Bottom end rebuild - what am I in for?

Bottom end rebuild - what am I in for?

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Discussion

richardmadden

Original Poster:

38 posts

43 months

Wednesday 30th December 2020
quotequote all
In Tier 4 and a bit bored so I thought I'd post an update on my bottom end woes.

All sorted now.

All the bearings were worn and one of them had partially disintegrated and the bits had knackered the oil pump. The engineer stripped everything and got busy with his micrometer. The crank itself was fine (no need for a regrind) and there was no damage to the top end - somewhat miraculously. The fragments of the bearing seem to have kept their integrity as there was no swarf in the oil. Seems I was very lucky.

Anyway, around £1,300 later I have a fully refurbished bottom end and new oil pump to go with the top end I had done a couple of years ago. I'm running it in and will change the oil and filter at 500 miles.

Interestingly, I've been recommended to switch from 10w50 fully synth to 10w40 semi synth. Presumably I don't need the thicker stuff to keep the oil pressure up any more.

Hope that's of some interest and adds to the sum of RV8 knowledge.

Classic Chim

10,953 posts

114 months

Wednesday 30th December 2020
quotequote all
richardmadden said:
In Tier 4 and a bit bored so I thought I'd post an update on my bottom end woes.

All sorted now.

All the bearings were worn and one of them had partially disintegrated and the bits had knackered the oil pump. The engineer stripped everything and got busy with his micrometer. The crank itself was fine (no need for a regrind) and there was no damage to the top end - somewhat miraculously. The fragments of the bearing seem to have kept their integrity as there was no swarf in the oil. Seems I was very lucky.

Anyway, around £1,300 later I have a fully refurbished bottom end and new oil pump to go with the top end I had done a couple of years ago. I'm running it in and will change the oil and filter at 500 miles.

Interestingly, I've been recommended to switch from 10w50 fully synth to 10w40 semi synth. Presumably I don't need the thicker stuff to keep the oil pressure up any more.

Hope that's of some interest and adds to the sum of RV8 knowledge.
Good news thumbup
It could be argued the thicker oil caused the wear especially from cold. Thicker oil is harder to push so though it might show an instant high pressure on the gauge doesn’t mean that oil is moving fast to the points it needs to be at. Thicker oil could = higher oil pressure but lower flow rate.
Bearing wear from a car that has a high acceleration rate is not uncommon though.
I think old oil can also be the cranks worst friend so I now consider 4000 miles to be more than long enough before replacing it.
They tend to run rich to aid cooling here and there which is depositing a lot of semi burnt fuel into the oil so it’s well worth just replacing it often. I’ve got a bit anal with it, as soon as it’s changed colour and gone black 2000-3000 miles I want to replace it lol.
I had a Crank regrind so want to look after it. If your crank was within tolerance you caught it early enough which is better than having to regrind it.

mikanel

64 posts

135 months

Wednesday 3rd March
quotequote all
I did a rebuild on a pre serp 400 2 years ago and the engine parts from TVR Parts came to £650. This included a cam, new tappets and timing gear but the crank was still in tolerance so replacement std shells fitted. The bores pistons and rings were good so reused. The oil pump housing was still in tolerance but the gears were worn and were replaced. Oil pressure now excellent.