I got my hands on a second Valiant, this one is a 70, it was converted from a column shift to a 3 speed (A230) on the floor. I traded a dirt bike for it and I think I got a pretty good deal. Anyways the motor isn't stock in it, it's a 198 supposively bored .040 over, shaved head (supposively), bigger stainless valves (supposively), Erson HiFlow AM 286/276 cam (this I actually have paperwork on, offy 4bbl intake and Clifford headers. The reason I am unsure of the motor work is because the only paperwork aside from the cam is the balance sheet, so it could be internally stock who knows :shrug:

Problem is even after rebuilding the carb it will only run choked, or higher than 2000 rpm. Turning the mixture screws in or out has no effect, I have ruled out vaccume leak and the timing is impossible to set because the cam on the carb will only let it idle as low as 1500 rpm anyway.

It is a Holley Street Avenger 570 with 54 jets in the primaries. 70 in the secondaries. No adjustments seem to make it any better.

Should I just buy a new smaller carb? Or should this in theory run on this motor...? 570 CFM to me seems ludacris for any 200 ci motor but maybe it's me and not the carb?

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19 Years young with a passion for all things old.

"Four doors for more....screaming passangers..(;"

"There's no replacement for displacement, but my \6 is still cooler than your V8"

Yes that carburetor is too big unless engine can turn 9000 rpm...

Probably idle A/F mixture needs more air at idle to lean out when throttle plates are closed. Problem can be caused by too much transition slot exposed when throttle plates are closed, and or secondary throttle stop allowing secondary side to close down too much cutting off idle air, and or low idle vacuum caused by big lumpy camshaft.

Remove carburetor and adjust idle speed screw so that just about 0.025" of transition slot is showing when primary throttle plates are closed, check to see if secondary idle stop is set the same in relation to transition slot; remount carburetor.

Test sensitivity of idle screw adjustment; if still not responsive pull off a vacuum hose to cause a vacuum leak at manifold, re test idle screw adjustment to see if it has to be turned in leaner to get engine to idle.

Sometimes with big carburetor on small engine with big cam & lopey idle with low vacuum won't get enough vacuum signal to allow the idle circuit to function correctly and supply correct A/F mixture.

One method to test this rich condition theory is to pull off a vacuum hose as above, or even PCV hose allowing more air in below carburetor to lean out idle mixture. Once you determine that idle is rich, and some amount of additional air improves idle mixture screw sensitivity, then one has to implement a means to deliver this volume of air at idle, and not at above idle rpm.

One way is to crack open secondary throttle plates being carful not to expose too much of their transitional slots which may or may not solve the problem.

Or, another method to correct for rich idle mixture with big cam and low idle vacuum is to get more air into manifold by creating a controlled vacuum leak at idle. This is achieved by drilling progressively larger holes in throttle plates until idle mixture screws can be set at about two and a half turns out from bottomed out and be responsive.


Drill method is trial an error, and drill holes can be closed-up with solder if this method fails.


All that said; probably pulling head and measuring engine volumes and dimensions to caculate just what you have, and sizing and locating a smaller carburetor would be the best solution. As well as mapping out the engines timing curve.

When I got my Dart in 08 engine was described as having over sized valves, big cam, and high compression. It did have a 390 Holley with Clifford headers and intake there for all to see. LOL

Long story short, head had been replaced with a stock part, cam was unknown, engine was pig with no guts. Until I pulled head, measured what was there including degreeing cam I was in la-la land trying to get it to run right.

After installing oversized valves, upping compression, tuning carburetor, installing high stall converter, manifold heat, recurving distributor, did it finally ran strong; a journey that lasted about four long years and a thousand posts here...

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I don't really understand why a larger than optimal carb will not idle anyway? A BBD probably flows close to the flow of the primaries on a 5-600 CFM 4 barrel carb and we would all expect it to idle. Maybe I just don't understand sumptin.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Running choked is too lean?

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51 Plymouth Cambridge with / 6

Generally when it won't idle down and idle screws do nothing, I would suspect a pretty good vacuum leak somewhere. And when he chokes it, it richens up the mixture. But he said there is no vacuum leak.

Rick

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Knowing the actual vacuum levels would be good.

If it only runs choked, then it sounds like it has excess air already. I would take off the carb and first look to see that the secondaries are properly closed; this could easily be the location for the excess air entry. This would also make the idling impossible; if you mean that the 'cam on the carb' will not close down the throttles any further, then the open secondary butterflies would be casuing the high idle.

You may have to try different secondary closed positions but the transition slots above the secondary butterlfies ought to be pretty well closed off for this small an engine.

Have you chekced to see that the secondary pod is not anywhere near opening at idle? (It should still have some downward spring pressure on the rod at idle.)

Are there any holes in the primary or secondary throttle plates? Sometimes these get drilled to cure a rich idle (somtimes caused by the socondary plates being adjusted off in the first place).

Have you been trying to set this up with the vacuum advance hose from the distributor off and plugged? That will at least any vacuum advance kick in. You could easily be having some timing advance and carb interactions at these RPM's.

