Ok guys been away for a while but here's the scoop. I have a buddy with a gennie Henry steel 32 roadster on an original frame - very nice traditional ride with a 3/8" x 3/8" stroker 8BA backed by a Toploader trans. The FH has an Edelbrock 3x2 intake, 3x97s, that I understand have been jetted down to either.039 or .040 sized jets and all accel pumps are working well, they are on a straight linkage which I dialled in correctly (was all over the place), Offy 375 heads earlier style heads and a 400 Jnr cam. The block have been relieved approx .100" from what I know. He was having problems with his Vertex mag, the car would barely run so we decided to freshen up the carbs, linkage, plugs/wires and I wired in a fresh converted MoPar single point dist. Initial timing is set at approx 6 deg BTDC and fuel pressure is around 2.5 psi with a gauge. The car starts on the first twist of the key and idles well, runs real cool with a little rumble from the 400 Jnr stick - idle mixtures are set at 1 3/4" turns out from seated on all carbs atm. I havent used a Unisyn cos I've never had much luck with them at all. Taking off from a standing start requires quite a bit of throttle otherwise she stumbles (like it needs more pump shot?) however Ive tried reducing/adding pump shot with no difference. After a while she began to miss at speed and run very rough down low as well. When she's free revved, the thottle response is VERY good, she simply CRACKS like a whip. Under load though, she stumbles, pops, and farts.....I don't get it. Plug colours are on the pretty rich side with an NGK B4L, a warmer plug. All cyls are the same. I've decided to check the following: Comp test to check CR (I'm guessing cyl psi will be high due to stroker and 375 heads?) Dial in air/fuel mix with a vac gauge Condensor (which one SHOULD I use, how do i know if its toast?) Cap, rotor Adjust timing (recommend setting?) Recheck float levels Any thoughts as to what could be causing this stumbling and missing problem under load? In my exp it usually means not enough pump shot off idle but thats doesnt explain the popping and farting at low /mid speeds? And its way better than what it was with the mag (magnets prob needs a replacement) but still has the above mentioned problems. Any input would be gratly appreciated thanks !! Rat
Jetting sounds kind of lean - what's the power valve size? Seems ignition related for the off-idle and stumble, but many ignition issues are really carb issues and vice verse... Try adding an additional condensor - I was able to get a car with the exact same issues running by adding a condensor - even though original condensor checked good. Eventually replaced original and went back to a single condensor, but... Let us know what you find with your proposed checks (looks like good places to start)
You said you have 2.5 pounds of Fuel Presure to the Carbs That sounds Low You Should have More Presure than That to Feed the Carb about 4 lbs. Just my 3.8 cents
You can adjust the Carbs with a Vacumn Guage since you dont like a Unisin also Total timming should be 38 degress I dont know what curve you have in the Dist Just another 3.8 cents
Strombergs don't like much pressure & 4lbs is bordering on the high side for them... Total timing on a flatty should be 24* - 4* initial, 20* in distributor, all in by 2000 RPM
39 jets are good enough for the 81 carbs, but shure too lean for the 97. You need to jet up at least to 44/45 size. And check fuel level, should be 15/32 from the top edge of the fuel bowl when running.
Sounds like some of the problems I recently had. Have you looked inside the carbs? I found that this shit fuel were paying top dollar for, leaves a slime in the bottom of the boils when it gass off. I found it was building up in the jets but not totally plugging them. You cant see it unless you dump the fuel out. Then it turns white as it drys. My setup 3 5/16 x 4 - 59A Two 97s with 45 jets Max one cam
I have found that a stumble under load seems to indicate a bad plug. why are you using warmer plugs in a big motor with high compression? Clean and gap plugs, run engine hard under acceleration and look at plug immediately. Might cut the gap back if you were running mag and went to coil. Stumble means not firing cylinders under load, poor high voltage, big gap, bad wire, bad plug or plugs. Rich mixture would indicate not problem with fuel availablity! But, have fun, and learn! traderjack
another $ .02 "popping" indicated timing. Do that first, then the carbs. Get out your tach and dwell, to go with your vacuum gauge.
Thanx for the input. Stromberg 97s dont like more than 2.5psi and the jets are not plugged. As TJ daid, the plugs indicate a rich condition so it should'nt be the jetting. Idle circuit can be fine tuned with a vac gauge to ensure its not too rich at idle and loading up the plugs, the fuel pump is electric with a reg and a gauge for accuracy - no guesswork here. TJ Im using those plugs coz they came out of his Flathead Merc and were fairly fresh. Ill change out the plugs first to a slightly colder set and gap to .030" as I learned a long time ago that when in doubt , stick in fresh plugs ALWAYS ! Then if no change, replace the condensor and go from there. Carbs are clean inside and out. Timing? As usual Ernie has it right. Anything else I could be missing? Thanx , Rat
Did you note which power valves the carbs had? Also can play with W & S settings on the accelerator pump to bring the PV in sooner/later. Doubtful that's your popping problem. Sounds like you have a good plan - let us know how your tests work out.
Im pretty sure the PVs are #60, but Ill confirm when I pull the tops to check the floats etc.... Stay tuned !! Rat
What resistance ballast resisitor should be used by the way? I think this one is .8 ohms atm. Anyone else? Bump? Rat
Rat, Ditto on everything you're going to check and fresh plugs. Stumbling under load but OK with no load seems to indicate weak or mistimed spark. Some things to consider: Are you getting a good full voltage at the coil? Does it stay regulated while running/stumbling? Coil / condenser breaking down with heat? Confirm vacuum/centrifugal advance is working correctly. (not much vacuum signal with 3x2 and bumpy cam) Stupid stuff: Confirming positive or neg. ground components. 6vdc and 12vdc stuff mixed. Good luck 37cpe
Would it be worth temporarily fitting a single carb manifold and a known good carb from another car (or leaving the triple manifold in place and blocking the end two carb bases off)? Then you could at least say the ignition side is good, (or giving problems). Then you could fit the three carbs, one at a time, and pass each of those as good. Then revert to the triple. I thought triples were best run progressive, so you only have one carb to get right until the others kick in. Sounds laborious, but there are a lot of unknowns here, and one thing could be fighting another. I'd also suggest (if you want to run them simultaneously) that trying to get the hang of the unisynch might pay dividends. Let us know how it goes. Mart.
Mart beat me to it! I was about to suggest blocking the end carbs off and trying it, eliminate some variables. The distributor....you said it's a Mopar converted, do you mean you put electronic guts in the Ford housing, or adapted the whole Dodge dist. to the flattie?
rat, I've had a similar problem after pulling my flatty out of storage. turned out I had a bad condensor and coil. took me a while before I changed them both out at the same time doh! also, 1 3/4 sounds quite rich on your idle screws. I've got 2 97's running 45 jets that i set the idle circuit at between 3/4-1 turn. any more than 1 turn and it runs PIG rich. 3x97's on straight linkage is a lot of carb to bring in all at once. I'm betting your vacuum drops down to almost nothing when you hit the gas under load. might be something you can never totally get rid of. maybe progressive linkage would help as well.
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