Those who have cracked blocks in the past, a question...

[RyanRs]

I am planning to head up to the rolling road for the mr2 to have its 'hopefully' final map! bringing it up to and possibly over the 600bhp mark! However, i am worried that this session is either going to go one of two ways.. Im either going to make the power and be happy or im going to end up with a cracked block!?!

Its currently holding strong at 500bhp without issue, however i know im already well into the 3s block fail margin! The RR is 120mile round trip for me and i intend to drive it there and back. What i need to know is, If the block cracks will i still be able to nurse it 60miles back home? I understand that cracked blocks only become a problem when you allow the engine to get too warm, so would perhaps making some 'cool down' stops on the way home be ok?

The reason for having to do it like this is because i cannot really afford at this moment in time to hire a trailer and suitable car to pull it on top of the dyno charges and fuel etc, and if all goes to plan 'ie the block doesn't crack, then i have wasted a lot of money for nothing! It has to be mapped now'ish whilst the weather is cold! it cannot wait till the summer.

I guess the ultimate backup plan if all goes pete tong would be to use my RAC membership and get it recovered, however i hear that RAC only take you to the nearest services and not all the way back home?

[Kongaroo]

I think it'll vary depending on how big your crack is. I had a very small crack that caused me to lose coolant quite slowly. In fact if I didn't boost I could drive the car around quite happily without issue for many days.

When I boosted the car for extended periods the coolant would be lost and the car would start to overheat.

Perhaps bring a lot of spare coolant with you in the boot? lol.

I think you will need to ring RAC and check what cover you have as there are various levels. I upgraded my AA membership to include them taking it to a garage of my choice.

Good luck with your car on the day

[Harold]

If you can't afford to get the car trailered, how are you going to afford to fix the car if the block does crack? I don't really understand, why not just stick at 500hp and enjoy the car?

[mattgt]

As Kongaroo says, check what level of cover you have and maybe spend a few extra pounds for it to include bringing you home. RAC and AA offer many different packages. This way if it all goes pete tong you will get yourself and the car home.

Good luck with the session.

[uglee]

If you have 500hp+ will an extra 100hp really be noticeable and worth running into big reliability problems? Is it a car for the drag strip, if so I can understand why you are doing it but for a road car does seem a bit risky pushing it.
By the sounds of a it a cracked block would mean a big financial burden and as Harold says, why not just enjoy 500hp, it must be pretty epic already?

I'd call and check your RAC if you are going for it there is a membership level where they will take you home wherever you are in the country. Probably an extra £60 on top of your existing cover, but well worth it IMO.

Good luck!

[Century Motorsport]

At 600hp if it cracks I imagine it'll be quite a display!

I cracked a block down the strip once and it looked like the engine had exploded with the water and oil trail.

It did run after (to get it on the trailer) but I would not recommend driving it 60 miles...

[ashley]

When my block went it emptied the coolant pretty quickly, and I struggled to drive the 10 miles home- spent a lot of time by the side of the road waiting for things to cool down and refilling the coolant system...

I think the answer is that if it does go on you, don't expect to be able to drive it home...although you might get away with it.

But enough of this pessimistic talk- I'm sure it will hold strong mate, can't wait to hear how you get on

[jimGTS]

why build a 600hp car and worry about it lasting 60miles and a session on the dyno!!!!

what you going to do the rest of the time you own it, dont boost!?

come on ryan, give it hell!

[greeny]

Is it a late 3s block? Because iirc you've had it sleeved haven't you?

Don't worry about it till/if it happens!

It all depends how severe and where it cracks that will determine if you can drive it out of boost to get home.

Mine cracked on the outside and would only open up when in boost.

Good luck! Itl be fine !

[Steve Horrocks]

why build a 600hp car and worry about it lasting 60miles and a session on the dyno!!!!

what you going to do the rest of the time you own it, dont boost!?

come on ryan, give it hell!

This. If you're worried about the mapping, you'll never drive it properly anywhere. You could be 200 miles away at a show & it let's go. If you're happy with the build & it's spec'd for 600 (ie not flogging it's titties off at 110%), then just go for it!

[RyanRs]

If you can't afford to get the car trailered, how are you going to afford to fix the car if the block does crack? I don't really understand, why not just stick at 500hp and enjoy the car?

Lol cheers Harold! knew i could rely on someone to pick up on this!!

Basically, when i started building this car some 5 years ago it was with the intention of hitting 600fwhp and i will eventually use it up santa pod once i am certain its all running good. Its not my daily driver, infact its only done about 3,000 miles since i purchased it! The reason i cannot afford a hire car and trailer etc at the moment is because i am near the end of doing my pilots license and i need to make sure i have enough wedge left so as i dont go skint the day before my test! This is my main priority before the car. At the same time tho, the engine build is practically done after 4~5 years of long long days and nights of building/designing/swearing etc and tbh i just want to see if i have achieved my goal! -I can afford the cost of the mapping session + fuel but hiring a 4x4 and trailer on top will almost double the costs, which i cannot risk atm.
If the block goes crack then that is not a problem, so long as i can get it home somehow. It will then just sit in the garage for another 6 months or so whilst i strip down the bottom end and slowly upgrade it to a 5sfe. It needs tuning now as i need to make use of the cold air temps and also if it does go bang, i might have just enough time to get it back up and running again before the '12 summer ends!

