HKS 2mm head gasket

[conedodger]

Anyone use these? Experience? Problems?

[jmortensen]

Moves the piston too far away from the head, killing whatever quench you may have had.

[conedodger]

Thanks Jon, So, if I use the P90 head on this engine build, I will have somewhere in the range of 8.5:1 which I imagine is ok. If I use the my E31, I will be somewhere in the 10:1 range which without a pretty big cam is going to be too much for pump gas.

[madkaw]

The 2mm gasket will be self defeating.

Altering the squish will be just as bad if not worse than running 10 to 1.

I would unshroud that e31 to it's limits and smooth out the chambers as much as possible.

I guess it depends on what octane you can get where your at, I would think with a decent cam and premium your would be fine. I'm running 9.55 and timing is not an issue. I would think the smaller chambers on the e-31 would also help dter detonation if properly prepared. IMHO

Edited March 20, 2013 by madkaw

[jmortensen]

I ran an E31/L28 combo with ~11:1 compression and wasn't happy with it because it needed 95 or 96 octane to keep from pinging. I think some of that is CA's crap fuel, but I had unshrouded the valves, had ground off the extra spark plug threads, etc. in an attempt to stop the ping. My options were to go bigger on the cam (already had .490/280 cam in there), modify the chambers more, or do a custom piston. After considering those options, I ended up with a V8 that should make 400bhp on 87 octane.

If it were my build to do and I had the option of the E31 or the P90, I'd do the old shave and shim trick on the P90 and just like Steve said, get it to ~9.5:1 compression. That P90 has a great chamber compared to the E31, and 9.5 is a nice CR as you can avoid the detonation and still run all the timing you want with pump gas. If you do go with the E31, go BIG on the cam if you want it to run on pump gas. As I mentioned to you on FB, Sunbelt has those cool single spring cams and Rebello has some pretty big cams too.

[madkaw]

So what block and pistons are being used in this combo?

[madkaw]

http://forums.hybridz.org/topic/85907-attn-flat-top-28-with-e31n42-head-guys/

This is a pretty good read. Googling this brought up several discussions.

Seems like 9.5- 10 is where you want to be however you get there.

My car slightly pings at 38 full advance, but the dyno showed the same power at 34- so I didn't need all that advance anyway. Maybe because the smaller piston / combustion area of the L24?

[Lazeum]

Using head gasket thickness as a variable for compression ratio is a bad idea. you will alter the quench if any.

When I've rebuilt my engine last year, I've faced the same exact situation. I've measured everything so many times to get it right...

I ended up disassembling everything to get the pistons machined to match proper clearance.

Engine has been designed with Braap from HybridZ & Rebello. I'm running a CR 9.0 with a P79 & a street Rebello cam. The engine is very nice! A lot of torque from 3000rpm up to 5000rpm. I haven't been able to go above efficiently; I was breaking the engine in + chokes in my DCOE's are too small (32mm)

=> the link to the thread on hbz

[conedodger]

Turning in to a pretty good discussion...

Some background. I started with a F54 turbo motor out of an 82. The car was an automatic so I am certain that it had never been over-revved. When I got it apart, I discover that there is no ridge in the bore and it still has great crosshatching. Probably didn't need a rebuild. I sold off all of the turbo goodies to someone in Puerto Rico on Ebay but still have the head, the block, pistons, rods, and crank. The plan for the bottom end is to sell the pistons to someone who wants to do a turbo build, as I said, everything is in really good shape so they should just need a clean up and new rings. I purchased new ITM pistons in STD size. I am told that these are the pistons the ITS guys are using. I also have ARP rod, main, and cylinder head bolts/studs. Now, if I were building a motor for one of my Porsches, I would have the rotating mass cryo-treated and bearings and piston tops coated. Not sure what Datsun builders do. The last L6 I built turned out really well without it with just balancing, lightened flywheel and a MSA 'Autocross' cam.

Most of my Porsche builds land just south of 9.5:1 and run well on unleaded 91 octane pump gas. As long as I brought up the flywheel, I kept the turbo flywheel and will be having it lightened.

I'm really only struggling with what to do with the top end. The E31 on the car came from the original owner (I am the second owner) with the E31 and lots of documentation for a build done in 1999. The head documentation is from BC Geralomy. It's hard to tell what was done but when I lived in Minnesota and was in to Datsuns, BC Geralomy was the go-to for cylinder heads. I am leaning toward the P90. Also struggling with induction. My good friend and professional Porsche engine builder suggests microsquirt and I would be ok with that but where we don't agree is that he wants me to get a Datsun EFI intake and go with a single TB and MAF. I would lean toward triple twin throat TB even knowing they would be more difficult to tune. If I didn't go with EFI, I would keep the triple Webers that are on it now or sell them and replace them with new 45DCOE 152's.

I have some studying to do obviously. Thanks for the links and thoughts. Jon, as always, I respect your knowledge and it will weigh heavily on my decisions...

[madkaw]

Sounds like you are at a crossroads. I would get that e-31 checked out as far as cc and what valves are in there.

The new pistons are flattops?

You could try the e-31 first since it's redone and see how you make out. I would see how much CC you can get out the combustion chamber to keep CR at the minimum. Then you can do a direct comparison for all of us between the e-31 and p-90.

[Lazeum]

A friend is running a 3.2L combo from Rebello with E31 head. The combustion chambers look quite normal and he's pushing 320hp at the crank on Rebello dyno. It demonstrates somehow the head is capable.