Help me decide on engine for 72 Chevelle

[bobs409]

Don,

I've got about 12 inches of vacuum sitting at a red light (hot)

I was wondering about the difference in cylinder numbers, especially since the 2 low ones are side by side.

These heads were ported out so maybe they hogged a bit more in those two cylinders? Would that lower the reading?


Bob

Originally Posted by Don Jacks

It wouldnt be a bad idea to do another compression test,as some cylinders were down about 14 psi lower than the others,but wait untill it has some more miles on it.What did the idle vac..come up to?
/
/

[MRHP]

12 inches sure seems low for a mild motor. Is it steady or does it bounce a bit? I would think you would be seeing 15 plus. You may have to up your initial timing and limit total timing. 12 just seems way too low.

[bobs409]

It is a pretty radical cam so that probably accounts for some of that. The needle is somewhat steady.

The vac reading was a little higher before when the idle was up some. I have it about 850 or so now.

I think my 409 always had low vac readings too. Can't remember off hand what that one runs at.

[petepedlar]

Great info on the timing Cecil !!!!!


Bob, if I remember you had one rocker that was a little tight.......... have you checked the rest to make sure the valves are closing properly ??

Dave

[bobs409]

Initially I had them all set to one full turn by mistake. I didn't see the paragraph in the Lunati papers that said 1/2 turn. That would have been too much anyway as I reset them all to 1/4 turn prior to finding the dead cylinder.

I just used the compression readings as a guide on if the valves are closing. I suppose I could try backing off a bit on the lower cylinders if that would help.

[Don Jacks]

12 in at idle on a 9.7 motor?MRHP is right,should be in the 14-16 in range.Dave's idea about readjusting the valves on the 2 low cylinders is a good one,I'd just give it a few more miles,then do it when you do the post break-in plug and compression check.Take a few minutes and read Cecils post,and you'll have a better idea of what we're talking about.All these ideas and practices will make your next engine builds eaiser and more rewarding.Let us know when youre ready to start tweaking that dist,as there's both power AND gas mileage hiding in there.

[bobs409]

Good news! I have 15 inches of vacuum, not 12. Feel free to laugh but I was reading it wrong. There is a little line for every 2 inches, not 1 like I thought. (my other car has it the other way so that's my excuse) Also, the way the gauges are mounted, your looking downward at an angle making a 15 look like a 14.

So looking straight at it and reading it correctly, I have a steady 15.

Got a few more miles on it today. Might take it on a longer trip tomorrow to deliver some parts to the machine shop for the other 454. That one might be coming home soon.

[58 Apache]

I hate it when I do stuff like that and don't feel like you are alone we all have those moments. Good to hear you are driving it and having fun. Oh bye the way that guy Murphy was here in today.

[bobs409]

You keep him there. I officially kicked him out of my garage!