MGB MGB Double Row Timing Chain

[kyreb1862]

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]

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

 

[kyreb1862]

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]

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.

 

[WA1KWA]

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]

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.

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]

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...

 

[PAUL161]

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!

 

[DrEntropy]

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

 

[billspohn]

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.

 

[Kuz]

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]

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

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!

Brian
1995 Legacy 2.2L
2003 Legacy 2.5L

 

[kyreb1862]

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)

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]

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

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!

Brian
1995 Legacy 2.2L
2003 Legacy 2.5L

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]

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

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!

Brian
1995 Legacy 2.2L
2003 Legacy 2.5L

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.