www.ka-t.org

So one of the BIGGEST issues facing our KA-T community when pushing to high horse power is head gaskets blowing, pushing coolant, then comes the air pockets and you struggle to even make it 5 miles down the road when these things happen. I know it happens to almost all the KA-T guys but a lot of them won't talk about it or whatever their reasons are but I wanted to share with everyone the solution I figured out finally. Besides having good machine work on the block, strong enough head studs, you need to know that when running L19 or 625 Head studs from ARP, DO NOT USE THE WASHERS THAT COME WITH YOUR STUDS!!!!! These washers are actually smaller in diameter and the clamping for required is too great for such a small stud. If you do this is what happens:

The fix to have ARP washer inserts installed in the Head which should be performed by a machine shop.

The ARP part number is 200-8598. 7/8" OD This insert spreads the clamping force more evenly across the head and is it stops the head from getting gouged. If you ever experienced trying to pull you head off with the studs installed you couldn't do it because its stuck. Then the holes in the head are starting to squish into the holes against the studs. That's why when you remove the studs the head will come right off with no issues however the smaller washer is actually digging into the aluminum causing you to loose clamping force.
For the very first time since hitting 600+whp I did 9-10 pulls at 30psi and up to 32 psi and my overflow tank didn't fill up one drop more than what I had in this morning. I wanted to share this because I know if was happening to me it had to be happening with others that probably too embarrassed to as for solution. I saw many posts of pushing coolant but no real solution but here you go. With the time serts installed into the block as deep as the factory threads start & The washer inserts installed NOW YOU CAN USE THE WASHERS THAT COME WITH YOUR STUDS SAFELY.

I've never heard of these before.

I did notice that some kits came with washers that had outside diameters SMALLER THAN STOCK which I thought didn't make sense. The 11mm stud kit I pieced together (but never used) has 7/8" outside diameter washers and have been verified to fit the cylinder head (ARP 200-8747)

If you look at the ARP part number I listed you will notice its more than just a washer. It also goes into the head bolt hole. What this does is keep the hole true. Have you ever notice over time when running high torque yield head studs you can't pull head off unless you pull the studs first? The reason for that is the aluminum is collapsing in the hole where the stud is. That's why even if you use a hoist you couldn't get the head without seriously damaging something. By using these inserts it will keep the top of the hole true and spread the clamping load better because its wider than the smaller ARP washers. So even just using the bigger washer help with clamping for however you may still experience the top of the hole squishing due to the high torque and cylinder pressure. I hope I'm explaining this clearly where everyone can understand. Let me know if not.

Alonso wrote:I've never heard of these before.

I did notice that some kits came with washers that had outside diameters SMALLER THAN STOCK which I thought didn't make sense. The 11mm stud kit I pieced together (but never used) has 7/8" outside diameter washers and have been verified to fit the cylinder head (ARP 200-8747)

You're making perfect sense. Apparently this is also a fix for the 7m Toyota engines as well...which says a lot. Those engines are notorious for hg issues.

Good info for sure, just seems odd that nobody ever mentions these inserts.

It bothered me so bad that none of the big powered KA guys never spoke of the problem. Once I tried the inserts and I verified it worked I wanted to share this with everyone because this is probably the number 1 problem causing ka-t guys to say I quit. You get to a certain hp level and you just can't keep a dam head gasket on the motor.

This is invaluable info for anyone looking for big power. I really can't understand why people wouldn't be sharing this with others though..? Sure, it's embarrassing when you put your time and money into something that doesn't pan out the way you thought it would. But helping others avoid costly mistakes should outweigh that.


First you figured out the fix for the infamous clutch pedal issue, and now this. Thanks for continuing to test and push the limits to hopefully save others some time and money!

This deserves to be in the Hall of Fame: viewtopic.php?f=23&t=62830



Edit: So does this: viewtopic.php?f=23&t=62831

Are u running these inserts with 10mm arp studds or the upgraded 11mm

These washer inserts are for anyone using high torque studs (L19,625 materials). As far as stud diameter it doesn't matter.
This is because the torque is so much higher than what the head was designed for in OEM application. Also the cylinder pressures envolved when making 600+WHP. For those running ARP 2000 material you stil wil gain more evenly distributed clamping force if you have 7/8" washers. ARP almost uses a standard washer that is smaller than OEM on a lot motors.

It bothered me a lot to see all these high power dyno numbers pop up then usually within a year or two use the same guy parting out their setup. I know life happens sometime but it was happening so often I knew there where other problems going on that no one wanted to talk about publicly and/or the shops their cars where in didn't figure out the problem and just blames it on being a "truck motor" then tell them to ditch the entire project. I'm trying to get on the dyno this week and I will see what the motor is making. So far I have 3,300 miles on the motor and pushing 28 psi daily with no troubles.

Awsome man thanks for your input. Ive been building my ka for almost 4 years now and have yet to be able to put it together. All because i got myself into alot of debt and then got layed off, but hopefully ill be back at it again soon.

This was one of the main drivers to parting out my 240. The head kept lifting repeatedly, and I was only in the low 400's. So thankful to see this Duncan, as I'm planning on making a return and this issue weighed heavily on me. Thanks!

Duncan, thanks for having a fix waiting in the wings for my next HG catastrophe.

I've been through a few headgaskets and it is definitely a weak link on our motor. I have learned how delicate the situation is. I had ARPs not holding the power, only to find I needed to really clean and bottom tap the block threads out. I have not graduated past the 10mm ARP 2000 + Cometic just yet but the car has not been thrashed as much in the last few years. I do know the spring action of a metal HG helps the issue and I have a thicker than stock HG on right now.

I think this would have helped 240sxTTC stay in the KA-T game. I believe he ditched the KA due to this same frustration.

