:confused:
Perhaps you guys can help me sleuth another elusive problem. Seem to have one every time I drive the car these days, but intent on working out all the bugs over the winter.
A few Sundays ago, I took her out for one last drive before the winter snow set in. Drove around for about 1 hour and it ran absolutely perfect..just a blast to drive, real smooth and gets way better gas mileage than my 2003 Dodge Durango.

Before bringing her back to the garage, I thought I would give her one last really hard run..if anything is going to break, best if it happened then so I could fix over the winter. I also wanted to test the 6600rpm pill I put into the rev limiter. I learned the hard way that the 6200rpm MSD pill I had in the 6AL could only rev cleanly to 5800. I wanted 6200rpm out of it so stuck in the 6600.

Found a nice big empty parking lot and dumped the clutch at 2,500 rpm. Being traction limited, she immediately jumped to 6200-6400 rpm or so. In the past when I did this sometimes it would bounce off the rev limiter and run crappy for a minute or so afterwards, then clear up and run fine. I figured the cylinders where loading up because the spark cuts out floored at peak rpm from the rev limiter, and that it was normal.

I then did a second high RPM blast and she bounced off the rev limiter, and the engine started running crappy when it idled down, but this time it just wouldn’t clear up. It won’t idle below 2,000 rpm and there is a slight constant popping in the exhaust. Played with it for a few hours in the driveway, noticing that it would start right up and run for a few seconds, then try to stall like it was running out of gas, if below 2000rpm. At 2000rpm+ it seems to run just fine, but below that she tries to die. I also have an air/fuel guage in the passenger side header and noticed the indicator lights would go out when I was below 2000rpm like it wasn’t working, but came to life and read normally above 2000rpm.

The following are the things I looked at or tried thus far, but have been unsuccessful in solving the problem?

-Fuel?: I have 2 fuel pressure gauges..one at the carbs and one in the cockpit. Both are reading a healthy regulated 6 pounds, so plently of fuel pressure. I have heard that anything above 6 pounds, will push the needle off its seat in the Edelbrock carbs and could cause too much fuel at idle. Therefore I lowered the fuel pressure via the regulator to 3.5-4 pounds and it did seem to run better below 2000rpm, but the general problem described above remained.

By the way, the plugs where a pale tan as I had been pushing the motor hard the last 2 times out…slightly lean at full throttle. She is slightly rich at low to mid-rpm. Needs a little more fine tuning, but close. Air fuel guage shows 13.5-14:1 at idle and about 12.5:1 at full throttle. I need to richen it to no more than 12:1 at full throttle, I think.

-Stuck float?: I tapped both carbs with a wrench in case a float might be stuck in the twin Edelbrocks.

-Spark?: I have had cases where plugs would become carbon fouled and NG after loading up on a motorcycles, so I put in all new spark plugs, freshly gapped. I also put a different pill in the rev limiter. All in vain.

-Valve train problems holding a valve open?: I looked under both valve covers..I thought I might find a broken valve spring, even though no strange noises where coming from engine. Everything looked fine, springs where all in one piece and I wiggled all the push rods and everything seemed to have the right amount of tension.

-Vacuum leak?: I have only one vacuum line for the power brakes and that looked fine.

Hhmmmm.. I have run out of ideas, but still thinking about the carb and vacuum. Everything is brand new with only about 600-700 miles on engine.

Thanks for any help/ suggestions you can provide.

Well, it does sound like you might have hurt a valvetrain part.

What does the boost gauge read,
obviously a bouncing reading at idle would be an indicator.

I'm working on a 454 with a similar setup.
I've had few problems with the Edelbrocks, they work pretty well at 5.5 PSI.

Here is what it looks like (http://hometown.aol.com/dseefeldt3730294/images/paul%20009.jpg) in a 71 Corvette

[ 12-23-2004, 09:24 PM: Message edited by: ZZ430DropTop67RS ]

I would say its deffinetly in the valve train sounds like a bent push rod if the springs aren't broken.Guessing from your cam specs on your signiture your cam redline is 6 to 6500 rpm sounds like you were pretty close to valve float.Hope its something simple.

First thing I thought was a bad plug or valve train.

After reading the whole post I bet it is a carb problem. I have read and have been told many times that the Edelbrock carbs are not good for blown applications. I worked on a guys blown 29 Ford (Chevy powered of course) and we ended up swapping out the Edelbrocks for a set of Holley blower carbs, once I tuned it the performance, starting, idle, everything was night and day.

I doubt you "broke" a carb, you might want to check the base gasket. Kinf of sounds like vacuum leak. Did your pop off valve hang open slightly? Or did you blow that gasket out? You might want to take a look in the distributor cap as well to make sure all is well.

With the hyd roller cam you are pretty much out of RPM at 6300 hopefully you didn't tweak a valve.

Why are you bouncing it off the rev limiter?

ZZ430..all 3 of those cars are beauties. Are they all yours? I have trouble taking care of one of these old girls, never mind 3. What size edelbrocks are you using on your blown 454?

I believe my cam makes peak power about 6000-6200, so I am trying to rev just a hair above that. I didn't rev more than 6400rpm. I have the AFR rev kit, the correct springs and my valve lift is moderate, so I should be close. The rev kit should keep the lifters from hammering themselves on the cam. I turned the engine over so I could spin & wiggle each of the pushrods with the valve shut and each seemed perfect. I would be surprised that it ran lean enough for that second to do damage..it is only a hair lean at full throttle and a bit rich at part throttle. Engine is making no weird noises either. One think I am concerned about is that I have CompCam roller lifters purchased in 8/03, before they came out with the new design and I hear the old ones had a reliability problem.