Steve, dont worry mate, soon as i see it survive the dyno and still drives home without a wheel falling off or what not, that gives me enough confidence to give it a blast here and there ;D

greeny, its a early rev3 block 1994 -iirc this is the worst one? but yes i have had it sleeved and the pistons im using are only .5mm oversized so the overall wall strength must still be considerably more than a stock size 3sgte? I remember yours cracking on the outside, above the A/C mount wasn't it?

[gazrev1tubby]

What sort of boost levels are generally considered block cracking territory ?

[greeny]

greeny, its a early rev3 block 1994 -iirc this is the worst one? but yes i have had it sleeved and the pistons im using are only .5mm oversized so the overall wall strength must still be considerably more than a stock size 3sgte? I remember yours cracking on the outside, above the A/C mount wasn't it?

Any of the early 3s blocks will crack, if you get a late 3s with the extra meat and sleeve it, you should be fine. Or get a late 5s block, which is the way to go IMO.

I doubt you'll crack a sleeve, itl be more likely to crack the outside first.

But I wouldn't worry about it if/until it happens!

[greeny]

What sort of boost levels are generally considered block cracking territory ?

It's more about cylinder pressure rather than boost pressure. All setups will vary with regards to boost vs power.

Anything over 500hp and you're pushing it, some will crack long before, some will last longer! Can be luck of the draw I'm afraid!

[gazrev1tubby]

What sort of boost levels are generally considered block cracking territory ?

It's more about cylinder pressure rather than boost pressure. All setups will vary with regards to boost vs power.

Anything over 500hp and you're pushing it, some will crack long before, some will last longer! Can be luck of the draw I'm afraid!

Thanks Greeny, i'm going for more mapping soon, but i'm not sure what sort of boost pressures to map for ?

I'm only running 1.2 bar at the mo, and my tuner asked what boost i'd like to run. I said 1.4 bar (rev2 forged block, with a precision 3431e turbo). I'm not sure whether going higher is chancing it ?

I guess ANY mapping for more power, is taking a risk. But it's just be nice to have an idea.

I don't want to ruin the op's thread here, but advice is most appreciated

[RyanRs]

Like greeny said, its more down to cylinder pressures than boost levels.Say you could crank a ct20b upto 2 bar, the block is unlikely to crack, but you would probally have melted your pistons from some white hot IAT's! I've heard of gen 3 blocks breaking at 300whp and some lasting past 600! its all down to luck.

Btw fwiw, Im currently running 1.6 bar on a billet GT3582r (which is sized between the gt35r and precision 6262) and 8k redline and its still uncracked. before this i ran a k1-380 (ct20b hybrid) pretty hot at 1.5bar & 420bhp 8k redline and that didn't crack it either

[gazrev1tubby]

Like greeny said, its more down to cylinder pressures than boost levels.Say you could crank a ct20b upto 2 bar, the block is unlikely to crack, but you would probally have melted your pistons from some white hot IAT's! I've heard of gen 3 blocks breaking at 300whp and some lasting past 600! its all down to luck.

Btw fwiw, Im currently running 1.6 bar on a billet GT3582r (which is sized between the gt35r and precision 6262) and 8k redline and its still uncracked. before this i ran a k1-380 (ct20b hybrid) pretty hot at 1.5bar & 420bhp 8k redline and that didn't crack it either

Thanks Ryan, that's explained it a bit more

I guess it would be best to look up the cfm of my turbo, and see how that compares to say a gt3071r or similar, to get an idea of how much boost pressure can be run 'safely'. Then just sit back and hope

I always thought it was boost that caused block failure, but it makes sense that it's how much air is being flowed at 'x' boost level

[gavinda]

Save ur money mapping and put it towards a 5s build then at least you can sell your 3s bottom end while it is in one piece. Or go dyno and crack block within 3months may destroy engine when it goes at that power level
it is not a question of if but when with the 3s block above 500




mine lasted fine for short bursts but when u drive hard for prolonged periods bye bye

[dawesy]

ive now cracked 2 at 470 FWHP and 1.8bar boost.
the last block was grouted and running evans coolant as well.
in both cases i could still drive quite happily off boost. just take some coolant and your bleeding tackle with you to be on the safe side.
it really is luck of the draw, early or late block sleeved or not makes no difference, its all down to a crap design in the block itself.
98> 5S is the only reliable way it seams

[greeny]

....early or late block sleeved or not makes no difference.....

You should be ok with a late 3s block, sleeved with the re-inforced corner, or are you saying you have already cracked a late sleeved block?

Did you cement it just to the water pump housing or fully to the deck?Where did you crack the cemented block?