The primary-only airflow of this carb should not be too big for a 3L engine so it ought to set up right for idle.

Wow a lot of info to absorb all at once here but it is all greatly appreciated!

Thank you WJA, Rick, NM9 and 51Camb. Sorry for being so unspecific but here is some more Information I have concluded.

The Erson High Flow Am cam is the biggest cam Erson makes...on the PBM website it says that the optimal operation of this cam is 3800-6500 rpm...

I did get the car to "idle" yesterday, but I had to set the idle screw in quite a bit and now it "idles" at 2000 rpm, LOL. But it DOES run off choke! So some progress there. Upon speaking to the previous owner he is convinced that he tried a 390 Holley and it was "not enough" and that this engine will only idle as low as 1500 rpm...even if this motor has 1.7/1.5 intake and exhaust valves, blended and shaved head and 9.5-10.5ish compression isn't 1500 rpm high...? I'm 100% positive there are no vaccume leaks, but I do agree that I should get a gauge and test the vaccume and see where it is at. It does seem like the idle circuit isn't working since it will only idle as low as 2000

Also, I fully advanced and retarded the timing both ways and neither will make the thing die out (is that odd...?) it runs worse too far Eaither way which is to be expected but the set screw is pretty close to dead center. I put the timing light on it but even at 1500 rpm it's nowhere close to the factory marks...

I'm not really able to pull the head and measure the volumes, 1. Not that skilled (I could easily pull it off but wouldn't know how to measure it or what I was looking for) and 2 I don't have much money to throw at it) (guess I bought the wrong car ) basically I need help with things I can try with this carb to rule out it being too big and possibly get a smaller 4 or 2 barrel?

This is a great start from you guys though you don't know how much I appreciate it! I will try some of what's mentioned above and keep you posted!

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19 Years young with a passion for all things old.

"Four doors for more....screaming passangers..(;"

"There's no replacement for displacement, but my \6 is still cooler than your V8"

Your engine should idle between 750 and 900 rpm. While 570cfm is technically "too big", the reality is that it is a vacuum secondary carb, with the primaries about the same size as the BBD.

You have a vacuum leak somewhere. Follow the suggestions above and that could rule out the carb as the problem. Another possibility is a warped intake or the manifolds aren't sealing due to different flange thickness.

Even with the biggest cam erson makes..? Small block Chevys usually have to idle a bit higher the bigger the cam that's put in them. 750-900 is about what these engines idle stock but won't a race engine only idle well quite a bit higher? I'm not saying my engine is a race engine but just for theory's sake, I know 2000 rpm is not correct regardless but would even 1200 be acceptable? I really do not believe I have a vaccume leak, maybe low vaccume from such a big overkill cam, I don't know for a fact whT was done with this motor besides the cam because I did not build it and haven't had the head off, but it has one of the thick remflex type gaskets, and I have tested all around every gasket with the carb cleaner/water and smoke methods. No vaccume leaks around any of the manifold or base gaskets. I am pretty certain it is an issue with the carb or possibly the fact that it may not pull enough vaccume with this big of a cam. But the guys who posted earlier gave me quite a few ideas to try which I will. Again I appreciate the feed back always!

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19 Years young with a passion for all things old.

"Four doors for more....screaming passangers..(;"

"There's no replacement for displacement, but my \6 is still cooler than your V8"

Also there are no holes drilled in the. Butterflies like is done on some of the V8 BBDs I have seen, and the secondaries are shut very tightly. I will get a vaccume gauge and see what it reads. What do you do if the vaccume is too low because of a cam though? I have heard of this problem
With small block Chevys but never dealt with it personally.

And by cam on carb I mean the little plastic cam arm on the throttle side of the carb, the one on it corresponds with an engine that idles at 1200-1500 rpm (Orange I believe) there is still an adjustment screw but I beleive it only allows for so much Rpms each way before having to change the plastic cam arm.

Also, is it possible if this motor is as as radical as I was told that it just does not like this 30-40 degree New York weather? Without manifold heat ETC could 30 degree weather atleast be an excuse for 300-500 rpm worth of higher idle speed?

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19 Years young with a passion for all things old.

"Four doors for more....screaming passangers..(;"

"There's no replacement for displacement, but my \6 is still cooler than your V8"

Well, I did have an Opel 1.9L rally car engine that never would really idle; it took constant work on the throttle to idle (by an occasional pump on the throttle). It had the biggest cam that Isky made for that engine, and it had NO torque below about 3800-3900... but it would rev past 8k no problem. It had a 500 cfm Holley 2 bbl with the air jets modifed to get it to work 'somewhat' and at least have usable off-idle performance with the low displacement engine. With that big cam and huge carb for 1.9L, it would bog like crazy. Even with 45 mm Weber sidedrafts, it did not idle well and the lower end was down to 3700-rpm.

