Topic: WHAT DID I WRONG ?
in Forum: C3 Engines
Lifetime MemberAbsolute bar or absolute psi both are at vacuum. Absolute bar is 1 bar at atmosphere, and absolute psi is 14.7 at atmosphere. One bar is 14.7 psi. Most gauges do not use absolute scales. Bar or PSI.
Barry, on a dual plane intake manifold (I also have a Weiand 8004, but that doesn't make a difference) The left side of the carb feeds the end cylinders on the left side (1 and 7), and the center cylinders on the right side (4 and 6). The right side of the carb does the opposite or remaining cylinders. This is for both primary and secondary sections. Cylinders not getting hot are 1 and 3, which are on opposite sides of the carb.
The coil is getting hot with the jumper wire due to the fact the coil is overheating at full battery/charging system voltage. That is higher than it is designed to operate. For a short period of time, that's okay, but long term it will fry the coil.
Red headers indicate that those cylinders are running too hot. This is usually a lean condition. You have enough fuel to the carb, but perhaps not to the intake and cylinders. I still wonder about a power valve in the carb failing.
Running compression at idle should be about 1.2 of cranking compression. At the throttle is opened, running compression raises to meet cranking compression at wide open throttle. This is a good test of the ability of the engine to breathe. Volumetric efficency. It will tell you if all the cylinders are moving air properly, if you care to do all 8 cylinders. If anyone wants to know more about running compression test, ask away.
Barry, try this. Put the stock coil back on and test the car. I have seen many cases where the stronger coil overpowers the ignition insulation and gaps in the distributor cap and rotor, and cause problems instead of cureing them. Spark goes everywhere except where it should. When you do this, inspect the cap and rotor for burning or arcing. That might do it.
Obviously your understanding of the Belgian language is lacking..... "pufpufpufpuf" translates to "the stupid motor is cutting out and stumbling over 3000 rpm".
Big Fish.. I guess I was all wet on the bar gauge reading. Barry has a high compression mill.
Ken... If you can't figger this out, Barry's car is broke. Sounds like you are on to something with the coil. Note that his coil is marked "12 volts" and was being fed by the resistor wire and he showed an improvement jumping from the alternator's 14 or so volts.
I'm anxious to find out what fixes it....
Dave
Thanx again Ken,Denny and Dave.
Yes my compression gauge starts at 0 (witch is in fact 1 bar atmosf.) We call it barg = bar gauge. Just the same as your tyre pressure meter.It is indeed a bit confusing as whe make pressure vessels and some clients give the design pressure in bara or barg so whe must pay attention .
Ken , crancking compression : do you meter that with all 7 other plugs removed or with those plugs in ? ( i think it gives a reasonble difference in rotation speed )
I have no stock coil. When i bought the car there was a "racing" coil from Accel.Now i bought a "standard" Accel replacement coil.
Can it be than that 1 and 3 are getting enough fuel and the others running lean ? Or is this test not representative , just let running at 2500 rpms with idle screw that high in ? Ofcoarse with no load ,engine picks up rev's easely with very litle throtle and resulting in a not equal distribution of gas trough the Weiand manifold. ?.
I'll check again the power valve and with vac meter in the car i will see if it drops below 6.5 in that 3000 rpm wall. 6.5 is from where the power valve should go working.( that's the number on the valve : 65. ) I understood that there are different numbers availeble so starting working from a different "low" vac.
i keep posted ! 
Cranking compression is done with all plugs removed. Just as you suspect, with 7 plugs in place the engine will crank slower, and give lower readings. In addition, if there is a problem between cylinders, the installed plug could mask the problem. Running compression must be one at a time, or it won't run. Just be sure to ground the disconnected spark plug wire so the arc does not cause problems or damage.
You can try putting propane or carb cleaner into the carb while it's running. This is fuel. If the engine speeds up or smooths out, you have one or more lean cylinders.
1 and 3 are on opposite planes of the intake, so it's not a problem common to the intake, unless an intake gasket is leaking, or a carb base gasket is leaking. You could also have a PCV allowing way too much air that could cause an inbalance in fuel deliverly.
I would be interested in a running compression test. Install the gauge one at a time, ground the plug wire, and start the engine. Of course it will run rough on only 7 cylinders. Relieve the pressure on the gauge while it's idling if you have a valve. If not, remove the schrader valve from the cylinder connection before doing the test.
Read the pressure at idle. It should be 50-60 psi or about 1/2 of cranking compression. The quickly open the throttle and rev the engine to about 2500 rpm. The reading should hit very close to cranking compression.
Try it on 1 and 3, then another one for compairson. Let me know what you get if you decide to try this. It actually measures the volume of air getting into the cylinder. It will confirm or deny a mechanical problem.
I would also still like to see a stock, or closer to stock coil, and see what happens.
nono, i also like a relaxing evening....
i'll do compression tests on each cylinder because now i want to eliminate eventually mechanical (BIG!!! ) problems.Want to be sure now for continuing ignition-carb trials.
As seen on Mick's description of her problems with hot engine starting now i understand how MORE difficult it is to estimate one's problems from reading over here than actually playing yourself with the engine ! there are so much details witch are not fully written by the author or"supposed" to be understand by the reader ! BIG
for the readers continuing interested !!!
i would give alot to have YOU as my teacher mechanics ! if only i was 30 years younger ..
( but i would 'nt accept " WHOOPPING " me !
) nono ,Ken with my vette now it would'nt be a problem ,but with the Viper....
see you professor ! !
had vac and dwell gauges up in the car driving.And yes , dwell stays very steady and once vac drops under 6 the pufpufpufs begin....
OK, that's the point where the power valve should go working... haha !
so i got that Holley back out to pieces and what do i see now : in the base plate there's a litle hole to pass the vacuum to the chamber where the famous power valve is located .A least that was what i have seen the last times.Looking now if nothing was restricting that bore ( dirt or something ) i find in there a tiny litle one-way valve ! I need my glasses to see that piece : it is pressed in the bore and has a bal and spring just like a common one-way valve.I did not check it if working but got it in pieces trying to push it out the bore.THAT could be the answer : if i had blown my power valve with a backfire AND stuck that valve , the new power valve now installed didn't got even vacuum !!!! that seems sens to me and so the problems remained the same ....That must be the famous protection for the delicate power valve , now got faulty on here own.
LET'S hope this is it !
Just not sure if i need a new valve or run without it ? that's why i didn't reinstall the carb for testing. Tomorrow ....
YIPIYEEHAA
tomorrow i will take some pic's of that power valve and one-way valve.