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  #31 (permalink)  
Old 11-05-2007, 04:27 PM
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Thank goodness I have you guys and this site. I havent taken the heads off of an engine so I was a little excited to rip em' off. But I'm really glad that I dont have too. Its definately oil, and I wasnt positive that it was coming from the heads. I think its probably the intake manifold gasket that is leaking.

I recently took the manifold off and put it back on without replacing the gaskets. Now I can do it right (shouldve done it the first time ). Im on a time crunch to get the car out of the unit and on the street within the next two weeks. I just want her running so I dont need to pay for such a huge storage unit. I'll get a smaller one and store the accessories, carpet kit, chrome etc. in that. I also have a few ideas for turning a smaller unit into a "workshop" that I can run a small ebay side business from.

Fbird88, the car has always been really rough and boggy off the line. Its never been this bad and I havent noticed that much oil from the manifold gasket as well as had this bad of an idle since I put the manifold and carb. back on. This time I'm obviously replacing the gaskets and Im going to run a bead of sealant along the front a rear of the manifold instead of using the rubber gaskets that have been on their (which is where the leak SEEMS to be comming from)

Thanks for all of the advice and words of encouragement. It helps more than y'all know (no we dont usually say y'all in Southern California but it seemed appropriate ) Have a wonderful week everybody!

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  #32 (permalink)  
Old 11-05-2007, 06:47 PM
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305 sbc good idle, Dies when in gear

for STOCK to MILD engines i used a safe bet rule(rules meant to be broken though) double the CI equals carb size...305 x 2 = around 600
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  #33 (permalink)  
Old 11-06-2007, 05:49 AM
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Quote:
Originally Posted by 1970Chevy
I think its probably the intake manifold gasket that is leaking.

I recently took the manifold off and put it back on without replacing the gaskets. Now I can do it right (shouldve done it the first time ).
Don't feel bad. I still have a front seal that needs "fixing". When I changed the cam, I got in a hurry and didn't feel like taking the time to loosen the oil pan to get the gasket on the bottom of the timing cover in place. So... I just pounded the timing cover on with a rubber mallet and smeard silicone all over down there.
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Old 11-06-2007, 06:32 AM
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While you have the intake manifold off, beg borrow or steal a dial indicator+magnetic stand and measure the cam lift at the lifter.. If you tell me the lobe lift of 1 intake and 1 exhaust lobe I can tell you with good accuracy what cam is in it.
If you r+r'ed the intake without replacing the gaskets its very likely you have a manifold vacuum leak. That would explain 90% of your tuning troubles.
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Old 11-06-2007, 07:38 PM
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what does the magnetic stand do for the dial indicator or measurement? would I be able to measure what I need to with just a dial indicator ?

If it is a manifold leak (and im almost positive it must be) then how would changine the gears decrease the vacuum as significantly as it does. I understand how a vacuum leak would cause the symptoms the engine has, but why does the gear change double the trouble?
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Old 11-06-2007, 09:10 PM
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Quote:
Originally Posted by 1970Chevy
what does the magnetic stand do for the dial indicator or measurement? would I be able to measure what I need to with just a dial indicator ?

If it is a manifold leak (and im almost positive it must be) then how would changine the gears decrease the vacuum as significantly as it does. I understand how a vacuum leak would cause the symptoms the engine has, but why does the gear change double the trouble?

The magnetic stand just lets you put the dial indicator anywhere, except on an aluminum engine.

What gears are we talking about changing. If the timing gears or off the cam can be retarded or advanced from where it should be, this would affect engine vacuum. Changing rear end gears would have no effect on idle vacuum but will change cruise vacuum because the amount of throttle open is changed for the mechanical advantage of the gears.

Bogie
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  #37 (permalink)  
Old 11-06-2007, 11:14 PM
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Sorry about the confusing post. Im wondering why the vacuum is so greatly affected by shifting into gear. At park the engine idles with 17 Hg" of vacuum. The moment I shift into reverse or first gear, the vacuum drops to 10 Hg". Im just wondering what is happening inside the engine that causes this significant amount of drop in Vacuum?

-Matthew
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  #38 (permalink)  
Old 11-07-2007, 05:37 AM
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Because the carb might be too big thusly when the rpm drops the airspeed cannot keep it's velocity due to the carb size??? Just a very random idea. I really couldn't tell ya.

But now that I'm on that subject, I don't recall what carb you said you had but could it be possible your secondaries arent closing all the way?

It's probably best you ignore my random train of thought
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  #39 (permalink)  
Old 11-07-2007, 04:16 PM
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main reason vacuum drops is because rpm drops. the engine is not pumping as much air at a lower rpm and therefore is not pulling as much vacuum against the butterflies of the carb. just like when you are cruising on the highway, higher load at a lower rpm vacuum will be higher, something like 20 to 25 or even higher depending on the engine size and whatnot, because of rpm and lack of opening in throttle blades. hope this blurb is correct and helps.
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  #40 (permalink)  
Old 11-07-2007, 10:47 PM
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I think, in your particular case ... with leaking intake gaskets ... that it has to do with engine load.

If the engine is not under any load, (not in gear) it would maintain enough port velocity to deliver a lean fuel mixture ... but still enough to make each cylinder "carry it's weight", at least partially. The momentum developed by the "good" cylinders would also help to carry the ones not making a full contribution.

Once you drop it in gear ... the load increases, the port velocity decreases, and the momentum effect is largely absorbed by the torque convertor. Those cylinders that are not carrying their own weight are much more of a liability now ... and idle quality suffers.

Similarly, if you have a header gasket leak ... you don't notice it nearly as much until after you drop it into gear and put a little load on.
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  #41 (permalink)  
Old 11-08-2007, 10:00 AM
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dial indicator w/magnetic stand. Take the lift reading off the edge of the lifter body to eliminate the pushrod plunger from depressing giving a false reading.
Push the lifter down in the lifter bore with your finger to ensure its contacting the cam lobe.
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