Late model 230 head on older block..

[maineSSS]

I was looking at my 1959 head with a view to getting the bypass circuit to work with my '49 block, and think this is what I'll do.

Pic #1 shows the internal bypass hole in the "bump" area- it will need to be plugged. The hole dia is 3/8"(12/32), which can be tapped for a 1/8" pipe plug. the question is whether an allen type plug will have enough thread engagement (green plug), since it's only 25/64" max dia. The other type (brass) is 13/32" max dia, it would have to be screwed in and milled off. Another option would be JB Weld epoxy after tapping the hole, though long term durability would be questionable.

The next item that's needed is the cast iron neck and the bypass elbow for the waterpump to convert to an external-bypass system. Fortunately, I have these parts, but others may need to find them.

Edited July 25, 2012 by maineSSS

[Young Ed]

Isn't the brass one only 1/64 bigger? 13/32=26/64 right?

[Niel Hoback]

I just came in from changing from external to internal passage. The pump to block gasket did not have a hole for the bypass and it did a very good job of blocking the flow for several years. I used a wood plug in the bypass outlet between it and the thermo housing. Also replaced the external use thermostat with one for internal bypass.

If I were changing back, would just replace the gasket, that will stop the flow.

[maineSSS]

I think I'd feel better with a plug behind the gasket, especially if the circuit is pressurized from the waterpump. The Allen plug is only 1/64" larger dia than the bypass hole (3/8 = 24/64), so there's not much thread engagement there, and since it's tapered, it's only at the top.

I looked at the bolt spacing on the head and the cast iron thermostat housing, they appear to be identical, so it should fit. I haven't removed the housing to measure the thermostat hole dia in the early head yet, will there be a difference in head hole dia (not thermostats) between early and late heads?

I'll be using the NAPA pump, which can be setup for either type bypass.

Edited July 26, 2012 by maineSSS

[Niel Hoback]

The seat for the thermostat is in the housing, not the head, so the head opening is really not important. I have put both kinds of thermostats in the cast housing because the stats are the same diameter. I think it would be easier to weld up the hole in the plate to block passage. If you are interested, I think I have a plate with no bypass hole that you could have for the postage.

[Niel Hoback]

Please excuse my stupidity. I did not put it together that you want to block the hole in the head. I have absolutely no experience doing that. Tapping and plugging does seem to be the way to go. The water pressure isn't that great so it should be alright.

[old rat 49]

The spare engine i bought last week is from a 51 for use in my P15 and is trashed, however I did get a new water pump and fuel pump and a much tighter coil with it. Am I correct in thinking that this newer head is better than the 48 style ? If so I will do as you are doing and send it off for a quick milling. 30 thou off maybe.

[maineSSS]

I'm going to be doing a plug operation fairly soon with the '57 head, so I'll take pics and report how it shakes out. The internal bypass gasket would seal the hole if the head/block surfaces are good, BUT- it's right at the edge of the head, with no clamping nearby, and if the edge of the gasket fails, you'll lose coolant pretty quickly. The glycol in coolant is flammable, and WILL burn your car down if the water evaporates off on a hot surface. This could happen here if the escaping coolant hit the fan blades and gets blown back over the exhaust manifold (Google "Coolant fires" for more info).

The 57-59 head is the one with good compression AND flow, the rest aren't very special. Whacking a big slice off to "improve Compression" at the expense of flow will be counterproductive. You want to get flow first, then go for compression. This approach isn't too popular with the bolt-on crowd, because it involves a lot of painstaking work, but it will yield the best result.

Edited July 27, 2012 by maineSSS

[maineSSS]

Here's some pics of the internal bypass plugging operation I did on the '57-59 230 head to retrofit it to the early external bypass block.

Pic #1 shows the bypass hole (at the pen tip).

I used a 1/8" pipe tap to thread the hole down about 13/64" (pic #2). I started the tap with the head in a Bridgeport mill to assure it was going in straight, but you can do it by hand if you're careful. Depth isn't critical, you just want the plug below the gasket surface. I found the thread engagement of the allen head plug was sufficient, which means no cleanup milling- very convenient. Since it's steel, use either white Loctite thread sealer or blue Loctite threadlocker to seal water out of the threads and prevent rusting.

Pic #3 shows the plug about 30 thou below the gasket surface. I haven't looked at internal bypass block, but the same thing will work if you have about 1/4" depth of hole to tap. Keep in mind that cast iron is soft and easy to strip when you tap and run the plug in, go easy with these operations, or you'll be bumming...

Edited August 2, 2012 by maineSSS

[Niel Hoback]

Excellent work! Walter P. would be proud of you.