5K-C Head Gaskets For Race Use

[ATOYOTA]

I'm really curious, what sort of head gaskets are people putting on their worked up 5K's out there?

 

Reason being that I keep blowing the crappy graphite ones with my above average compression and I need something much stronger.

 

Are there any copper or 2/3 piece metal ones I can get WITHOUT having to go custom made? What are your recommendations for something strong that can handle a lot of revs?

Edited June 30, 2013 by ATOYOTA

[filfrederick]

In my opinion a weaker head-gasket is a good thing, a gasket is a lot easier and cheaper to replace than a piston or block.

the main reason for head-gasket failure is pre-detonation which makes cylinder pressures skyrocket, a shitty rubber o-ring could handle the pressure from a non firing cylinder(under 200psi) the firing pressure would be around 800-1000psi and if pre-detonation occurs it goes above 1500psi.

 

i raced that engine with a good tune many times running at full-load and full-rpm without any gasket issues, so i would get the tuning right and i would expect your problems to disappear.

without having a wideband o2 sensor and data-logger it is almost impossible to know if your tune is anywhere near right.

-Phil

[Taz_Rx]

I now won't use anything but genuine toyota head gaskets. They've held over 20 psi for me. Actually have one to scrape off the block still as they seal so well!

[altezzaclub]

i raced that engine

ohhh!! Fascinating! Did you buy the 4K twincam Riley, or is that another engine of Phil's??

 

So jealous....

 

What is the chance of a few more Kg on the torque wrench?? I assume you've checked for the bolts bottoming out and the threads are lubricated. A change to studs might allow for more torque for better sealing.

[philbey]

I run 11.5:1 or thereabouts on the standard ACl jobs. No problems. I had it dynoed so the tune is good.

 

I also support filfderricks comments, beefing the head gasket up isn't actually addressing the problem, it's really just sweeping the problem under the carpet.

Edited June 30, 2013 by philbey

[ATOYOTA]

Yeah, it has occurred to me that a stronger head gasket might push the problem further down the line, but it just seeme that I'm going through them far to quickly.

 

An O2 sensor is in order and has been on the list for some months now but I just haven't gotten around to it yet.

 

Could a lean mix be the cause of pre-detonation? I think it's the needle taper that's making it lean out at higher throttle positions but I'm not game enough to try altezzaclub's method of sanding them down. Not on four of the bastards anyway.

 

I got fresh head bolts last time and cleaned all the threads with carby cleaner, then used a dab of engine oil to lube them up before torquing. And yes, I snatched up the twinky. Just couldn't let something so incredibly awesome get away.

 

Cheers for the help guys, much appreciated. I still don't know how Phil puts up with all my annoying questions. I can just imagine him sitting at home minding his own business when *DING MESSAGE FROM RI-* "I swear to god if it's that Riley kid again I'm jumping out the window".

[ke70dave]

lean mixture could definatly cause detonation.

 

I would be getting the tune sorted out before touching anything else in the engine.

[altezzaclub]

Cheers for the help guys, much appreciated. I still don't know how Phil puts up with all my annoying questions. I can just imagine him sitting at home minding his own business when *DING MESSAGE FROM RI-* "I swear to god if it's that Riley kid again I'm jumping out the window".

LOL !

 

Run it richer this time, what the hell if it uses more fuel for a month or two. If it solves the detonation/head gasket problem you know what the trouble is.

 

Do those needles have a series of grooves at the top where you attach them?? If you move the clip down by one groove it richens the mixture right through the range, and if you're on the bottom groove get one cut just below it by someone with a lathe.

 

The O2 display will sort it out, I saw one for very cheap at some Chinese guage website over the weekend.

 

here it is- throw away $20..... get a couple of suitable exhaust sensors from the wrecker and you're away.

 

http://www.ebay.com/...d=290687426338

Edited July 1, 2013 by altezzaclub

[ke70dave]

where would you get a wide band sensor from a wrecker though?

 

you're probably better off buying a proper wide band guage and sensor with included brand new wide band o2 sensor.

