Transit 2.4 tdci. Problem with main bearing clearance.

[Schott82]

Hello everyone, my name is Antonio and I'm writing from Sardinia. Sorry for my poor English.

I purchased a Transit 2.4 tdci with a Duratorq H9FB engine that had melted bearings. I had the cylinders, crankshaft, and cylinder head refaced. The crankshaft was refaced: main bearing seats at -0.25 and the connecting rod at -0.50. So I purchased oversized main bearings with a 0.25 main bearing and a 0.50 connecting rod bearing.

Before reinstalling everything, I preferred to test with plastigage as recommended in the Ford manual. Main bearings 2, 3, 4, and 5 are fine with a clearance of ~0.04 mm, but #1 has a clearance of 0.076 mm. Ford specifications indicate a clearance of 0.005 to 0.051 mm. So I fit perfectly with bearings 2/5, but the first one has a clearance of 0.025 mm more than the engine specifications.

I reported this to the reconditioning department, but they told me it was fine anyway. Searching online, I only found that it could be a major mistake with serious repercussions. There are three alternatives at my point of view:

1) grinding of bearing no. 1 to -0.50 and using a larger bushing +0.50, and leaving the others as they are

2) Find a custom bushing with a thickness of +0.32, which would give me a play of 0.04 like the others.

3) Don't care about the fact that I'm out of tolerance with the No. 1 bushing and reassemble everything.

I hope someone can help me find the most correct solution.

Best regards

[metalworker0]

this is the rule that all engine re conditioners go by .. it's in inches, so will rewrite in metric underneath (rounded)

inches
A common rule of thumb for main bearing clearance in engines is 0.001 inch per inch of shaft diameter. This means that for every inch of the crankshaft journal diameter, you should aim for a bearing clearance of 0.001 inch.

metric
A common rule of thumb for main bearing clearance in engines is 0.025mm per 25mm of shaft diameter. This means that for every 25mm of the crankshaft journal diameter, you should aim for a bearing clearance of 0.025mm

transit 2,4 main journal diameter is 69.5 mm - so 0.025 +0.025+ maybe guess 0.022 = 0.072 ... so your only like 0.006mm outside of the rule of thumb specification - if i have this right . which is bugger all.

please someone else confirm if i have this in the ball park

all the best.mark

[knobby1]

this is the rule that all engine re conditioners go by .. it's in inches, so will rewrite in metric underneath (rounded)

inches
A common rule of thumb for main bearing clearance in engines is 0.001 inch per inch of shaft diameter. This means that for every inch of the crankshaft journal diameter, you should aim for a bearing clearance of 0.001 inch.

metric
A common rule of thumb for main bearing clearance in engines is 0.025mm per 25mm of shaft diameter. This means that for every 25mm of the crankshaft journal diameter, you should aim for a bearing clearance of 0.025mm

transit 2,4 main journal diameter is 69.5 mm - so 0.025 +0.025+ maybe guess 0.022 = 0.072 ... so your only like 0.006mm outside of the rule of thumb specification - if i have this right . which is bugger all.

please someone else confirm if i have this in the ball park

all the best.mark

Agree..!

Lord Knobrot

[Schott82]

Many thanks Mark for your answer, really appreciated!

Crankshaft Dimensions description mm
Main bearing journal end float 0.090 - 0.305
--->Main bearing journals 1 to 4 diameter 64.950 - 64.970<----
Main bearing journal 5 diameter 69.950 - 69.970
Connecting rod bearing journal diameter 52.980 - 53.000

In my case, it's the first one, so the dimension is 64.950. Subtracting 0.25 from the correction already made, it should be 64.75. So, according to your calculation, 64.75/25*0.025 = 0.06475 - 0.076 = I'm outside the rule about -0.011. Correct? Is it easily negligible for you?

[metalworker0]

negligible ,... well if it was a race prepared engine they advocate even more clearance than that rule, so yes i would say below

well what could you do anyway, have the crank reground and then oversize bearings £££££... or the botchers way - sand (surface grind) the face of the journal so its tighter some shops they do that, but line bore afterwards to get it round again.

read this ..

https://www.motortrend.com/how-to/1907- ... -clearance

several times they state extra clearance of the magnitudes your talking about is not necessarily bad .

negligible with the info provided above, make you choice , it's your decision really, not mine .

oh ROUNDING - and ive knocked off the 0.4mm off the inch .. so your 0.011 will be a little smaller than that .. that's all the maths im up to .. im not great

all the best.mark