RWD Cooling Option

[Flintstone Chaz]

Hi All,

I'm doing a RWD swap into a 68 Datsun Roadster. It is a long slow project but I'm having fun dealing with the various issues and challenges. Mr. 914 SHP has encouraged me to post a build thread and I may do that one of these days....

Anyway, the question of the day deals with an out of the box idea for dealing with the rear thermostat and cooling outlet challenge. I'vegot the engine shoved way back and it is sung up against the firewall. I've removed the DIS and mount and inverted the manifold crosstube and have the whole rear of the engine back under a shelf across the rear of the engine compartment.

I can't go back any more in the center of the firewall without intruding into the space inside occupied by the stock heater. I guess that too is negotiable but I wanted to explore another idea. I've never found anything on the net about it and if it has been discussed previously please forgive...

First, let me make sure I under stand the stock cooling layout: There are basically two coolant loops. One is from the suction side of the water pump, through the pump, into the transfer tube, into the heads then block and back to the suction side of the pump via an outlet in the front of the block. The second loop is via the lower radiator hose to the suction side of the pump, through the pump to the transfer tube, out the thermostat (when warm of course) to the upper radiator hose, through the radiator and back to the lower hose. Do I have that correct?

The "engine cooling loop" is always active and circulating. When the coolant is not up to temperature and the thermostat is still closed this is the only actively circulating loop. However, when the coolant reaches operating temperature, the flow from the transfer tube splits at the back of the engine and part of it goes through the engine loop and part through the radiator loop. Again, please let me know if I've missed anything. Obviously there are a few extra paths through the engine cooling loop such as the heater, manifold ans oil cooler loops but I'm including them in the engine loop.

So, the only common path the two loops have is from the suction side of the pump through the pump and transfer tune to the distribution spider at the rear of the engine. The relative flow balance or flow split between the two loops is a function of the relative restriction in the loops. The resistance in the radiator/cooling loop is in fact variable and is a function of how wide open the thermostat is as controlled by coolant temperature.

What might the impact or concern be if I were to block off the rear outlet and instead modify the pump housing or front of the transfer tube to allow the thermostat and outlet to sit at the front of the valley and exit forward?

The pressure in the cooling system will be higher on the outlet side of the pump and lower on the suction side. That is a function of restriction in the two loops. However, it seems to me that it makes little difference whether I split off the cooling loop at the front of the transfer tube or the rear. I don't see that it would have any appreciable effect on the flowthrough either loop. Seems like the flow out the thermostat and through the cooling loop would still be a function of the thermostat just as it is at the rear.

It is not a simple problem to accomplish the modification to the pump housing, or alternately, a create a thermostat housing that could pick up from the transfer tube but if successful it would cleanly resolve the rear outlet issue and put the thermostat and outlet up on the front of the engine.

There is space in the valley to accomplish this modification and the outlet would not be close to the timing belts. I don't have all the brackets and belts on my 3.2 so I can't verify that a center outlet doesn't have a belt clearance issue with all accessories in place. It would not be an issue on my application but I think the alternator will be the only accessory on my

If there was a concern that the thermostat when closed was a short way down a "dead" flowpath I would think that could be resolved by putting the outlet tube for the manifold heat loop at the front of that housing thereby making sure warm coolant could reach the back of the thermostat in a timely manner.

Thoughts?

 

[rbruso]

Where in AZ are you?

I've always fantasized about building a 2000 roadster, blending the good interior and good exterior bits from '67-'69 or so. I imagined 20DET under the hood, though.

Your understanding of the two loops syncs with what I've found.

I'm not sure if anyone has actually abandoned the factory thermostat location, though I've looked at and discussed this issue with Gerard (of 914 Porsche fame). I think it would be difficult to get an outlet at the front of the engine if you retain the engine-driven water pump, though it might work. It will be tight, that's for sure.

If you go with a 3.0 accessory setup, you could ditch the water pump and go for an external electric. The 3.0 setup has two belts: A/C,Alt,Crank and P/S, W/P,Crank. I assume you aren't using the P/S (and possibly A/C, but that's another matter), so dropping the water pump would lose that whole belt routing and maybe clear up space for a water passage.

Of course, we're going to need details on transmission and rear end setup

 

[rubydist]

There are some 90 degree thermostat housings that can be put on (with some modification) to allow you to use the factory thermostat location and still get a hose on there near the firewall.

One is from the modular 4.6, and one is from the V6 Contour. While I have not finalized either of them, it appears to me at the moment that the 4.6 might be the better choice.

Rather than having the thermostat buried at the rear of the engine, I think a 'in the line' thermostat housing will be fitted to the hose that comes off the modified housing.

