That's someone's opinion at Holley. So if you can feel the added acceleration when the secondaries open, then it's out of adjustment ? Want to explain that ??
they explained it to me..."if you feel it, it's a bog down it's recovering from...should be a steady pull." the mech. 4bbl kicking in does the same thing...
You're exactly right, Frank. Any carb tuner will tell us the same thing as Holley to. The power curve should swell up very seamlessly.
"Feeling them open" has nothing to do with the basic physical airflow requirement of these SMALL.. and.. short stroked engines. Do the math and you'll see what the OP's engine actually requires. Hint.. it's well UNDER 500cfm. Why?.. because as the OP already knows.. his heads are putrid and the exhaust if absolutely horrid. Anything much more than about 10% over that physical demand just creates unnecessary fueling requirements to bury the bog created by the booster signal not matching the fueling requirements. AND.. without any gain in absolute power production. BSFC will rise and efficiency will quickly fall off. And a dyno will show exactly that. I'll say it again. The engine will feel crisper with tighter secondary opening rates because that signal will stay consistently high as the secondary's open up more gradually. And I wouldn't call several hundred rpm differences between 2 or 3 springs apart.. "insignificant". ESPECIALLY on this smaller and under-cammed motor. We have to remember that Holley rates these springs on mid-sized engines around 350 inches.. not 300.
Well update time. Initial timing is 18-20 and all in at 38-40. Can I stick with that? Pulled #1 plug to verify tdc and plug base is black and top of electrode is white... lean idle???? Swapped secondary spring to purple as suggested.
Another expert here The only 'bog down" I felt was with the 650 cfm Mech sec carb it replaced when the go pedal with the go pedal was mashed suddenly. With the 600, that bog down disappeared to be replaced with a surge in acceleration then a kick in the pants a few seconds after the go pedal was mashed. You believe what you want, it's just your opinion your spouting here. I KNOW what works.
Test drive update: Idle and timing all feel correct. Think I could move to a lighter mechanical advance springs to bring in the timing sooner. All in around 3000rpm. During my short test drive everthing fealt smooth. Didn't do any 1st gear low rpm hard pulls as I'm a little concerned about my driveshaft being too short at the moment and a stock replacement clutch lol. But all in all it fealt smooth all the way through the rpm. I didn't experience any breath taking gains but the car runs better at idle and accelerates smoothly. Still feels a bit flat on the top end ( probably my heads ). I have a guy locally who has a set of worked E7's off his mustand ( AFR's replaced them ) who will trade for my spare edelbrock 1406. Not sure if I should go ahead and get them since they are a trade deal. anyone know if my stock rocker arms and pushrods will work with the E7 heads or do I need longer pushrods? Thanks guys
And how much experience do you think that "tech" guy at Holley have ? Mine's not an opinion, it's a fact based on practical experience. I've been toying with them for 40 years, I think I've learned to tell what a "bog" situation is. And how to feel when the secondaries kick in.
from Holley setup instruction... VACUUM OPERATED SECONDARY THROTTLES: Many people have the misconception that opening the secondary throttles sooner will provide increased performance and quicker drag strip times. Others think they must “feel” a kick when the secondaries engage. Mechanical secondary carburetors all utilize a secondary pump shot to prevent bogging when the secondaries are opened. Secondly, those who “feel” a kick when the secondaries engage are actually feeling a flat spot during initial acceleration because the secondaries have already begun to open and have weakened the fuel delivery signal to the primary boosters. The engine is struggling to increase speed and what they actually feel are the secondary nozzles “crashing in” as the engine finally reaches he speed where it provides the proper fuel delivery signal to primary and secondary venturi. Third, opening the secondaries early causes the situation described above. The secondaries must not open until the engine requires the additional air. This allows torque to increase along the peak torque curve. Performance is compromised less by holding the secondaries closed a little longer than by opening them a little too soon. If the opening rate of the vacuum operated secondaries is properly calibrated there should not be a “kick”, only a smooth increase in power should be felt.
You're preaching to the choir here. I KNOW what a bog situation is. What I experienced was nothing of the sort. What I felt was a surge in acceleration then an extra surge when the secondaries kicked in. The engine was not struggling to begin with.
hmmm.. like Holley.. I always thought "power swells" should be somewhat linear in nature with a fat spot somewhere based on the cams sweetspot. Anyone else ever see a sudden surge on an engine or chassis dyno? At the end of the day.. this is a forum to help people out. Not toss ego's around to show who's top dog and better at "this or that" than everyone else. And FYI.. some people are fast learners and don't take 40 years to figure these things out.
Anytime you can trade an Edelbrock carb for something even remotely usable, do it! Sounds like you are getting a handle on it. SPark
