Porting Rb20 Head

[ORIGIN]

Hey guys just bought a rather large turbo for the old rb20, been thinking about pulling the head of and getting it ported lightly around the intake and exhaust ports, also heard something about ca18 valves being 1mm larger in diameter compared to rb20 ones depending on price would it be worth getting the valve seats ported/bored out 1mm to fit these, thats if they fit in without any other mods first or even if its true?

cheers guys

[battery]

whats it cost to get done?

[Roy]

Looking at Supertech cat i cant see how the CA18 valves fit, as they are different lengths (i had heard the same thing). So not convinced that the CA18 thing is true.

I am thinking about the same thing as with the strong dollar then some valves out of the US are not going to be that expensive. The question is will the small little combustion chamber allow for oversized (1mm) inlet and exhaust valves, or should we stick with just doing the exhaust side?????? Being such a small chamber, you can crowd the chamber too much with valves and end up going backwards after great expense

Its in these such cases that i wish i had an RB26 as porting on them would be a known qty vs RB20 heads

[ORIGIN]

no idea on price had no quotes done which would lead to my next question who knows what there doing with rb heads around brisbane, gold coast area?

never thought of that roy, yeah no one knows much about 20's but until i get my shed built there no room too build a 30 so im stuck with the 20 witch aint a bad thing if it becomes too much trouble i will just get some light porting around the inlet and exhaust ports but still dont know if that would be worth it?

[Roy]

Yes, i have read some good things about JHH in Brisbane for head work. They all seem to be very expensive, which isnt really the problem if they can guarantee the results or give you good feedback on what works and value...rathe rthen just take 2.5k from your wallet (+ the rest) to give you a head that may make 2% more power or possibly make it even laggier

[ORIGIN]

yeah cheers roy will track down there number and give them a call, not planning on spending 2.5k though lol if thats what it costs it can stay how it is just after a light port

[Roy]

Was thinking thats what its going to cost (min) if you go oversized valves and chamber work as well. For inlet and exhaust ports you seem to be able to get it cheaper... but thats where i would love meaningful feedback. On an RB20 do you get the most gains in the combustion chamber and bowl or on the ports, lol or both ?

[ORIGIN]

yeah would be interested too know that too... anyone got an idea?

[battery]

to be honest i think it is much more cost effective to just slap in an rb25...

i have just replaced my blown rb20 with a rb25 i bought for $1600 it is 15000k old from rebuild but if you get unopened ones they can be had for around 1k, the whole conversion cost me no more than 2k and was dead easy.

i gained a good 40kw and a bucket load of torque, most of this 40kw was due to the larger rb25 turbo but still the power delivery between a rb20 with a 25 turbo and the stock rb25 is very noticeable IMO.

this is abit OT but im just trying to find out how roy and the other rb20 fanatics justify investing buckets loads of $$$ into an inferior engine.

that said i did enjoy the rb20 and i think its a highly underrated engine, i would never replace a running rb20 with an rb25 because i was happy with the power and response of a stock turbo'ed rb20.

but i think if you are considering a turbo upgrade on a stock rb20 you should look at a rb25 conversion first.

just makes sense to me if you are considering rebuilds and even turbo upgrades to start with a better base engine especially seeing as rb25's are not much more expensive than the rb20 these days...

not having a go at you guys just wanna know your reasoning for staying with the rb20 or in roys case rb24's or whatever else hes planning for it

[ORIGIN]

got a 30 block sitting around just need a shed too build it up, until then staying with the 20, not spending heaps of coin on it as due to my trade i can do all the work myself witch is where i get most of my enjoyment, would love to build one up and see its limits but yeah not a millionaire so i know what you mean cant justiy the money either so just doin it bare essential style for now i can live it due too my roster only get too drive it once a week

[Roy]

Because RB25s are SHIT!

I have an RB26 at home and would use it before the RB25, but they both have the same problem. To do the conversion i would need to subject my car to an engineering inspection and there is no way it will pass, as whislt safe and well "engineered" too many bits are not legal. So no way i am going to go from 260rwkws and a pretty quick jigger, to a std 160-180rwkw RB25 for registration purposes only to then start again.

