Limitations of Toyota Bottom End Components - Specifics?

[dandan]

Gents,

 

I have been trying to find out where people seem to think the limit is regarding certain components in the stock bottom end and have a few specific questions. I am pricing up a sensible rebuild of a spare motor I have with the intention of having an ultra reliable 500-550bhp road car at the end of it, combined with a good single kit, and all associated parts fuel and ign wise.

 

I will be replacing oil and water pumps, piston rings, rod bolts, valve springs and top caps, and consumables like flywheel bolts, gaskets etc. I'm 50:50 on the con rods themselves at this point and looking into this further. Head will be mildly ported and tidied up in the combustion chamber/squish area. Not planning going up a valve size at the moment as I've found little justification for a road car pushing under 550bhp although this is one area (along with cam choice) I have not explored fully yet.

 

These questions assume ultra clean working environment and true blueprinted rebuild conditions - we're not talking about 100,000 mile old engines pushed to breaking point. Basically I'm looking to establish which parts needs replacing when aiming (with a bit of headroom) for a potential 600bhp capability from a reliability stand point. No more than 8000rpm max. When I mention studs/consumables I'm thinking new parts, not re-used obviously.

 

Stock main and big end bearings.

Stock main studs and nuts.

Stock head studs and nuts.

Stock pistons and ring set.

Stock wrist pins.

Front crank damper/pulley.

Stock valves and collets.

Editted: Let's throw the stock rods in for discussion too, with and without upgraded fastners.

 

If you've had any experiences with any of the above failing or perhaps know anyone who's stripped a motor and something has been just about hanging on about to go - I'd like to hear about it.

 

Dan

[dandan]

Any thoughts guys?

[RobSheffield]

surprised nobody else has replied

[dandan]

I think there may be a few different "camps" on this subject.

 

1. Supraforums fans who believe the bottom end can take anything we throw at it, fullstop. No holds barred.

2. Those who have appreciation that they may be on the edge of reliability (perhaps not knowing which component is the next weak link) but they are happy to see how things go and deal with a rebuild if needs be.

3. People who truly know when certain components are at their limit and design their engine build to suit appropriately, upgrading economically where necessary to suit their requirements.

4. Those who believe almost all stock components must be replaced as a matter of course, anything other than a full set of aftermarket rods, pistons, rings, bearings, flywheel, valve gear etc is suicide.

 

With engines I have worked on in the past I'd like to think I have always been in group 3 (creeping into 4 where there's any uncertainty) but that's due to great familiarity and experience with those particular engines, knowing what is and what isn't a problem.

 

Having not really got into the nitty gritty of pushing a 2JZ to its limits - I am a mix of 2 and 4 at the moment and looking for the sensibles compromises that can be made. Basically gathering as much first hand information off people as I can.

[Guest Terry S]

Its tricky Dan as the condition of the engine will really determine the answer. It kind of been proved with Ian C that you can get 600 bhp reliably from a stock bottom end, with the proviso that #1 it's in good condition, #2 it's tuned properly.

 

The Americans have seen huge figures on the stock bottom end, but, a 5 second dyno pull is very different to a long motorway pull.

 

You will get many answers, but try and sift the "Bench Racers" from those who have actually tried various things mate.

[Ian C]

I'm #2

 

As long as someone else is running a stock bottom end with more power and less mechanical sympathy, I'm as happy as I can get. You know who you are

 

-Ian

[dandan]

Yep, I appreciate that Terry. All taken on board.

 

I know Ian's is a fairly low mileage motor and well cared for too. It certainly seems to be holding up nicely and seen as i won't be pushing that much power that's a nice "safety blanket". (Pushing me towards installing my single into my car with the engine as is). Editted: I see you've got a safety blanket too Ian!! Out of interest what boost and rpm does your engine get pushed to and are you on stock rod bolts?

 

However, if starting from scratch with a full strip down, inspection and rebuild the condition of all parts should be spot on. Anything not perfect shouldn't slip through. I was wondering where the limit of certain stock components actually lies. For example... Can the stock main or big end shells actually handle 700bhp for XX,000miles and is this at the manufacturers recommended clearances? Tweaking an extra half a thou here or there may make all the difference to oil supply in certain scenarios that we will never know about. Will the stock piston happily put up with 30psi and 8000rpm assuming no det? These are the things that will make the more experienced 2JZ engine builders stand out as the most reliable and this sort of knowledge can only come with experience. No harm in doing a little digging though to see what may well be common knowledge somewhere.

