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engine bogs down, dies
https://slantsix.org/forum/viewtopic.php?t=55242		 Page 2 of 2
Author:  DeeceDartSix [ Tue May 06, 2014 4:31 pm ]
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also - I bought an edelbrock 4 barrel manifold. the carbs seated well, with the gaskets all new and in place
Author:  oldskoolracer [ Wed May 07, 2014 1:48 pm ]
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Edelbrock manifold for a slant?

I cant say why it was fine at first but now theres an issue besides the plugs fouling out (or points if equipped)... I still feel 600 is a bit much, even for most stock small blocks... The slant is such a slow turning, low compression, long stroke beast they dont need much carburation to run good. It will take a little finesse and time to dial it in right. Need to find the right balance in the power valve, vacuum secondary spring, pump cam, as well as different jet sizes and squrtiers until everything works properly together.

A 225 c.i. engine with a max RPM of about 5500 rpm (very high side for a slant) will only need about 300cfm or less, add compression, better head design, larger cam, timing etc... Volumetric efficiency rises, as well as your usable RPM range, thus requireing a larger volume of fuel/air to be available...

Best bet on ignition is HEI conversion first if you havnt done so. Drives a hotter spark for a longer duration and eliminates the ballast resistor. Allows the use of a larger gap on the plugs and allows the use of a low resistance high output coil. Add on a set of good wires and your ignition will be ready to light anything you pour into the intake! :D
Author:  cpslntdchrg [ Wed May 07, 2014 3:54 pm ]
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If the ignition, and overcarburation are the problems, you might want to pull the plugs, and check how good it was burning... If they are fine, the problem might be somewere else
Author:  DeeceDartSix [ Thu May 08, 2014 3:13 pm ]
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the plugs have some carbon deposit on them. while it may be over-carbed, i still dont think that its the root of the problem. if i have spark and gas, then it has to be a vacuum leak, right?
Author:  oldskoolracer [ Thu May 08, 2014 3:40 pm ]
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Yea it could be a vacuum leak, should be the first thing checked when a running issue comes up after swapping an intake or carburetor. Is it actually a 4 barrel intake, or are you using an adapter plate? Check manifolds to head nuts, manifold to manifold bolts/nuts, carb base, EGR (if equipped), and make sure that the vac advance on the distributor is ruptured and bleeding off vacuum.

I still dont think you answered what ignition your running... Points, electronic, HEI?
Author:  wjajr [ Fri May 09, 2014 5:43 am ]
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We still don't know which 4160 you have; 8007 (390 cfm) list or otherwise.

Also is this a stock engine build?
Author:  oldskoolracer [ Fri May 09, 2014 9:36 am ]
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Quote:
We still don't know which 4160 you have; 8007 (390 cfm) list or otherwise.

Also is this a stock engine build?
He did mention earlier its a 600cfm vacuum secondary 4160....
Author:  wjajr [ Fri May 09, 2014 2:17 pm ]
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Sorry, I miss read post quoting 600 cfm as from someone else.

With a bigger than stock cam compression most often needs to be increased to compensate for increased over lap. 600 cfm is kind'ah on the big side for a close to stock engine, and way too big for a stock compression engine with a large cam.

Between the overlap, and the engine seeing too much of the sky when throttle is opened, the A/F mixture leans out because engine just can't move enough air.

A good idea would be to connect a vacuum gage reading manifold vacuum with a hose long enough to be able to reach and sit on top of dash for easy reading, and go for a ride taking notes listing rpm, vacuum, throttle position, and if engine is under load, steady level cruse, or down hill at different speeds. A friend is helpful for this data recording.

You may find that vacuum drops into single digits with only the slightest opening. At this point there is not enough air flowing through that large carb to pull fuel through the main jets and enrichment circuit (power valve), and a good percentage of fuel delivered via accelerator pump drops out of suspension and puddles on manifold floor during acceleration; hence lean stumble or bog condition.


Let us know what you find.
Author:  DeeceDartSix [ Fri May 09, 2014 7:46 pm ]
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my distributor has points with a vacuum advance. im going to do a wide variety of tests tomorrow, starting by measuring the vacuum on the carb.

wjajr, the test you suggested sounds like a great idea. ill surely try that out if i can get it running well enough.
Author:  oldskoolracer [ Sat May 10, 2014 8:08 am ]
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Quote:
my distributor has points with a vacuum advance. im going to do a wide variety of tests tomorrow, starting by measuring the vacuum on the carb.

wjajr, the test you suggested sounds like a great idea. ill surely try that out if i can get it running well enough.
...Start at your points and condensor.... Thats why I asked that question several times. Point are prone to failure without any warning, either from arching and burning out, condensor failing, or not being lubed right and the arm that rides the cam in the middle of the dizzy wears down. All will result in incorrect timing, incorrect dwell, and weak spark or no spark at all.

You should REALLY consider switching to electronic at the very least. HEI is best overall, but you can do a Pertronix swap (their quality has come WAAY down over the years), or swap over to the factory Mopar electronic ign. It will also allow you to run a larger plug gap and hotter coil (HEI) to really light the mixture, and gives you better control and accuracy over the ign timing all together 8)
Author:  wjajr [ Sat May 10, 2014 3:06 pm ]
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Oldskoolracer:
Quote:
Start at your points and condensor.... Thats why I asked that question several times. Point are prone to failure without any warning, either from arching and burning out, condensor failing, or not being lubed right and the arm that rides the cam in the middle of the dizzy wears down. All will result in incorrect timing, incorrect dwell, and weak spark or no spark at all.

DITO, run through all of the above making sure it is all working. Points can fail just sitting unused while car is in winter storage from corrosion. They are an unreliable short service life infernal device. In the old days before electronic ignition came along we replaced points & condenser yearly in fall, and or every 12000 miles, they are a PIA.

Quote:
You should REALLY consider switching to electronic at the very least.

Yes, yes, and yes, dump the points, install GM HEI or stock Chrysler EI, your automotive life will become simpler, and car will run better longer.
Author:  DeeceDartSix [ Sun May 11, 2014 3:28 pm ]
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noted. any advice on a specific distributor and coil that's worth the investment?
Author:  oldskoolracer [ Mon May 12, 2014 8:53 am ]
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Best bet on distributor is to read through a few threads and find out what dist #s will best suit your vehicle. Its still a shot in the dark on getting what you actually order especially with a rebuilt unit. Look for 1975+ model years slants. This distributors are almost all the same besides the vac can and govenor inside.

The coil will depend on how much you want to spend and wich electronic ignition you go with. The Moper ign will require a pretty standard coil designed to be used with a ballast resistor. HEI will open the door to many other options. On mine and a lot of others on the forum run the square Ford coil from late 80s early 90s cars and trucks. Another option would be the mid 90s gm external coil, its another low resistance high output coil. The modern square coils will require a custom made coil wire, or you might get lucky and find a local part store that sells single wires that you can just match to what you need. Im running Accel 8mm "cut to fit" wires with 90* boots on the dist end. They're time consuming but woth it IMO.
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