Team Camaro Tech banner

Holley 450 cfm economaster troubleshoot

67K views 69 replies 10 participants last post by  joelunchbox 
#1 ·
Just bought and rebuilt by me for a gas mileage experiment on the 327. Idles as smooth as a rock, pulls an unwavering 17" of vacuum, but there is a huge flat spot right in the middle of the primaries' travel that is spiking the A/F ratio up above 20:1, causing a big stumble. Once you open the secondaries(mechanical) it takes off pretty good but that primary side is killing me.

There are 2 primary jets and 2 larger secondary jets and one large jet that I am not sure what it does.

I have almost $60 into this carburetor so I really want to get it sorted. :D

Problem #1, huge flat spot midway through primary travel.
Question #1, are jets for this the same as other holleys? I have nothing to compare to.
Question #2, is that large, centrally located jet a power valve of some sort?

Three things I've thought to try but have not tried yet:
1) disconnect PCV as this could cause a large enough vac leak to have it go lean in the primaries.
2) Adjust pump shot. Not sure if this will help as the take off is fine until I hit the mid-travel of the primaries. Should the acc pump even be needed at mid-travel?
3) Swap secondary jets into primary side to see if just being richer kills the flat spot?

I know the Holley economaster is kind of 'fringe', especially for this forum, and I've read about all I can find on the internet about them(which isn't much) but if anybody with experience with this carb can make suggestions I am willing to try. Thanks.
 
See less See more
#4 ·
If a Q-jet worked on the manifold them your Economaster should as well. By mid throttle on the primaries you should have over come any rush of air the squiters would be needed to over come. To go lean like that suggests maybe you are running out of fuel on the primary side. Maybe remove the secondary linkage and see if the issue is actually with the primary side or if the secondary side is opening letting in air before it's fuel is flowing.

I've never worked on one but have never heard any good about this carb. Holley's attempt at a Q-Jet that never gained popularity. If you want a great small cfm Holley, I don't remember the list number but they make a 600cfm single inlet dual bowl spreadbore with vac sec's that is a great match on a 327. I know you don't want to eat the $$ you have in this carb though!
 
#5 ·
If a Q-jet worked on the manifold them your Economaster should as well. By mid throttle on the primaries you should have over come any rush of air the squiters would be needed to over come. To go lean like that suggests maybe you are running out of fuel on the primary side. Maybe remove the secondary linkage and see if the issue is actually with the primary side or if the secondary side is opening letting in air before it's fuel is flowing.

I've never worked on one but have never heard any good about this carb. Holley's attempt at a Q-Jet that never gained popularity. If you want a great small cfm Holley, I don't remember the list number but they make a 600cfm single inlet dual bowl spreadbore with vac sec's that is a great match on a 327. I know you don't want to eat the $$ you have in this carb though!
Dennis, I also think the squirter shouldn't be an issue at mid-throttle. I did change the pump rod position for max travel and it didn't seem to make any difference. I haven't heard much good about this carb either but did run one back in the 80s on a buddy's 350 RS LT and it was quite responsive. No doubt the car would have been faster with a larger carb, though.

Trying to disable the secondaries is a good idea for a test. I've looked at it closely and I'm 90% sure the problem is all about the primaries but it's worth at try. What's really stumping me is the larger jet with a spring-loaded valve in the middle that seems to have passages that lead to below both the primary and secondary jets. I am not 100% certain these passages are clean/free flowing. Under what conditions should this jet operate assuming it mimicks a Holley power valve? I think I'll take it apart again and look into that. Thanks.
 
#6 ·
I used one back in the 80s on the current spread bore performer manifold...
I got it out of the box, had to lean off the primaries a little, thu it ran fine..but liitle rich.
From there was reliable as...could never understand the bad rap this carb got..always put down to people tu tuing with stuff they did not understand..I then used the base plate later on the Impco 465 till wore out the butterfly bushes about 1yr back...unfortunately the body ..everything went to the metal recylers couple months back .
I think you and Dennis are on the right track thu

Get it sorted and it is a very nice carb for your application.
 
#9 ·
I have been looking for one of my old holley books....in it it has jet powevalve cam etc etc for holley carbs and engine applicantions carbs
Covers several pages , columns etc, fairly fine print and from memory its about 10 pages in....it covers this carb towards the back..just over 2/4 of the way thru... at a guess it would be published about mid to late 80s??? I have not had it out for over 15yrs and cant find it.
Does the description ring a bell in any of your holley books?
 
#10 ·
Part 34: bottom spring keeps the middle plug in the upper jet.
Part 23: has a spring on the bottom of the upper piston.

