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Old 07-08-2008, 06:11 PM
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Old 07-10-2008, 09:48 AM
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What was your question?
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Old 07-10-2008, 10:26 AM
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Never got a response so I deleted the original.

My car backfired hard a couple of times. I have a Street Avenger on my 327 in the 32. I think it has the check valve in it to stop blowing the power valve. However, the last time I started the car I was getting a surge like it was getting extra fuel from somewhere. It would surge, idle back and surge again. It kept doing that.

Is it possible to blow the power valve out even though it has the check valve in the carb??? That was my question. If not, then I have another problem.

Steve
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Old 07-10-2008, 11:28 AM
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Quote:
Originally Posted by reflog
Never got a response so I deleted the original.

My car backfired hard a couple of times. I have a Street Avenger on my 327 in the 32. I think it has the check valve in it to stop blowing the power valve. However, the last time I started the car I was getting a surge like it was getting extra fuel from somewhere. It would surge, idle back and surge again. It kept doing that.

Is it possible to blow the power valve out even though it has the check valve in the carb??? That was my question. If not, then I have another problem.

Steve
Yes it is possible but highly unlikely. You can take apart the carb still on the motor to check the condition of your power valve. You haven't done anything to the motor lately that could have changed it, right? Check your manifold vacuum with a gauge. How are your carb's float levels? Fuel pressure? Engine timing? How does the motor act when driving?

Last edited by Sixtyninemercury; 07-10-2008 at 12:00 PM.
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Old 07-10-2008, 01:12 PM
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Quote:
Originally Posted by Sixtyninemercury
Yes it is possible but highly unlikely. You can take apart the carb still on the motor to check the condition of your power valve. You haven't done anything to the motor lately that could have changed it, right? Check your manifold vacuum with a gauge. How are your carb's float levels? Fuel pressure? Engine timing? How does the motor act when driving?
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

Yeah, I did do some work on the carb. The car has never run right since I installed the cam. Always had a bog in it on acceleration. I followed Lars Grimrud's recommendations on what to do with the Street Avenger to get it set correctly. The first time I started the car up it ran good except I couldn't get the timing below 12 to 14 degrees BTC. I fooled with that a little and when I started it back up again the damn thing wouldn't idle at all. Had the surge problem. Also, this is when the backfire came.

With the carb, all I did was up the jets in the primaries from 68.5 to 72 and I put the 68.5's in the rear. That was what Lars recommended. I also had to adjust the secondary throttle plate as it was all the way closed and according to Lars it should be open the same amount as the primaries to get a balance. I set both of those at approximately .020 per his instructions. The float levels were right on in front and maybe a little low in the rear.

Lastly, when I pulled the distributor I found fluid in the vacuum cannister. I am still getting fluid out of it. The dist. is a MSD Ready to Run unit. Don't believe it should have fluid in the vacuum cannister so it must be coming from the carb but I am not sure how it gets the fluid though the vacuum line.

Steve
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Old 07-10-2008, 01:46 PM
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Quote:
Originally Posted by reflog
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

Yeah, I did do some work on the carb. The car has never run right since I installed the cam. Always had a bog in it on acceleration. I followed Lars Grimrud's recommendations on what to do with the Street Avenger to get it set correctly. The first time I started the car up it ran good except I couldn't get the timing below 12 to 14 degrees BTC. I fooled with that a little and when I started it back up again the damn thing wouldn't idle at all. Had the surge problem. Also, this is when the backfire came.

With the carb, all I did was up the jets in the primaries from 68.5 to 72 and I put the 68.5's in the rear. That was what Lars recommended. I also had to adjust the secondary throttle plate as it was all the way closed and according to Lars it should be open the same amount as the primaries to get a balance. I set both of those at approximately .020 per his instructions. The float levels were right on in front and maybe a little low in the rear.

Lastly, when I pulled the distributor I found fluid in the vacuum cannister. I am still getting fluid out of it. The dist. is a MSD Ready to Run unit. Don't believe it should have fluid in the vacuum cannister so it must be coming from the carb but I am not sure how it gets the fluid though the vacuum line.

Steve
Usually when a engine bogs off of the line it's an initial fuel delivery problem. Usually a lack of enough fuel. I would first look into the accelerator pump circuit - not the jets. Depending on which cam your motor now has - and also which type of intake manifold you have - plus your compression - and heads and on and on - would help in picking your carb's jetting. Myself - rather than read the plugs after cruising - I have installed A/F ratio meters inside my car so I can read real-time how my motor's combustion process is doing at idle, part throttle cruising, and WOT. I also have a manifold vacuum gauge installed inside my car. For most street driving the orange colored pump cam works 95% of the time. I would try the next size larger of the accelerator pump squirter nozzle on your Holley. Or even two sizes up - but try one size and a time and drive it and figure from there. I always have to use a larger size (.037") out of the box because of my lumpy carb and intake manifold. It depends on how lumpy your cam is in adjusting your throttle blades. A real lopey cam will necesitate modified your blades to get it to idle right and to take off good, too. What are the specs on your cam?

