I have a 4000 lb 1953 Cadillac with a 454 and turbo 375 transmission and a 3.42 rear. the engine is a 73 lo compression motor 2 bolt main oval port open chamber heads cast iron. the cam is a blue racer 480-490 lift. a edelbrock c-396 intake and 1407 edelbrock 750 manual choke carb and 1 inch edelbrock spacer. HEI ignition 14 degrees initial timing 34 total.full tube headers and 2 1/2 inch exhaust. My question is : Do I have enough carb or do I need to rejet?? She fires up immediatelly and idles and drives with no problem . there is no noticeable difference from half to full throttle. if I floor it from a dead stop she goes but doesnt hit really hard like I think it should and lite up the tires . I am running bias l-78.
Have you tried a 50cc accelerator pump ? It may get you going a little better , especially with a big tanker like that.
sounds like it leans out, how is the pump shot? after the initial launch does it pick up? if the pumps weak it'll have a hard transition from idle to main circuit. maybe wire the choke half shut and see how she runs. if its not the pump check out the charts edlebrock has online for metering rod and spring swaps. the rod is held by vac*** and pushed back by a spring when manifold vac*** drops to regulate fuel flow through the venturis. their pretty tunable if you check the charts and buy and rod and spring kit. good luck man!
I bought the carb used and have not had it apart . I have never tuned a carb before but I have a good baseline to start from. thanks for the suggestion I have a tuning kit coming in on tuesday
Are you sure the throttle is opening fully when you floor the pedal? That would be the first check. If it doesn't bog at the hit you've probably got enough accel pump shot. You may have to start playing around with metering rods and primary jet size. We had one on a student's Mustang here at the school that did kind of the same thing on the ch***is dyno. More fuel really woke it up in the low and midrange.
It doesnt bog and the throttle opens fully. it has a new gas pedal and throttle cable. Its just sluggish.
I am running holley electric fuel pump with a byp*** regulator. 5 pounds set pressure 1/2 supply line and 3/8 return.
What exhaust, try raising the fuel pressure to 7 psi for a test run.Are you sure the guage is correct,it is not fluid filled is it?
I will try raising the fuel pressure . It is not a liquid filled guage and dont know if its reading correct. spintech mufflers they are very quiet.
The exhaust is from the collecter 3 inch reduced to 2 1/2 custom bent to the mufflers in front of the rear end then up and over and straight out the bumper . BNR customs did a really nice job. I forgot to say that when the throttle is floored it is constant it doesnt pickup after time
Keep the fuel pressure under 6 psi for that carb. You can improve initial throttle response by moving the accelerator pump rod to the center hole. A 750 should be adequate out of the box for that low compression motor. I doubt it is leaning out at the top end. You can make a hard run, turn it off and pull over and pull a plug and check it.
If I read correctly, you have an Edelbrock (AFB type!) carburetor. So...you "can't change the fuel pump other than the two adjusting holes in the linkage. On the other hand, there are many adjustments that no one has mentioned. I'd pickup an Edelbrock "jet kit". It has jets, metering rods, piston springs. The springs that go under the pistons will have a LARGE effect on the way that carb. works. As others have noted, your problems sound like jetting problems. Along with the jet kit, it has very good instructions on how to tune your carburetor. I'd get one and go from there. Mike
thank you for everyones response . I have a edelbrock tuning kit coming in on tuesday . this gives me some great information to start. I will keep good notes and can always go back to my starting point.I will move the accelerater pump rod once momma gets home.
I just went out and looked at the carb .the link is at the hole closest to the carb which edelbrock is the most aggressive
Hi I would check all the above as mentioned. But, I have a feeling it could also be your timing. Are you sure the timing mark is correct? Have you put the engine top dead center to check? What is your engine vacuum? If you don't have enough vacuum on acceleration under load, then the vacuum advance might not be kicking in, and the car will feel like it is just going flat at around 3500 rpms to 5,000 rpms. I don't think the acclerator pump is the problem, unless it is stalling as you floor it. That is the only time the acc pump will affect it. The carb is big enough, actually too big if anything. You will probably pick up quarter mile times at the drag strip and fuel economy by going to a 600 cfm since you are not reving over 5,000 to 5,500. Cool car Good luck Wil www.sakowskimotors.com www.ridefree.com Motorcycle and Cl***ic Car Tours
Most likely it is not the carb that is the problem. Unless there is a problem. I really am thinking ignition timing under load is not enough for some reason, like stated above you have the timing wrong or markings are wrong, etc.. Or, you are running out of fuel, or spark plug gap way too huge for some reason? Also, how many volts going to the coil? Are you disconnecting the vacuum line for the distributor when you check initial advance? Is the line hooked to the metered not constant vac ******? ( hook to one where there is no vacuum at idle? Wil
I have stock timing cover and harmonic balancer. I have not verified tdc or the amount of vacuum. When the timing was set it reads 14 and with the vacuum hooked up it goes to 34 at 2500 rpm
is that part number a vacuume secondary? if so you may have to stiff of a spring in it not allowing the secondaries to open. they come like that from the factory. kragens out here has a few speed parts for holley so we picked up a secondarie spring kit and started playing. with a car that heavy you wont want them to open too fast but with the black spring our carb came with it does not open at all. hope this helps. shoclkey.
When the motor was first put in I had the vacuum advance hooked up to constant vacuum and was pulling 50 degree of timing I now have it hooked to the metered source on the carb.
Does your transmission kick down when you go wide open throttle? If so, sounds like your secondaries are opening too slow. Also, your ported vacuume souce usually shouldn't change your initial timing when hooked up unless your primary throttle plates are open too much.
yes it does kick down and i dont get the womp sound of the 4 barrel kicking in.The increase of the timing is when the vac advance is hooked back up
Once I get my tuning kit what should I change first?? secondary jets??the rest of the drivability of the car is perfect it just doesnt have a big hit after 1/2 throttle.what controls the speed of the secondaries kicking in?
I suspect you have several problems, when the manual choke is pushed in does the secondary throttle valve open completely up? Also the timing should be at least 36 degree with only initial and mechanical, add in another 15 or so with the vacuum hooked up! Lastly if the torque converter is set up too tight it will be sluggish, should stall above 1400 rpm. The carb is on the large side for a heavy car and under 5k rpm . With cams, carbs,& headers always error on the small side for anything but flat out racing!
The torque converter, transmission, and rear came out of a chevy truck that was running a 396. I dont have a clue what the converter is set at. I will check if the secondaries are opening with the choke open to see if there is any binding.
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