BJ8 Overheating - Need dimension

[Lotuswins]

Hello all,

Well the temps up here in Oregon are getting higher, and of course my BJ8 is not responding well to them. I've done all the usual items like recore, texas cooler, water wetter, fan shroud, thermostat, etc. but it still will climb up to 220F at idle, no problem. I can though put it into neutral and rev the motor to about 2500 rpm, and the temp will start to come down. So I was hoping to do some experimenting with a different impeller on the water pump to see if that won't improve my situation. In talking with a very nice fellow at the Brass Works down in SoCal, I found out they may be able to ship me an impeller with an improved design but I need to know the depth from the waterpump gasket face to the no. 1 cylinder wall. In other words, how deep can the impeller go into the block?

Does anyone out there have an old block sitting around that would be able to measure this for me?? It will take me some time to remove my pump, and the car will sit idle until I get the impeller and machine it to fit. I do have a spare pump, but I want to maximize the depth and hopefully the flow.

thanks in advance,

 

[Randy Forbes]

Before that, are you sure the ignition timing and fuel mixture are correct? Unless the block's internal water jacket is totally coated with deposit's, acting as an insulator, there should be no reason why that engine won't run at the thrermostat opening point.

I mean, my Healey's been in southern Louisana, then the midwest and now SW Florida, when it would be expected to overheat__but it doesn't!

 

[Keith_M]

I think Randy is right, the problem is unlikely to be the rate at which your water pump moves water. (You might check to be sure that the impeller is actually turning though. Sometimes the key comes out.) In addition to the things that Randy suggested you might check your generator bearings. My sprite suddenly started overheating at idle a few years ago and I finally traced the problem to bad (really bad) bearings on the generator, which apparently put enough load on the engine to cause it to overheat at idle.

As a reference, I also have a re-cored radiator and a 5-bladed fan on my BT7, and I run at 185F unless I'm climbing a pretty high mountain pass in 90+ heat. Even then, it rarely goes much above 200.

I would look for other problems before trying to make a new impeller.

 

[TimK]

Are you using the original type thermostat which closes off the recycling port? If you have recored the radiator, and using a Texas fan and shroud, It's something else...

 

[Bob_Spidell]

I'm currently running a Texas Cooler in my BJ8, but previously ran a Hayden 7-bladed SS flex fan. The SS flex fan is good for about 5deg over the Cooler at idle, but noisy as heck (esp. at idle). I've also wrapped the downpipes, and I think that helps some but can't quantify it.

Also, something doesn't compute to me. The coolant flow will be limited by the thermostat; a larger impeller may only serve to pressurize the coolant in the block. Not sure that will help cooling.

 

[Lotuswins]

Hi All,

Just to respond to your concerns:: all valid too....

Timing is at 8 degrees BTC, 35 total advance. All centrifigul as the SU HS6's don't have a vacuum connection. Basically like a BJ7. Mixture is on also, as I continually check that with the slight needle lift and very slight rise in rpm. Have to be quick though or temp will rise fairly high. I also calibrated the temp gage on the stove with boiling water.

I too had the flex fan from David Nock, it was okay at speed, but didn't generate as much flow on my car at 2500 rpm, i.e. the temp wouldn't come down with the flex fan.

Thermostat is the original type, bellows with the blocking off sleeve. I have run a wax type with a piece of aluminum blocking the passage to the pump off permanently. No difference from now though. I'm thinking of putting a plug in the pump passage to block that flow and run one of the high flow thermostats to help things, but I don't think that will help much based on previous experience.

I'm running an alternator off of a Toyota Corolla which is silent and working very well, so that isn't an issue. I have aluminum air deflectors too that are larger but essentially the stock design. Also running an oil cooler.

I just disassembled my spare pump today and made a drawing of the impeller. Only a 4 blade impeller, and the newer designs are 8 to 16 blades so I believe the flow can be improved. In speaking with the guy at Brass Works, he said the thermostat will restrict flow at the higher rpms, but not at idle, which is where I hope to pick up some flow. The bad news is the impeller diameter is only 2.68 OD, which isn't too large. I hope to make up some with an increase in depth.

Still no spare blocks out there?? Help!!

 

[tahoe healey]

Have you verified the temp gauge accuracy with an infrared laser meter? My BJ8 runs cool (smoother and quieter) with more advance (about 14-15 degrees). No pinging and lots of power. This was suggested by a major dizzy re-builder. TH

 

[57_BN4]

Jerry, it sounds like your impeller might be too far away from the water pump body or maybe corroded on that face. 15-20 thou is the recommended distance IIRC. My cooling system starts making gentle glugging noises at about 200F if I turn off the engine, I'd imagine it'd be chundering out of the overflow by 220. How does your behave? Andy.

[edit] in a somewhat vague answer to your original question, I seem to remember that I could push the impeller back into the (2.6l) block by about 1/4" with the pulley removed. The early pumps are bolted together, unlike the later pressed ones and the impeller shaft is free to move back and forth once the pulley is removed. Sorry I can't be a bit more scientific than that.

