LM 5000 Engine rebuild

[heathcr]

Hi everyone.

Looking for advice from anyone who has more knowledge than myself..

I have an LM 5000 and about to embark on an engine rebuild.

Main goal is to keep it original as possible with only minor mods. Will remain a weekend driver not track.

So far we are thinking balancing and blueprinting, roller rockers, cam and double row timing chain.

It already has the B cast heads. 5 speed manual. Has been stripped down and no wear issues noted other than single row timing chain.

Any advice would be appreciated

Cheers
Heath

 

[Smitty]

an LM engine is a basic Holden 308 V8
and the process/parts required are as per a rebuild of any 308

careful measuring and installation, quality parts.... will give a great result
Stick with what Holden made originally pretty much. Maybe a rubber sump gasket instead of cork

oh.. and a double row timing chain

 

[heathcr]

an LM engine is a basic Holden 308 V8
and the process/parts required are as per a rebuild of any 308

careful measuring and installation, quality parts.... will give a great result
Stick with what Holden made originally pretty much. Maybe a rubber sump gasket instead of cork

oh.. and a double row timing chain

Thanks for your reply Smitty.

Any particular brand of parts we should be looking at? I have a guy down in Wollongong doing the build however I would like to make sure we are using the best parts.

You would stick with the original cam? My builder suggested getting a new cam ground to the exact same specs as the one we have taken out.

Roller rockers help much? The builder reckons not but I see a lot of guys on forums have used them.

Cheers
Heath

 

[_R_J_K_]

You would stick with the original cam? My builder suggested getting a new cam ground to the exact same specs as the one we have taken out.

Roller rockers help much? The builder reckons not but I see a lot of guys on forums have used them.

The builder wants to use a new cam as the original may have wear that effectively changes the cam specs. This kind of wear is normal with an engine this old. They probably hadn't moved to steel cams at that point either. Usually you wouldn't reuse a cam either in a rebuild as the tappets and lobes uniquely wear into each other, or you would have it reground.

Depending on which source you read and which engine you're looking at, the stock 308 roller rocker ratio is either 1.6 or 1.65, and most brands don't offer more than a 1.65. If you're wanting to add roller rockers based on results from the big ratio ones you can use on the V6s, the 308 can't go anywhere near as far. Usually you would also just factor the extra lift from roller rockers into your cam selection, particularly if you're going to roller lifters which can deal with a "sharper" lobe if you wanted the extra lift but not the duration that you might need for a flat tappet cam to work.

 

[Smitty]

The builder wants to use a new cam as the original may have wear that effectively changes the cam specs. This kind of wear is normal with an engine this old. They probably hadn't moved to steel cams at that point either. Usually you wouldn't reuse a cam either in a rebuild as the tappets and lobes uniquely wear into each other, or you would have it reground.

Depending on which source you read and which engine you're looking at, the stock 308 roller rocker ratio is either 1.6 or 1.65, and most brands don't offer more than a 1.65. If you're wanting to add roller rockers based on results from the big ratio ones you can use on the V6s, the 308 can't go anywhere near as far. Usually you would also just factor the extra lift from roller rockers into your cam selection, particularly if you're going to roller lifters which can deal with a "sharper" lobe if you wanted the extra lift but not the duration that you might need for a flat tappet cam to work.

poster said -
Main goal is to keep it original as possible with only minor mods.
adding roller lifters based on LS cam geometry is NOT minor mods..! and it is needing lots of machining to fit this ( as I found)
so
grab any off the shelf Crane/Comp/Crow 308 cam that is mild (remember the LM ran a stock VK 308 factory cam)
+new hydraulic lifters (and pushrods) with any brand bolt-on roller rocker (YT, Crane, Crow all good) and
with that double row timing chain, you have a very good valve train setup. Just don't complicate things...

 

[_R_J_K_]

adding roller lifters based on LS cam geometry is NOT minor mods..!
Just don't complicate things...

Wasn't really suggesting to go for that if it wasn't on the cards originally. Except for machining for the rocker and spring setup with bigger cams, what's the machining involved that makes it such a problem? I know people who have had plenty of success even with 286 equivalent roller cams. Is it the same for close to stock sized or stock roller cams?

 

[Smitty]

Wasn't really suggesting to go for that if it wasn't on the cards originally. Except for machining for the rocker and spring setup with bigger cams, what's the machining involved that makes it such a problem? I know people who have had plenty of success even with 286 equivalent roller cams. Is it the same for close to stock sized or stock roller cams?

.. a 286 cam is fine, but it needs compression. You MUST machine the heads and got the comp up from the low 8 it is standard
to at least 10.1

and you don't need to machine for springs or roller rockers. You can buy very adequate roller rockers and springs...
bolt on, no machining required !

 

[heathcr]

.. a 286 cam is fine, but it needs compression. You MUST machine the heads and got the comp up from the low 8 it is standard
to at least 10.1

and you don't need to machine for springs or roller rockers. You can buy very adequate roller rockers and springs...
bolt on, no machining required !

So Crow cams have a group a spec - model 5770. This coupled with the bolt on YT rockers (crow have told me their rockers won’t fit under the standard hdt valve covers I have) should be an ok upgrade? Will match with my reconditioned quaddy? Remember we have the B cast heads and the HDT dizzy already.

Do we need to look at higher compression with the above mods?

Thanks