FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: Stangman on October 16, 2022, 04:56:50 PM
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Well I’ve been playing with the front carb on Friday I took the 5.5 power valve and exchanged it with a 6.5 and it had 70 and 71 jets in front so I put the 71 were the 70 was and a 72 were the 71 was and now at a steady speed on parkway it feels better less like it’s holding back. I actually think I need either air bleed change or PVCR a little bigger. After all this I adjusted mixture screws and it wasn’t to bad. But that’s not why I’m writing.
I’ve got the motor back with NGK iridium plugs and I wanted to put Autolite in there because I’m chasing an intermittent runs rough and I’ve been thinking it’s carburation. So today I figured I would start from scratch and go over everything before I changed the plugs so I was letting it warm up and it started to run a rough. So I figured screw it let me pull plugs and of course the last one #8 is wet. So I put the new plug in start it up and it’s still missing I check for spark and it has spark although it did seem to miss once or twice out of 10 times. So I pulled the brand new plug and it was wet. So I got my compression gauge and I pulled 6,7,an8 of course my compression gauge wasn’t working I think the Schroeder valve was bad so I went to the shop and got another and they were all between 170 and 175. So took an old plug put it in #8 and swapped #4 and #8 wires to see if the miss would follow it didn’t so I put the wires back the way they were. The wife called it was dinner time so I figured sausage and peppers would stop me from being aggravated.
So when I finished I went out and started it up and it seemed like it was running ok so I took it for a ride around the block and brought it back pulled #8 plug and it was clean. It still has the original problem carb wise but not missing so I cleaned up and called it a night till I get more time to play with it.
Now being the way it was with the plug being wet then not I was thinking maybe I have a pickup starting to go bad. I did have a extended cranking no start even at the reunion so I guess it’s possible. I had put one in already like 3 years ago with the old motor and it can’t have more than 300 miles or so on it. So I guess I’m gonna try one. Of course it’s a MSD I think it’s really a ford pickup so maybe I can get one from the part store?? I have an 8594 ditributor.
Or is someone thinking something else I’m all ears.
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I think I'd likely look close at the plug wires to start, maybe you have some issues at the crimped end, however certainly could be a bad pickup but I just don't see a lot of pickups fail. Ohm every wire and wiggle it around and look close at the cap side
Of course you are starting to find something with that dead cylinder, but also what size carb? LIST number even better 71/72 is pretty small jet for anything other than a 750, and even then to run a 72 in the rear of a 750 it would need a secondary PV, otherwise they are usually in the 76 ballpark.
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Hey Ross so I have 2 quick fuel 750s from Barry. Blair went through them but I think it ran good on dyno but not in my car. Originally carbs came with 72/81 so that’s what I have in the front carb except he had a 5.5 PV and I put a 6.5 in which it came with. I haven’t taken the rear carb apart because my carbs are progressive so I was just trying to get it to drive around fine because when I stomp on it it runs great except for a little bog off the line which I really can’t duplicate on the street because it just spins the tires but at the reunion my 60 ft times were way off. I do know that the rear carb has the rear PV bolcked with the jets upped to make up for that. I guess it could be wires I was swapping them around maybe it was making connections and loosing it. I also thought about the cap and rotor so I changed them last week. I even bought one of those adjustable rotors which I haven’t used.
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What are the wires you are running Joe? If you are due for an upgrade that might help rule out the old set if problem disappears.
While the adjustable rotor might line up the spark under the cap better that probably is not responsible for one cylinder acting up. They would all be impacted if the spark jump was way off. Seeing as how you invested in that rotor I would try it at some point. It can be eye opening to see how much the spark has to stretch if it is in need of adjustment.
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Hey Ross so I have 2 quick fuel 750s from Barry. Blair went through them but I think it ran good on dyno but not in my car. Originally carbs came with 72/81 so that’s what I have in the front carb except he had a 5.5 PV and I put a 6.5 in which it came with. I haven’t taken the rear carb apart because my carbs are progressive so I was just trying to get it to drive around fine because when I stomp on it it runs great except for a little bog off the line which I really can’t duplicate on the street because it just spins the tires but at the reunion my 60 ft times were way off. I do know that the rear carb has the rear PV bolcked with the jets upped to make up for that. I guess it could be wires I was swapping them around maybe it was making connections and loosing it. I also thought about the cap and rotor so I changed them last week. I even bought one of those adjustable rotors which I haven’t used.