 

Any searches on SF are a little fruitless as they're all talking of 800bhp. Mention reliability on 550bhp or less and you almost get laughed at for being so foolish as to think there's ever a component in this engine that could fail below 600bhp.

 

It's the guys who don't post up about their failures that hold the key, not the keyboard tuners regurgitating third hand opinions.

 

Points taken on board and rest assured the tuning will be spot on.

 

ps Did you get my email Terry?

[Guest Terry S]

Ok personally I wouldn't run much over 600 on a stock bottom end and expect longevity. I would always be nervous a rod bolt was going to have enuff and stretch a bit. Thats not saying that with really good, safe tune it wouldnt be OK, but I think 600 is a safe figure for a good condition motor.

 

will check me emails in a bit Dan.

[Alex]

Think Ian's covered about 15,000 on his two singles....

[Christian]

After ~30k miles mostly at 1.4bar, we found a weak point in the rear crank seal. We've fixed that & now found the next weak point; the front one :-(

[Ian C]

Mine is up to 65k miles now, which I suppose isn't bad for 10 years old It's never been below 450bhp since I've owned it. The single has been on for two years and yeah about 15000 miles.

 

My usual driving is:

Between 1500 and 2000rpm when going slow, like villages and in traffic.

Cruising at 3000 to 4000rpm on dual carriageways, and I don't bother changing down if over 60mph and I want to accelerate

Blatting away rapidly using the midrange, 2500rpm to 3500/4000rpm

The occasional WOT hoon from roundabouts or, well, whenever I want But I'm no leadfoot. However when I do cane it I'll usually take it up to 6500rpm+, my rev limit is now 7200.

 

So it's not the hardest life a Supra can lead.

 

Charlie (B'have) just did a stripdown of his engine after 5 years of single turbo on an AFC and ITC and it was it excellent condition, which also warms my heart.

 

I just closed the breather system again in an attempt to stop any crank seal issues before they begin. I also did a cooling hose mod when I installed the DBB turbo that Matt Harwood told me about as it apparently makes the rear of the block run less hot. The FMIC is ducted, the pod filter is cleaned and heat shielded, I keep an eye on EGTs and the probe is positioned so if it breaks it exits via the wastegate, I got rid of a lightweight crank pulley after talking to Digsy about it, I make sure the oil is good and topped up, the coolant is 4Life, the rad is in good nick, anything that needs doing gets done, Basically I try to stop known problems before they manifest - so far it's worked. Now I've fixed the electrics

 

*touches wood*

 

-Ian

[Lucifer]

It's all relative though. Ive always though an Engine should be measured by RPM life rather that miles.

 

If you sit on the ringroads or motorways a couple of hours aday racing anything that comes along then expect Circa 10k if you lucky at 600bhp, If like Ian you drive sensibly and use the power sparingly then you will get a lot more.

 

As Terry S says, its all in the Map and the condition you will start from.

[wkdtime]

Good work Ian, i really do envy your setup, what sort of BHP do you make on low boost i.e 1.0 bar and medium high boost i.e 1.2 bar?

 

 

Sorry to go a bit of the thread guys.

[dandan]

Pretty much the same kind of use mine will be seeing Ian. Possibility of the odd track day here and there but not 100% as I have other cars for that.

 

Crank seal issues - yes. I must admit I didn't think of that relative to this thread. Christian are you running stock seals still or have you made an ungodly discovery of something better?

 

Surely the less restrictive the breather system is the less pressure there will be in the crank case from blow by. Where and what have you closed back to where Ian?

 

Has anyone modified their oil pump and/or drain hole?

[Paul Whiffin]

I did about 20,000 miles with my car running around 720bhp on a stock bottom end, took the lump apart and everything was in perfect condition. As long as its all setup correctly it should be ok, bit like Terry says though, depends a bit on the condition of the engine in the first place.

[b_have]

Mine is up to 65k miles now, which I suppose isn't bad for 10 years old It's never been below 450bhp since I've owned it. The single has been on for two years and yeah about 15000 miles.

 

My usual driving is:

Between 1500 and 2000rpm when going slow, like villages and in traffic.

