Main cap straps

[otanica]

Hello all

Is it worthwile installing main cap straps on a 4AG to lock the bottom end up a bit more? I have access to all the necessary machine so it will cost nothing just wondering if it will make any difference to a high rpm engine.
Does anyone make a girdle or is the deep skirt block make them redundant.

Will ARP main studs with standard caps be fine


Thanks Brad

[wilbo666]

Sean (MS-75),
Had a good discussion running in his thread...most of the talk should apply I'd think!

Check it out here...
http://www.toymods.net/forums/showthread.php?t=11181

Cheers
Wilbo

[jeffro ra28]

That link doesnt work for me wilbo ?

Brad, Main girdles are said to be beneficial to block rigidity. It would depend on the torque you are trying to acheive as to whether it would make a difference to your engine/bearing/crank life however.
Short answer is yes, they are advantageous.

A solid OEM design is the Nissan RB series of engine. They have a one peice main bearing cradle which has been proven to hold up to anything in the region of 1000hp out of the 3 litre variant.

[Sam_Q]

not related but I think the F20C is a most interesting one, it uses what diesels use and thats a split block with one massive section housing the equivolent of bearing caps.

Back on subject I have seen a japanese product for a main cradle to bolt to the top of a set of 4age bearing caps but its pretty obvious sometimes that the japs make some products that do absolutely nothing, many of their so called body braces come to mind.

[SeptemberSquall]

some later model toyota engines use a similar design

[oldcorollas]

some of the jap girdles (i can think of 2 or 3 that were available) looked reasonably solid, but given the number of 4A's runnign over 200kw with few issues, is it a large problem?

in a bigger engine with more mass, or V8 with more mass moving between bearing supports, maybe there is more of a problem with crank noodling?

some engines are notorious for it.. some you hardly hear of it... maybe they just haven7t been pushed hard enough yet

[oldcorollas]

SS works do one.. it has step down to the caps
http://www.ss-works.jp/partslist2.html (those caps are removeable, and i think stock?)

there is also another "power deck plate" パワーデックプレート listed, but it looks flat, and uses an alloy under bit to space out the oil pan etc...

[oldeskewltoy]

The A block is different from some... In many engines the crank rotates on the centerline of the oilpan flange. The A series engines "bury" the crank up inside the block. The skirted block adds considerable rigidity...

The Ford FE engine series use this same method... location the crank inside the block. The best of the design was when Ford also cast the 3 internal main bearing caps with a boss on the side. This boss was then drilled and threaded... Finally bolts were run THRU the side of the block, through a spacer, and then into the main bearing cap.... the system is called cross bolted mains.... and I BELIEVE it first appeared on Fords 406 racing engine in 1963...........

[wilbo666]

That link doesnt work for me wilbo ?

Fixed the link!

Cheers
Wilbo

[30psi 4agte]

I think the straps are a waste of time! the girdle is the way to go but pricey ....... unless you are making more than 250rwkw + the high RPM i wouldnt even bother. Id be more concerned with the splitting a bore than i would be about the crank walking around at that sort of power level.

EDIT: just noted .... i think we are talking atmo here so disregard the bore issue

[GasedT18]

It's odd when you are thinking about a topic and someone posts on the same topic.

How do 3T-GTE bottom ends fail - would bracing help?

oldeskewltoy: + rep, I wonder how much tension on that bottom bracket influences bearing wear - it might be a real bugger to tension up and do test fits for new clearances.

I came across this recently - it's a Honda engine.



D