I could really use some help. I have a Edelbrock 1406 basically reset with springs rods and jets to a 1405. I am running a Ford E303 camshaft in a 90 5.0. car runs strong but no matter what I try I cannot get it to idle without being rich. I am assuming that the cam is causing a low vacuum situation. if so, how do I remedy this? Any help would be greatly appreciated. Thank you!
Few ideas... Carb Gasket could be leaking. Have you tried turning in the idle screws while its running? Does it start to stumble? Do Edelbrocks use power valves? FUel pressure? I think Ive been told 4.5 psi is the sweet spot for those guys.. And finally... Float height. I came around long after FI become mainstream but I still remember dad telling me something about some carbs need a 3/16th - 1/4 difference on the float height, cause the ethanol were getting now changes the density of fuel...
Excuse the Edelbrock question.. but what's the difference between a 1405 and 1406? Too lazy to google it right now.. does the main-body's venturi size change at all between those 2 parts numbers? That cam is one of the milder EFI type grinds and should be making decent idle vacuum due to lack of overlap and delayed I/E openings. 14-15" inches should be a piece of cake and I probably wouldn't stop tuning till I hit 17 or 18". Another question of the day around here lately. What's the initial timing set at and what vacuum source is the vac advance pot on the disty connected to? Ported?.. or full manifold? If you have much less than 20 degrees of initial advance at idle?(as you would when running ported vacuum to the disty).. it'll run pig rich until you start screwing around with optimizing emulsion tube size. And even then.. it'll just be a band-aid for the other main issue of retarded timing. So, if you are running heavily limited initial advance with no vac advance at idle?.. swap over to full manifold vacuum real quick and watch the engine vac jump up 4 - 5" beyond the current manifold readings. The rich condition will likely go away completely. Not sure of manifold, gear, trans/convertor, exhaust, etc.. but here's an ignition curve I'd be looking at running with that cam. 14* initial 24* centrifugal all in @2,800rpm 10* vac adv running off full manifold source This safer tune gives you 24* @ idle and slightly more at light throttle cruise. Then at higher loads/heavier throttle inputs and @WOT.. the 10* of vac advance supplementation cuts out when manifold vacuum falls away completely and gives you 38* of total advance. Don't stick with cookie cutter advice and use vac gauge to tune the timing and fuel requirement of that particular engine. Give it what it wants.. not necessarily what you think it wants.
1406 is a 600, 1405 is a 500cfm. Thanks for the distributer advice! Will try it and update the results. Thanks again!
lol.. now I'm even more confused than I was before. Doesn't take much sometimes. Why would you "jet down" your larger 1406 to a smaller 1405 spec carb? Any answers to my above questions? I'm most curious as to what your initial timing is set at.
The 1405 is a 600cfm carb, its the same as the 1406 but with manual choke. IIRC the 1405 is jetted slightly richer than the 1406 from the factory. How many turns are the idle mixture screws backed out?
You are correct Dave. I was mistaken. I actually reset it to the 1404 jets rods and springs. The 1404 and 1406 are the same other than those things. I felt the 500cfm made way more sense on the 5.0 than the 600cfm.
Ok.. after a quick spec' search.. now I'm finally getting it. All the 500's and 600's have the same 1-3/16 primary sizing and 1-9/16 secondary. You just detuned it for a smaller motors fuel curve, is all. I think adding some.. maybe much.. extra timing will sort you out in the right direction.
Thanks Groberts! I took your advice and went to manifold vacuum. Seems to have taken care of about 70 percent of the rich problem. I will try advancing the timing a little and see how it works out. Thanks again for your help!
Glad it seems to be working out for you. You should also be aware that just advancing the timing will cause the total advance to become too high when the engine rev's a bit. What you add to the initial setting has to be taken away from the mechanical sweep. Because of that.. you need to be extremely cautious with timing advance due to the fact that it also leans out other area's of the fuel curve too.. and may even lead to detonation that can be inaudible under heavy throttle and/or higher rpm's. Excessive timing for the fuel being used can be especially damaging on cast pistons, stock style head gaskets, valves if you have a louder exhaust that prevents you from hearing the pinging and the damage is usually cumulative right up until the popping sounds and rough running.