 

[DerekJ]

The thermostat is there to ensure a minimum operating temperature but it cannot control the maximum. Definitely check the temperature gauge. Mine isn't working properly and will only read up to 85 degrees in boiling water. Yours could be out the other way.

 

[Lotuswins]

Hi Tahoe,

Yes, my IR gun verified w/in 5 -10 degrees of the gauge.....got to be careful with the gun though since the reads can be off by quite a bit if you try to read a shiney surface....but the top of the radiator and hose (black and not shiney) were consistant. I could try putting more advance in, but if I do that then the total advance goes much higher than what the manual recommends. You must have the vacuum advance functioning then when you set your timing? that would pull the initial advance to that figure. Since I don't have the vacuum connected due to the HS6 carbs, I probably can't get away with 42 total advance, but I can easily try it. Thanks, Jerry

 

[Bob_Spidell]

Side note on the safety (temp/oil pressure) gauge: My temp gauge went askew a while back (wouldn't read over 160, with a 180degF thermostat). Sent it to West Valley Instruments for refurbishing and, lo and behold, I now have oil pressure at hot idle! On a hot day at idle my gauge used to show close to zero, now shows almost 20. I also replaced the oil pressure line from the block--the old one was brittle and cracking--but don't know if that helped or not (probably not, but saved me from a potential disaster on the road).

Jerry, your problem is confounding. Assume you're running triple HS6es, right? Gotta believe that non-standard carburation setup has something to do with your overheating problem, though I don't know what. Also, hate to say it, but you're not getting any exhaust gasses in the coolant, are you?

 

[Lotuswins]

Hi Andy,

It may be that the impeller gap is too large. The manual says 20 to 30 thou, and I did rebuild the pump. The radiator does make a few noises, escaping gas I imagine, when it is shut down at 220F. No vapor lock so far though, knock on wood.

Thanks for the 1/4 inch figure...I'll see if that will work if no one else comments soon with the exact dimension. I can get a deeper impeller by 1/4 inch then trim to fit once I pull my pump to verify. The last item on the pump when rebuilding is the impeller anyway.

Jerry

 

[Lotuswins]

Thanks Bob,

I'm running 2 HS6's, engine is pretty much like a late BJ7 with BJ8 cam but smaller carbs and centrifugal advance only. I have a set of HD8's awaiting rebuild, but haven't justified the expense in my mind yet (kits $200, air cleaners $120 or so, and the HS6's seem to be fine). No bubbles in the radiator....thought of that too.....Jerry

 

[57_BN4]

There is/was a guy selling 8 vane water pumps on Ebay. Don't know if they are for BJ8 though

 

[Lotuswins]

Hi Andy,

Just checked and its for a 100-4, but I sent off a message to the seller to see if he has anything for a BJ8.....impeller looks similar to the BJ8 though. Thank you for the tip.

 

[DerekJ]

Seriously though. Have you verified if your gauge is working properly? Its the simplest and most obvious thing to do.

 

[Lotuswins]

Derek,

Yes, the gauge is spot on. I took the face off, pulled the needle for the water temp, went in the house and boiled some water, put in the probe and at boiling I reinstalled the needle. Then pulled the bulb in and out of the boiling water to confirm its repeatability, and it performed well. I also purchased a new gauge from Moss, installed it and it confirmed the temps I was seeing, then the oil side of the gauge stopped working so I sent it back and got a refund and reinstalled the old gauge after confirming the performance yet again.....yes, easy to confirm its performance, unfortunately its working quite well. Thanks for the suggestion.

 

[Richard Dickinson]

The dimension from the face of the block to the cylinder wall is 1.25 ". Don't have a gasket installed. There's got to be some other problem. With the stock setup and everything in good order the temp could be marginal under extreme conditions, but with the mods you have done it shouldn't be running hot.

 

[Lotuswins]

Richard,

Thank you!! Pump/impeller height is approx. .940 so that gives about 0.3125 minus clearance to play with. Andy's approximation of .250 was very close.

As some one suggested, it may be the clearance from the pump to the vane isn't close enough thereby losing some flow at low rpms. The guy from ebay says he has pumps for all healey's and I'm awaiting his response to flow improvement and head pressure improvement for his 8 vane pumps. I also talked to the Brass Works guy after I drew a detailed drawing of the impeller and took pictures for him. He said he doesn't have any of his improved impellers that are deep enough and it would cost $500 or so to do the engineering and testing to make an improved impeller. He was going to call the owner of Moss to see if he would fund the research and machining if they could sell enough of the improved pump versions. He'll call me if it is a go, but I'm not holding out hope.

Thank you again,

 

[57_BN4]

Kind of random bit of info... I bought a cheap old car while living in Australia and it had a habit of suddenly overheating when driving along for no reason and it'd come right back to normal as soon as I stopped. After much head scratching somebody noticed that the bottom radiator hose would suddenly collapse from the suction of the pump if the engine was revved up.

If you do fit the uprated pump it might be worth revving the engine while squashing the bottom hose with your fingers and seeing how close to collapse it is. Andy.