So my 7/72 build 240 has the coolant passages in the E88 manifolds to warm up the carbs. Seeing as how this car will never see temperatures below, say, 50°, I'd like to block them off and clean up the engine bay.

To that end, I've removed the hoses and the pipe that goes around the back of the cylinder head. On the spark plug side of the block, I've capped the Y-pipe outlet with a rubber plug.

Today I bought a set of brass screws to plug the intake manifold and t-stat housing ports. The (generally knowledgeable) counter guy at CarQuest seemed to think it was an SAE thread size; however, they don't seem to fit.

Questions:

1. Will I damage my engine by tying off the system? I suppose all the coolant will be flowing through the heater core now as opposed to being split off at the Y-pipe.

2. Does anyone know the thread size/pitch for the manifold passages? I'm going to go back tomorrow and it'd be helpful to have a number to reference.

Thanks!

The threads for most of the fittings on the engine itself and the thermostat housing are BSP (British Standard Pipe) threads. The BSP thread is a little different than the NPT (National Pipe Thread) common in the US. We used NPT with good results. If you want the use the BSP you can order them from McMaster-Carr or other harware suppliers. I forget the sizes used in the Z but you should be able to get what you need at a good hardware store. Take the fittings you removed with you and match them to the plugs.

Here is a good one.

Coolant Circulation Bypass Line - HybridZ

Edited May 8, 201212 yr by black gold man

The threads for most of the fittings on the engine itself and the thermostat housing are BSP (British Standard Pipe) threads. The BSP thread is a little different than the NPT (National Pipe Thread) common in the US. We used NPT with good results. If you want the use the BSP you can order them from McMaster-Carr or other harware suppliers. I forget the sizes used in the Z but you should be able to get what you need at a good hardware store. Take the fittings you removed with you and match them to the plugs.

Thanks for the input. I'll see what I can find. The threads on the plugs I have are really close. I may just use them since there's not going to be anything in the manifold galleries anyway.

Here is a good one.

Coolant Circulation Bypass Line - HybridZ

Good discussion. So earlier Zs had a "bypass line;" it just didn't go through the manifolds? Looks like I need a peek until the hoods of some of the local guys' '71s and '70s.

The consensus seems to be that the thermostat needs to have a small (~1/4") hole in it to circulate coolant to avoid hot spots in the head. I just replaced the thermostat, and I remember it had a small hole in it already with a kind of one-way check valve:

I'll pull off the thermostat cover tonight and make sure the check valve allows coolant to flow in the correct direction (from the radiator into the engine?). If so, I'll button things up and call it a day.

Edited May 8, 201212 yr by BoldUlysses

Hey Matt, FWIW, I blocked off my intake manifold with no issues whatsoever. It takes a bit longer to warm up in cold temps, but that's all.

Cheers, Mike

Thanks Mike. Do you remember by any chance whether the screws you used were BSP or NPT?

For the holes in the manifold, find some little freeze plugs and some stick'm and the press in and stay forever.... They're silver and chick will dig'em

Thanks Mike. Do you remember by any chance whether the screws you used were BSP or NPT?

1/4" BSP, see http://www.classiczcars.com/forums/thread36524.html#post308808