 

[Off Road SHO]

I believe you have the flow backwards. The water pump pushes coolant into the block, which then feeds it up into the heads. At the back of the heads, the manifold directs the coolant into return pipe and back to the pump. If the thermostat opens, SOME of the coolant is diverted through the radiator before being sucked up by the water pump again.

I'm pretty sure that is how it flows.

Tom

 

[Flintstone Chaz]

Good Morning,

Thanks for the thoughts. Maybe I'll go out to the garage and tear down the front of the engine enough to look at the pump and see if the block return is on the suction or pressure side of the pump. However, with the flow direction still to be resolved does it really matter? Whether I remove flow for the adiator loop at the back of the motor at the spider or at the front near the pump it is still effectively the same place in the engine loop.

I've never pulled one of these apart so correct me if I'm wrong but doesn't the transfer tube just push into an O ring at both the front and back? If so I was thinking I could make a piece that replaces the front couple of inches of the transfer tube and incorporates the forward facing outlet for the new thermostat housing.

Guess I should go out there and work on it rather than sit here and talk but it is 11 degrees this morning here in Prescott.....

Thanks again for the knowledge and help you all provide.

Charlie

 

[Flintstone Chaz]

There were acouple other questions somewhat off the cooling question that I'll answer here. Guess I'm hijacking my own thread...

This is going in a 68 Datsun Roadster. They have a traditional ladder frame and double A suspension in the front. So, the engine compartment is narrow down low between the frame rails and then wider at the top. It isn't overly long front to back. Since this is a big and rather heavy engine I wanted it back as far as I can get it. I removed the DIS pad from the manifold crosstube and inverted the crosstube. With the tail of the motor therefore lower I was able to tuck it back under a the shelf and hood latch at the rear of the engine compartment. That took a little intervention on the firewall with the sawsall but while snug, everything inside can still sit in basically stock locations. I've got the engine sitting far enough back that the rubber boots for the crosstube are under the shelf at the back of the compartment.

The heater sits inside on the top of the transmission tunnel so if I go any further back l'll need to do something with it. Unless I move the heater and do more firewall work there is absolutely no space to deal with the rear outlet which is why I'm looking hard for options other than the 90 degree neck and tube around the motor. At the moment the temperature sender on the left head is sitting about half an inch in front of the firewall. I've got the brake master cylinder above the head and fairly close to the manifold on the left and the computer close on the right. There wasn't enough depth inside under the dash for the computer because there is a fairly large cowel and floor vent arrangement inside. So I made a box for the computer that intrudes into the engine compartment a couple of inches. That occupies the space on the right side of the engine by the manifold.

This swap requires relocating the steering column and pushes width at the head to just about all there is space for. Of course, with a sawsall I can always make more space but a more elegant solution for the rear outlet would sure be a better option.

A few other details for the RWD crowd. The transmission will be a Toyota W-58 5 speed. They are wonderful transmissions, have great ratios for this application, are a delight to shift and came in lots of Toyota vehicles for many years. The Supra crowd runs 300+ HP through them without problems and full rebuild kits are an ebay item and will be for many years. They are physically fairly small and come in a number of differing shifter positions depending on what Toyota they came in. Roadsters are small cars and with the engine shoved as far back as I have it I needed a transmission small enough to not be a big issue in the tunnel and with a rather short bellhousing to shifter dimension.

I've completed an adapter plate that ties the W-58 to a Vulcan A4LD automatic bellhousing. That was a challenging build and I may post info on that if folks are interested. Flywheel and clutch are a still to be resolved issue. I believe there is a bolt together option via a Centerforce dual friction clutch cover (in 9 1/4") the matching aluminum flywheel and a 9 1/4" Toyota disk that will fit the transmission spline. That would be a nice setup, would be light, have a good clutch and would all be off the shelf parts. The only drawback is that I just listed $700+ in parts.... I may try my hand at turning an aluminum flywheel that would take a standard Toyota clutch cover and disk. Also, I still need to mount a concentric clutch slave cylinder. Funny, the automatic bellhousing seems to have no provision for a clutch cylinder...

The rear end in also a still to be resolved. The Datsun differential is not up to the power. These cars are very narrow at the rear so there is not a junkyard axle option that is good for the SHO power output that is anywhere close to narrow enough to fit. So I'm either faced with having an axle narrowed or working out an IRS of some kind. At this point I'd rather try to get an IRS under the back of the car but there will certainly be challenges there. A Nissan 240SX 5 link is the best bet but it would require major frame surgery. However, you can't do a build like this if you let minor details like the frame being in the way limit your thinking.....

Charlie

 

[Off Road SHO]

Charlie,

Cool project you got going there.

I have a complete Supra rear end, complete, wheel to wheel if you need one.

