Twin/single oil sump drain plugs and crank bearing size
Discussion
Good morning all,
On AJP engines, is there any relationship between the style of oil sump (early featuring two oil drain plugs, late only one) and the crank bearing size (early 2.3" vs late 2.5") ?
Asked differently, will an early engine fitted with an early "twin drain plug" sump necessarily run on an early, smaller bearing crankshaft?
Inversely, will an engine running on a late, larger bearing crankshaft necessarily be fitted with a late "single drain plug" sump?
On AJP engines, is there any relationship between the style of oil sump (early featuring two oil drain plugs, late only one) and the crank bearing size (early 2.3" vs late 2.5") ?
Asked differently, will an early engine fitted with an early "twin drain plug" sump necessarily run on an early, smaller bearing crankshaft?
Inversely, will an engine running on a late, larger bearing crankshaft necessarily be fitted with a late "single drain plug" sump?
1485 might know. Other than that try Jason at Powers. I suspect the reason noone here knows is because noones ever run a survey. Why the intrigue though (genuinely interested in what you're planning)? If looking to purchase you wouldn't be able to tell 100% just by a photograph as the engine may have gone back to TVR for a rebuild and had the larger crank fitted. Could be a good rule of thumb though.
All I really have to add is mine is a '96 with the twin plug sump and had a small journal crank until rebuild.
All I really have to add is mine is a '96 with the twin plug sump and had a small journal crank until rebuild.
CerbWill said:
A cast crank that looks like this. I'd heard that there were two versions of cast small journal crank, 1 with larger counterweight than the other.
There is indeed.. The earliest ones had less counterweight (insufficient) and were very prone to cracking. Can't imagine there are many (any?) of them left still going!
Thom said:
So you are saying you are running a large journal crank now with a twin plug sump?
If yes this should answer my question without the need for any survey.
Yes I am. As part of my rebuild I had the large journal crank fitted and my block line bored to suit. Sump is still the original twin plug.If yes this should answer my question without the need for any survey.
For un-rebuilt engines it may or may not be an indicator of crank size still.
They did a later cast small journal crank, which is less prone to snapping (did they actually even snap?)
They also did a billet small journal, mostly found in early 4.5's (GTs). Which is the ultimate small journal.
The only reason the AJP swapped to large journal was the RV8 did and it shares bottom end bearings.
They also did a billet small journal, mostly found in early 4.5's (GTs). Which is the ultimate small journal.
The only reason the AJP swapped to large journal was the RV8 did and it shares bottom end bearings.
Ok, so can we set up a list of all different AJP crankshafts supplied from the factory?
- Cast - small, 2.3" journals - narrow counterweights
- Cast - small, 2.3" journals - wide counterweights
- Billet - small, 2.3" journals - wide (?) counterweights
- Cast (?) - large, 2.5" journals - wide (?) counterweights
Edited by Thom on Thursday 20th June 10:44
Jhonno said:
Twin drain was with the early small journal cranks. Probably the most fragile version of the crank.
Well I did 60K miles of abuse in mine. It was still good when I had the engine rebuilt last year, just the brass valve guides had worn.CerbWill said:
Thom said:
So you are saying you are running a large journal crank now with a twin plug sump?
If yes this should answer my question without the need for any survey.
Yes I am. As part of my rebuild I had the large journal crank fitted and my block line bored to suit. Sump is still the original twin plug.If yes this should answer my question without the need for any survey.
For un-rebuilt engines it may or may not be an indicator of crank size still.
Byker28i said:
Yup - me too. No-one would warranty a rebuild without having the large bearing crank fitted. £600 of machining, £1750 for the crank...then VAT.....
£1750 would be for a billet crank though, not a cast one?I imagine TVR Parts would supply a cast large bearing crank these days?
https://tvr-parts.com/tvr-parts/part-details/tvr-e...
Thom said:
Byker28i said:
Yup - me too. No-one would warranty a rebuild without having the large bearing crank fitted. £600 of machining, £1750 for the crank...then VAT.....
£1750 would be for a billet crank though, not a cast one?I imagine TVR Parts would supply a cast large bearing crank these days?
https://tvr-parts.com/tvr-parts/part-details/tvr-e...
Side question - if a billet small journal crankshaft can be sourced, why go through the extra expense of line boring the block for a large bearing crank? Are the small journal bearings difficult to source or is there any problem with them?
I cannot believe a billet crank using 0.2" (i.e. less than 10%) smaller journals should be massively weaker than a large journal crank.
I cannot believe a billet crank using 0.2" (i.e. less than 10%) smaller journals should be massively weaker than a large journal crank.
Edited by Thom on Thursday 20th June 14:33
You need to consider torsional load, which is distributed towards the outside of a cylinder so the 0.2" has more of an effect than the dimension or mass increase might first suggest.
Byker, not sure if your crank was really early with the small counterweight. Interestingly mine (registered Sept 1996,l) had a small journal with the larger counterweight. I wonder if mine had snapped its crank at some point and gone back to the factory to have the larger counterweight crank fitted during rebuild. I have no history for the car that far back so I cannot prove or disprove. It does have the later type dipstick though. I'll have to have a look at the engine number this weekend.
Also, it's been a while since I was looking for a crankshaft but TVR Parts didn't have any in stock.
Byker, not sure if your crank was really early with the small counterweight. Interestingly mine (registered Sept 1996,l) had a small journal with the larger counterweight. I wonder if mine had snapped its crank at some point and gone back to the factory to have the larger counterweight crank fitted during rebuild. I have no history for the car that far back so I cannot prove or disprove. It does have the later type dipstick though. I'll have to have a look at the engine number this weekend.
Also, it's been a while since I was looking for a crankshaft but TVR Parts didn't have any in stock.
Edited by CerbWill on Thursday 20th June 15:03
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