![]() ![]() On the plus side,the wife has agreed to let me get the new carb.I hope to hold off till I get this recurve worked out.Otherwise I'll be chasing too many problems at once. Is there an easier way to get this curve right?Change the springs,set the initial,road test,next day do the whole thing again,and I haven't even started with the vacuum advance.Also the 406 seems to be sucking the carb dry at high rpms,so testing is frustrating to boot. So at lunch today I swapped the springs and of course without a timing light at work,drove home and put the timing light on it.Full advance now pulled only 25-28 total with the original 8 degrees initial.I advanced the initial to 15 degrees,but by then it was getting too late to be revving the engine in the garage.I assume total will come in at 32-35 degrees at around 3500. ![]() I've also been reading up on recurving and it seems the preferred curve is one with more initial,and less mechanical advance.The total ends up the same ,but I guess the low end torque is improved with more initial. Just finished setting the initial timing and total advance on my 67 289 just for fun to see any seat of the pants improvement.Using the timing light, examine the timing mark on the harmonic balancer. Step 5: Increase the vacuum to the reading obtained during the driving test. this is a far more common scenario than you would think, by far the best 'performance mod' for an engine is simply a correct tune.This is the timing light I. Start the engine and instruct your aide to crank it up to 2,000 rpm. This occurs roughly at around 15 to 17 degrees After TDC (ATDC). Connect the vacuum pump to the distributor vacuum advance using a gauge. Seems the springs were allowing some advance at idle,and with the advance,the idle speed came up.I could switch to a ported vacuum source I guess. More Steps To Set Timing On Sbc With Vacuum Advance. So it takes a little time and effort to get everything set, but in the end, it's well worth it.Still messing with the distributor curve,and decided to try the medium springs that came with the Summit kit.The softest springs allowed 8 initial,and 34 degrees in by 3500 with the stock weights.The problem was with the idle speed after the engine was hot. Springs can be replaced to change how quick the timing curve comes in. Ive read the forums up and down about initial timing and total timing, but this is one aspect of the. If total mechanical advance is to high or to low, then you have to change the restrictor plate or modify your current one. So Ive been battling with optimal timing and carb issues for a year on my 66 68 mild 400, Holley DP 750 electric choke vacuum secondaries, 16 heads, MSD pro billet dist with 6A box, headers). If that is the case, you have to rework the distributor to limit the advance. When you bump the initial timing up, the total timing can get out of hand. But that moved my total advance to 40 all in at 3800 rpm. 340 was running fine but wanted to know where I was at. The mark at 36 degrees (or so) is just to verify that the centrifugal advance is correct. I just put a timing light on my engine for the time since I re-purchased my old car from college. In order to find this number, you have to have timing tape on the balancer or a dial back timing light. You always use the TDC mark to set the initial timing. Now the back side to this is that now that you have the initial at it's peak performance, the total may or may not be totally off. By using the vacuum gauge to set initial, you are finding where in the timing scale, the engine draws the most air. Should be pretty well on the money, although. Then use the timng light to set the total mechcanical advance around 34-38, lock it down and test drive. Then install a timing tape on the pulley, disconnect the vacuum line and plug it. The higher that number, the more air being drawn into the engine. why not set your timing the right way Use a spark plug piston stop to find true TDC and mark it on the pulley. This Innova digital, dial-back timing light displays the total advance (32 degrees) and engine rpm (2,580). But can be tuned with different weights and springs to come in sooner, or later. Some folks call this 'all in' at a certain RPM. So by putting a vacuum gauge on your engine, you are basically seeing the rate of air into the engine. Total timing: this is the total mechanical advance your distributor provides (with vacuum advance unhooked). This range should give easy starting and no diesel on shutdown. So set total timing, adjust centrifugal and vacuum advance to get 6-10 degrees initial timing. The more air you take in, the more fuel you take in. Most old Ford vacuum advances can be adjusted with an Allen wrench in the vacuum port. Ideally, you set the total timing and the base takes care of its self. That's why better flowing heads and intakes produce more power. Base Timing or Initial timing: is what you set with a timing light on the damper Total timing Is the base timing PLUS all the mechanical advance. ![]()
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