The damn thing only cranks up to 4000 before shifting automatically.

 

. My '86 Chevy MonteCarlo LS was like that, shifted at only 4000, although stock engine pulled well to 5,000 plus... stop at a stop sign, start up and round a corner and it was already in 2nd gear... MonteSS auto shifted at 5500, but had bigger cam and heavier valve springs... My '78 F150 doesn't have a tach. so I'm not sure what RPMs it's turning, was wondering what the WOT shift RPMs was, prolly 4000, as well... I have a tach here to put in it, but don't know if it works...

 

I'm hoping that once I put the high speed shift governor In it will perform better and hold off the up shifting a bit.

 

. I'm not that familiar with C6's... had the truck a long time... had the C6 rebuilt a long time ago... but only discovered a year or so ago that they have a vacuum modulator like a GM TH350... I thought they used a kickdown/upshift linkage... wasn't sure if an adjustable modulator or different governor springs (or both) were the way to change shift points...

 

Modulator will adjust part throttle shifting. Tailshaft governor controls WOT shift speed.

 

. So you're saying the modulator controls the shift points but only within the max range set by the governor?

 

Yep. That's how it works.

 

And for good reason. I took her to 5500 tonight and she popped. Right about here.

 

What exactly do you mean "she popped"?

 

I think it's a head gasket. It blew coolant out from under the head as well as out the exhaust. She started getting warm. But it was still running ok at first. Started Mis firing a bit later.

 

Never mind on the head gasket, it blew out a freeze plug. I think that's the problem.

 

. What's the pressure on the radiator cap? ... and is it in good working condition?


. The engine sounded really good in the video... wish you would have included the tach in the picture...

 

Radiator cap is 13psi. It's fairly new. I pressure tested the radiator and block to 16psi just a couple months ago and everything held tight.

I don't know why the hell it blew out.

 

Replaced freeze plug and all is well.

 

.
. Glad to hear it...

. Did you put some LockTite or something on it?