[Gator67]

Our faithful 68 Firebird 400 had some coolant seepage for a while, which I thought was from a leaky water pump gasket. I went to replace the gasket yesterday only to discover that the timing cover had deteriorated (see photo), so my little Saturday morning project snowballed somewhat. Anyways, trying to decide whether to go with another '68 8 bolt timing cover or a '69 and up 11 bolt. It's a numbers car and everything's mostly correct, and I'd like to keep it that way. However, we like to drive the car, but it does get a bit hot in the summer with the A/C on, and I've been told the 11 bolt pumps cool a bit better. Is it in fact true that the 11 bolt pump cools more effectively, and if so, how much of a difference is there?

[b-man]

The only reason to go 11-bolt is if you can’t source the one year only 1968 cover (8-bolt pump/late balancer).

There’s no discernible difference between 8 and 11-bolt pump cooling capabilities. A friend who’s built numerous engines for himself and many others even found his coolest running engine had the 8-bolt pump.

Of course there are numerous factors affecting how well an engine cools in any particular car but for the sake of originality and ease of accessory parts compatibility I’d be trying to source the correct 1968 cover.

The 11-bolt pump is not the magic bullet, running hotter during the summer with the A/C running is to be expected. Maybe a radiator or fan clutch replacement or upgrade would be worth looking into.

[gtobird]

I've had several cars with 68 engines and the original 68 style water pump & timing case. Many years ago I had a severe overheating problem on a fresh rebuild. I tried all of the usual backyarder stuff and nothing seemed to work. Then one day I found out about the need to space the divider plates properly that reside in back of the water pump. You may already be well ahead of my knowledge, but this is just a reminder not to forget that and at least for me, I found that pairing those plates using an original style water pump with the cast impeller helped a lot.

Old joe

[Gator67]

Thanks guys. Since there's not a consensus that 11 bolt WP set-ups are better, I'll just stick with the 8 bolt. I'll definitely be adjusting the divider plates...the gap between the internal housing plate and the (cast) impeller vanes was .25", plus the plate was pushed into the timing cover a bit...no wonder she would heat up a bit more than my 67 goat (I did clearance the internal housing plate on that one). I also ordered a new Cold Case radiator. May also try a Hayden 2731 clutch to get the fan into the shroud a bit more.

Before I install everything, I should flush the engine...I found a few gelatinous in the timing cover...Is there a way to do this with the engine as pictured without making a complete mess?