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Discussion Starter · #1 ·
Ok. I have a 75 Nova that has been completely rebuilt. Running a Holley 670cfm street avenger with an edelbrock dual plane performer RPM intake. Recently installed a 1" carb spacer. When leaving from a stop it acts like it is starving, almost dies, then roars back to life. Can't tell if it's starving or flooding. But on acceleration it misses on one or more cylinders. Once it reaches the higher(3,000+) RPM ranges it does fine. And at stops I have to put it in nuetral or it will die. I thought maybe the idle was set too low but it idles at 1300-1400rpm. Ive tried adjusting the timing, but it doesnt help. I time it by ear to when it seems to run best. I did find one spark wire that is sparking against the headers. Would that cause that big of a problem? I was also thinking that the fuel pump may not be putting out enough. Any help is great.

Here are the total specs I know about the engine.
350 4 bolt main motor is brand new rebuild,
high compression forged flat top pistons,
hyd roller elgin cam, valve lift .450 int. .460 exh.,
1.5 roller rockers,
bigger valves on heads.
piston chambers bored out .40 over,
stronger push rods,
forged crankshaft.
brand new holly street avenger 670 cfm carb.

And here are the specs on the cam
lobe int. - 114 exh. 114 .
SAE dur. - 292 int. 288 exh.
.050 dur - 224 int. 224 exh
SAE timing - BTC 32 ABC 80 BBC 78 ATC 30
0.50 timing - BTC -3 ABC 47 BBC 46 ATC -2
 

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change all the plug wwires first get a 19 dallar or 9 dollar (depending on if you have the spare cash at the time) and see if that fixes it cause i gauentee iff you see it sparking on the header your car will be missing and that could be all of your problem and if not it is definetly part of it
 

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Get a timing light.
Timing by ear is doing you no good.

No one is going to attempt to diagnose your "missing" or "stumbling" issues if you can't tell use where your timing is set.

Start there, I bet a lot of your problems will get better or disappear.
 

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and if your problems dont dissapear you just have to **** with it till you get it right.

Im going thru it myself. ive so far changed the vacuum advance unit, replaced the fuel pump, changed distributor springs,changed spark plug wires,set the idle mixture using a gauge,set the initial advance with a timing gun. everthing helped a bit but its still bogging from idle

Im picking it up from the shop for 4.11s tomorrow, which should also help, then Im doing the following in order.(my carb is an edelbrock)

1. install a fuel pressure regulator at 5.5 psi(which is what edelbrock carbs like) right now Im running 8.5

2. and adjust floats

3. move pump closer to carb for more fuel

if necessary, change rods and jets, and spring as needed

Im definitely gonna get this bad boy fixed.
 

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oh, if you get a timing light, make sure you get the dial back type. at autozone its $49 vs 39 for the regular one and it is so much easier to use
 

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and if your problems dont dissapear you just have to **** with it till you get it right.

Im going thru it myself. ive so far changed the vacuum advance unit, replaced the fuel pump, changed distributor springs,changed spark plug wires,set the idle mixture using a gauge,set the initial advance with a timing gun. everthing helped a bit but its still bogging from idle

Im picking it up from the shop for 4.11s tomorrow, which should also help, then Im doing the following in order.(my carb is an edelbrock)

1. install a fuel pressure regulator at 5.5 psi(which is what edelbrock carbs like) right now Im running 8.5

2. and adjust floats

3. move pump closer to carb for more fuel

if necessary, change rods and jets, and spring as needed

Im definitely gonna get this bad boy fixed.
cyanjaguar... make sure the rod that moves the eccelerator pump is in the right hole... it can make a big difference if it is not:mad:(from idle that is... no problems at higher rpms:D:D:D)
 

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cyanjaguar... make sure the rod that moves the eccelerator pump is in the right hole... it can make a big difference if it is not:mad:(from idle that is... no problems at higher rpms:D:D:D)
thanks, will do as soon as it comes back from the shop. I want it closer to the body right?
 

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Discussion Starter · #8 ·
Bscman-well the only problem with using a timing light, is that it has a performance cam in it. So my timing mark actually ends up somewhere around the middle of the engine.

Nova-So new wires will solve the missing problem. But I'm sure it won't take away all the hesitation. Here's what I'm going to try and do. My 68 Junker has a brand new fuel pump on it. It seems to put out alot more that my 75. I'll swap that out. If it doesn't solve my problem, I'm taking the spacer plate out. Seems that's when all my prblems started. I was just hoping to get it running right with it.