As vacuum decreases, as in opening throttle (load), pushes the plug out the jet to add fuel before the main power circuit comes into play.
Spring rate on Part 23 determines the opening point, lighter spring, open sooner, ie, 12 inches of vac, heavy spring, open later, ie, 6 inches of vac.
 
#11 ·
Part 34: bottom spring keeps the middle plug in the upper jet.
Part 23: has a spring on the bottom of the upper piston.

As vacuum decreases, as in opening throttle (load), pushes the plug out the jet to add fuel before the main power circuit comes into play.
Spring rate on Part 23 determines the opening point, lighter spring, open sooner, ie, 12 inches of vac, heavy spring, open later, ie, 6 inches of vac.
Thanks Everett, that is exactly the kind of logical explanation I was looking for. This thing is tiny, maybe the size of a standard holley jet, so could be tunable by changing the jet or drilling out. Do you know thread size of typical holley jets? The rebuild kit included all 3 new parts of #34.

Different springs for part #23 are not part of the rebuild kit and there is no trick kit for this carb so I'd have to get creative with the spring tensions but before that I think I will disassemble the whole thing and soak the body because I believe the jet and powervalve passages are somewhat calcified. I sprayed them but did not soak the body of the carb. I know NAPA sells carb cleaner by the gallon...what is the best to use for soaking it... the NAPA brand or some other?
 
#12 ·
Actually, I have it wrong after reading my statement over and over again.
'Lesser vacuum indicated requires a weaker/lighter spring than a higher vacuum indicated.'

As far as spring rate goes, place two springs end-to-end on a pencil, steel rod, etc.
Then squeeze them together. The most compressed spring is the lighter spring of the two.
 
#13 · (Edited)
Well, I proved that the jets in this carb are not the same thread as QJet jets and I am told they are not the same as Holley jets either so there's not much chance of rejetting without drilling out. I wonder if Edelbrock jets could work? But that's not really a concern at this point...

Pretty sure now that most of the trouble is coming from aluminum corrosion/calcification build up in the passages below the power valve/fuel bowl/jets. Tried an experiment using CLR on an old, really cruddy Qjet last night and it really cleaned out the calcified passages well after soaking overnight so I'll try that on the Economaster next. I still think I can make a happy little carb out of this 450.:)
 
#14 ·
Carb bodies ..well most al alloy parts are cleaned up in a citric acid based bath and washed.
In the case of carbs they then get a caduim plating to prevent they alloy corroding in the future...which I believe that notoruios bad batch of corrosion in holly bowels was about.
I learnt the hard way yrs ago rebuilding old zenith carbs for my vintage cars...seemed as perpetually had crap in the bottom of the bowl... These are little single barrel....ends up itsonly 20 bucks more to get these rebuilt (36 hr turn around) than the cost of the kits.
 
#15 ·
If this cleanup doesn't work, I'll just have to keep searching the swap meets for more of these for parts. I inquired with one place yesterday about purchasing a body but they said no parts are available for these aside from the rebuild kits. Will know better if I get the chance to disassemble it tonight after work.
 
#16 ·
Took the whole carb apart again tonight and washed it out with CLR. Didn't really see anything idicative of plugged passages but if nothing else I got to study it quite a bit and see which passages go where. I noticed the jets have 3 digit numbers on them. They are 215 on the primaries and 255 on the secondaries. Anybody familiar with 3 digit jets?

Will put it all back together and get it running on the weekend. Then try these three tests:
1) plug of PCV
2) disconnect secondaries
If neither of those helps, 3) leave secondaries disconnected and put secondary (larger) jets on the primary side to see what happens.

Better check the float level again too. Too low could cause leaning out I guess.
 
#33 ·
Took the whole carb apart again tonight and washed it out with CLR. Didn't really see anything idicative of plugged passages but if nothing else I got to study it quite a bit and see which passages go where. I noticed the jets have 3 digit numbers on them. They are 215 on the primaries and 255 on the secondaries. Anybody familiar with 3 digit jets?

Will put it all back together and get it running on the weekend. Then try these three tests:
1) plug of PCV
2) disconnect secondaries
If neither of those helps, 3) leave secondaries disconnected and put secondary (larger) jets on the primary side to see what happens.

Better check the float level again too. Too low could cause leaning out I guess.

Did some additional troubleshooting to work on the flat spot on the primaries again.
1) Disconnected secondary linkage. Surprisingly the car ran almost the same. :confused: I think the secondaries could still be tipping in at WOT even though the linkage is disconnected. I didn't wire them shut.
2) Blocked off PCV. No change other than lower idle; no surprise there.

I think I will raise the float level farther to see if that helps because that seems to be the one thing that has improved the flat (lean) spot in the primaries to this point.
 
