with an RB20, and i have never heard from anyone that has done it for over 6 months and 10,000kms of real use. So not saying they can or cant, just wondering how you came up with those numbers.

My thoughts on the strength of the bottom end, keep boost under 20psi, revs under 7,800rpm and whatever power your thing is making, i think it will do so pretty reliably.

Can you tell me the difference in pin height of the RB30 piston and RB26? There are plenty of cheap R32 GTR cranks around due to their being no love for their oil drive. I wonder how running thre std RB30 bore with the longer stroke crank and GTR rods would go in a little RB20?

The standard pistons let go a bit earlier than that, I wouldn't trust them past 300rwkw but the rods are definately good for that amount. It's a matter of getting it to run smoothly at that figure though. Just because they break at that point is not an indication of how much you can get to safely.

Of course if you're nearing 400rwkw you would change them regardless. Not only for strength but for their weight difference.

Yeh pistons are a given...though again i suspect the RB20 pistons are at the stronger end of the std RB piston thing. But original poster was going to throw pistons at the engine...

About 12 months ago i priced up a lot of gear from Tomei, basically 10.25mm lift cams, solid lifter conversion, springs etc. All up including cams it was just inder 3k, so inlcuding the price of a spare head, rebuild and some porting...i wonder how much difference a 5k RB20 head would make to an RB20.

Its very expensive...and on an RB25/26 dead money for the gains you will make...but an RB20?

I think from the factory the RB20 has the basic strength sorted, just lacks some of the good bits to make good power. So rather then spend money on rods, pistons etc, i think if its a live and running, then any money spent is best spent on things that will make better power, like cams, better exhaust manifold, headwork etc.

...and of course the gearbox behind thenm isnt as durable either so consider what you do up front with regards to power may end up needign something done to what hangs off them

400hp is more like 300 kw not 500

sorry mate i was supposed to divide the hp not times it. an yes ur rite 298.5hp

Like Roy said, their is not too many people that have cracked over 300rwkw for an RB20DET.

Like I said earlier, the bottom ends should handle more horsepower than you could get the RB20 to breath in air!

I'll find out before too long once my drag racer is running, cause I'm only going to use stock conrods and crankshafts in it.

cheers