Also just curious, anyone know what all these letters mean when refering to timeing? I know two of them BTC(Before Top Dead Center) and ATC(After Top Dead Center). But what do the others mean?
SAE timing - BTC 32 ABC 80 BBC 78 ATC 30
0.50 timing - BTC -3 ABC 47 BBC 46 ATC -2
 

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oh, if you get a timing light, make sure you get the dial back type. at autozone its $49 vs 39 for the regular one and it is so much easier to use
I'm going to disagree...because I can!
I'm not a fan of dialback lights...especially lower end ones. They aren't always all that accurate. Off by even 1-2 degrees is too much, IMO. :eek:

Save yourself some $$$ and buy the basic light--or better yet, put the cash you save towards a higher quality non-dialback timing light...then just measure out and mark your balancer. Assure your TDC mark is in the correct spot, then mark another at 36° BTDC. This way there is one less thing to go wrong. ;)

JMHO

Bscman-well the only problem with using a timing light, is that it has a performance cam in it. So my timing mark actually ends up somewhere around the middle of the engine.
:rolleyes::rolleyes::rolleyes:
Hey, mine too.
And I set my timing with a timing light :p

Hmm...last time I checked, the camshaft does not affect when the piston reaches TDC. Care to tell me how, in your special case, it is? :confused:
Top dead center is top dead center no matter what camshaft you have--or even if you don't have one installed!
(In other words, your arguement is completely invalid. Do you know how to properly set the timing?)

The air/fuel mixture inside the cylinders takes time to combust. This is the reason you set your ignition timing to ignite the mixture BEFORE the piston reaches top dead center. The whole idea is to advance the timing enough, as engine speed increases, so there is adequate time for the fuel mixture to ignite--too soon or too late and you'll end up with a sluggish motor, or one that doesn't last long due to detonation.

Timing by ear will almost ALWAYS over-advance the ignition timing...which will lead to poor performance and pre-ignition (detonation) which is EXTREMELY hard on the engine.

Get a timing light and set properly set your timing.

Once you get the timing set correctly, chime back in and let us know how you're doing. You'll probably need to change out your accelerator pump cams/discharge nozzles to get it turned right--and common thing with new holley's.
BUT there is no point in trying to tune anything until you get your timing right. Otherwise you'll just have to re-tune it all when you finally get around to setting your timing.

-Brett
(This is good advice...take it...or you're going to be chasing your tail forever trying to get this thing to run right)
 

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Discussion Starter · #10 ·
Hmm...last time I checked, the camshaft does not affect when the piston reaches TDC. Care to tell me how, in your special case, it is?
Top dead center is top dead center no matter what camshaft you have--or even if you don't have one installed!
(In other words, your arguement is completely invalid. Do you know how to properly set the timing?)


First of all I was not arguing. I was simply stating what I knew about my engine. I do not appreciate people twisting my words into something they're not. I don't care how long you've been doing this. Just explain it to me so I understand.

The air/fuel mixture inside the cylinders takes time to combust. This is the reason you set your ignition timing to ignite the mixture BEFORE the piston reaches top dead center. The whole idea is to advance the timing enough, as engine speed increases, so there is adequate time for the fuel mixture to ignite--too soon or too late and you'll end up with a sluggish motor, or one that doesn't last long due to detonation.

I know why timing is set the way it is. But if your cam changes the duration of your valves, then you have to change the timing of your ignition. Right? So therefore if my cam is not the same as someone elses then my timing will be different than theirs.

I also want to know if someone knows the meaning of the other letters I posted.
 

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First off, if your plug wires are arcing, then they need to be changed!!!
Second, if all of the idle (only idles high) problems and the stumbles and bogs started when you added the spacer plate then it sounds like you've got a first class vacuum leak!! I bet if you start to cover the carb while it's idleing like you're gonna choke it with your hand that it'll idle up.
Third, if the timing marks are in the middle of the motor, either your balancer ring has slipped, timing is WAY off, or you've got one of the odd year balancer that's meant to have the timing tab in the middle of the timing cover behind the water pump. In any case, take the drivers side valve cover off, take off the #1 rockers, get a piston stop that screws into your #1 spark plug hole and turn the motor over BY HAND until it hits the stop. Put a small mark on the balancer where it lines up with "0" on the timing tab. Then turn it over the other way until it hits the stop again. Then mark the balancer with another small mark again lined up with the "0" timing pointer. The mid-point between your marks will be TRUE TDC.. Make a bold mark on the balancer and continue the mark onto the crank pulley that way you'll have a referance to look at in case you ever think the outer ring may have slipped. Now you can either buy a dial back timing light (I like my good ol' Craftsman...I've got three so I can check them back-to-back periodically for accuracy.) or some timing tape and set your timing accurately.
Oh yeah, put your rockers and valve cover back on....:D
 

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Bscman-well the only problem with using a timing light, is that it has a performance cam in it. So my timing mark actually ends up somewhere around the middle of the engine.

Nova-So new wires will solve the missing problem. But I'm sure it won't take away all the hesitation. Here's what I'm going to try and do. My 68 Junker has a brand new fuel pump on it. It seems to put out alot more that my 75. I'll swap that out. If it doesn't solve my problem, I'm taking the spacer plate out. Seems that's when all my prblems started. I was just hoping to get it running right with it.

