12 replies to this topic

[AndrewT]

I'm putting an A+ engine into my 1275gt and am looking at ways to resolve the lack of bypass hose. I know I could drill the thermostat but there's also the 4th cylinder hotspot issue if that isn't opened out so my plan is this:

Ditch the thermostat sandwich plate and drill out the heater take-off. Then put a diverter valve in place just after the heater take-off so that in the open position the flow goes via the heater matrix as usual but in the 'closed' position it goes via a new pipe that re-enters the system near the pump inlet like the heater return pipe does.

This would seem to act as a bypass before the thermostat opens and ensure that adequate cooling is given to the 4th cylinder.

Does this sound ok or is there a risk that it will unbalance the system in some way?

[nicklouse]

do do not need to worry about the lack of bypass, yes drill out the water take off and plumb as original.

[AndrewT]

Where does the water flow to before the thermostat opens then?

And is the lack of circulation around the no 4 chamber no longer an issue?

Not being argumentative but I've got no real experience of A+ engines.

[cal844]

What you can do is drill the heater tap at #4 Cylinder end, fit a take off stub and hoses as needed for your set up.

I'm unfamiliar with 1275GT cars, I will assume the heater has a hose on each side of the matrix instead of the 89 onwards set up?

If so you can fit a DSN Retrosport right angle take off to supply the heater, although it would be 'hot' constantly.

I had to drill the head and fit the Retrosport take off on a 1275 engine I temporarily fitted in my 1980 Clubby Estate, it drilled out with no hassle at all but I did use a 3.5mm drill, then worked up to the correct size as needed. I then plugged the hoses and filled the engine with water, to flush the metal filings out the motor. The two small stud holes were pre tapped ready to take studs, be careful if you need to buy these as some sellers (Ebay) have the wrong size in stock.


A long post but a description of how I done it and my findings

Cal

Edited by cal844, 23 June 2020 - 09:35 PM.

[AndrewT]

It's already got the take off stub, it's just the valve and the 'always open' factor that I'm looking for opinions and thoughts on.

The new engine is out of the car so the technicalities of doing the work aren't an issue. The question is really about whether it will unbalance the cooling system and create new problems.

[nicklouse]

Where does the water flow to before the thermostat opens then?

And is the lack of circulation around the no 4 chamber no longer an issue?

Not being argumentative but I've got no real experience of A+ engines.

A+ and A are nodifferent. just plumb it up as it was before and ignore the fact there is no bypass.

 

some reading. http://www.theminifo...t/?hl= by pass

 

 

[cal844]

As Nicklouse says it will be fine. You can use the later floating type heater valve which are the most reliable.

The valve that mounts to the head at #4 cylinder end is of debatable quality. I believe these have been updated but I had two blow up on me so I went to the Retrosport type and just drive with the windows open

[Spider]

I just block up or more usually, remove the By-pass and that's all. Fit a standard Thermostat and let it do it's job.

I've done countless this way over the past 35+ years and never had an issue.

[AndrewT]

Where does the water flow to before the thermostat opens then?

And is the lack of circulation around the no 4 chamber no longer an issue?

Not being argumentative but I've got no real experience of A+ engines.

A+ and A are nodifferent. just plumb it up as it was before and ignore the fact there is no bypass.
 
some reading. http://www.theminifo...t/?hl= by pass

Thanks, that's very interesting and useful reading. I'll be following this advice. It begs the question as to why the bypass was originally fitted on the A and then continued in kind on the A+ with the sandwich plate.

Cal, what is the 'floating' heater valve?

[cal844]

Where does the water flow to before the thermostat opens then?

And is the lack of circulation around the no 4 chamber no longer an issue?

Not being argumentative but I've got no real experience of A+ engines.

A+ and A are nodifferent. just plumb it up as it was before and ignore the fact there is no bypass.

some reading. http://www.theminifo...t/?hl= by pass

Thanks, that's very interesting and useful reading. I'll be following this advice. It begs the question as to why the bypass was originally fitted on the A and then continued in kind on the A+ with the sandwich plate.

Cal, what is the 'floating' heater valve?

The floating heater valve was used from 88 to 96, you could fit it with little modification to your existing system.

Minispares.com JJB10011

http://www.minispare...|Back to search

If that direct link doesn't work just search the website for the part number above

Hope this helps

Cal

Edited by cal844, 23 June 2020 - 09:59 PM.

[skoughi]

I have a set up that kinda goes the same as you're suggesting. I have the heater takeoff at no4 end of the head but it's couple of stainless steel 90 deg bends, no valve, then a rubber pipe around the back of the engine through the pipe on the inlet manifold to avoid a high spot and possible air trap. The feed then goes into a later model heater box with the floating valve that is described above. I also have a front mounted MG Metro rad, should've used an MPI front mounted rad to save on space, and therefore an expansion tank. So on the feed pipe to the heater I have a smaller dia pipe coming off and looping higher up, but still lower than the expansion tank, and joining in with the return pipe to the pump. There is a smaller dia pipe coming off this pipe going to the expansion tank to stop any air blocks. If I shut off the valve at the heater then coolant will be pushed up the smaller dia pipe and back into the pump thus keeping a constant flow of coolant going from one end of the head through to the other. I have fitted a clear pipe to confirm this happens. How much it actually reduces any hotspot at no4 end of the cylinder head over a set up with no heater takeoff or no takeoff I simply do not know! I've maybe done a bit of work regarding the extra couple of pipes for no gain? But it does keep a constant flow of coolant. You can get a coolant valve, thinks it's described as a taxi heater valve(??) on fleabay that has one inlet and two outlets that means you can switch from either outlet so if one was to supply a heater and you closed it off it would divert it direct to the pump. Don't know anything about their quality though.  

[AndrewT]

Those taxi valves are actually 4 way which would work but would mean an extra run of heater hose back across the engine.

I think the easy answer is to leave it as standard and revisit only if I start to experience problems. Was just trying to get a neat solution in place while the engine is in bits and I need to replace parts anyway.

[KTS]

you could possibly block one of the runs off to give a one in, two out setup

 

i've modifed a saab9-5 valve to replace the standard cylinder head mounted one - no idea if it'll work though