So thats part of it...the other is i simply dont believe an RB25 will make my car any easier to drive or any quicker. Perhaps i have jsut stumbled accross a good combination on my car but every RB25 pwoered R32 or RB30, whatever simply spin up into 3rd gear. So whats the point of 330rwkws when it comes with the sort of low rpm torque that simply overpowers the capability of the rear tyres and suspension. So put simply, i like the power delviery and 4,000rpm spread of power that my RB20 gives me.

Anyway, in 3-6 months we will see if i was right or not

[battery]

Because RB25s are SHIT!

I have an RB26 at home and would use it before the RB25, but they both have the same problem. To do the conversion i would need to subject my car to an engineering inspection and there is no way it will pass, as whislt safe and well "engineered" too many bits are not legal. So no way i am going to go from 260rwkws and a pretty quick jigger, to a std 160-180rwkw RB25 for registration purposes only to then start again.

So thats part of it...the other is i simply dont believe an RB25 will make my car any easier to drive or any quicker. Perhaps i have jsut stumbled accross a good combination on my car but every RB25 pwoered R32 or RB30, whatever simply spin up into 3rd gear. So whats the point of 330rwkws when it comes with the sort of low rpm torque that simply overpowers the capability of the rear tyres and suspension. So put simply, i like the power delviery and 4,000rpm spread of power that my RB20 gives me.

Anyway, in 3-6 months we will see if i was right or not

well the first excuse is valid i guess, still weak but valid.

second one is BS, if it wont make it any quicker to drive then how is an rb24 gonna make it quicker???

i do see your point with the wheel spin but i'd say this could be controlled with a good EBC like the jaycar IEBC.

[Roy]

Weak? I can go to town on my car with an RB20 and it never needs to be put in front of the authorities short of being pulled over and requested to do so. Yet put something with a non RB20 engine number in my car and all of a sudden the whole car gets called into question I have seen friends go through it and when servicing at rallies the guy who helps out is a CAMS and Snr Vic Roads guy so have a good understanding of what the expectation is...even if you can short change his expectations a little.

Re the RB24, i want to run my TD06-25G and on an RB20 will be a cop yet in Japan they seem to be very popular setups on RB24s and at the end of the day i am hoping for a reliable 300rwkws. Also, all the RB20 valve gear etc works with the RB25DE R32c head so still leaves me with plenty of options with regards to running the 26 bottom end, RB30 bottom end, my current exhaust manifold, plazmaman inlet manifold etc. A change to an RB25DET doesnt mean i can use all those parts

So, lol, not saying its for everybody...but i can justify it for my circumstances....and i do believe that i would be wiser to simply use 82mm pistons and a bump in compression to around 9.0:1 and stick with RB20 crank, std head etc. BUT, i want to see if the 25G can for shits and giggle and plenty of boost pull a wanker figure on the dyno

[ORIGIN]

back on topic anyone know wether its worth doing a little port job on20 head or money best spent elsewhere?

[scotty nm35]

Its nothing you cant do yourself with a die grinder, just remove the valves, clean up the casting marks, match port to the gasket size and then get the valves installed with re-seat.

Grab a stuffed head from somewhere and practice, after all it will only cost you time. Its not hard to see where to remove material to make flow improve, just got to make sure each runner is the same.

The way I see it, the more I can teach myself to do, the better. I wouldnt pay for that much labor unless I had to and it adds a personal touch to the car mods.

[_Ryan_]

.and i do believe that i would be wiser to simply use 82mm pistons and a bump in compression to around 9.0:1 and stick with RB20 crank, std head etc. but with GTR cams and adjustable cam gears and mild porting, over sized valves etc

could be interesting for someone after a more streetable RB20 IMO.

[Roy]

GTR cams dont work in an RB20 unless they are modified. Also, i am yet to be convinced about the oversized valves...i have some concerns....doesnt matter. I am hoping that using the choice RB20 from the factory solves the head problems

[_Ryan_]

GTR cams dont work in an RB20 unless they are modified. Also, i am yet to be convinced about the oversized valves...i have some concerns....doesnt matter. I am hoping that using the choice RB20 from the factory solves the head problems

I read the rest of the thread between our posts... seems only SK managed to fit them and get them working...