Also just curious, anyone know what all these letters mean when refering to timeing? I know two of them BTC(Before Top Dead Center) and ATC(After Top Dead Center). But what do the others mean?
SAE timing - BTC 32 ABC 80 BBC 78 ATC 30
0.50 timing - BTC -3 ABC 47 BBC 46 ATC -2
The sae will be the actual seat-to-seat opening and closing points (also called adv or advertised duration and total duration) and the .050 will be the events at .050 of lift off of the seats.
Oh, btw, with that much spread between the duration #'s and that little lift, that's gotta be a 30yr old cam design!! SLOW ramp speed!!! There's bound to be some better profiles out there if you ever wanted to upgrade!!! Everything I've seen in the Comp and Lunati line-up for the same power range would make gobs more power and have better vacuum and idle characteristics than what you have now. Same .050 duration with probably around 20* less advertised (or seat-to-seat) duration and a bit more lift!!
Just a thought..:cool:
 

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Discussion Starter · #14 · (Edited)
D-man-So with the vacuum leak, are you suggesting that the gaskets arent sealing? Or a leak somewhere else? As far as the cam goes. It was made by elgin and the guy I bought it from had it recuilt just a few months before selling it to me. It's not really a racer, just kind of my weekend warrior. So I'm not worried about having ALOT of power right now. Maybe once I get it up to MI with my Dad.

Edit: In a different email he tells me the valve lift is .450 int. .460 exh. Is that good?
 

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That's cool.
Yes, I'd suspect either one of the gaskets under the carb and spacer is leaking or when removing and re-installing the carb, one of the vacuum lines or plugs was pulled lose or missed all together. :rolleyes: We've all been there at one time or another. Mine are called brain-farts.. :eek:
 

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I know why timing is set the way it is. But if your cam changes the duration of your valves, then you have to change the timing of your ignition. Right? So therefore if my cam is not the same as someone elses then my timing will be different than theirs.
I'll agree and disagree.
Not all motors will require the same timing curve...there are a several things that will slightly alter your timing needs. Swapping cams can have a (small) effect on your timing needs...I won't argue that.

The problem is, you are saying it's not possible to set your timing because of this "performance cam"--that is entirely untrue.
If you are having problems with setting you timing with a timing light, my first question is always "Do you know how to set the timing?" the second is "Have you verified your balancer/timing tab correspond to true TDC?"

The general rule is that a typical SBC engine does best with a total timing of around 36° BTDC all in by 3,000rpm. The sooner you can get that advance in (without detonation) the better.

First, you said your engine is timed by ear. VERY bad...this almost ALWAYS means it's over-advanced. The "guess and test" method will rarely yield positive results.

Second, you said that if you put a timing light on it and try and set the timing, the timing marks moves towards the middle of the engine?

The reason I asked if you know how to set the timing is because of that statement!
Turn the distributor the other way and the timing mark will get closer to your timing tab ;) Pretty basic.

Now, if your engine will not run when the timing is properly set (again, this is with a timing light, NOT by ear) you may have a problem.
Depending on which timing tab and balancer was used, you might have the wrong combo of parts--which means the timing mark and TDC on your #1 cylinder won't line up. Also, it is possible your balancer may have slipped. Any of the above will affect your abilitly to properly set timing.

The first step should be to verify your timing mark on the damper corresponds to the TDC mark on the timing tab (of your #1 cylinder).

Again, if refuse to get your timing set before you do anything else you are just setting yourself up for more problems.
A LOT of hesitations, bogs, and even overheating problems stem from improper timing.
Properly set the timing and see how your engine responds.
You'd be suprised how much better properly tuned engine will run...and how much better mileage you will get.

FWIW, your engine shouldn't need to idle at 1,300-1,400rpm.
If the hesitation and inability to idle started after you added the carb spacer, it is likely you have a vacuum leak. Putting a square bore carb on a spread bore intake can be problematic as well (vacuum leak around the secondaries).
They make a small adapter place for this very circumstance.
 

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After installing on painted balancer, spay a coat of clear coat to help keep it from flying off.
Or just use a paint pen and mark 0° and 36° and you're done. No tape to worry about falling off. :p

-Brett
(36 is 1/10th of 360°...so make the 36° mark 1/10th of the circumference away from 0°)
 

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Discussion Starter · #19 ·
First-
Swapping cams can have a (small) effect on your timing needs...

So then If I set my timing to your suggestion, it may not be right. You say 36, it could be 34, or even 32. Even that far off could cause problems.

Second-
The problem is, you are saying it's not possible to set your timing because of this "performance cam"--that is entirely untrue.

Again, your putting words in my mouth. I said that is was a PROBLEM, not that it was impossible.

Third-
If you are having problems with setting you timing with a timing light, my first question is always "Do you know how to set the timing?" the second is "Have you verified your balancer/timing tab correspond to true TDC?"

I'm not ignorant. I know how to set timing. I've just never had to do it on an engine that has been modified like this one has. That's why I'm asking for help. Not for someone to criticize my knowledge. The engine was built by a proffesional shop, so I hope they put the balancer on right.

Fourth-
Again, if refuse to get your timing set before you do anything else you are just setting yourself up for more problems.

I am not refusing to do anything. I haven't had a chance to do anything yet. I'm still at work.

As far as the spread bore vs square bore, I didn't know that. I'm going to have to look into that.
 

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As far as the spread bore vs square bore, I didn't know that. I'm going to have to look into that.

Bingo!
 
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