Bottom End Bolts?

[MPO]

When refurbishing a bottom end on a later cross bolted block what bolts require replacement (can’t be reused)? Also, would it be ok to use OEM bolts and only ARP on the conrods and still have maximum strength?

MPO

[caduceus]

What have you done? Polished crank and new shells?

[Sardonicus]

ARP dont list rod bolts for the full serp engines IIRC they do for the earlier pre serp and intermediate serp engines with rod nuts and bolts though (not interchangeable with full serp) personally I wouldn't use rod bolts twice on anything especially yield/stretch too much at stake IMO

[MPO]

caduceus said:

What have you done? Polished crank and new shells?

Hi Caduceus

The crank has been reground with new undersize shells, I just need to get the flywheel lightened (or purchase), upgrade the cutch and send everything off for re-balancing…

I’ve heard conflicting views on the reuse of the later block (Large Main and Cross Bolted) bolts. Some say they can be reused, some say they can’t, some say they are stretch…

I’m looking at:

1. The cross bolts
2. The Big End bolts
3. The Mains

MPO

Edited by MPO on Wednesday 17th February 14:06

[MPO]

Sardonicus said:

ARP dont list rod bolts for the full serp engines IIRC they do for the earlier pre serp and intermediate serp engines with rod nuts and bolts though (not interchangeable with full serp) personally I wouldn't use rod bolts twice on anything especially yield/stretch too much at stake IMO

The block is a very late coscast block but will have an intermediate cover from a donnor engine I have:-

Here is a shot of the coscast bottom end:-



Any further thoughts on reuse of the bolts and if ARP can be used for the big ends?

MPO

[OleVix]

I did this last year on my xbolt 4.6. Conrod bolts are stretch so you need new. Mains and xbolts are not stretch and can be reused. ARP should not be needed since the xbolted bottom end is very solid unless you are building a 7k rpm race engine. ARP head bolts on the other hand are a good idea.

[phillpot]

As a general rule of thumb aren't stretch bolts usually torqued to a set figure then turned a further number of degrees whereas normal (re-useable) bolts only torqued?

[caduceus]

phillpot said:

As a general rule of thumb aren't stretch bolts usually torqued to a set figure then turned a further number of degrees whereas normal (re-useable) bolts only torqued?

[Sardonicus]

caduceus said:

The serp bolts are yield type but even if they was not I still wouldn't re-use them a thrown rod will fk the crank block and if you have nicely ported expensive BV heads for example it will take at least one of those too potentially and just as a bonus possibly the camshaft and all this carnage more likely if you use the engine in anger

[MPO]

Sardonicus said:

caduceus said:

The serp bolts are yield type but even if they was not I still wouldn't re-use them a thrown rod will fk the crank block and if you have nicely ported expensive BV heads for example it will take at least one of those too potentially and just as a bonus possibly the camshaft and all this carnage more likely if you use the engine in anger

Sardonicus

Are you refering to the Con Rod Bolts only? OleVix, seems to think these particular bolts are the only stretch bolts in the bottom end?

Cheers
MPO