Dead 7M decision time...

[Grandavi]

So, my head has suffered from a bit of detonation and was pushing exhaust into the intake side of the headgasket on 5/6. All this after a massive amount of time and money to ensure this doesn't happen and a locked up R154 under boost that kind of ensured it did happen...

I am considering my options....

7MGTE repair/rebuild - which means I keep the engine and all the numerous parts I already have for it and still worry about the fact that the head does not handle heat well....

or....

2JZ swap - which still has some issues but would be more bullet proof and most of my parts would still work with it...


or...

LS1/T56 swap - which is not really well documented (now that IJ took his threads out), but would be a less problematic, lighter and probably cheaper option (plus... the v8 with dual exhaust is kind of a nice thought).


Any opinions?

 

[Grandavi]

 

[GC89]

I am a 7M guy so that is always the first option I like to see. If I ever get burnt out on them I would likely go 2J or 1UZ as my next option. Have you considered the 1UZ at all?

I like to stay in make personally. It also has to have a turbo on it to do it for me so 1UZ or LS twin turbo would be my direction to take a V8

good luck ans sorry to hear about the loss.

 

[Grandavi]

Not really a loss, but thanks! I consider it part of the "mod" game.

Lim hoping kaizen sends me a ballpark figure for a 2jzgte VVTI swap soon, but I think I may be pulling out of the 7m game.

The Ls1 option was solely due to engine size/weight/hp/torque and availability of parts. Every swap has its concerns, and the ls1 isn't native, but I think overall it may be more cost effective than a 1uzfe. Not sure on any of this yet and just starting research.

If I go v8 it will stay NA.

 

[themadhatter]

A warmed over 5.3 can be done for cheapish and make around 400whp or you could do a 2jz-ge(T) on your 7m electronics for a decent price

 

[Grandavi]

The ls1 is a bit tempting because of the weight difference and I won't be worrying so much about fuel. I'm quite happy with 400 whp as well.

 

[emericaskater285]

2j. if you have a late 89+ subframe itll bolt right in. use 7m electronics, jz bellhousing and flywheel, done. I have a 7m in both of my cars, and have wished I would have went jz a long time ago, or keep my shit more stock and enjoy it. I am too burried now to change it, but would consider it someday, or if i got into a new project.

 

[Grandavi]

Yeah, I'm at the point with my 88, that I'm tired of beating the 7m donkey. Easy to bulletproof at stock setup, but take it to 400 rwhp and its finicky

 

[3p141592654]

What does it mean, "a locked up R154", and why would changing the engine prevent a transmission problem from happening again?

 

[SeeUSmile]

pretty sure you'd get the same result if the 2jz saw the same kind of detonation.

 

[Grandavi]

The transmission was built wrong (Jack Transmission Stage 2) and fifth gear would slip out. Jack told me to use it and he would build me a stage 3 R154 to replace it and cover the cost involved.

While driving home from my daughters (a 5 hour cruise) I was passing two cars, was at 12-14 psi of boost doing 150 kph and the tranny locked solid. Stopped the engine dead.

It started again, and seemed perfectly fine... However, 4 months later when I got the replacement, it started pushing fluid out of the overflow. My guess is that the head was lifted. The MHG is perfectly intact but you can see where exhaust started to creep into the intake side coolant ports. I believe it detonated at that point.

Jack said they would pay for all damages, so I will ask, but the car takes so long to build, that too much time may have past regardless of the fact that I haven't even drove enough to break in the tranny.

 

[Grandavi]

The question relates to that I know have to build a 7m. Again

With all the problems that the 7m is renowned for, I am investigating alternatives and the two that strike me as smartest is the 2jz or LS1 swap... Both for different reasons.

Basically, I want input from people who have walked this path.

 

[SeeUSmile]

Ahh fair enough.

Im still yet to walk that path of branching from the 7m blehh. For me in Australia the jz are more in abundance here, it feels too much of the norm. having 7m appears to be more appreciated for its auththicty.

But if starting a new page and having a different challenge is more thriving by all means go for it

 

[Grandavi]

The 7m platform is okay, but best for someone who does his own work. If you build for 300-350 rwhp, it's fine, but once you start going after real power, you have to monitor things. I learned a lot so far... Lol.

