Pontiac Owners Club UK

I'm restoring my 1974 formula 400

I have started filling the cooling system but can't remember is there is a blanking plug or where a pipe needs to go, the hole is the ones at the back of the cylinder head, I have a pipe in one that goes to the heater matrix hat should I do to the other??

Thank you in advance,

2 years into my resto all is going well I must add some pictures soon

Has any body got pictures of there engine block so I can see where this goes, thank you

must be someone with a pontiac engine and a camera

please can you look at the picture and tell me if this is a core plug? or should i have a pipe going somewhere?

have, found this is a blanking plug

On my 400, there is definitely a pipe which goes from the heater matrix outlet to a connection on the back of the cylinder heads towards the distributor. The pipework originates at the water pump outlet on the left hand side as you look from the front, to the heater matrix inlet, then the outlet from the matrix goes to the connection on the head.

Just read online that the flow is actually the opposite directon. The flow comes out of the head, into the heater matrix and then out of the matrix back to the inlet on the water pump.

heated water from engine/head should go to heater matrix first

you will need 1 blanking plug as 1 is the heater nipple at the back going to the matrix i will try and find a spare plug for you most parts places will have no idea what your talking about and try and sell you block core plugs not head plugs the head ones are made by doorman you can get from rockauto you should really change all the head and block plugs as if they have been left dry for some time they tend to start to leak straight away once the engine gets hot i forgot once to change the head plugs and then rememberd why i normally change them lol