#19 ·
Nah non in my box of holley bits...this goes back quite a few yrs, BUT
maybe weber carbs or some other mfgr that uses 3 digits.
That rings a bell.. I had a heap of SU stuff around back then.
 
#20 ·
Well, it's back together and running again. The two things I improved were 1) made sure the passages below the power valve were clean and the power valve itself had full travel below the jet. There was some sediment in the plunger recess. 2) raised the float level considerably. My suspicion is that the float level made the greatest improvement. I think Steps was right about that. :thumbsup:

So just went for a short drive around the block after warming it up in the driveway. It's dark, 30 degrees F and there's way too many cars on the streets for much horsing around but it is GREATLY improved. It still has a slight flat spot on the primaries but when I boot it from a roll in first gear IT BREAKS LOOSE ALL OVER THE PLACE!!!! I CAN'T BELIEVE IT !!:hurray::cool::hurray: Neither of my Qjets have ever been this responsive. I was giggling when I put it back in the garage.:D

I'll get a drive in tomorrow morning early. Hopefully an economy run if I can keep my foot out of it.

Here's some photos of what the guts of this thing look like. The primary/secondary jets are located lower than the power valve which is the large jet in the photos. So that may have been why the float level adjustment is so important. The thing coming out the front wall is the needle/seat and the hole below it is plugged but looks open in the photos because of the shadow.


This photo shows the plunger attached to the top of the carb that is vac activated to push down and open the power valve.


This is the acc pump. Shaft is plastic. You can still get this part from Holley or Jegs/summit but a new diaphragm (red part) is included in the rebuild kit. I had to email Holley and ask about that and they were helpful.


I think I am going to buy every one of these $5 Economasters I can find at swap meets and horde them. $55 for the rebuild kit. Not a bad deal for the $$ and time spent.:D
 
#21 ·
Just did 107 highway miles this morning. Car ran great for all of it. Speeds were 70-75 mph for most of it. 70 mph in my car is ~2,550 rpm because of the 2.73 rear gear. I tried to keep my foot out of the secondaries for most of it. At 70 mph the Innovate A/F LM-1 meter is telling me about 16.2:1. A little slower, ~65 mph, the A/F ratio is down in the high 15's.

And the gas mileage result?....(drumroll).....

18mpg on this trip. Hmm. My JET Performance Stage 1 Qjet still holds the record with 20mpg on the same highway run. However, the mechanical secondaries on this Holley 450 make it real fun to drive when you put your foot in it. Even on the highway the acceleration from 65 up to 95 mph or so in 4rth gear is fantastic and you can drop just about anybody with the twitch of a toe. The lean stumble at mid-travel on the primaries is barely noticable now, I believe due to the raised float level. I don't think I'll put too much more time into tuning it in the near future. Probably move onto my disc brake/sway bar swap next.

So, what have we learned?
1) Carbs are fun to mess with! :D (Although the wife doesn't much like them disassembled all over the dining room table.:noway:)
2) A well tuned Holley Economaster 450cfm is a darn good little carb for a mild, small displacement engine like mine. The thing fires on the first whirl and idles smooth as a rock. It does tend to run out of smoke about 5k rpms but that's not much of a problem for the kind of driving I typically do.
3) NO parts are available for Holley Economasters (model 4360) except for a rebuild kit and accelerator pump from Holley, Jegs or Summit. Rebuld kit is Holley p/n 37-1540. Acc pump p/n is 135-1. Search "Holley 37-1540" or "135-1"on their sites.
4) Mechanical secondaries are more responsive and hence more fun to drive than vac secondaries.
5) As much as I like Qjets, the ultimate carb for a mild-street 327 like mine may be a somewhat larger cfm mechanical secondary Holley, maybe somewhere between 500-600cfm but jetted down. I know you can get a 600cfm double pumper, just not sure about smaller. Maybe I'll try that when the a deal comes along. Meanwhile, the Economaster stays for now. :)
 
#22 ·
I think Steps was right about that.
I take no credit, u just jogged my memory form 20 odd yrs ago.

lat spot on the primaries
Check accel pump????
but when I boot it from a roll in first gear IT BREAKS LOOSE ALL OVER THE PLACE!!!! I CAN'T BELIEVE IT !!
And u are running 277 rear gears.....thats the difference of a small carb working in its rpm range down low...people normally have no idea just how sensitive carbs are to their rpm range.....how many ppl build their tweaked up engines with a 600 or 850, whatever....then drop a small carb on and see what happens on the street?
I know 2 Tom and I.