To me it seems like a miss that comes and goes, with no other indicators, and valves adjusted correctly, etc, two sets of plugs, almost has to be a wire. The cap end can be tricky sometimes and I have seen them break where you fold them over. Not often but can happen
As far as the carbs, the 6.5 would bring fuel in earlier, but I'd probably see if you can find something with the plug first, then tune later. As far as tuning the carbs, I generally like to start with basics, get them to a known good setup, usually as delivered, make sure accelerator pumps are working immediately and adjusted correctly, make sure both primary and secondary idle are correct and float levels are correct, and then start making one change at a time.
My gut says the dyno liked a little less fuel, and one jet size isn't going to fight you either way, my guess is intermittent spark on one or many. There is an old saying that most carb problems are ignition problems, can't say it IS the case, but seems like it here
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I have the exact same carbs that you do. Also have the dreaded intermittent miss especially when engine first starts. Running a Mallory Unilite with new wires, plugs and pickup. I have experimented with jet and PV sizes with no real difference. But the engine runs like a raped ape when fully warmed up (195* thermostat). If you figure it out I would be all ears. Good luck.
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I will probably get a new set of wires of course i will be checking at least #8. They are 9 years old but like alot of you guys that dont mean much.
Maybe 1500 miles and 100 passes. Ross thats what i meant about starting from scratch. Going through the floats and everything. I was really throwing it out there if sombody thought it was something weird like a pickup even though having one bad cylinder is not a common problem for a pickup. I did twice have a cranking no start but i will start with ohming wires and doing a wiggle test.
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Having the secondary carb with no power valve is kinda meh.
The linkage isn’t THAT progressive. Anyone with a little gear is cruising on both carbs.
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I missed that..the short 4160 style carbs won't have secondary PVs, but I wouldn't run the second carb without a primary PV unless maybe drag only, but still odd for me in that application unless somehow you were fighting it coming uncovered at launch or something.
That being said, I'd still want to chase the ignition first :) After that, I have found carbs really like being normal...
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Having the secondary carb with no power valve is kinda meh.
The linkage isn’t THAT progressive. Anyone with a little gear is cruising on both carbs.
I know that I have my truck set up just so it can get up to 35-40 mph on one carb. You can just feel the resistance in the throttle as it wants to start on the other carb. Being a stick shift surely makes it more possible then an automatic (especially if it has any stall in it).
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so thats sort of what it feels like when im driving on parkway its telling me hey give me more gas call it resistance or I need to change i believe the inside bleeds and make them smaller which would make that curcuit richer right drew. If I go from 1/4 throttle to1/2 throttle or more it takes off. I believe that i am on the progressive portion of throttle i can fell the extra resistance of the next carb.
I geuss a air fuel meter would tell the tale but i would like to avoid that. The car is a street car so i dont mind throwing a power valve in the back.
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Ya, thinking about it, it seems like the 2nd carb is just into the transition slot and leans out a touch, thus it noses over until you get past it.
I think mine is a bit like that at times. Not sure you can fix it for all driving conditions? This is where my buddy rides my case about Fitech! Ah, no, not in the budget.
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Changing hsab does waaaay more than just make it richer. Do not alter unless you want to go down the wormhole of chasing the tune. (It’s a lot of fun, but kinda beyond the scope here).
Typically a lean spot between idle and mains can be closed by either richening mixture screws, or raising float level.
Often a combo of both is the magic bullet.
The higher the float level, the less pressure differential required to lift fuel.
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thanks Drew i will try this weekend. I havent had a chance all week and my dads birthday is sunday so its gonna be tough.
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And it makes me wonder if a 1:1 linkage would be better overall? Even street driving. Would fuel economy really tank that bad or would it be negligible??
I have the 1:1 linkage off the wagon since I changed intakes. Wonder if I put it on my truck and see how it does. Not that mileage is a consideration on a truck with 428, 2x4s, 4 spd and 4.56 gears.
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Mr Larry,
With those gears it wouldn’t matter.
3:1 rear? You’d probably be on the primary booster before on the second carb at 55mph
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If I was to run 1to1 linkage I think I would have to go back to the power valve in the rear carb. I’ve always run progressive so I know I’m gonna get it but when your trying to tune and have a misfire that comes and goes it can be a little annoying.
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or raising float level.