If I rebuild the 7m I will be going water meth because the head can't handle the high heat properly. It's either that or race fuel. No e85 here and our octane levels are questionable. Timing has to be altered too much to reduce knock on pump gas for 400+.

There are a lot of factors that can lead to detonation but it only takes once to get where I am. I tried really hard to get it stable and that one incident changed it all. With the 2jz I would have the same concerns, but not as greatly.

 

[Backlash2032]

I really doubt that the engine being stopped from the transmission locking up would lift the head or cause any sort of detonation. You were probably just detonating and never even knew it.

That being said... An LS in a Supra would make for a pretty damn good track car. Really lighten up the front end, gain a ton of low end, and response... Id love to have one.. But MAN I love the sound my Supra makes! Maybe one day I'll buy an N/A hard top shell and make a 100% dedicated track car out of it... That sounds like way too much fun

 

[Grandavi]

When the trany locked up it sounded like someone hit my engine with a 20 lb sledge hammer. A black cloud came out of the back that was bigger than the car. Scared the crap out of me... Especially at that speed. No idea what the cars I was passing thought... Lol. No idea if it truly lifted the head, but it sure sounded like my engine exploded. I didn't realize the trany was toast until I tried getting into neutral.
The car started right away and ran perfectly fine. Shut it down until the trany was replaced. From that moment on, it was pushing coolant out of the overflow bottle.

...so you tell me. What damage was done?

Also, it should be noted... Pistons are perfectly fine in appearance. Spark plugs are also perfectly fine. Head gasket has no damage. Block has no damage. (Visible)

The car wasn't misfiring and there was no white smoke. No coolant in the oil or oil in the coolant. But you can see in the block where the carbon was pushing into the intake side of the coolt jackets. Leakdown test was fine. Only leaked at over 10 psi boost.

I'm not an expert, I just no what the conditions were and what was going on. The engine build had about 8000 km of perfect trouble free existence until that event.

 

[Nick M]

What does it mean, "a locked up R154", and why would changing the engine prevent a transmission problem from happening again?

Reminds me a bit of a TSB Toyota had about....15 years ago. The Yamaha produced engine for the Celica with variable valve timing and lift had a TSB for shifter springs in the transmission to save the oil pump and engine. Drivers would downshift to 2 instead of putting it in 4 and the pump would have an overspeed condition and crack. Not really the engines fault.

 

[suprarx7nut]

Sounds like you know what you need to do pretty well. You can build another 7M, but they are a bit more "finicky" than a 2JZ at higher power levels.

Despite the damage done to your existing motor, a 7M build would likely be far cheaper in the short run. I suppose that depends on exactly what needs to be addressed, but as long as you don't have a cracked/horribly distorted head/block the rebuild should be pretty standard.

I haven't done a 2J swap, but just listing out all the needed parts and pieces put it WAY over the cost of a 7M rebuild when I considered it a couple years back. I was assuming all my own work as well. I'm guessing you'd have a higher labor charge on a swap making the 2J swap even more expensive.

I think you know your situation and options pretty well. Just have to decide if you want to go a little slower for a little cheaper or dive into a 2J, spend more, have more power and potentially more reliability.

 

[Grandavi]

I'm at the point that I'm going to have to spend money anyway. If I rebuild the 7m, I'm going to have to magnaflux everything to make sure I'm not building a damaged engine and then I would replace the Pistons with blanks that get a pin offset put in (for better knock control and run chromoly (spelling) rings similar to OEM.

I built originally more for race, not thinking that the oil control rings wear quicker and I'm going for modest power gains (350-400 whp) with reliability being most crucial.

The 2jz swap would probably be the most effective and most expensive. But I would still have the issue of fuel quality giving a potential for catastrophic failure at higher boost levels (would stay with my SP6262 single turbo).

The LS1 would probably be the cheapest swap (hoping IJ can give me info because his thread was removed) and the shop doing the work would be using my car as the guinea pig to come up with a kit for the swap that they would sell, so I would get a break on the customization side.

 

[3p141592654]

To me it seems straightforward. Replace the head, transfer over any titanium springs or other goodies in the old one, and carry on. The rest of the engine is fine. Should be no more than a few k if someone is paid to do it, or much less for DIY. To swap to a different engine family, that's an order of magnitude difference in cost and complexity. The issue of why it is detonating is more likely an ecu issue than poor fuel.