I tried to keep my foot out of the secondaries for most of it. At 70 mph the Innovate A/F LM-1 meter is telling me about 16.2:1. A little slower, ~65 mph, the A/F ratio is down in the high 15's.............18mpg on this trip. Hmm. My JET Performance Stage 1 Qjet still holds the record with 20mpg on the same highway run.
16.2 and drops to 15s at lower speed.....something is wrong...the higher speed u do the more resistance on the car , the more throttle to cruise the richer it gets.
Mine 60mph is 2100 rpms (calcuated, and speedo etc)
Once I hit around the 1700/1800 rpms I start to richen 1 full point.

Also 16 is the high end for petrol....but lets leave that there for now....
The mixtures between the 2 carbs different at the 70 cruise...if so the engine is loaded the same, leaner mixter therfore will require a little more advance at cruise at that rpms.
Rem the cent is not all in and u are reliing on the VA for that extra advance.

The lean stumble at mid-travel on the primaries is barely noticable now
,
I think u will find that could also be in the accel pump.
 
#23 ·
On the accel pump, I did increase the travel on the first driving test but really didn't notice any change in behaviour. Right now I probably have it set to deliver greater travel than the 7/16" called out in the rebuild kit docs. I could reduce the travel, but I think that might be going in the wrong direction. Since the flat spot is not noticeable when the choke is on, it would seem richer is the way to go.

The 16.2 A/F at 70 mph (~2550 rpms) may be directly related to that point in the primaries' travel where the (now minor) flat spot is exhibiting itself.

Test ideas:
- could still raise the float level a bit more
- could still do a test with the PCV disconnected. (PCV is a vac leak after all)
- could still disconnect secondaries to see if the lean spot is occurring just where the secondaries are beginning to crack open.
 
#24 ·
greater travel than the 7/16" called out in the rebuild kit docs. I could reduce the travel, but I think that might be going in the wrong direction. Since the flat spot is not noticeable when the choke is on, it would seem richer is the way to go.

The 16.2 A/F at 70 mph (~2550 rpms) may be directly related to that point in the primaries' travel where the (now minor) flat spot is exhibiting itself.
I think it is all related back to the primaries being over lean to begin with...get the AF back down to mid 15s.

this 16 is rather high..the enginew should be running slightly warmer than normal on the gauge.......even with stock cooling system...and relates to the lower mpg.

You do know that if u have the slightest misfire..may not even be able to tell.....then the O2 goes lean...about .5 to 1 afr.
just keep that in the back of your mind for now
 
#25 ·
I think it is all related back to the primaries being over lean to begin with...get the AF back down to mid 15s.

this 16 is rather high..the enginew should be running slightly warmer than normal on the gauge.......even with stock cooling system...and relates to the lower mpg.

You do know that if u have the slightest misfire..may not even be able to tell.....then the O2 goes lean...about .5 to 1 afr.
just keep that in the back of your mind for now
Steps, I've run with the Qjet up to 18:1 (not running well, mind you). At that time (not winter but don't remember exactly) I noticed a temp increase; no noticable T increase here going down the highway on a below freezing late-fall morning at 16:2.:noway:

Don't believe I have any misfires but good to know.

Sidenote, how did you attach the baseplate of the Holley to the Impco carb? That's some serious DIY engineering, Sir. :thumbsup:
Are they similar to begin with?
 
#26 ·
Holley to the Impco carb? That's some serious DIY engineering, Sir
1/ love it when ppl get my name right lol
2/ yeah real serious...just make sure on has the correct gaskets...best to make your own...and simply bolts up....and so does the Q jet base which /im currently running on the new impco lol
18:1 petrol will not ignite ...17:1 petrol will ignite but not burn well very slow getting into exhaust valve open while still burning terrortory...hence lot more fuel for same power (cruise rem) 16 to 17:1 getting marginal 15 to low 16 nice burn but slower..hence more advance...thats where the VA comes in. 15.5 to 16...good economy.
And rem u are cruising in the upper 2K rpms so the cent is not all in....thats where another 10 to 12 VA degs kicks in....make sure the VA is all in at the 75mph cruise engine vacuum.
 