Often a combo of both is the magic bullet.
The higher the float level, the less pressure differential required to lift fuel.
Sometimes I used to tune at EMC by moving the float level a flat or two.
Faster than juggling jets - unless you need a macro change.
Takes two guys to do a jet change really fast....
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I’m still hoping to get this done this weekend but not looking good. Barry good to hear from you.
So on the quick fuel 750s I usually go about 35 to 50 percent in the sight glass is there a stock spec. I know some of the pro form carbs like 25 percent up the glass.
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I’m still hoping to get this done this weekend but not looking good. Barry good to hear from you.
So on the quick fuel 750s I usually go about 35 to 50 percent in the sight glass is there a stock spec. I know some of the pro form carbs like 25 percent up the glass.
On dual quads I ignore the sight glass or plug.
Factory Holley carbs have the sight plug at different heights on primary and secondary bowls.
This was done to compensate for the angle mounting on most OEM intakes.
Since Ford dual quads are mounted backwards it screws everything up - they did not alter the locations.
I set the floats to be parallel to the top of the bowl.
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Ok that’s easy. Thanks
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So I had about an hour to kill today so I figured I would go out there and at least OHM some plug
Wires. The #8 wire had the most at 95 OHMS so I didn’t experience that problem today so I’m just gonna save for some wires and put a fresh set on for the upcoming season.
After I let it warm up for 15 minutes I went over the floats and bumped one primary 1 flat but other than that floats are good. Went and adjusted idle mixture screws and it wasn’t to bad. I took it for a ride and it feels ok not perfect.
I came back and figured I would readjust carb and something told me to check timing. Got out the light and timing was at 14 degrees. I know Blair said he had it at 18 so I figured why look at it but good thing I did. So I bumped the timing to 18 and had to lower the idle by 250 rpms. Went around and readjusted the carbs and it just sounds much better like less stressful.
Took it for a ride and throttle response is better and at cruise speed it’s doing less of that like holding back littlepopping noise.
I didn’t get to get on it way to much traffic but feels better. I am going to try and go for a ride on the parkway tonight.
Now things rolling threw my mind are did the distributor gear spin or somehow while Blair was trying things time got backed off. I guess I will know when I take it for a ride tonight. I guess making a spirited run on the parkway should spin that gear right.
And this could be why my 60 ft times were way off and the only reason why the car was faster is because after it got rolling it was Good. So many things which I guess will be sorted out eventually. I’m just glad I checked the timing. I did have Blair put a gear on for me because of the roller cam so it’s not like the pin is old. I don’t know we will see after the ride.
Then I was thinking 4 degrees of timing has got to be worth 20 horsepower.
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Well I’ve been out of commission the last few days got the covid crap. Not bad but still enough to keep me out of my car. Well I did finally go for a ride and it definetly has much more throttle response. It’s not the same as being on the track but it feels like it use to. I’m not gonna be able to get to the track but I think I’m on the right track.
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Is your timing locked out? Mine is on my Comet. While chasing my tail tuning my BP motor Blair said I should check my timing at 3000 and sure enough there was a 4 degree (retard) difference compared to checking it at idle (1000rpm). Not sure why or what is doing that but it is repeatable and consistent. I have checked with 3 different timing lights to verify this. Jim
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Timing is not locked I was under the assumption that it was 18 initial and 16 in the dizzy. I gave him the dizzy with the 18 degree bushing. I can’t remember if that’s the biggest one or in this case the biggest for the least amount of degrees. He was talking about my timing could be off because of the difference between my MSD box and his, it confused me a little because I just figure timing is timing. Regardless it’s good now as a matter of fact I’m gonna put my original squirted in also. We talked a lot about timing including putting as much initial as it could stand and lower what’s in distributor. But we were just throwing stuff around. Just found out from a buddy of mine that a few tracks are gonna be open till thanksgiving. I want to save for a converter but would like to get to the track and see what 4 degrees does.
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Joe, I don’t know if there were different boxes between the dyno cell and your car but 7 series boxes automatically pull 4 degrees of timing out.
At the track I aim for fuel levels 2/3 of the way up in the sight glass. That was a suggestion from someone who worked for Quick Fuel and knew my carbs were destined for an FE “ backwards” application. However, Barry’s tip has me thinking that the next time I’m in the carbs I will check the parallel float rule against the 2/3 sight glass rule and see if the floats are in a similar location.