overzealous1: I pmd you. Please call me if you can or PM

 

with this much money and time involved, wouldnt you feel better going ahead and sleeving the block. i mean, we know people are making 700whp now, why solve the head lifting issue and not sleeve the block, only to find out that the cylinders fail at say, 100 more hp. then youve gotta do it all again.

 

The only people that have reported no problems are using 1/2" studs. I'm in the process of confirming that this will fix this specific problem and should have data in a few weeks.

It's been stated that sleeves or just liners will not have any positive or negative effect under 25psi. There's data that shows positive results with both the stock and Cometic head gaskets when paired up with 1/2" studs.

 

I've been so busy, I didnt even see this thread! Well, here are a couple more things to think about.

Headgasket failure can be caused by detonation, or just extreme cylinder pressure (too much power). 1/2 studs may be the solution, as you will increase clamping loads by at least 25-35%, assuming you trq the studs down to 100 ft/lbs or so. But this is not a surefire solution...yet. As Philthy aluded to, drilling and tapping the block is not for the faint of heart. Our threads are resessed, which adds time and complexity to the operation, and you also need to drill and tap deeper into the block. My honest feeling on this, is there there is more of a chance of you damaging, cracking, or warping your block, by over torqueing larger studs on our aluminum block. Only time will tell. I know PM has done this on their race engines, and they offer that service. I am working with another machine shop in CA, that actually uses steel inserts to secure the studs, which insures you will not pull the threads out of the block, and should add some added protection against cracking your block.

All that said, I'm also looking at having some ARP studs (standard size) made in their L19 material. Machining the block to accept larger studs can cost around $1000, so swapping to L19 would be a straight plug and play operation, but still offer a 20-25% increase in clamping load, as you can trq the studs down further.

Over...let us know your findings on whether the studs backed out. Gurgen checked his on teardown, and noted that the studs were fine. Either way, I also agree that retorqueing is not feasible, and likely, not even necessary.

At the end of the day, Darton sleeves, cometic head gaskets, ARP hardware, and a solid tune should keep the heads from lifting. Mjedean's car is running 800whp+ with this setup, and hasnt lifted the heads yet.

 

I would definately be interested in the standard sized studs in L19 material. I'm just looking at doing a mild engine build for now to run a max of 14# before eventually going buckwild with sleeve's etc on a new engine build. Hopefully a viable and relatively cost effective solution can be found to keep the heads mated down with stock sleeve's up to 15psi or so with a drop of reliability.

 

Sharif perhaps investigate pre-existing L19 studs in a size close to stock if you are going to use steel inserts anyway. Custom ARP = $$$

 

ya light detonation was another thing that came to mind in my situation as i never had a problem in oregon for months now. yet it starts to happen when i went to cali and used the lower octane and oxygenated fuel there.
either way, i know the way i drive and want the car to hold together under any condition i could throw at it. i'm strongly leaning towards the o-ringing since it will aid in supporting the upper cylinder from moving as well as creating a more solid seal for the combustion. then the 1/2" bolts too.

 

Scott,

I have experience with aluminum wet sleeve blocks w/steel and aluminum(Nikasil). Lotus Turbo Esprit, Hence the name!!

Zero deck height on sleeved blocks wont cut it. The aluminum grows so much more and faster than steel. I'd guess about .004" above deck height would be good for steel sleeves. Just shim up at the bottom of sleeve to block socket.

 

i'm going to try and find a very effiecient fix, as sleeving the block can get pretty expensive. want to explore other options first.

 

Are these steel studs threaded into the AL block? Yuck. I guess it's common practice with engines but not ideal. I don't know for sure but I would think that the AL threads would move before the studs stretched unless the steel used in the studs is low quality. It wouldn't take much distortion to effectivly loosen the head. If the AL moved just 0.001" or so it could be a problem. Just the steel threads digging into the AL side might do this.

With industrial equipment the fix/prevention for this is to use steel inserts (helicoils). This prevents the galling of the AL when tightening and gives you more surface area on the AL.

my $0.02

 

a helicoil will not strengthen the threads. it is still a steel to alum. contact. i have thought about this steel insert and don't see a way of it being any benefit as you will always have to lock it into alum. now if the block was cast originally with the inserts, then it would work, but no way to put a steel insert into a smaller alum hole, meaning, if the steel insert had a deep alum shouler to hold it in, then you would have something. you will always have a steel/alum interface no matter the threading. the only way to increase thread strength is to drill deeper and have more threads to bite into. but the fact no one has torn out the stock threads, who's to say the tread depth is even an issue. one for the engineers there, and should be easy to find the pull out strength by present equations. once finding that pull out strength, match it to the correct size bolt that has a matching pull strength value.

 

one more thing, i understand the values of the heliciol in your reference being that the helicoil will have more surface area due to the larger dia interface with the alum block. one thing to remember, the more material removed for the helicoil, could result in less strength the block can hold due to water passages or casting.

 

ok, now on to the fun stuff. i sat down with my mashinist this morn and we came up with an incredibly easy fix for strengthening the cylinder tops. i am playing phone tag with a head gasket maker today, but hopefully we can get the details figured tomorrow on the gasket.
right now i need someones blown block (preferably in oregon or washington) so we can make sure the block fits in the tooling needed to make the block modifications. this combo of machine work and head gasket should easily fix the issue and make the block capable of ALOT more power. the mods should hold alot more cylinder pressure than sleeves alone and cost half as much.
i have a very good lead on both a block and head, but never bad to have more than enough to play with. they will be getting cut apart and all passages inspected to make sure the combustion dome is not a weak link in the heads.

 

Bro your getting me all excited.... If you find this out this will be huge for the future of high hp z's...Good **** man...

 

yup, i'm excited myself. it ends up being a simple machining process. materials are cheap and time is only about 1.5 hours. just need to make sure the block will fit in the machine required to do it. if not, i will find one, lol.

 

Keep me posted scott, I might be able to get some heads that were damaged by a piston hitting the valves. Let me know if i can be of some help.

-George

 

hey george, ya a damaged block is the main concern right now. i want to look at a cut away head though to see the coolant passages though. keep me posted if you know of some.

scott

 

I would like to see cut-up heads. I have plans for some rather heathy mods(weld up work/reshape) but only have good parts. It's very informative what you learn with a bandsaw. I also get 4 days off in a row so I can come to Portland area to view the head butcher.

 

I wonder if we can get a Nissan factory tech or engineer to become active in the forum.

 

Bri, I had the problem you experienced. Blowing coolant all over the engine bay. Everyone at Zcargarage was wondering if i was blowing my headgasket or lifting the heads. I noticed problems with my cooling system at the same time. Noteably, stalling, ruff Idle when cold and the pressurizing of my cooling system. After my Nismo thermostat started sticking, causing my engine temp to rise, we switched back to the stock thermostat, flushed and got all air out of the system, and its been fine since. No coolant blowing all over, nothing. So, maybe your just getting a thermostat problem. Keep an eye on that temp guage.