#27 ·
1/ love it when ppl get my name right lol
2/ yeah real serious...just make sure on has the correct gaskets...best to make your own...and simply bolts up....and so does the Q jet base which /im currently running on the new impco lol
18:1 petrol will not ignite ...17:1 petrol will ignite but not burn well very slow getting into exhaust valve open while still burning terrortory...hence lot more fuel for same power (cruise rem) 16 to 17:1 getting marginal 15 to low 16 nice burn but slower..hence more advance...thats where the VA comes in. 15.5 to 16...good economy.
And rem u are cruising in the upper 2K rpms so the cent is not all in....thats where another 10 to 12 VA degs kicks in....make sure the VA is all in at the 75mph cruise engine vacuum.
Have to check one of my Edelbrock tech papers when I get home. Seem to recall that they said 20 something:1 was the lean limit.:confused:
 
#28 ·
20.9 is per atmoshere....so if u let the car sit over night, turn on and heat up the 02 sensor and it reads 20.9 u know it is still calibrated.
Even so do not confuse flamabity with exposivabily ratios.
And the ranges depend on pressure, temp and concentration
Then detonation comes into the equation...

u have a knock sensor bolted to the block somewhere.....?
With that u can get good lean cruise and advance with out fear of inaudable detonation
And MAPI sensor hooked into the manifold vaccuum...
Then have those and RPM all graphed up on the logworks....THEN u can definately see where u are going .
 
#30 ·
yeah see what u mean the 20 to 25 afr.....
Either the author doesnt know what thwe hell he is talking about... or they are talking about something complelet different
like I said the atmoshere is 20.9 to get any higher one needs to take the air and inject O2 into it...never mind about diluting it with burnt fuel gases
That graph is pretty right but not the cruise at 4000 + looks like a bloody desk jockt drew it up and never had a o2 in a car...when one gets up to those cruise speeds that throttle is getting down, engine vac has droped and the AF dropped way off

Sry m8...I see this sort of thing so often...even if a deskjockey with a string of PHds after his name...he just has not thought it thru.
 
#31 ·
O2 is 20.9% of air by volume.
AFR meters read by mass.
Several manufacturers (Japanese mainly) have built "lean burn" engines over the years that can operate at 22-25:1 AFR.
 
#32 ·
Yeah pont taken....
But from memory O2 is still about 22 or 23 % by mass.
And a wideband O2 sensor starting around 19 afr and espec around the 20 and above is inaccrurate and at the limits of its range anyway.
And get into lean ranges in our engines above 16 to 16.5 we have burnt valves melted pistons and detonation.
Which still leaves the orginal comment.

Note When one works with OH, lpg , cng one is working in far higher afr than petrol
petrol is 14.6 14.7 lpg is 15.7 and by nature is able to run far leaner mixtures than petrol....ie petrol burn valves etc 2 piots up from 14.7 lpg 2.5 to little over 3 before heat and detonation takes place...and NOx emissions start to be an issue.
 
#34 ·
yeah the float is a easy check worth a go.
But I still come back to that very lean cruise.
When one stomps on it, the pump supllies a shot to ricnen up very quick, but if for that instant the cruise is very lean, and the sec supply is still moving its way past the valves....
I had a hell mof an issue a few years back on the PLG...very different setup metering ...and doesnt have jets..doen with levers in the converter....but it boiled down to a very similar issue...too lean cruise
The same issue can arise in lpg systems with to long feed hose between converter and mixer...momentary delay before the good rich mixture hits...

I think with the lean cruises a 'patch fix' could be adjust the pump shot...but patch fixes always end up being a long term headache popping up further down the line.
 
#36 ·
Any jet wizards have comment on this?
I rem on old comment made by a holley expert yrs ago...I spent a lot of timelisting to those who know stuff...numbers on holly jets dont always relate to diameter but rather flow, and things like things champhers and position change how the fliuds flow thru them.

but it actually runs like it's fuel injected except for this lean flat spot
yeah..that because most of your rpm range is in the effective range of the carb....
Which then gives the engine a very fun response in that rpm range....
Thats why with my engine, cam , carb, manifolds valley cover, all down low is so bloody economical plus in that rpm range 1200 to 5000 its so responsive....damp road, forget pulling out into a smallish gap in trafics, and take off normal at a interection, cars are why behind, if damp rear wheels break away.

I have been thru all my old boxes looking for jets but non for that carb...yes I understood what u meant in the 1st post.
Just had a thought thu, will check out a local speed /workshop guy he may have old stock/ bits.
 
#37 ·
I rem on old comment made by a holley expert yrs ago...I spent a lot of timelisting to those who know stuff...numbers on holly jets dont always relate to diameter but rather flow, and things like things champhers and position change how the fliuds flow thru them.


I have been thru all my old boxes looking for jets but non for that carb...yes I understood what u meant in the 1st post.
Just had a thought thu, will check out a local speed /workshop guy he may have old stock/ bits.
Thanks, Steps. I looked into Holley jet info and found similar data. Thanks for trying with the local guy. Ive seen a guy mentioned here in Colorado who knows these carbs but cant find any email address, not sure he's still in business.


Sent from my iPhone using Autoguide
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top