If the cam you have is advertised to start at 3800 rpm, then it sounds like it is perhaps just too much to idle low, even with a small carb. And a 3800-6800 rpm range is pretty narrow for most uses.

As for vacuum, I don't know that cam, but I would not be surprised to see it down in the low teens with that kind of advertised RPM cam range.

The highest vacuum secondary springs are up around 8.5 inches, so that is a concern. Have you checked the vacuum secondary spring color and looked up it's vacuum activation level? I would expect you would need one of the low vacuum springs in there with this cam.

As for heat, I would think that after being fully warmed up, the riser would not matter much. But I am not sure that you have reached that point...??

One other problem now recalled, early on I found with my carburetor that also would not allow engine to idle down was its base had been over tightened to intake and was deformed; cupped because bolt ears drooped below carb base. There was a massive vacuum leak on all four sides between intake flange, gasket, and carb base that no amount of carb-cleaner squirted would impede vacuum leak enough to change idle speed. I chased that condition for a long time with everyone here reiterating; "you have a vacuum leak". Check base with a known straight edge in 45 degree increments with a flash light it see any space between edge and a base. If you see light under straight edge, you have a whoop that needs to removed.

Fix for deformed carburetor base was to use a #12 mill bastard file, that would be a big 12" flat file, (it's stout enough and long enough so as not to deform when worked) and about an hour or so machining down the high areas working the file in two 90 degree configurations offset 45 degrees. In other words I would file north south-east west, than NE, SW - NW, SE, and back taking a little bit off until the file would take a full bite the full width of base in all directions.

Once base was flat in all directions, all the fillings removed from carburetor, then installed, the engine idle settled down, and idle mixture screws started to have some input. But there was more tuning to do before engine would idle right.

Currently my engine idles in "N" at 1100 to 1000 rpm, and around 800 rpm in gear with brake on. In gear 7-800 rpm idle is very finicky to idle mixture, an I have to set it by the tachometer and voltage readings from an o2 sensor installed to aid carb tuning. Also the lash is loosened to 0.024" to 0.028" based on compression tests to even out cylinder pressures. My cam has a lot of overlap, and like yours it is designed to run at the high end of the rpm band with no grunt below 3500 rpm, but pulls like hell past 4500 rpm.

Lots of over lap, and low idle rpm = low unstable idle vacuum. My engine draws 3 to 6 inches at 700 rpm on a good day, and jumps to 10 to 11 inches at 1100 rpm. At 3000 rpm it only pulls 16 inches, but at 4500 it is up to 18 inches. Carburetors don't adapt to low pulsing vacuum conditions and can't deliver a constant A/F mixture; it will probably be a trade-off between poor idle at stop lights, (I kick her into "N" when sitting), for better running at speed on the road.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I have had the car running for approximately 30 minutes at the longest, all the while messing with every adjustment I could one at a time seeing if it ran worse or better (obviously without much luck on the better side) the only issue is my only working gauges are Amperage, Oil pressure, and the Tac, (oil pressure is great at 60+ psi btw!)

I understand that this engine may in fact be quite radical for street use because of this cam, I'm really not sure what the previous owner was trying to prove by putting such a big cam in a 198, I'd much rather have something more mild that just runs good and healthy instead of being a pig that only runs wide open, especially since the rest of the car (chassis) is stock (for now ) . But I want to get it to run as well as I can, and even if it does not have the best street manners I'm sure if I can get it to run decent it will still be a fun car to toy around in.

I did not really think about the carb base being warped WJA, and thank you for pointing that out, I did spray all around the base with both carb cleaner and water in a spray bottle with no noticeable change but I sort of believe these methods to be some what of a farce on older carbed motors, especially ones like mine with an aftermarket cam.

I don't really have the time during the week to play around with it but this weekend I will be printing out your responses and trying as many as I possibly can. Hopefully I can borrow a vacume gauge from a friend or rent one from my local auto parts store and see what its reading.

Honestly I would be okay with it if this car did idle around 1200-1500, is that wrong of me? I mean I'm sure I could chase it around for months and spend money on a new carb trying to tune it correctly in order to get it down to 800-1000 but if I can get it to where I feel that it runs okay at idle and doesn't have major issues while driving would that be "half-assed"? I'm no expert and I really wouldn't mind a slightly higher idle as long as I can get it to run to the point where it isn't so hard to start and will feel and sound healthy at "idle" (even if that happens to be 1500 rpm) and all throughout the rev range (I don't intend to spin it past 5500 rpm)

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19 Years young with a passion for all things old.

"Four doors for more....screaming passangers..(;"

"There's no replacement for displacement, but my \6 is still cooler than your V8"

I'd put in a new cam that is better for torque and mid range before spending $$ on a new carb if need be. And you can check the cam timing while there; the cam being retarded could make it run badly down low.

In fact, since it sounds like you have the cam card (or have the model and thus can get the cam card from Erson), it would not be hard to check the cam timing with just the valve cover off to make sure it is set right.

Have you set the secondary idle screw?

CJ

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Part of Tyrde-Browne Racing