7 replies to this topic

[whooshee1380]

bypass hole blanking off!!!
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1380.twin 1 inch half.
Description of problem (please be as in depth as possible):
Hi there im new to the forum and im stuck with my stage 3 head its on a 1380 an will be running twin 1 half su an i have had it running before an it run really hot so i have fitted a blanking sleeve in were themosta was and a waterpump with no my pass hole .i did buy a blankney plug for the head but it didnt fit the thread.i was wondering if i just fitted the bypass water pipe to both would it matter or more important would it make a problem with the cooling.All reply would help as this project has taken 7 years now an it need to be done once an for all.


Any non-standard parts that might be involved with the problem?

Edited by whooshee1380, 14 February 2011 - 10:39 PM.

[bmcecosse]

My experience is that it's far better to have the bypass blanked off. The plug should fit the head. But I have done it simply by plugging the (solid type) hose. NOT the ghastly concertina hose. It should not be necessary to fit a blanking sleeve, which is really only for competition use -a thermostat is a much better option - so you will have faster warm up, and a heater! There must be a reason for overheating - blocked radiator? Head gasket problem? Porous block ?

[Monte chris]

Im sure that when you blank off the bypass hose, you also need to drill the thermostat, about 5 or 6 1/8" holes around the outside if I'm not mistaken.
I did notice that before I drilled my thermostat that when the engine was warming up, the temperature gauge had a tendency to go into the red briefly (or close to it!) until the thermostat opened.
However I'm not exactly sure what difference there is between blanking off the bypass hose and not as I thought with the thermostat drilled, it acts the same as having the bypass

Cheers

Chris

[whooshee1380]

My experience is that it's far bett
er to have the bypass blanked off. The plug should fit the head. But I have done it simply by plugging the (solid type) hose. NOT the ghastly concertina hose. It should not be necessary to fit a blanking sleeve, which is really only for competition use -a thermostat is a much better option - so you will have faster warm up, and a heater! There must be a reason for overheating - blocked radiator? Head gasket problem? Porous block ?

Thanks for replying everthing on engine was new apart from the rad but it was fine before the engine change.so do you think i should but a bypass water pump back on and a stat back on the engine???

[bmcecosse]

I would fit a thermostat - maybe a low set one ~ 74 deg C since summer is approaching (!), and yes if you like drill 2 X 1/8" holes in the rim - although I didn't do this - I just kept the heater valve open all the time - and I have the bypass closed off. Made for fast warm up - the heater was giving warm air within 1/4 mile .

[Guess-Works.com]

The thread in head for the bypass hole is the same as the crankshaft bolts, 5/8" x 16 Whit' form, so finding a plug which will actually fit it off the shelf is unlikely.

It's common for an inlet blanking grub screw to be mistakenly sold as plug for this, which is probably what you have got, and the reason it does not fit...

However a bodge option is to cut the head off an old crankshaft bolt, cut a grove in the top and screw that in with a little PTFE tape.

[Big_Adam]

I just took it to a machine shop, £15 later no more bypass pipe.

[whooshee1380]

The thread in head for the bypass hole is the same as the crankshaft bolts, 5/8" x 16 Whit' form, so finding a plug which will actually fit it off the shelf is unlikely.

It's common for an inlet blanking grub screw to be mistakenly sold as plug for this, which is probably what you have got, and the reason it does not fit...

However a bodge option is to cut the head off an old crankshaft bolt, cut a grove in the top and screw that in with a little PTFE tape.

Thanks for that ,thats agreat help.Would you fit a themostat and drill some hole in it or would you leave it as it is. I have also fitted a 6 blade fan to help in the cooling an the rad is a 2 core rad.Any ideas would help know end.thaks whoosh...................