 

http://www.ebay.com.au/itm/Innovate-3801-Motorsports-G2-Air-Fuel-Ratio-Gauge-plus-LC-1-Wide-Band-Kit-Tune-/151063094367?pt=Motors_Automotive_Tools&hash=item232c0fe45f

 

ive used that one before, works good. and you can plug it into a computer if you want to log it. (we used it on megasquirt ecu)

[ATOYOTA]

Phil recommended an Innovate sensor too; I'll probably get one of those.

 

I've switched to bigger main jets and raised the jet needle position to the highest, then spaced them out with a washer to get a little more height. The problem is that I've gone from 70mm velocity stacks to individual pod filters, so the carbies breathe a lot differently now.

 

I can't really tell if it's either really lean or really rich but it seemed to splutter a lot soooo rich maybe? Either way I'm not keen on running it for long. The plan is to replace the gasket, start it up to make sure it's running, then just trailer it to the carby tuners.

 

I just hope I've fixed the oil leaks once and for all. That's the problem when you combine high oil pressure with external oil feeds. WHICH REMINDS ME: How can I drop the oil pressure a little? I'm running HPR 10W-40 fully syn. and it peaks at ~80PSI at full noise. I've never shimmed an oil pump before so I don't know how to adjust it.

[altezzaclub]

You want a softer spring on the oil pump relief valve, the one we normally put a washer under to INCREASE the let-off pressure.

 

Sadly it means pulling the sump off so you can see the system where it bleeds off the pressure over the stock setting. It may have been shimmed already for higher pressure, so you can take that out if it has. Otherwise you either change the spring, make the housing longer, or do something farm-spec like trim the spring a little shorter.

 

You can see it here-

http://www.toyotapartsoverstock.com/showAssembly.aspx?ukey_assembly=525989&ukey_make=1060&ukey_model=15450&ukey_category=21646&ukey_trimLevel=18320

[philbey]

Forget the o2 sensor for now. Google how to read spark plugs and perform the most cursory check there is for lean mixtures. Spending 300 on a wideband is a luxury not a necessity right now. Thatgauge will still require a wide and sensor and the right controller. The wrecker won't have these.

 

Narrow band is probably less useful than reading your plugs.

 

A couple of key questions. Have you had it dyno tuned? What timing are you running? If you have pulled the head a couple of times, are you getting it planed? A warped head will kill gaskets

 

And lastly, have you identified the failure point on the gasket each time? Can be hard to do with a fresh blowout, but it would be important to see if it's in the same place each time.

 

 

[philbey]

Shortening the spring will increase the spring rate and still result in high oil pressure.

Edited July 2, 2013 by philbey

[altezzaclub]

Shortening the spring will increase the spring rate and still result in high oil pressure

 

It will increase the rate, but that is only with a situation like a car sitting on its suspension. In a fixed length tube like this shortening the spring will relieve the valve of pressure so it bleeds oil out earlier, and only stiffens up later when the spring is getting more compressed.

 

Really it delivers a different spring force curve, less at the bottom end, more at the top. Something to experiment with anyway.

 

Another thing to look at would be to drill the splitpin hole at 90degrees and as close to the end of the housing as possible. That would reduce pressure on the spring. A nice mod would be to cut a thread in there and have the spring base adjustable by winding it in or out. That would allow you to set the max oil pressure you wanted.

[ATOYOTA]

I know about spark plug reading, but simply getting an idea about it from the internet and then trying it for real only spells disaster.

 

The pump has already been shimmed, so I gather if I just grind a bit off the washer/shim under the relief valve that'll drop it a bit?

 

Seems like an awful amount of work just to take the oil pump out :S

 

And in answer to your questions: No it's never seen a dyno, I've pulled the head off a couple of times now and the first time Phil skimmed it for me because it'd slightly warped, and lastly, the first blow was between 1 & 2 whereas now #3 is down on compression and I *think* it's between 3 & 4. What do you mean when you ask what timing settings I have?