Squish Pads And Rb26 Heads

[bigmikespec]

Personally I would want a very good demonstrable reason to remove the quench pads from an RB26 head particularly one on a higher capacity block . My reason being the greater the engines capacity becomes the less the issue with chamber volume becomes . It gives you freedoms with piston crown designs because you don't need substantial raised sections on the piston crown to get the static CR up to a reasonable figure . Great lumps of aluminium have often been put on pistons because the CR took priority over extreme power potential . In an ideal world I'd like RB25 Neo sized chambers on a 26 head and more ideal piston crown design than R33 RB25s and all 26s have .

Sad fact of life is that the RB26 design is an escapee of the late 1980s and its showing its age .

This doesn't sound right... piston acceleration goes up with stroker engines as will squish velocity. More reason to spend time modifying (removing material) squish pads.

[XKLABA]

I suspect that when the power levels start to get really high, the need/want to reduce compression so as to enable more boost starts to win out over the real benefits supplied by decent squish design, and the pads just get thrown away. Engine still makes bulk power, courtesy of monster boost.

This, removing the pads was an easy way to lower compression so they could run more boost, technology and E85 changes that

[XKLABA]

My 26/30 has both pads untouched, I ran over the chambers with steel gause to remove any sharp edges and once milled to get desired chamber capacity i ran around the head with a small fine file to round off any sharp edges

I also use stock valves, if i had oversizd the valves i would have deshrouded them only

We have run 28psi from the GT-RSs and made 458kw at all 4, at 30psi it blow out the spark from to much backpressure

I wonder how much the rods stretches with more then 250psi pushing down on the piston on the compression stroke plus ignition before TDC

[Piggaz]

I spoke to the guy the guy that builds the Tilton Evo's engine the other day about this topic. He has seen one of the Gibson heads and they took both sides out. He also said that the way E85 burns changes alot of things and he recommended to leave both in. He has seen quite a few heads where the intake pad was chewed out/pitted from det. Maybe thats where the whole taking out the intake comes from?

Interesting to say the least.

[Gts-t]

Call up jhh engineering and see what they have to say pete, will certainly knows whats up.

Nismo do the inlet side on the z-tune but it may not be as hardcore as you want to go.

[jangles]

I spoke to the guy the guy that builds the Tilton Evo's engine the other day about this topic. He has seen one of the Gibson heads and they took both sides out. He also said that the way E85 burns changes alot of things and he recommended to leave both in. He has seen quite a few heads where the intake pad was chewed out/pitted from det. Maybe thats where the whole taking out the intake comes from?

Interesting to say the least.

I was under the impression that's the main reason the intake gets taken out.

[Aggroman]

old head was mad.. do same as old head and win again..

/thread closed

[BakemonoRicer]

Bump, interested to hear other peoples thoughts

I'll be taking out both quench pads on my SR head

[discopotato03]

I personally think if you had money to burn go all out on a 25 Neo Turbo head casting . Smallest chambers and better piston crown design .

Granted a bit harder to get 26 spec inlet manifolds on but at least the variable inlet cam timing is free . 

Correct me if I'm wrong but I don't think the RB 26 head castings changed much if at all from R32 in 1989 till the last of the R34s in what 2001 ? The piston crown design is quite basic - big decked plateau across the middle to get a barely acceptable static CR . 8.5 is really low by todays standards and a bit pathetic IMO with ethanol fuels . I seem to remember the GMS engines being more like 9.6:1 particularly with restrictors and later less boost . They were not slow by any means . I think the formula is smaller capacity chambers with a flatter piston crown design .

I reckon if Nissan had the money to develop the 26 right through the 90s it would have ended up more like a slightly stroked Neo 25T with the 26s externals and maybe bucket over shim valve train .

 

[Borci88]

^ Agreed with discopotato. Am an advocate for going 25 head as well.

I don't think there's really much point in taking out the squish pads, you would only start thinking about that in 800+hp drag cars and none of us are doing that... A lot of us are running E85 nowadays also so squish pads can stay in for that too.

[33GTRV]

Do some research on burn patterns in hemispherical chamber designs. In particular, spark plugs.  Once you get your head around that, come back and share your thoughts.

 

Head and porting is still a closely guarded topic, not secret by any means, but closely guarded. Ive seen very lightly modified heads, done so in strange areas, make huge amounts of power. Upwards of 2khp, but the principles remain the same, or at the very least, very similar between most engines.

[GTSBoy]

If I was o be modifying the combustion chamber of a 26 head it would be to put MORE squish in.