and the VG30 had a crank Girdle to hold it all together..

the Toyota/lexus 4lt v8 has 6 bolt mains..

no wonder the new outlaw class Jet boats with Turbo 4lt v8's hang together..

Whatever you decide to do,just make sure you replace the big end bolts with new ones if it's going to get the big rev(about $100.00 the last set for memory from Nissan)cause they have been known to fail .I have seen the aftermath on 2 occassions,very nasty!

Quote: The second V8 Chev design was produced in 1955 & displaced 265 cubic inches [4,343cc] & the main bearings, all 5 of them, did a good job, but the design was eventually expanded out to 350 cubic inches [5735cc] & used in larger trucks. At this point, the constant high levels of output in a heavily loaded truck meant that the company upgraded to a 4 bolt bearing cap design.

As far as I know, passenger models never got the 4 bolt blocks.

Datsun A series with 5 mains & 4 cylinders do not usually need a 4 bolt upgrade, even in the 10,000 rpm engines used in Formula Pacific & F3 racing.

seems like I opened a can of worms here...

DD,
So if its is the revs that warrent it, then I would have to say that the Revs are the symptom, rather than the cause.

Would it be that standard cranks are not always well balanced, and that high revs in larger capacity, bigger cranks would cause more siginificant vibration and flex than a smaller crank, in something like the a series.

Dman,
you speak about it as though its got to do with the load placed on the engine rather than the revs??
Since I would expect trucks motors to be a low reving unit, at constant-ish revs, whereas a passenger unit which may rev higher, and a more varied rev pattern.

The web pages that i have looked at all say that 4 bolt mains are better cause its stronger, and should be considered in any high performance engine. We all know that. The reason for it still seems to be a bit vague.

reuben i think your reading too much into it most engines even very worked motors withstand more of a punishing than a series motor without 4 bolt mains. if this question is in relation to the motor you bought off me, i think if they were needed jeff taylor would know whether or not to use them.

I can't pretend to know the specific reason why four bolt caps are used but in American V8's it's the high load engines that get the caps. Engines like the previously mentioned 350 truck engines, Ford NASCAR side oiler big blocks & SOHC engines, Chrysler Hemi's, I'm sure there's a Chev big block in there somewhere, & anything that needs to REALLY hold the crank into the engine block.

Keep in mind that the piston is trying to push the crank out through the bottom of the oil pan & the only think keeping that from happening is the bearing caps.

As the loads increase with climbing power outputs, regardless of whether it's a zillion RPM or some massive torque at lower revs, it is all derived from the piston pushing down towards the crank & it's just those poor little caps holding it in. The greater the power, the greater the push.

Some engines are able to produce so much power that the ability of the caps to maintain their shape & integrity is compromised.
The best way around it without casting a whole new block design is to beef up the bottom end with better quality cap material, stronger bolts/studs or bigger/ 4 bolt caps & any combination thereof. 4 bolt caps can help increase the rigidity of the block too if it's one of those flyweight 'thinwall' engines, but Hemi's wouldn't know anything about 'flyweight'.

As for your question about the lower reving truck engines, I don't know as the truck engine normally runs at a lower compression & lower power rating, so perhaps it's simply the hours of full load pounding that is enough to allow caps to deform enough to cause bearing wear problems or cap fatigue problems.
Passenger car engines rarely see full power at full load for more than a few seconds as the load is usually relieved by the spinning wheels or an increase in speed that allows a power reduction.

The A13 engine of Feral's produced it's best power at 10,200 rpm in 'endurance' trim. It uses billet steel bearing caps with only 2 studs/bolts to secure them. That's Datsun tough. ['endurance' & '10,200' rpm in the same sentence seems a contradiction in terms for most engines]

Click here for Ferals webpage on this engine.

This engine uses the "stronger fasteners & better cap material" method.

thanks folks for all the info. Its my inquisitive nature that probes for specific answers. i guess that since some of the answers were different and there didnt appear to be a consesus on what was the reason exactly. Revs, HP, torque, poor design, or a combination of any of them, it was a little difficlut to decide what the actual answer was.

Dodgeman, you hit the nail on the head with
Quote:

and power really is the result of revs, hp, and torque. I guess there isnt a formula the engine builders use to decide this and its decided by prior experience rather than science.

Thanks yet again for all the informed opinions peoples. I think its time to put my pestering to rest.

Kegs, the question was intially was about the donk i got from you, but I decided about 10 posts back not to bother since it was clear that the a series doesent need any extra beefing up.

Quote: I'm surprised & disapointed that with so many motorheads here that nobody picked me up on this, so here's your challenge.

If the second OHV Chev V8 design was released for the 1955 model, then when was the first? [I was looking at one just over a week ago]

Everybody knows Chevrolet had a V8 in 1914.

But it seems there is no agreement on 4-bolt mains. No one has changed what wikipedia says...

I would say it has more to do with the V8's greater reciprocating mass.
Take a massive engine like a mega HP hemi V8, some of them have a 6 bolt main. But at 9800 rpms (Well, maybe if it's a Ray Barton motor) the reciprocating mass is unbelievable. With a balanced A series turning at say 10k, the mains are more than adequate to withstand the loading.