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Old 08-07-2021, 07:24 PM   #1
shoestring
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Default Here is the answer to what is OHC interference

OK, measured this on an untouched B230 head with a correct base measurement of 146.1mm. That's the distance from the deck to the valve cover surface.

The intake valve is 9.80mm below the head deck, the exhaust is 9.58mm below. A stock head gasket is 1.2mm compressed. That means that if you have a stock engine, and your piston is EXACTLY zero deck, the M cam's exhaust lift of 10.5mm is about as far as you can go. Therefore, the A cam (10.5mm lift int/ex) is going to be ok, but the B cam (10.6mm int/ex) may not be, depending on piston position. Yeah, I know, 0.1mm is very little, but you've got to draw a line somewhere. If you mill the head, whatever you take off REDUCES the maximum lift you can run and still be non-interference.

Anything with 11.0mm or more is definitely interference.

So there you go. Moral of the story is change your timing belt. They couldn't have made it easier.
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Old 08-07-2021, 10:48 PM   #2
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Sticky the hell out of this.
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Old 08-08-2021, 03:22 AM   #3
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B230F and B230FT pistons go above deck about 0,4 mm.
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Old 08-08-2021, 11:01 PM   #4
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B230F and B230FT pistons go above deck about 0,4 mm.
Not all the time.
Piston heights are all over the place, just like chamber volume.
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Old 08-10-2021, 12:13 PM   #5
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Not all the time.
Piston heights are all over the place, just like chamber volume.
I've found that Mahle pistons are pretty dead on with the compression heights. Volvo conrod length has wider tolerance, 0,1 mm can be found in same engine.
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Old 08-10-2021, 12:25 PM   #6
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I think the bigger variable is the block height from Volvo.
Connecting rods and pistons are easy to accurately make, block heigh it one that a lot of manufactures seem to have gone “good enough!”
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Old 08-10-2021, 01:14 PM   #7
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I think the bigger variable is the block height from Volvo.
Connecting rods and pistons are easy to accurately make, block heigh it one that a lot of manufactures seem to have gone “good enough!”
+1 to this.

Without climate control, thorough process controls, and other advanced monitoring methods it will be the most difficult for a manufacturer to nail down a routine block height. c-c lengths on rods and pistons are fairly easy to control in comparison.
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Old 08-10-2021, 04:13 PM   #8
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Also, tractor engine.
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Old 08-10-2021, 10:52 PM   #9
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Also, tractor engine.
I mean, we’re not talking about pushrod Volvo engines here. We are sophisticated individuals.
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Old 08-11-2021, 10:12 AM   #10
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I had my machinist refer to a 530 head as "sophisticated European hardware" once. His delivery was so dry it wasn't until I'd left that I realized he'd been busting my chops.
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Old 08-11-2021, 11:42 AM   #11
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I mean, we’re not talking about pushrod Volvo engines here. We are sophisticated individuals.
I for one like my OHV sports-tractor.
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Old 08-12-2021, 04:27 PM   #12
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I mean, we’re not talking about pushrod Volvo engines here. We are sophisticated individuals.
Excuse me, but. Modern tractor engines are pretty sofisticated creatures.
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Old 08-18-2021, 12:32 AM   #13
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Ha!

And yes, just to spell it out in yet another way… Almost, it not all, all modern engines are interference. So, if you really want to get every last dollar out of your $17 timing belt, stick to a lame engine. Otherwise, be smart and make more power at the same time by modernizing your engine with an interference setup(yes, there’s more to it than that).
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Old 08-18-2021, 10:17 PM   #14
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Yah but most modern engines use chains now, people wreck the car or other parts deteriorate long before that chain breaks
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Old 08-18-2021, 11:24 PM   #15
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Yah but most modern engines use chains now, people wreck the car or other parts deteriorate long before that chain breaks
Modern Volvos don’t, but I don’t know much about other brands.
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Old 08-19-2021, 06:30 AM   #16
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...or other parts deteriorate long before that chain breaks
Like the guides, for example. MINI N12/N14 and this GM 3.6 V6 come to mind.
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Old 10-07-2021, 10:31 AM   #17
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Yah but most modern engines use chains now, people wreck the car or other parts deteriorate long before that chain breaks
Chains might not break as easily but they do stretch. It's because on modern engines they often use 1 narrow simplex chain. It's cheaper to make, keeps rotating mass acceptably low and as a consequence keeps mileage reasonable.
But many modern VAG, Mini, BMW and PSA engines (and probably more) suffer from cam chain stretch.
It's also common on motorcycle engines.
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