For the love of a tractor engine: The life and times of the 18R-G

[Steve M]

The chain in these engines will usually go from tight to slack when these engines are turned by hand.

This is caused by the inlet cam being acted upon by valve spring pressure. As you slowly turn the engine the cam inlet cam will be spun ahead a bit by the cam lobe angle and valve spring pressure. This results in the chain suddenly going quite slack between the cams if there is not adequate tension on the chain from the tensioner. This is quite normal.

Usually I notice this when I am setting cam timing, at which time the tensioner is slackened back.

I would not be surprised if the chains have some wear in them, but I doubt that the issue is entirely due to that.

The tensioner is primarily operated by oil pressure but has a light pre-tension spring in it.

If the engine has been sitting for a while (or been hand turned), the oil will likely have drained from the tensioner to some extent and this will make the tensioner slack when hand turning the engine.

I wouldn't worry about it too much. I'd always replace the chains and bearings in an 18RG that I bought; it's just safer to pull them apart, replace some wear/tear items and check everything over by eye before running them if their condition is not well known.

[Javal]

The chain in these engines will usually go from tight to slack when these engines are turned by hand.

This is caused by the inlet cam being acted upon by valve spring pressure. As you slowly turn the engine the cam inlet cam will be spun ahead a bit by the cam lobe angle and valve spring pressure. This results in the chain suddenly going quite slack between the cams if there is not adequate tension on the chain from the tensioner. This is quite normal.

Usually I notice this when I am setting cam timing, at which time the tensioner is slackened back.

I would not be surprised if the chains have some wear in them, but I doubt that the issue is entirely due to that.

The tensioner is primarily operated by oil pressure but has a light pre-tension spring in it.

If the engine has been sitting for a while (or been hand turned), the oil will likely have drained from the tensioner to some extent and this will make the tensioner slack when hand turning the engine.

I wouldn't worry about it too much. I'd always replace the chains and bearings in an 18RG that I bought; it's just safer to pull them apart, replace some wear/tear items and check everything over by eye before running them if their condition is not well known.

Thanks for that Steve - it's good to know i haven't bought a munted one.

It was sold to me in good running order - 140psi flat compression. It'll still be recieving some VRS kit love and a few other things though

[o_man_ra23]

I am with Steve on this, replacing rings and bearings before the motor is in the car is a lot easier. Usually a quick hone, an acid bath, shave the head and you are away. Also a good time if you have the spare coin to throw in things like decent head studs and rod bolts. Oh, and a crank linish is normally a good idea too. I have also found metal spraying the rear main seal surface is a good option, though this can be quite costly.

As for the chain issue... yes, it is normal operation when you don't have oil pressure up to the chain, and Steve has described exactly what causes it.

[Javal]

I am with Steve on this, replacing rings and bearings before the motor is in the car is a lot easier. Usually a quick hone, an acid bath, shave the head and you are away. Also a good time if you have the spare coin to throw in things like decent head studs and rod bolts. Oh, and a crank linish is normally a good idea too. I have also found metal spraying the rear main seal surface is a good option, though this can be quite costly.

As for the chain issue... yes, it is normal operation when you don't have oil pressure up to the chain, and Steve has described exactly what causes it.

She won't be getting a rebuild for sure - once the head comes off we'll see where we sit, but 140 flat comp is enough for me. That's more than most LS1's have It's a lot of trouble for me to rebuild it anyway - more money and MORE time. After the fuck arounds i've had...

[river]

Hi,

Just because the top end looks okay and you have good compression does not mean the bottom end is fine.

I agree with the others that if the engine is out of the car then do it properly and do a full rebuild.

The engine I got recently had fine compression across the pistons and the top end looked very clean. However, when the engine was pulled down you can see scoring from the bearings and there was some freeplay in the crankshaft. If the engine was not rebuilt properly it would only be a relatively short matter of time before I'd hear some grumbles from the bottom end.

Sure it initially costs more to do it properly, but it's money well spent to be confident your engine is fully rebuilt with new components, balanced and honed. In the end it saves you time and money 'cos you don't need to pull the engine out after a while to fix something you should of fixed before the engine was put in the vehicle.

seeyuzz
river

[LTJET]

i'd have to agree with river as it'll cost more later on. i got mine rebuilt so i didn't have to do it later.

[Javal]

Right.

So, reasearch time for rebuild parts.

Bearings - Same as 18R-C? Readily available.

Rings - I was under the impression that 88210 pistons use the same rings as 18R-C, but what about my 88253?

[hosking1991]

rings iirc are all interchangable between each other (18rc<>18rg) expect the 88270 (8.3:1) pistons which have a thinner ringland

bearings are the same

[Javal]

rings iirc are all interchangable between each other (18rc<>18rg) expect the 88270 (8.3:1) pistons which have a thinner ringland

bearings are the same

Thanks for that. I'll wait for confirmation before i order them

[river]

Hi,

PM YelloRolla as he is rebuilding my engine and has done Witzls and Norbies... so he quite familiar with the 18R-G. I'm sure he can advise on the bearings and rings etc to make sure you get the right stuff for your engine.

seeyuzz
river

[RAd28]

If you can get clarification on this matter, i'd love to hear, I've got my 18RG mid-rebuild atm too...

[The Witzl]

18RG use the same bearings and rings as an 18RC.
As mentioned, only the 18RGEU 8.3:1 pistons use different rings.

I rebuilt my other 18RG myself - i just got an engine reconditioner to do all the machining and speccing of the bearings, and pointed out the ACL bearings and rings to order.

For gaskets - i used the ACL DG690 kit (iirc), but used a genuine toyota 18RGEU head gasket, as it is MUCH higher quality than any gas miser or ACL headgasket... and only cost me $55 on trade from castle hill toyota.

I think the whole rebuild cost me $600, which included machining and balancing bottom end, block/head surface grind, honing, replacing all 4 exhaust valves, all 8 valve stem seals, and checking/servicing valve seats.

Quite cheap really.
I did all the assembly though....

[o_man_ra23]

Yes it is only the 18R-GEU pistons which have the unusual and impossible to get rings. I got my ringlands machined on my 8.3 pistons though to suit the 18R-C rings, as the GEU rings are thinner. Oil control rings are the same though.

I used the gasket set from Stewart Wilkins Motorsport as they are a high quality kit, and use the genuine Toyota headgasket. Something you will find though, is that they only have one dizzy oring, and you need 2. They are about 20c from your local seal shop though. My rebuild cost a lot more, but involved things like machining extra manifolds, and sleeving the bores. These were necessary expenses. Oh, and the cam end seals are not included in the gasket kits, I bought 2 genuine from Toyota, at the time they had 3 in melbourne, not sure if they are getting more in the country, they are about $13 each.

[Sagluren]

my entire build from top to bottom including carbs and tune cost me $1200 i did all the assembely and the honing myself. But what ever you do dont hone yourself, get it machined even if it means oversized pistons, i did it all myself, and had a good bore still within spec but had blow by. i really do highly recomend the bore getting machined, it was silly of me to hone my self, but when your dad is a engine builder and says it will be ok, you kind of think it will be, oh well


cheers sam.

[Javal]

Thanks for all that guys, it's been a big help.

I got Spare parts at work to quote me on std size rings and bearings - $150 for the lot

Crank will be linished, bores honed. Clearances i will do myself. I'll be using the SW motorsport VRS kit. Should be a simple build with good results. I'll keep you all posted.