Help me decide on engine for 72 Chevelle

[bobs409]

I gave it a good workout today. It now has 100 miles on it so I guess I didn't forget any bolts or anything.

I tried to set the total timing at 34 degrees but it pinged. Dropped back to 32 and still has a very slight ping, more noticable once engine is fully hot. Probably just the lousy gas they sell today. Next time I will back it down another 2 degrees and try again.

I noticed it still smokes a bit, nothing heavy, just a light waft that passed me by when I would come to a red light. I guess that's normal until the rings seat in. When is that by the way? :? Which leads me to something I thought of while out driving. Why doesn't a new car smoke until their rings seat?

The car got alot of thumbs ups today. Looked real sharp after being washed.

 

[jdk971]

what rpms are you running around 60mph. check when ya get time no hurry. thanks
jim

i am thinking of going that way with the autogear. i have a 4.10 or 4.11.

 

[Don Jacks]

Okay,more questions is the vac. line to the vac. advange hooked to ported vac. or manifold vac?.as far as ring seating time 500-1000 mi.should do it.I dont think that other than make sure that the vac. advance is hooked up to manifold vac. that you just run it around untill you can get all 93 octane fuel instead of the mix you have now.You are having to take out too much timing. All vin all iit sounds great,but theres still some tuning too do

 

[bobs409]

jdk: I'll check that for you next time I have it out. I think I recall about 2600 at 55mph but don't hold me to that. Rear tire height will have alot to do with it too.

Don: I have it hooked to ported vacuum. So I should changed to manifold vacuum then?

I did put more premium in it yesterday. Should be very little 87 octane left in there now.

Some things that may help with your diagnostics , the new distributor has heavy springs on the weights. They included an X shaped metal piece I can add to limit the vacuum advance. It has 4 settings.

Also, the new distributor doesn't have an adjustable advance. I can put the new one in if you recommend.

 

[Don Jacks]

Yes,put it to vacum,then reset your idle.If no more , ping,then go up to 36 and see what happens.It should run at 36 to 38 with out ping.Try to see where the mechanical advance stops advancing.We'll now sneak up on it one change at a ti me.Watch the idle vacuum as it should increse

 

[bobs409]

Don, I changed to manifold vacuum and that made a huge difference. The ping is gone. I'm at 32 degrees total. I tried 34 but could hear the ping coming back again so put it back. It seems to like 32. It's got oodles of power, doesn't feel like it needs anymore timing. :eek:

I went through a 1/2 quart of oil in the first 100 miles. I didn't see any smoke yet today. I just got back from driving it all over the place. Everyone turns when I drive by! I'm getting thumbs up, people yelling for me to spin the tires, etc. no1:

I'm very happy with the way it's running now. I feels like a well oiled clock. Hard to believe this was sitting in a junkyard a few months ago. Hadn't been run in about 25 years.

 

[bobs409]

Jim,

I'm running 2,750 at 60 mph. If I put a taller tire on the back, I'd be doing even better.


Bob

what rpms are you running around 60mph. check when ya get time no hurry. thanks
jim

i am thinking of going that way with the autogear. i have a 4.10 or 4.11.

 

[MRHP]

Remember, A lean condition can cause spark knock. So can pulling oil vapors through the pcv valve. The pcv valve could also account for your blue smoke and oil consumption. Just some food for thought.

 

[bobs409]

Yeh, I should take another look at the plugs to see if it's running lean. Feels good though. The PCV valve has a baffle in the valve cover so probably ok there.

The smoke isn't really blue looking, just light. I would think normal for the break in. (he said hopefully)

Got another 56 miles on it today. I'm probably going to regret saying this but it actually seems decent on gas! Now that I said that, the needle will probably start dropping like a lead balloon.

Well, it gets a few days break now. Got to get back to some body work on my stepside so I can paint it before the flakes start falling. :eek: Can't believe it's September already.

 

[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?
/
/

 

[jdk971]

thanks bob, i am hoping to get closer to 2k. i have a feeling it will take a tranny and
a new gear in the rear. thanks again jim

 

[oldskydog]

Bob,
Don has been giving expert advice .
Here's a few really good articles by Lars Grimsrud, a well respected engine/ignition tuning guy......great for a good understanding of vacuum advance and timing issues.
These are pdf format so I guess you have to download them first.

http://www.lbfun.com/warehouse/tech_info/timing & vacuum advance/Vaacuum_Advance_Specs.pdf

http://www.lbfun.com/warehouse/tech_info/timing & vacuum advance/How to Set Timing.pdf

http://www.lbfun.com/warehouse/tech_info/timing & vacuum advance/HEI Tuning.pdf

 

[Don Jacks]

Thanks for posting this,Cecil.I hope it's some help for all the guys here looking for the best performance from thier hard earned money,It did for me.Another good reason to perform a "degreeing operation when doing the final assembly,this will allow you to correct things like keyways not in thier proper place,balancers not marked quite right,so you know where top dead center actually is,then you can dial her in from there..

 

[64ss409]

Good advice on the degreeing operation Don. The last build on my 409 I found the balancer marks were right on, but something was off with the cam or gear set or both. I had to run the gear set (Cloyes Tru Roller) in the adv 4 degrees keyway to get the cam (Isky) straight up according to specs sent with it.

 

[bobs409]

Thanks Cecil. I'll read through those when I get a chance.

I've learned alot so far, still a few things to go.

 

[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

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.