Why no thrust recess in Main Cap ?

[Exminiman]

Morning folks

Any one got an idea why these 4 bolt main caps dont have recess for the Thrusts ?

Have googled and cant find any info at all

Could it be so that you get machined yourself or do you not use top pair thrusts....or ....

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[mk1]

Yup, The thrust recesses need machining in as part of the line boring process. If they were already in, they would still need doing again when the cap was fitted. Just a way of the manufacturer saving a few quid.

[agricola]

I think I would go with the save a few quid Mark . My S block was line honed with out re-maching the caps for the thrust
If you need to line bore them which is aggressive as opposed to hone them that much these new caps are not worth buying

[Spider]

Some of the Competition Engine Builders will fit only the Uppers. There's a few things to take in to account as to which way to go and why.

I know one of our top line builders, while fitting thrusts in the caps seriously thins them down so as they are only effectively holding the uppers in place ans stopping them from spinning.

[CooperTune]

As we know the Midget and Spitfires have only half thrust. They also suffer thrust area crank wear. Steve (CTR)

[Exminiman]

As we know the Midget and Spitfires have only half thrust. They also suffer thrust area crank wear. Steve (CTR)

Hi Steve, this is the 1275 inline A series, assume you are referring to the 1500 Triumph engine ?

[Exminiman]

Thanks for help, will have chat with machinist and see what he thinks.

Cant help thinking though, without the thrust recesses machined, makes it look like an expensive part..

Wondering what benefit there is in running without bottom thrust bearings, apart from no chance of them spinning....

[Spider]

The MED ones have the Thrust Face machined, though, it may need trimming

https://www.med-engineering.co.uk/engin ... t-main-cap

Can I also suggest, that if you have the original cap and there's nothing wrong with it, run with that, no strap, just fit it and go.

[Exminiman]

The MED ones have the Thrust Face machined, though, it may need trimming

https://www.med-engineering.co.uk/engin ... t-main-cap

Can I also suggest, that if you have the original cap and there's nothing wrong with it, run with that, no strap, just fit it and go.

Agree, but there is some porosity in the casting, not a massive amount, but not in a great place ......just not worth the risk, IMHB

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[Polarsilver]

The Archbishop of Canterbury was on BBC TV News today suggesting that we worry too much..
If mine i would bung it all together & prove the Archbishop wrong .. "unless it is a race engine".

[Exminiman]

Cheers Mate....appreciate what your saying, I also suffer from acute “Mechanical Sympathy” .....it would stop me putting my foot down....