Good stuff... thanks for the pointers.

duncan351 wrote:So far I have 3,300 miles on the motor and pushing 28 psi daily with no troubles.

What kind of daily commute do you have that allows for 28 psi runs? And just as importantly, what tires are you running?!?!

What are your thoughts on 12mm RB26 head studs? I installed mine after issues with time serts. The RB washers just barely fit the entire machined boss on the head. They are obviously much larger and cover more surface area.

Apparently everyone has this problem. Z32 guys are using larger washers. Just got done reading a 10 page thread about this issue on 2JZs and 7Ms. Found this on Z1 Motorsports website.

https://www.z1motorsports.com/engine-pa ... -7019.html

Time somebody offers at billet block KA24DE. No more core shift or head gasket issues.

I just installed these on my head as well. Motor is still at the machine shop getting worked on. Did you run the supplied washer and the insert together? Also is it necessary to install time serts ito the block?

lazysk8er2 wrote:I just installed these on my head as well. Motor is still at the machine shop getting worked on. Did you run the supplied washer and the insert together? Also is it necessary to install time serts ito the block?

Yes, you can run the supplied washers with the insert. If you run 11mm head studs then yes you want to run time serts.

PM sent h

Great thread, I am pulling my engine for rebuild. Going 11mm head studs, I had A11 10mm head studs but they don't make those anymore.

Maybe after this season I will pull the motor and rebuild it so I can machine out the head stud holes. I lifted at 580hp last year and ended up just pulling the head off throwing in a new set of ARP2000s and a new HG.

So do these need to be machined to fit in the head or do you just put them under the ARP washer and torque like normal?
I saw you said a machine shop needed to install them so I wasn't sure if they could just be dropped in.

This is my explanation of the head stud situation and video of what my setup looks like. First video just shows the block machined and second video shows them bolted down. You can also see how big the RB26 washers are. I compared them to factory washers which are bigger than the 11mm washers and the arp 2000s. The RB washers are larger than all of them. In my opinion going 12mm is more cost efficient. RB studs are cheaper and vertical milling threads vs timesert the block is a no brainer. I don't foresee this head lifting.

1st video: https://www.youtube.com/watch?v=2XpC_tQ ... Z1XkKh3EWE
2nd Video: https://www.youtube.com/watch?v=cM5eAzQ ... WE&index=5

depends how hard you push your motor, cylinder pressures,etc... Since I couldn't find 12mm RB headstuds in L19 I decided L19 11mm will have more clamping force than standard 12mm's

KA24ETZTM wrote:This is my explanation of the head stud situation and video of what my setup looks like. First video just shows the block machined and second video shows them bolted down. You can also see how big the RB26 washers are. I compared them to factory washers which are bigger than the 11mm washers and the arp 2000s. The RB washers are larger than all of them. In my opinion going 12mm is more cost efficient. RB studs are cheaper and vertical milling threads vs timesert the block is a no brainer. I don't foresee this head lifting.

1st video: https://www.youtube.com/watch?v=2XpC_tQ ... Z1XkKh3EWE
2nd Video: https://www.youtube.com/watch?v=cM5eAzQ ... WE&index=5

Actually the ARP2000s in 12mm have a higher torque value and you have more surface area and less stress on the studs being larger. I had ca625+ 11mm and they torqued to 100 the 12mm RB 2000s torque to 105.

What did you do to the oil galley hole for 12mm hedd studs?

I measured a factory head oil galley hole and the stud to get the difference and determine the diameter needed around the stud. Then I measured the 12mm stud and did the math of what drill bit I would need to maintain that same diameter around the stud as was there with the 10mm stud.

Can we just drill the block with Milwaukee hammer drill for ARP RB26 head studs, then thread for the 12mm and call it a day or do we need to take the block to have a machine shop do it via drill press?

My impact drill seems very true or maybe I could make a jig of sorts to keep it guided in the hole the same way Timesert has their kit. I just bought a used set of 10mm arp but maybe if I could save some money on the labor I will drill and tap for RB26 studs myself if I could save the extra $300-400 that a local shop is charging me out here to drill and tap.

Maybe even using a harbor freight drill press would be cheaper and I can work at my own pace. The way I see it is... as of lately most machine shops over charge and under deliver so I am debating extending the DIY route even further... any suggestions?

s14fiend wrote:Can we just drill the block with Milwaukee hammer drill for ARP RB26 head studs, then thread for the 12mm and call it a day or do we need to take the block to have a machine shop do it via drill press?

My impact drill seems very true or maybe I could make a jig of sorts to keep it guided in the hole the same way Timesert has their kit. I just bought a used set of 10mm arp but maybe if I could save some money on the labor I will drill and tap for RB26 studs myself if I could save the extra $300-400 that a local shop is charging me out here to drill and tap.

Maybe even using a harbor freight drill press would be cheaper and I can work at my own pace. The way I see it is... as of lately most machine shops over charge and under deliver so I am debating extending the DIY route even further... any suggestions?

I personally would not go that route. It is such an exact tolerance that even with a vertical mill the back two studs were just a dick hair off and I had to massage it very slightly. Plus Im not sure how much metal is available in those holes if you were to be off a bit you may risk the integrity of the block. If you fastened a jig to make sure the hole was straight I would say go for it. Otherwise make sure you lubricate and step up your drill bits one at a time until you get the correct size hole. I was fortunate to have family who do this for a living, but after all the headache and money I spent on the 11mm stud I was not taking any chances. ALSO MAKE SURE YOU COUNTER SINK THE HOLE LIKE IT IS FROM FACTORY...YOU WILL CRACK THE WATER JACKETS WHEN YOU GO TO TORQUE IF YOU DON'T DO THIS!!! Already been there done that.