explain headgasket sizing to me

[allwheeldrifter]

anyone?

[Dragon Humper]

You always want to run the tightest quench area possible if you have quench pads in your cumbustion chambers (which the RB26 has). The best case is to have the pistons just lightly kiss the pads at the max rpm that you will ever run (indicated by a very clean slightly shiny spot on the pads). However, that costs money in trying a thickness then tearing the motor down, then trying another thickness...etc.

Opening up the quench area is just asking for detination issues. 9to1 is not that high in an engine with such a small bore size.

A buddy of mine ran 18lbs of boost with no intercooler and no water/alcohol (even though the kit was already to go) on a 408ci V8 with 11.5to1 comp. and had zero issues on C16. His quench clearance was .040" (1 mm) at 7400 rpm which contributed to the ease of pulling off that feat. If he openend the quench up (much thicker head gaskets) to lower the comp. it would have been an issue even with the lower comp., it matters that much. I've seen it before on other builds WITHOUT power adders.


At 9000 rpm though, I would err on the stock side (1.5mm IIRC) to compensate for rod strech at that RPM.





Jon.

[bellis_GTR]

You always want to run the tightest quench area possible if you have quench pads in your cumbustion chambers (which the RB26 has). The best case is to have the pistons just lightly kiss the pads at the max rpm that you will ever run (indicated by a very clean slightly shiny spot on the pads). However, that costs money in trying a thickness then tearing the motor down, then trying another thickness...etc.

Opening up the quench area is just asking for detination issues. 9to1 is not that high in an engine with such a small bore size.

A buddy of mine ran 18lbs of boost with no intercooler and no water/alcohol (even though the kit was already to go) on a 408ci V8 with 11.5to1 comp. and had zero issues on C16. His quench clearance was .040" (1 mm) at 7400 rpm which contributed to the ease of pulling off that feat. If he openend the quench up (much thicker head gaskets) to lower the comp. it would have been an issue even with the lower comp., it matters that much. I've seen it before on other builds WITHOUT power adders.


At 9000 rpm though, I would err on the stock side (1.5mm IIRC) to compensate for rod strech at that RPM.





Jon.

Sorry to be OT but how can a turbocharged engine run with out an intercooler? Wouldn't it just be really hot air going in to the intake? How does this work?

Sorry if thats a stupid question.

[archaeic_bloke]

it is really stupid, but it still happens all the time (i see it mostly on hondas)

[cortexx]

Original 70's porsche 911 turbos had no intercoolers .

[Dragon Humper]

Lot's of vehicles never came with intercoolers (and the same amount with intercoolers that are so useless that it may as well not had one).

I personally ran my Omni with no intercooler at 18 psi and at 22 psi with water/meth on pump 94 (Husky FTMFW!!!!).


The 408 was run on C16, you can get away with ALOT on C16.




Jon.

[allwheeldrifter]

this might be a stupid question, but i work on cars and engines for a living, and i also asked the guys who build engines at my work, and we all dont know what "quench" is. we figured maybe its the "squish" but then the term "quench pads" doest make sense. ive already taken apart an rb26 head and dont remember seeing anything that would fit the "quench pad" description thx

[Shadao]

Original 70's porsche 911 turbos had no intercoolers .

they were also air cooled at the time...

[Skym]

From what I understand, squish/quench = same thing, different name.

I think they are talking about the squish/quench area around valves. From memory it looks like a pad in the middle of the 4x valves and talking about not removing metal from that area.

[Dragon Humper]

this might be a stupid question, but i work on cars and engines for a living, and i also asked the guys who build engines at my work, and we all dont know what "quench" is. we figured maybe its the "squish" but then the term "quench pads" doest make sense. ive already taken apart an rb26 head and dont remember seeing anything that would fit the "quench pad" description thx

Yikes.....really.......dude, this took like 10 seconds:

http://www.theoldone.com/archive/quench-area.htm

and that is just the first thing that popped up when I did a YAHOO search.



Squish is bantered about but is not the same thing it's a laymans term for compression, the quench pads are ment to cause radical turbulance in the combustion chamber to promote a controlled burn. The clearance is critical and you will bugger it up by adding a thicker gasket to try and lower the compression.

Like I said before, you want the piston to just lightly kiss the pad at the max RPM that your engine is capable of running (to compensate for rod stretch), that will make the combustion as efficient as possible. It's very critical if you can only run lower octane fuel like 91.




Jon.

[GTRADDICT]

Is there info on how much rods stretch vs. RPM on the rb26? If so, some good calculatons should go a long way for us 91 octane guys