As far as your water manifold problem goes, make your own. You just need to get the coolant from the outlet on the heads, back to the water pump. On the way, put in a "T" for a thermostat housing. The existing coolant manifold is already a two-piece afair, just take it apart and using the head interface part, cut and tig on a new outlet ****** and weld shut the old ******.

Or take a piece of 1/2" thick aluminum plate and make a whole new outlet for each head. Once the coolant is out of the new outlet and in a hose heading back to the pump, you can insert the two temp sensors anywhere in that line.

Tom

 

[3d914]

Good Morning,

Thanks for the thoughts. Maybe I'll go out to the garage and tear down the front of the engine enough to look at the pump and see if the block return is on the suction or pressure side of the pump. However, with the flow direction still to be resolved does it really matter? Whether I remove flow for the adiator loop at the back of the motor at the spider or at the front near the pump it is still effectively the same place in the engine loop.

I've never pulled one of these apart so correct me if I'm wrong but doesn't the transfer tube just push into an O ring at both the front and back? If so I was thinking I could make a piece that replaces the front couple of inches of the transfer tube and incorporates the forward facing outlet for the new thermostat housing.

Guess I should go out there and work on it rather than sit here and talk but it is 11 degrees this morning here in Prescott.....

Thanks again for the knowledge and help you all provide.

Charlie

Charlie, here are some images to help with the discussion. I'm visually oriented (or impaired - depending) so I rely on them heavily.

Waterpump - showing the two o-ring sealed outlets; one to the block, the other to the transfer tube.

Next is the coolant flow - speaks for itself.

Also thought I'd throw in one for the outlet housing. On mine I didn't change the housing itself to reduce impact at the firewall, but I did cut the thermostat tube down to almost nothing. This is mostly because the bulk of the outlet housing is hidden by the front (left) head. You see more of it from the right side because that head is biased forward of the left one.

 

[3d914]

. . .
I've completed an adapter plate that ties the W-58 to a Vulcan A4LD automatic bellhousing. That was a challenging build and I may post info on that if folks are interested. Flywheel and clutch are a still to be resolved issue. I believe there is a bolt together option via a Centerforce dual friction clutch cover (in 9 1/4") the matching aluminum flywheel and a 9 1/4" Toyota disk that will fit the transmission spline. That would be a nice setup, would be light, have a good clutch and would all be off the shelf parts. The only drawback is that I just listed $700+ in parts.... I may try my hand at turning an aluminum flywheel that would take a standard Toyota clutch cover and disk. Also, I still need to mount a concentric clutch slave cylinder. Funny, the automatic bellhousing seems to have no provision for a clutch cylinder...

. . .
Charlie

The 9 1/4" clutch sound familiar. Don't have their catalog in front of me, but Kennedy Engineering does countless kits for these types of applications. Wouldn't be surprised if they have one to fit.

This is an awesome project - definitely a brain teaser. Couldn't resist posting a sample pic of the roadster of topic, though this may be a 69.

 

[3d914]

PS: Charlie, I have the intake and valve covers off mine at the moment, so if you need any pics in the area of the thermostat - nows the time. I'm more than happy to help.

 

[Shovert]

Awesome project. Mine is 3.2 RWD in a 93 Mustang Vert. I cut the rear coolant fitting off and used a 90 degree hose. While I am not happy with this. It is ok for now until I make a welded 90 out of the old one or do a use rubydist idea. [I like that better].
Now on the rearend. Got a idea. Use a 7.5 rearend out of a 86 or older turbocoupe has limited slip. Or one out of a Ford Ranger and shortened. [some of them have limited slip.]
Reason I know I have a 2.3 turbo Mustang and building a 2.3 turbo MGB [project on hole].
Here is a 86 turbocoupe rearend modified and altered for a MGB. Note the factory 4 link setup has been removed and MGB perchs and springs added.
http://i177.photobucket.com/albums/w224/mgman75/mgb project/100_5967.jpg
On the intake to bad can't find this intake. It was a one off project by Ford. Maurice
http://www.bigblockranger.com/images/pic0189.jpg

 

[3d914]

Awesome project. Mine is 3.2 RWD in a 93 Mustang Vert. I cut the rear coolant fitting off and used a 90 degree hose. While I am not happy with this. It is ok for now until I make a welded 90 out of the old one or do a use rubydist idea. [I like that better].

There's just no end to the cool projects around here.

Now on the rearend. Got a idea. Use a 7.5 rearend out of a 86 or older turbocoupe has limited slip. Or one out of a Ford Ranger and shortened. [some of them have limited slip.]
Reason I know I have a 2.3 turbo Mustang and building a 2.3 turbo MGB [project on hole].
Here is a 86 turbocoupe rearend modified and altered for a MGB. Note the factory 4 link setup has been removed and MGB perchs and springs added.
http://i177.photobucket.com/albums/w224/mgman75/mgb project/100_5967.jpg

Were either of these cars stock with a rigid axle? I would think they were independent for their size & weight.

