stopping a blacktop from spitting rods

[AE85coupe]

before you say do a search, i've already been there and done that

so heres my questions: when blacktops throw rods, is it due to the small weak size of the rods and the rod itself breaking? or is it due to running a bearing then spitting a rod because of this?

If its just becuase of the bearing problem, why not just use good quality shells and good arp rodbolts? would this stop the problem of spitting rods without having to use silvertop etc. rods?

cheers

[Dell'Orto]

Purely speculation, but I'd say its the rod size, they just dont look physically strong enough to handle a constant hammering.

[flygt4]

rod size. i have held disturbs old half remains of one in my hand , and there is a notch in the rod at its thinnest point about halfway down. apparently they all break through that point
they are also tiny in comparison to silvertop and early gze rods. i dont know if tiny really gets the difference across

[Mr Revhead]

yeah the rods.

and yes they all break at the same point. with proper prep they maybe ok though.
have a look at one and youll see where it is

[crnkin]

No its not just the rods, as in, they are not the main reason an engine will spit them out the side.

When sustaining high revs for a long time the oil tends to not lubricate the crank as well, this in turn means the big ends of the rods do not get much oil, so excess friction is created.

The effect of this friction, combined with high inertia on the conrods, produces an amazing amount of stress, which toyota under engineered for the first time in a 4a series engine.

The rods then break, but not just because theyre weak, its because the engine has been abused in the way it was not designed for.

How to fix?

Yes new bearings
Yes new rodbolts
Silvertop rods? be great
Uprated oil pump? thatd do
Dry sump? Hells yea

Just build an engine for its use. A 160hp engine designed for 300 thousand kilometres at 3500 revs dont take to 7800 too well, for long periods of time

Peace

[Mr Revhead]

No its not just the rods, as in, they are not the main reason an engine will spit them out the side.

while that can happen in engines, its not the cause of the blacktops issues. it is quite simply the rods them selves

[mr pad]

No its not just the rods, as in, they are not the main reason an engine will spit them out the side.

while that can happen in engines, its not the cause of the blacktops issues. it is quite simply the rods them selves

What? Of corse it has to do with what crnkin said too... They may be weak but im sure there are ways you can help increase reliabilty etc...

[Mr Revhead]

no.

while that can cause rod failure.
in the blacktops the rods fail on their own.... ie no bearing failure

[mr pad]

And nothing to do with friction and other nastys created by sustained high revs?

[Mr Revhead]

rod stretch.

they simply cant handle sustained high RPM.


thats not to say that ARP rod bolts and good bearings shouldnt be use in a rebuild. imo ARP should eb compulsary in a 4age

[RedMist]

rod stretch.

So your saying that in a blacktop rod break situation, the piston slaps the head?

[Mr Revhead]

yeah.

hence the 2 bent valves on the TV at home

[AE85coupe]

so you can safely say that in a race car running sustained 8000 or so rpm, we will need more than just arp rod bolts and good bearings?

[Mr Revhead]

yes.

the 1st blacktop i saw with the ventilated block had just that. TRD bearings and ARP rod bolts.

put a hole in both sides of the block

[AE85coupe]

yes.

the 1st blacktop i saw with the ventilated block had just that. TRD bearings and ARP rod bolts.

put a hole in both sides of the block

awesome, thats exactly the answer i wanted

[crnkin]

rod stretch.

So your saying that in a blacktop rod break situation, the piston slaps the head?

after the break or before? cast steel must stretch alot then

[Mr Revhead]

haha obviosuly after.
which would suggest it breaks on the way up.
of course is could just get fired upwards after it breaks, but its not likely to break on the way down is it.

[bluemaumau]

if you replaced blacktop rods with silvertop rods, would it rev as well?

surely the blacktop rods are lighter therefore rev happy?

?

[Mr Revhead]

you know i seriously doubt you could tell the difference.

[bluemaumau]

true