[trshman]

Hi,new member here and first post. I have a '66 LeMans and am told the engine is a "70 GTO/400 and the heads are from a '78 TA. Compression is all 160 except 1 & 3 which are 155. Can anyone tell me what the pros and/or cons are to this combo? Any tangible benefit to going with modern heads e.g. Edelbrock Performer? Engine runs 10-15 degrees hotter on hwy than city/(4 core stock radiator just cleaned/pump/thermo ok). Could "stock" ignition settings be wrong for this engine/head combination ? Thanks in advance.
RG

[trshman]

Hi,new member here and first post. I have a '66 LeMans and am told the engine is a "70 GTO/400 and the heads are from a '78 TA. Compression is all 160 except 1 & 3 which are 155. Can anyone tell me what the pros and/or cons are to this combo? Any tangible benefit to going with modern heads e.g. Edelbrock Performer? Engine runs 10-15 degrees hotter on hwy than city/(4 core stock radiator just cleaned/pump/thermo ok). Could "stock" ignition settings be wrong for this engine/head combination ? Thanks in advance.
RG

[Goatman]

What you have is a 6X head (most likely) 400 ci. It will be fine, as 6X heads are one of the best D-port heads you can get. "Stock" timing should be fine, anywhere from 34-38 degrees if you're using good gas.

As far as the engine running hotter on the highway, its probably a case of your water pump spinning too fast and not allowing the water to "sit" in the radiator for long enough. Yes, that happens. You may want to try swapping a bigger pulley on the water pump. Pontiac used several sizes over the years with diffeterent options and motors. The key is finding one that allows the engine to run cool on the highway and city.

[trshman]

Goatman, Thanks much for the reply. You're right, heads are #9799914./Amoco or Chevron premium only

Unless there's a way to pinpoint pulley size I'm inclined to replace pump with one that won't cavitate. I drive it every day and experimenting takes time. Do you think I'd see a big drop with an aluminum radiator in daily use? I found a source for "slightly" used Fluidynes at under $200/just waiting for them to get one that would fit [img]/infopop/emoticons/icon_smile.gif[/img] Thanks again Goatman-I appreciate the help.