On the intake to bad can't find this intake. It was a one off project by Ford. Maurice
http://www.bigblockranger.com/images/pic0189.jpg

What about intake that I saw where the TB was mounted on one side of the intake - on the surge tank? Doesn't someone on the forum have that setup?

 

[Flintstone Chaz]

I got some time in on the car today. I'm working on the steering column base, pedals and such. When I get that stuff sorted out I'll close up the firewall.

In the meantime, I took a look at the front thermostat option. I don't see any reason it wouldn't work just fine. Here is an idea what it would look like.

This is a piece of 1 1/2" electrical conduit. The transfer tube is about 1 1/4" (actually I measured it at 1.330") So a piece of 1 1/4" aluminum tube would be very close. If the piece of 1 1/2" fits the smaller should go without a problem. I'll turn a piece for the front to slip over the tube and weld. That will have the well for the thermostat and ears as needed to bolt on a neck.

So, what problems does anyone forsee?

[/ATTACH]

 

[Shovert]

I can't say on your idea. I hope works. I am just a little too unfamiliar with the flow.
On 3d914 question MGB was a solid axle design. Some have put independent but modified it into that size car is a challenge from what I read.
Maurice

 

[Off Road SHO]

Charlie,

So your idea is to just move the thermostat housing to up front?

Tom

 

[Shovert]

His idea my be a good one. I remember seeing this picture and found it. True got rid of the intake. But maybe. Only thing that bothers me he never got it on the road. So I assume cooling system never really tested. Maurice
http://i168.photobucket.com/albums/u200/mizlplix/SHO30.jpg
Where picture came from. Posting #20
http://www.diyelectriccar.com/forum...d-vehicle-rwd-anyone-experiencei-47616p2.html

 

[Flintstone Chaz]

Hi All,

Tom, just to be sure we are communicating, the plan is to start with a 1 1/4" aluminum mandrel bend trimmed to Y into the transfer tube in the valley and sneak out the front between the pump housing and injector boss on the right head. Once out through the timing case I'll cap it with a custom turned end that slips over the tube on one end and has the step, diameter and ****** to support the thermostatand bolt on a neck. The tube will be welded at the Y and thermostat end. I'll likely set things up so the thermostat ****** is about flush with the belt cover.

Since that puts the thermostat fairly far down a "dead" leg until it is open I have some concern that I need to get warm water to the back of the thermostat to be sure it opens. I was tinking I could tap my new thermostat housing and put a tube fitting near the thermostat and feed the throttle body IAC coolant loop. If I put the other end of that loop at the rear of the engine it should have positive flow and deliver engine temp water directly to the thermostat area.

At the rear of the engine I could just cap the existing thermostat location since I still need the support for the rear of the transfer tube.

This seems like an elegant solution for a front outlet which gets the thermostat in an accessible location and doesn't require the around the engine path.

More info on axles. The closest stock axle in the junk yard is the 1st generation RX 7 axle. It comes in two different bolt patterns including the 4 on 4 1/2 that matches the Datsun. There is a version with disk brakes and a limited silp. That diff carrier and axles also cross to other Mazda stuff so Quaifes and numerous ratios are available. However, it is 8 inches wider than the stock Datsun axle. Which gives you an idea just how narrow the rear of these cars really are. If I wanted to go to a fat tire option at the rear with significant flairs I could use that axle with a FWD type offset wheel. It would still take putting the needed brackets on the axle and when finished I would still have a leaf spring and live axle setup. I may end up there but I was thinking that if I have to make custom parts or have an axle cut down I should see if my efforts can net a much better rear suspension.

The frame on these cars are setup for the leaf springs so it runs just inside the tire. So, basically any IRS option (strut or otherwise) will require narrowing the frame width to make room for outboard suspension components. However, it is a simple box frame and modifying it should be comparitively simple. I'm thinking I can build and weld in the narrowed section before I cut out the exterior rails so keeping things dimensionally correct, square and true shouldn't be too hard.

Charlie

 

[rubydist]

You either need to use a thermostat with a jiggle valve in it, or else keep the thermostat close to the crossover tube - the thermostat needs to 'sense' the heat of the coolant in order to open at the appropriate times.

 

[rubydist]

revisiting this again, I think that one could tap into that plugged opening at the top of the water pump for the thermostat plumbing and avoid having to tie into the crossover tube.

 

[Off Road SHO]

What Rubydist said. I'd also drill a couple of extra 1/8" holes in the thermostat to help get more flow through on warm-up.

That plug on top of the pump might be another, even more elegant solution. Have to make sure it has the same "suckability" as the crossover tube location.

Tom