forged internals vs stock internals

Hi everyone :-)

Ok so I'm building my supra for track and drift on a budget and I'm looking for some advice regards to the engine.

I've got it stripped down completely as we speak and to be fair it's no where nere as bad as i thought it'd be! Crank is spotless, bores are good BUT the pistons where coked up to high heaven! No doubt due to poor fuel.

I've now cleaned them but i'm toying with the idea of forging the bottom end for reliability, now my question is -

What parts are best for a budget? I've got most parts ready to go single and i'll hopefully be pushing 750bhp give or take!

Now i know people will argue that the standard engine can take that but i'd rather spend a little more for the reliability. I've been looking round at different makes, looking at prices and looking for advice.

What are peoples opinions on eagle rods or crower sportman rods? Not a big price difference on price between them!

Now pistons, would likely end up getting cp pistons but could i use the standard pistons with the uprated rods or would it be a waist of time?

All help really would be appreciated :-)

Brendan

Heres an idea, why don't you just re-assemble the engine and run 600/650? You wont need/notice the extra power on the road anyway.

As much as the rods are always quoted as being the weak point, from what I remember it's actually the rod bolts that fail at that sort of level. Other than them most things will hold till quite a bit higher. If you replace those then you should be absolutely fine. Not a nightmare of a job, and no real need to split the entire engine. Engine out, oil pan off, bolts replaced

I actually looked at doing it with the engine in place, but decided I would just get a spare engine for when it let go...... for all they cost

Cheers for the replies

The car will be used on track so it will see hard use!

The reason i split the engine was due to the headgasket going and with the pistons being coked up i stripped the lot down!

If it's the case then I'll stick to the stock parts as it'll certainly save me money! Haha

Guess I'll save up and build another engine for a year or 2 down the way!

Cheers for the replies

 

The car will be used on track so it will see hard use!

The reason i split the engine was due to the headgasket going and with the pistons being coked up i stripped the lot down!

If it's the case then I'll stick to the stock parts as it'll certainly save me money! Haha

Guess I'll save up and build another engine for a year or 2 down the way!

Upgrade the fixings though mate. ARP all round will see you good for a bit of abuse.

As Scott says, ARP rod bolts, also main bearing caps and bolts, sorted.

I still don't get why people say the rod bolts need doing if you aren't raising the rev limit? If you increase the power just by upping the boost/bigger turbo etc. but keep the stock rev limit then the bolts will see no extra stress.

I still don't get why people say the rod bolts need doing if you aren't raising the rev limit? If you increase the power just by upping the boost/bigger turbo etc. but keep the stock rev limit then the bolts will see no extra stress.

Surely they must, the change from a down stroke to an up stroke must be harder when more power is forcing it up/down.

Invest your money into engine management and the map. Forged internals won't compensate for the former being off.

Surely they must, the change from a down stroke to an up stroke must be harder when more power is forcing it up/down.

No, it's virtually totally RPM related, although the firing downstroke will try to deform the big and small ends, so to a small extent bolt loads on the cap will increase. But by and large bolt failure is RPM related.

No car can be good as a drifter *AND* a circuit car. Driting is all about making a car griip badly and disproportionately, front to rear. Track use demands balanced handling and benign transitions. Any fool can build a drift car, the science is in proper motorsport

I also have to say the terms 700BHP and "on a budget" are mutually exclusive! Even just a "proper stock engine rebuild" and "on a budget" are mutually exclusive.

No, it's virtually totally RPM related, although the firing downstroke will try to deform the big and small ends, so to a small extent bolt loads on the cap will increase. But by and large bolt failure is RPM related.

I understand that, but the conrod bolts are always stated to be the first thing to go when power is increased past the "safe" limit. Is it possible that this information has came from people messing around too much with the RPM in order to get the power that they have been after?

I'm yet to hear of any cars failing at 700hp without having other issues already in place (low compression etc etc). For the most part it seems that it's 800+ for them to pop, normally piston rings I believe.

Their stress is virtually 100% RPM related, honestly!! People's expectations of huge power figures like 700 plus BHP are totally unrealistic if they expect the thing to last. I used to argue the point but have grown tired of that, if someone thinks a genuine 700 BHP plus 2JZ-GTE engine on pump fuel is going to be viable in a road car, fine, let them build it and find out It's not BHP that kills the rings it's a combination of ludicrous cylinder pressures, bore deformation, and probably detonation that kills them, plus the stock pistons certainly won't like that sort of abuse, for more than a few seconds at a time. My answer to those that say they have 7** BHP Supras that are 100% reliable is let me take it around Donington for 15 consecutive laps, driven hard, and let's see what happens. The stock car will survive that just fine, brakes aside Most are point and squirt machines, terribly traction limited, and never allowed to be really thermodynamically tested.

Jamiep built an all around black beast that took the abuse hard .

There is bugger all load on the rod bolts at all times apart from TDC on the exhaust stroke when the crank starts accelerating the unloaded rod and piston downwards while it's trying to go upwards still. The higher the RPM the faster this transition happens and therefore the higher the tensile loading on the bolts. The stresses increase something like to the power of four as well, deffo not linearly. So even a small bump up in revs increases the forces on the rod bolts massively.

Jamiep built an all around black beast that took the abuse hard .

Mine takes the abuse as well but after 7 or so 10-90mph pulls in 3rd on an airfield to record sound, the oil temps were up from 95degC to near 130degC. I had to let it cool down before continuing. You just don't drive like that on the road, on a track it'd last about 2 laps, Chris is wise and knows these things

Jamiep built an all around black beast that took the abuse hard .

That wasn't a stock engine mate, I killed two engines in that car, stock engine bent a rod at 730bhp, then the first built engine I put in it lifted the head at high boost and trashed it, second built engine was fine, that had L19 head studs.

I'd stick to 600ish BHP if you drive it hard and on a stock engine, I'm going to push the Goose hard but I don't really care if it lets go.

I meant fully built engine , that was one hell of a car you built JP.