sbaker25

I guess this question belongs here as much as anywhere.

On my race car, there is no heater core. I am also not using the stock water pump housing where the heater core return is.

Therefore, I would like to remove the coolant nipple from the rear housing and plug it rather than loop a hose around.

I have removed the nipple. For plugging, I see a couple of options:

1. Tap the hole. I like that idea most, but the area is pretty thin and I don't want to crack it.

2. Install a freeze plug. The hole appears to be 17mm and I haven't found any compatible plugs.

3. Weld something in there. I don't want to do that unless I have to. If I do go with welding, I'll fit in a threaded bung.

I just thought I'd throw this out there in case anyone else has solved this problem.

Silkworm

Or go down to the local autoparts store, get a 5/8 heater hose cap, cap it and use a small hose clamp. Badaboom, badabing.

PaulC

sbaker25

I have concerns about whether or not that would hold up. Considering the pressure that would exist with my powerful electric pump in conjunction with a closed t-stat, that's a lot of pressure to hold off at a dead end with a hose clamp.

Consider also that this will run at even higher pressure because, with a stock setup, when the t-stat is closed, the pump can still circulate through the heater core. In my case, the only relief will be through the t-stat's bleed hole.

Maybe I'm making this more complicated than I have to, but I've never seen anyone plug this that way. I guess it's pretty easy to test with an electric pump .

j9fd3s

iTrader: (3)

the early cars had a screw in hose barb, or they had a bolt to block it off. mazdacomp will know what it is, you will have to thread your housing for it though

mike

Silkworm

At the most it's what, 19psi? That's when the pressure cap pops, so I doubt there's a heck of a lot of pressure there.

PaulC

Silkworm

Oh, and just to say, I have a cap on the end of my heater line, ran it for two events now, no problems.

PaulC

tims

I have done this three different ways on three different engines. best and last one I tapped out the hole to a pipe thread and installed a threaded plug. I have also filled the hole with A/B epoxy and I have used the rubber cap and clamp. all have worked without failure, but I like the security of the threaded plug.

peejay

The in-block pressure is typically a lot higher than the radiator cap pressure, so saying the cap pops at x PSI doesn't mean much.

I went a long time with a simple block off that worked very well, although it was a bit heavy. It was a 2" length of heater hose clamped onto the nipple, and a pipe plug doped up with aviation sealer (the brown icky stuff that never washes off, gets everywhere, and smells awful in the process) jammed in the other end and clamped with another hose clamp.

I wouldn't trust most of those cheap parts-store block off caps... most of them are rather thin rubber that likes to blow out, because they go soft when they get hot. If you must go cap, get a thickwalled one, the kind that are like a REALLY BIG vacuum cap.

TeamWireRacing

I used a Toyota part on my last race car. 86-91 Supras have a heater hose block off that is a very thick rubber cap. I held up perfectly for 5 years of racing.

I think the part number is 90339-16001 and should be about $4. I may be off with the part number, since it's been 4 1/2 years since I left Toyota.

sbaker25

May I ask what size you tapped it with?

I like the security of a bolt as well. I REALLY don't want to have my cooling system blow out for something so trivial.

The only other person I've seen with a track only engine, actually looped the cooling system from the rear housing to the front. I don't want to do that.

j9fd3s

iTrader: (3)

that seems to work too, although it looks messy, and it puts another hose in the engine room

mike

tims

I believe it was 1/2"NPT but check the size after removing the nipple.

sbaker25

I checked 1/2" NPT but I thought it looked slightly large. I thought 7/16" would be good, but I've never seen a 7/16" NPT anything before.

Does anyone know if I am correct in believing that the only way to tap for AN fittings is going to be welding in a bung?

Thanks for all the responses. I think I'll try the 1/2" NPT. Should be easy enough to repair the cast housing if something goes wrong .

tims

on your tap or tap chart it should give the drill size for the 1/2"NPT tap and verify before using. if it is slightly larger you will be ok, if smaller drill out to correct size. I didn't have to drill, I just cut the new threads. next larger pipe size would be 3/4" NPT. sorry cast iron can't be repair very easily so be careful.

spigot

iTrader: (4)

I tapped mine and installed an an fitting with a cap on it in case I want to/ need to use the heater at a later date. I'll have a look to see what size it was for sure but I think I used 19x1.5 so that I didn't have to drill the hole (since the wall is so thin.)

Matt

sbaker25

That would be appreciated! The size of the nipple that came out is 17mm, so 19 is probably quite close. Like tims said, I can just check the drill size recommendations to figure out what size to use based on the 17mm. So, you didn't use an NPT thread then? I suppose you must have used something to seal the threads? Pipe dope or RTV or something?

I am honestly a bit concerned about using an NPT thread anyway, I worry that the surrounding cast would crack when I try to tighten the plug.

tims

use the straight thread AN fitting if your worried about the NPT fitting. use some pipe dope on the npt and the AN should have a crush washer and a cap. either will work and neither needs to be tightened a great deal. remember all these fittings are aluminum.

Scalliwag

Have you ever seen a rubber freeze plug? They are a rubber cylinder with a washer on each side and a carriage bolt running through the middle. The washer on the outside is a little larger than the rubber. When you put it in and tighten the nut the washers compress the rubber and WALA! problem solved.
When I used to race Pontiacs I ran through so many blocks that all I used was rubber freeze plugs. I'd break and yanks 'em all out and throw them in the next one and go. They were mainly designed for when you have a freeze plug go out and you don't have enough room to knock a steel one in. As long as you can get the old one out all the way it keeps you from pulling an engine in many cases.

Silkworm

WTF did this get moved? That's a race car topic, pure and simple..

PaulC

Greg

im moving it back

Silkworm

thanks Greg!

Nice Avatar btw

buttlips

We've always used freeze plugs.

88GTU

Dangerous. This is the approach we took in building our car. During OTC we began leaking through a cap on the third day. (at Willow Springs.) We replaced it and continued on... This last weekend the rear one ripped open out at LVMS. We may have lost the engine because of it. (although there is some question now).
There is no way I am taking my car out on the track without using a more secure solution again. Its too damn risky. Two failures in 8 track days when messing around with a $4k rebuild is too much...
-Matt
'87 Turbo II
'88 GTU

spigot

iTrader: (4)

I just checked the tap and apparently it was a 16x1.5 not a 19x1.5 as I mentioned earlier. Best thing to do would be to check the hole with a drill bit, since I beleive mine is not in the block, but in the part of the press fit nipple that is stock. (The nipple was cut off flush with the block, but I don't know if there is still some of the nipple in there since I wasn't the one that cut it off but I'd guess there is part of it left if you said that the nipple that came out was 17mm)

I used pipe dope and a crush washer for my install.

Matt

Silkworm

Agreed, but 8 days of hard racing is hard on parts, no question. Plus it's a turbo car. I need to wire a warning light for water temp so this doesn't bite me in the ***, but so far i've run 2 events, no issues. We'll see.

PaulC