No secondaries! Help!

So...

In investigating my max RPM and the potential that I am over propped I found that I can only get my 2003 350 CI in 300 HP Crusaders up to about 3900-4000 RPM- Not good or to spec. (conformed by an independent digital tach)

Out of curiosity, I removed the flame arrestor while a buddy drove and found that the secondaries on the Holley 4 bbls are not opening at all. I manually opened them and it was like ... whooosh and we were off to the races.... RPMs not an issue!

I know nothing about Holley carbs. Where would you start to figure out why the secondaries don't open? I believe these are vacuum secondaries as there is a large diaphragm / dome thing to one side of the carb.


Thanks as always,

JD

on one side of the rod that goes through the carb thats atached to the four barrel butter flies theres a lock sometimes from it openin when its still cold..look down an see if theres a little arm thats holds it closed ..have a look..let me know or research ur model an see the pics of a breakdown of it,,i hope i can help...flungdunket

Start here:
http://www.holley.com/data/TechService/Technical/Carburetor Tech Info.pdf

You'll find lots of other 'tech data' in the same area of Holley's www site.

Could be the diaphram is violated or disconnected (some people will ensure economical operation that way) or the spring in their could be too strong. The vacuum port could also be clogged.

Don't forget, the secondaries won't open unless the engine is under a significant load.

Another item to consider - HP and other tech publishing houses have a slew of books on Holley carbs. I usually buy them of amazon, sometimes used for the older ones.

Gents,

Thanks. I won't see the boat until next weekend and will check the various things that you have suggested.

Makomark,

The motors were under a full load at 24 knots and throttles wide open!

understand - just want to make sure that anybody else that reads this - with a similar issue - doesn't think they have the same issue if they rev their engine at the dock and the secondaries don't move.

Mark, Got it!

I did a whole bunch of reading on the Holley site last night and this SEEMS pretty straight forward. The mechanisms are quite simple. If you have the right spring, an intact diaphragm, and vacuum to the correct side of the diaphragm it should work. I'll have to double check that the PO did not simply disconnect the vacuum actuator. The fuel burn on this boat has always been low. This was noted by the PO so I suspect the boat has been this way for a long time.

Now to find time before I have to winterize.....

Thanks,

JD

If your boat pops right out of the water on hte primaries alone (as mine does) then there's nop need of using the secondaries. Mine only open for WOT testing.

Jeff