What sort of fluid are you getting in the vacuum cannister? That does sound strange. If it's fuel you will know by it's scent. Is it motor oil? Does the inside area under the distributor's cap of some oil, too? That could be because of not an adequate crankcase venting system.
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Old 07-10-2008, 01:57 PM
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Here's a copy of my cam profile that I got with it from Engle. The engine is a 275 HP out of a 68 Chev. Heads are World Products Street Replacement units with comp. ratio of I think 9:1; has a Edelbrock Performer RPM manifold. Running a 400 turbo behind it. Not a world beater but just a little juiced up.


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Old 07-10-2008, 02:04 PM
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My error. I was and still am a little confused. I put the 68.5 jets in the primaries and 72 in the secondaries.

Steve
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Old 07-11-2008, 02:12 PM
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Quote:
Originally Posted by reflog
The first time I started the car up it ran good except I couldn't get the timing below 12 to 14 degrees BTC. I fooled with that a little and when I started it back up again the damn thing wouldn't idle at all.
Steve

Why were you wanting to get the timing down below 12???

With your cam that's probably a little low...
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Old 07-11-2008, 02:43 PM
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a blown power valve will make it run rich.

surge and backfire is a sign of a lean mixture and/or retarded timing.

A cam like you have will like 15 to 20 degrees of initial timing plus another 10 to 12 from the vacuum advance connected to a manifold vacuum source.

Adjust the idle mixture screws for best idle (highest vacuum).

Put in a bigger squirted, a 72 primarys, 76 secondarys, and a 5.5 power valve. If the surge and bog goes away, then start lean the primarys until the engine starts to complain again and go back up 2 jet sizes.
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Old 07-11-2008, 02:45 PM
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Quote:
Originally Posted by CarbGuy
Why were you wanting to get the timing down below 12???

With your cam that's probably a little low...
%%%%%%%%%%%%%%%%%%%%%%%%%%

I could live with the 12 or over if the damn thing wouldn't stall out when you step on it. Secondly, I finally just got it running again and it is doing the same as it did prior. Step on the gas and bog, recovers real slow. I took the dial back timing light and put the RPM's at 2200 and dialed it back. It only came to 19 degrees total and that was with 12 or so initial set in. I am now thinking I have a problem in the dist. with the springs possibly being to heavy. Didn't want to take it up to 3000 but may have to just to see what advance I am getting. Will look for some lighter springs also.

When I bought this cam I was told that it should idle around 8 degrees. Do you believe that is a little light for this profile?

Checked the vacuum also and had 12 hg at RPM. Also did a pull on the vacuum advance cannister and it did not move until about 8.5 hg. My carb had a 6.5 power valve in it. Not sure how this matches up.

Steve
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Old 07-11-2008, 02:53 PM
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Yes, only 7 degrees advance is a problem (19 total). You need around 38 degrees total (mechanical) plus another 10 to 12 vacuum advance during light load.

Nothing wrong with revving the engine up to 3000 rpm or even 4000 rpm in park.

lighter springs could help, but don't go too light. The weights need some spring pressure to return back to their starting point.
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Old 07-11-2008, 03:02 PM
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Quote:
Originally Posted by 454C10
a blown power valve will make it run rich.

surge and backfire is a sign of a lean mixture and/or retarded timing.

A cam like you have will like 15 to 20 degrees of initial timing plus another 10 to 12 from the vacuum advance connected to a manifold vacuum source.

Adjust the idle mixture screws for best idle (highest vacuum).

Put in a bigger squirted, a 72 primarys, 76 secondarys, and a 5.5 power valve. If the surge and bog goes away, then start lean the primarys until the engine starts to complain again and go back up 2 jet sizes.
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

I replaced the power valve already. Not sure that was the problem but I had a lot of fuel getting to the motor. The fast idle screw was fouled up also. When I shut the car off I still got some muffled ignition in the exhaust like to much fuel and it was retarded in timing. Was thinking of possibly moving the dist. one more cog advanced to see what happens.

Steve
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Old 07-11-2008, 03:15 PM
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Quote:
Originally Posted by 454C10
A cam like you have will like 15 to 20 degrees of initial timing plus another 10 to 12 from the vacuum advance connected to a manifold vacuum source.
IMHO 12-14* of initial timing would be adequate for that cam. Trying to start a hot motor with 15 to 20* is not fun - I know.
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Old 07-11-2008, 04:02 PM
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[QUOTE=Sixtyninemercury]IMHO 12-14* of initial timing would be adequate for that cam. Trying to start a hot motor with 15 to 20* is not fun - I know.[/QUOTE

@@@@@@@@@@@@@@@@@@@@@@@

Will do!! Found out something else. Called MSD to check about the advance problem. I was told that MSD ships the distributor with the heaviest springs installed. They do not open fully until 4000 RPM. They told me that I got a spring kit with the dist. and I should read my instructions to find the correct advance curve that I want. I located the original box and they the springs were. I studied their diagrams on the springs to use for different full centrifical advance and found that they recommend a light silver and a light blue for the advance to come in fully between 2000 and 3000 RPM. I have installed those.

I am currently under a tornado watch so had to quit trying to get this thing going for now. Hopefully I can get at it after this watch passes.

Steve
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