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Bond Engine Rebuild


Algy
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Well the Bond Special rebuild continues and now I come closer to actually putting bits of engine together. I decided to keep the original engine cylinder head and inlet manifold to one side (very high compression ratio not conducive to road use) and have a spare 2ltr head converted to lead free and port it. So far I have matched its inlet manifold to it and now ready to send it away to have hardened seats and porting.

So I looked at the rocker shafts of both to see which one was most usable, not expecting to see any difference, but again this Bond Special through up the unexpected.

As you will see from the photo the rocker on the left (Bond) is of a lighter construction and has a larger oil hole in the top. It doesn’t look like it has been modified from a standard one but is a good chunk lighter. The engine numbers between the head donor and the bond are only 50 different so I doubt it was something Triumph did as an update (but I could be wrong).

Anyway the Bond rockers will go onto a new shaft, as they are the least worn (the other one looks like it was lubricated with sand!).

Rocker 2.JPG

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Here is a photo showing how much the inlet manifold needed to be dressed back to match the head. Well not a full match but so it has a small lip equally all the way around of 0.75mm as this is actually better than a full match. I will flow the duct later.

IMF3.JPG

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I have replaced the ring gear as the flywheel is going to be skimmed and the crank reground  0.010” undersize and the whole lot including pistons and rods balanced. It had seen better days! As I intend to use a pre-engage starter motor I chamfered the inner edge of the ring gear to allow it to fit flush when fitted in the back to front from normal (not strictly needed). The ring was heated in boiling water and the flywheel chilled with liquid nitrogen, the ring dropped on with no need to press or hammer. So now ready to be refaced and balanced.

Old and new starter ringgear.JPG

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The cylinder head has now been matched to the exhaust manifold and inlet manifold. The exhaust a smooth match and the inlet with a small even step (as recommended by a tuning friend).

I need to flow the carb side of the inlet manifold and then vapour clean it before making up the cooling union for the rear, as I don't have a heater and the original has damaged, thankfully the threads in the manifold are good.

CH6.JPG

IMF5.JPG

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As this is a mk1 with the small 3/8 head studs its important (well even on mk2)  that you use 

Heavy duty nuts and washers , the torque of 42-46lbft needs special nuts and washers 

Std 3/8nuts only take 31 lbft and  strip easy  and std soft washers deform and you loose the  torque applied

Pete

 

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Thanks Pete, the heavy ones look the same as the ones on the 1600 engine and mate's MK2 2ltr so matches what you say (thought the my 1600 ones may have been swaped at some point). They may be specials as the engine was breathed on (by a tuner working to Vizards spec) in 1971, according to the bits of history I have with the car (but no mension of rockers, just ballancing, flowing, raised compression 10:1 large inlet valves and manifold matching and tube exhaust manifold). Hence the spare head and inlet manifold being used to go unleaded and reduce the comp ratio to 9.5:1 to sope with modern fuel, but keep some of the performance.

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Now here is a different problem. The manifold from the original cylinder head didn’t have the union on the end for pipe work but the head did have the brass adaptor coming out of the back of the head, yet there was never a heater in the car (no place to put one and open); The spare head came from a car that didn’t have a heater and had a damaged single outlet from the manifold and the hole in the head blanked off.

Here is the twist, the notes that came with the car (dated 2 Sep 1970, so after engine tuning carried out) says “Due to head temperature appearing high, yet coolant gauge showing normal, I have fitted a double ended outlet to the inlet manifold, retained by banjo bolt from the normal GT6 outlet. It has been machined out of brass and has a 1/8” hole in the branch leading to the rear of the head and full bore to the pipe leading to the pump. This is in an attempt to reduce the chance of airlocks in the head. This appears to have worked and reduced pinking during hard acceleration.”

So obviously I can’t buy one of these and would have to make it (not too much of a problem), but has anyone else heard of airlocks in the heads of cars without heaters?

I have looked through all the box of bits that came with the car and can’t find the item but that is not a surprise considering the engine was partly stripped in 1975 after the crash and so has probably been filed under B1N.

I look forward to you knowledgeable Straight Six Triumph fixers passing on your knowledge.

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4 hours ago, JohnD said:

Algy,

Re: your block.   Extraordinary "crack repair" down the midddle!   Never seen that before.    I presume it was a defect in the original mould - it wouldn't be worth repairing if it was a crack!

John

Yes

I noticed that too, it certainly looks like a crack that's been repaired but surely not?

Never seen a Triumph 6 Block with that before.

Gary

 

 

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2 hours ago, Pete Lewis said:

it came after some 3 cylinder trials  ??? 

 its the prequel to 3 cylinder trials ??

 

surley thats a mould repair, its not stitched like a block weld repair would appear as.

if thats the story then there's got to be a good few more around 

Pete

Pete, I agree as I have seen it before in the same place. The joke used to be" Arr" that's where they stuck the other cylinder on!

Dave

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After the normal bleeding never had any more air lock problems with either type of heater arrangement. Under road use the part of the engine closes to the air flow, front, would be cooler. Also the front is closes to the rad, hence the temp through the head likely to be hotter at the rear, number 6 cylinder. The engine cooling is old technology. 

Dave

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