Camaroman7D: Royce..I think you have to change your BB name now that you are Camaro-less. The carbs were working great. The reason for the choice of Edelbrocks was their excellent gas mileage and part throttle response which was important for a car that I wanted to be able to driver anywhere like my daily driver. Holley's would be my preference for pure all-out performance. Edelbrocks also have no power valve to blow out so I thought that would also be a plus for the blower motor. It also didn't do anything that would move the pop-off valve, but I will take a look to see if it moved. I did take off the distributor cap and it looked fine.

DragFab: With the BFG street tires, anytime I put my foot into this motor, before you can blink she goes immediately to the rev limiter...there is no gradual build up of rpm when the tires break loose..it is almost instant like punching it while driving on ice and a challenge to keep it off the limiter. The 4.43 effective drive ratio in first gear doesn't help, but she is like this all the way up to about 60mph as the shorter duration roller cam is making more low rpm torque than I can use.

I think my next check will be a leak down test of the cylinders.

Tokyo Torquer, they are 1407 carbs, with a Weiand 8-71. I'm normally a Holley guy.

Thanks for the kind words, the 'vette is a friends car, all I did was build the motor. It's not real nice to the rear tires either.

I recently built another 454/6-71/69 Camaro seen here (http://hometown.aol.com/zz430droptop67rs/images/img_0004.jpg) for a guy, with 2 Holley 750DP carbs with milled air horns. I couldn't tune those carbs to this altitude (6000 ft), I tried every trick in the book.

So we switched to a pair of old Holley 660 center squirters that cleaned up the bottom end real nice.

Any chance you blew out your power valvle in the carb?

Tokyo Torquer,
I can't change the name. I have owned so many Camaros it just fits (3-70's). I may own another one in the future, plus Skylarkman6d1 doesn't sound right.

I beginning to wonder if I blew a head gasket as I am running on the high side of boost. Need to do that compression test next.

ZZ430, In have the same carbs and they have been rejetted with the biggest main jet possible. Acually it was a jet specially made as edelbrock does not sell that big a jet for the 1407. I need to go a bit richer so I may have to go to different carbs on my 355. I wonder if the 1407's are big enough for a healthy blown 454.

GregO: Edelbrocks don't have a power valve.

Royce: "Skylarkman6d1" may not ring well, but "Blown6d1" might work. Anxious to see your track times with that blown 385 when you get it together.

mike

CamaroMan7d, the admin can use SQLYog to connect directly to the Mysql database that runs this forum and change your user id without changing the # of posts or current settings.

I did a compression test today.

First test with engine warm (but forgot to open the carb blades). Did the test a second time with carb blades open, engine a little cooler, but still warm. Not much difference anyway. My average cylinder compression is 136 PSI. This is a 7.6:1 static compression engine, thus the lower PSI values:

Cylinder PSI#1 PSI#2
1 130 132
3 135 140
5 131 130
7 142 132
2 132 152
4 137 140
6 148 130
8 132 135

Since the lowest value is within about 12% of the highest value in either run, it looks like I do not have a head gasket or valve train-related problem.

However, I did notice something when I removed the new spark plugs I had just put in while trying to figure out this problem. I had only run the engine in the driveway between 1000-2000 rpm, but the front 2 plugs on both cylinder banks where white.. indicating a lean condition. The back 2 on either side looked ok. This may have to do with why my air-fuel guage reads fine when I rev it to about 2000+, but the air-fuel guage lights go completely out at any rpm below that.

With this in mind, I would guess that the primaries on the front edelbrock carb are not flowing fuel. The exhaust popping I hear at only low rpm is the lean condition, I think. I have two 4-barrel 750 edelbrocks on the blower, so at less than 2000rpm, it seems that I have no flow from the primaries to the front 2 cylinders, but only the back 2 cylinders since on the primaries in the back carb are working. Above 2000rpm, the secondaries in the front carb kick in and that probably explains why the lean condition seems to go away at higher RPM.

Does this seem to make sense? I have a big FRAM fuel filter on her, so I wonder what would happen in the carb to prevent fuel from flowing from the primaries in one of the carbs?

I would do a leak down test first aswell just because it's easy but I agree with Royce I think you sucked a gasket in the carb's or the intake Fast Jack

Fast Jack,

I checked the carbs and both primaries are squirting fuel.

If it were an intake gasket, I wonder how it would make just the front 2 cylinders on **both** cylinder banks run lean.

cause they're right next to the water jackets,and antifreeze has an unhealthy effect on rtv sealants?
E

You have a good point about both cylinder banks kinda rules that out. Since it won't run well under 2000 it seems like a vaceum leak. As far as the primaries squirting fuel, thay don't move fuel at an idle. Check your idel jets on the front carb maybe they are cloged, and check the discharge nosels. We used to try to clean carbs out by chocking them out by putting a rag over the carb at half throtle or so. the lack of air would suck fuel through the other chanels and clean them out. I don't think you should do this I'm just saying that some dirt may have got sucked into the idel jets on your hard run

Cool car Brian (Drag Fabricator) everything is very clean, and a nice color choice. What size tires are you running in that photo I want to run the new Mickey Thompson ET street radials 275/60r15 buy I'm not sure they will fit