Cruising at 3000 to 4000rpm on dual carriageways, and I don't bother changing down if over 60mph and I want to accelerate

Blatting away rapidly using the midrange, 2500rpm to 3500/4000rpm

The occasional WOT hoon from roundabouts or, well, whenever I want But I'm no leadfoot. However when I do cane it I'll usually take it up to 6500rpm+, my rev limit is now 7200.

 

So it's not the hardest life a Supra can lead.

 

Charlie (B'have) just did a stripdown of his engine after 5 years of single turbo on an AFC and ITC and it was it excellent condition, which also warms my heart.

 

I just closed the breather system again in an attempt to stop any crank seal issues before they begin. I also did a cooling hose mod when I installed the DBB turbo that Matt Harwood told me about as it apparently makes the rear of the block run less hot. The FMIC is ducted, the pod filter is cleaned and heat shielded, I keep an eye on EGTs and the probe is positioned so if it breaks it exits via the wastegate, I got rid of a lightweight crank pulley after talking to Digsy about it, I make sure the oil is good and topped up, the coolant is 4Life, the rad is in good nick, anything that needs doing gets done, Basically I try to stop known problems before they manifest - so far it's worked. Now I've fixed the electrics

 

*touches wood*

 

-Ian

 

Ian, is the cooling mod similar to mine? ie additional line from pump to rear? Also looking at crankcase breathing as I hit 7320 rpm last week, thinking about a second large breather from ex cam cover to compessor intake area.

Can you explain "closing the breather system"?

[Ian C]

I did about 20,000 miles with my car running around 720bhp on a stock bottom end, took the lump apart and everything was in perfect condition. As long as its all setup correctly it should be ok, bit like Terry says though, depends a bit on the condition of the engine in the first place.

 

Woohoo! You see, it's these results that I like to hear

 

1.2bar is probably pfft, what, 500 to 550bhp? Dunno, but it's not slow anyway. I've done a couple of trackdays as well and I'm always up for TOTB.

 

Wastegate pressure (0.8bar) felt like my old hybrids (at 1.4bar) through the arse dyno so that's about 450 to 480bhp.

 

It is a lot about the revs though, big time. High revs kill engines.

 

-Ian

[Ian C]

Ian, is the cooling mod similar to mine? ie additional line from pump to rear? Also looking at crankcase breathing as I hit 7320 rpm last week, thinking about a second large breather from ex cam cover to compessor intake area.

Can you explain "closing the breather system"?

 

That sounds similar, it's linking the two coolant feeds to the old stockers together and feeding the turbo water jacket from a T off that.

 

I closed it by routing a hose from the cam cover (hot side) to the intake pipe pre-turbo. Like stock, instead of that little K&N filter.

 

Gotta go, bus to catch

 

-Ian

[b_have]

That sounds similar, it's linking the two coolant feeds to the old stockers together and feeding the turbo water jacket from a T off that.

 

I closed it by routing a hose from the cam cover (hot side) to the intake pipe pre-turbo. Like stock, instead of that little K&N filter.

 

Gotta go, bus to catch

 

-Ian

 

 

Yup, same as mine. Think those little K&Ns are scary if you lose a piston. (ala Gamer)

[dandan]

What do you mean Charlie?

[Gamer]

What do you mean Charlie?

 

 

I think he is referring to the fact that I blew a piston in my Soarer (1JZGTE), the crankcase pressure was high enough to shoot oil through the breather system and make contact with the glowing hot manifold. She then caught fire and the rest is history....

[dandan]

Oh sh!t I see what he's talking about now. Enough said.

[Guest Usmann A]

We did 5 dyno pulls on a 50K motor. at 2 bar, equated to 740rhhp. didnt even get home. LOL

 

it was rod bolt failure .... not pretty at 5400rpm, near peak torque too.

[dandan]

These are the stories I've been looking for, I bet that made a mess! Thankfully significantly higher loading than I'll be putting mine under though.

 

Thanks Usmann.

[fastisnice]

its all down to tuning..Rod bolts usually suffer from high revs not so much from power, it also obviously depends on the condition of ur motor, stock cylinder heads are not good for >600, struggling to get above that with stock head..If good upper block is built then should be good.I run [email protected] and its all good,im planning to take it further though.My friend in Greece was running close to 800 for 2 years stock bottom end-8K revs no probs...it really depends on how well is tuned..