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MGB MGB Double Row Timing Chain

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kyreb1862

kyreb1862

Jedi Knight
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I have read that changing from a single row chain to a double row chain on my 77 mgb would possibly be a performance upgrade. The explanation was that it would give the 77 18v engine more mid range power. Anyone have any experience with this? Would it be worth the time and expense?

Regards John
 
tony barnhill

tony barnhill

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Don't know about more power but I always do it for security!
 
OP
kyreb1862

kyreb1862

Jedi Knight
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I had heard that they used an offset key with the single row chains to (correct me if I'm wrong) advance the timing to give more low end power to the smogged 18v engines. The theory is that changing to the double row chain and gears gives more mid range power. I also think your right Tony that it would be be worth while if just from a security stand point.

Regards John
 
DrEntropy

DrEntropy

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Chains stretch, they stretch a quarter as much with a double row chain. In "RealWorld" circumstances I'm not sure that's as true as it seems in theory but it can't HURT. :smile:
 
WA1KWA

WA1KWA

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I changed to a double row chain when I rebuilt my 1974 MGB engine, because it's more robust. No reason it would give more power anywhere in the range. Leyland went to single row chains because they were cheaper. That's all.

Colin
 
tony barnhill

tony barnhill

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DrEntropy said:
Chains stretch, they stretch a quarter as much with a double row chain. In "RealWorld" circumstances I'm not sure that's as true as it seems in theory but it can't HURT. :smile:
Click to expand...
One of the weak links (pun intended) in my 380SL engine was its single timing chain setup...Mercedes went to it for who knows what reason & then quickly put out a message that owners should convert to the double chain to protect the engine in the event of a catastrophic failure (guess they had a few!).....when they replaced the 380SL with the 560SL. they went back to the double timing chain.....its just good insurance in our little cars & isn't real expensive to do (couple of good used double sprockets, chain & tensioner - heck, MG didn't even change the tensioner when they went to single chain).
 
DrEntropy

DrEntropy

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Yeah, Colin, longevity would be the only benefit. Offset keys can be used with either. But in all honesty I've not seen a single row chain disintegrate unless the engine had been TOTALLY abused/neglected.

Lotus used a single row to drive the cams and offset dowels to tweak the timing, I've run those for hundreds of thousands of miles. New chain fitted on rebuilds after 80K miles or so was an average but likely unnecessary. Now "Gilmer" belts on the other hand, well... :sick: :pukeface:
 
PAUL161

PAUL161

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I agree with the double row chains for security reasons, but, look at this modern Subaru engine and the length of their single row chains. The scary part is, they convert this engine for aircraft use and use the same single row chain set up! Break a chain on this engine and four cams stop turning and so does everything else!
screwy.gif


E62.jpg
 
DrEntropy

DrEntropy

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Aww, c'mon, Paul.... where's yer sense of ADVENTURE!?!
 
billspohn

billspohn

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Is the single row inferior? Yup, from a reliability point of view, although in the real world, as has been pointed out, single row engines can do high mileage without failure.

I don't know that I'd bother changing over unless you need to buy new sprockets anyway.
 
K

Kuz

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My understanding is they retarded cam timing by 4-5 degrees,in the smog motors. They did this buy changing the key slot in one of the two timing gears in the single chain system.By changing to the double row chain you would advance the cam back to earlier specs, and should gain some low-mid range performance.( The cams are identical)
 
MGBGT_noob

MGBGT_noob

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Depends on which Subie mill you're talking about. Many of them will free-wheel, with a broken timing chain.

PAUL161 said:
I agree with the double row chains for security reasons, but, look at this modern Subaru engine and the length of their single row chains. The scary part is, they convert this engine for aircraft use and use the same single row chain set up! Break a chain on this engine and four cams stop turning and so does everything else!
Click to expand...

Brian
1995 Legacy 2.2L
2003 Legacy 2.5L
 
OP
kyreb1862

kyreb1862

Jedi Knight
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Kuz said:
My understanding is they retarded cam timing by 4-5 degrees,in the smog motors. They did this buy changing the key slot in one of the two timing gears in the single chain system.By changing to the double row chain you would advance the cam back to earlier specs, and should gain some low-mid range performance.( The cams are identical)
Click to expand...

OK, this is what I had in mind. Good way to pick up a little performance and it would put it in better tune if I wanted to change to twin SU's.

Regards John
 
PAUL161

PAUL161

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MGBGT_noob said:
Depends on which Subie mill you're talking about. Many of them will free-wheel, with a broken timing chain.

PAUL161 said:
I agree with the double row chains for security reasons, but, look at this modern Subaru engine and the length of their single row chains. The scary part is, they convert this engine for aircraft use and use the same single row chain set up! Break a chain on this engine and four cams stop turning and so does everything else!
Click to expand...

Brian
1995 Legacy 2.2L
2003 Legacy 2.5L
Click to expand...

I was talking about using it in an aircraft, which they do now on experimental aircraft! Who cares if it freewheels! There aint no parking places up there!
 
Hap Waldrop

Hap Waldrop

Yoda
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MGBGT_noob said:
Depends on which Subie mill you're talking about. Many of them will free-wheel, with a broken timing chain.

PAUL161 said:
I agree with the double row chains for security reasons, but, look at this modern Subaru engine and the length of their single row chains. The scary part is, they convert this engine for aircraft use and use the same single row chain set up! Break a chain on this engine and four cams stop turning and so does everything else!
Click to expand...

Brian
1995 Legacy 2.2L
2003 Legacy 2.5L
Click to expand...

That is correct, by changing to the double row timing gear set up, you get tow thing a more advnced cam timing, which will give you a noticably seat in the pants performance gain, and the security and long wear of the double row chain set up. I do all late model engine this way when I build them.
 
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