Rb20det Head Port Size Differences

[sav man]

A guy I know got his head ported, then blew his engine. he got a new head and found that the factory ports were bigger than is port job (the casting marks were still on the ports). The first head had L1 cast above the exhaust, at the front of the engine. The second head had L2 cast on it. Looking over a few different cars we've worked out they go upto a L6.

Does anyone know what the go is, do they get bigger each number? what does the L1 - L6 signify, i havn't been able to find anything on fast about it. don't think my mates will be keen on me ripping all their heads off to find out.

Thanks

[nIsMo86]

Very interesting. I have never heard of this. Any RB20 nuts know about this?

[SLAPS]

Sure its an RB20 head?

My R32 RB25DE from memory has L6 stamped in. Ports are quite a bit bigger as well as the combustion chamber (obviously) and valves.

Grab some measurements will be interesting to see.

I'll double check my pics and the measurements I took. From memory the RB25DE head was ~4.5-5mm wider so 10mm overall compared to the old 1992 RB20DET head.

When talking to nissan regarding inlet gaskets there was only 1 gasket for the 20 and 1 for the r32 rb25 of which was fairly rare understandably.

Externally unless u have a keen eye for the valve and combustion chamber size (most noticeable is the quench areas of the rb25) the R32 RB25DE head looks identical to that of an RB20DET.

The RB20 head has next to no quench pads in comparison to the r32 25 head.

Edited June 9, 2009 by SLAPS

[Cartman]

wouldnt suprise me as i ran into a problem with the tomei solid lifter kit a while ago as it only works with some castings of the rb25 head apprently.

[R31Nismoid]

you talking RB25 vs NEO 25?

Anyhow Ben - there are at LEAST 3 series of heads i know of.

RB20 NICS

RB20 ECCS REDv1 (different CAS to V2)

RB20 ECCS REDv2

RB20 ECCS SILVER

They all had varying electronics/sensors across the models the earlier two different intake setups.

Could well be someone's grabbed a red-top head perhaps as it was cheaper. Without knowing full car history its very plausible - only issue is are they direct bolt-on interchangeable... if so then could be a certainty, if not it perhaps opens up a further can of worms

[SLAPS]

Good point. I completely forgot about the old redtops and NICS.

In my post I was referring to the Silver tops

[sav man]

my mate has a rb25de, the head has a completly different number cast on it. They are sure it's a silvertop rb20. I wondered if the redtop rb20det-r (gts-r engine) had different ports. the old L1(small) head is off the engine, and I'm going to have a look at it and get details on it soon. But the owner is 100% possitive that the orginal (L1 small) head and new (L2 big) head are both silver tops. Cause a few of us have asked that question.

Be interested to see if anyone has any unported silver top rb20 heads laying round to compare.

Was the R32 RB20 ever raced, cause anther theory was it was a homligation/cheater special. I know Subaru got EJ25 blocks cast to look like EJ20's for the factory sti rally cars (a local bought a ex crocker car, and couldn't get ej20 head gasket to fit, ony a ej25 would fit).

Edited June 9, 2009 by sav man

[SLAPS]

The secrets out... Troy is so quick because he must be running one of those R32 homligation/cheater special rb20's

I'll check my photo's when I get home see if i can grab one with the head cast numbers.

Edited June 9, 2009 by SLAPS

[GT-RZ]

i'v got an rb20det silver top sitting in a tyre. says 73L 5 above the exhaust. i can measure them if you like.

Edit

43mm wide 32mm high rounded to nearest mm.

what does the 73 stand for? 43+32 =75 which is very close to my width/height measurments.

Edited June 9, 2009 by GT-RZ

[Roy]

LOL, i do have the ultimate RB20 spec'd up. Have to decide that or big cube yank donk

[R31Nismoid]

my mate has a rb25de, the head has a completly different number cast on it. They are sure it's a silvertop rb20. I wondered if the redtop rb20det-r (gts-r engine) had different ports. the old L1(small) head is off the engine, and I'm going to have a look at it and get details on it soon. But the owner is 100% possitive that the orginal (L1 small) head and new (L2 big) head are both silver tops. Cause a few of us have asked that question.

Be interested to see if anyone has any unported silver top rb20 heads laying round to compare.

Was the R32 RB20 ever raced, cause anther theory was it was a homligation/cheater special. I know Subaru got EJ25 blocks cast to look like EJ20's for the factory sti rally cars (a local bought a ex crocker car, and couldn't get ej20 head gasket to fit, ony a ej25 would fit).

GTS-R was nothing special, perhaps cams, that it. No 100% answer.

Still though, how do they know 100% its a silvertop?

[GT-RZ]

i cant imadgine the ports to be different sizes imo. more like a batch number. but would be cool to have some comparisons.

[N1GTR]

LOL, i do have the ultimate RB20 spec'd up. Have to decide that or big cube yank donk

RB30 mate

Join the revolution

[Roy]

RB30s are shit for track GTSt Too small to go NA, too big for turbo as the torqe torches tyres

[SLAPS]

LOL that didn't take long for a bite.

Checked out a few pics of my old RB20.

She has L7 on the head. I did notice the inlet ports had what looked like some sort of sprayed on rough coating of which was not on my Rb25DE head.

Hard to tell from the pic but it definitely looked sprayed on.

For reference - I've attached a pic of the RB20L7 inlet manifold port with the rb25de gasket sitting over the top. The RB25de ports are ~5mm wider each side.

Edited June 10, 2009 by SLAPS

[sav man]

GTS-R was nothing special, perhaps cams, that it. No 100% answer.

Still though, how do they know 100% its a silvertop?

don't know, but i'll getting a look at the head soon, so i'll get some pics then.

there might just be a batch of special rb20 heads for all we know. Might also be noting.

Be nice to get some measuments to compare