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New M600 Carb - Issues

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    Posted: May-22-2019 at 8:28pm
I finally got everything put back together on my '79 SN. I did gt40p's, roller rockers, performer intake manifold, brand new QF M600 Carb. On top of the intake manifold i have a gasket, then adapter plate, then gasket, then 1" block that was on the original setup (with the PCV port plugged), then a gasket, then carb (with PCV hose hooked up to carb port).

Got the boat fired up on the trailer for the first time this afternoon and seem to be having vacuum issues.

I was able to get the engine started pretty easily with a little throttle. Adjusted my float to the proper level, adjusted the idle screws to smoothest/best RPM at idle, and have the idle set screw on the throttle linkage backed all the way off. The boat idles pretty smooth at 750-800 rpms (not perfect, but not loping or stuttering either). If I stab the throttle there is no stumble, seems to rev right up. After warming it up I can start it at idle or maybe a touch of throttle.

So here's puzzle #1:
I have my vacuum gauge hooked up to the port on the carb and it is reading ZERO at idle. Maybe almost 1, but closer to zero. If I stab the throttle it runs up to the mid teens and holds steady there. But at idle it drops right back to zero. Seems a little odd that it idles smooth but shows no vacuum. Is this because there is no load on the engine - if I try to take it out on the lake will it die at idle in gear? Is my vacuum gauge not working (its brand new and was a higher quality unit on Amazon)?   I've read a lot about leaking on the adapter plates and wedges with the Performer intake, so I will likely pull the carb and remove the stock 1" block. Any other thoughts on this?

Puzzle #2:
When I shut the engine off, I immediately get a couple drips of fuel from the arm beneath the plunger for the Secondaries. This is on the back, drivers side of the carb and I understand it to be the spring/plunger for the secondaries, but I could be wrong. Fuel is running down the brass arm that sticks down below the plunger. I will say that when I first started the engine up, the float level was way high - not sure if this could have pushed fuel somewhere it doesn't belong, and now I am just seeing the residual? But I think it should have cleaned itself out by now (10-15 minutes of run time with plenty of on/off).

I am going to pass #2 on to Holley customer service, but would appreciate any thoughts here!

OT
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Orlando76 Quote  Post ReplyReply Direct Link To This Post Posted: May-22-2019 at 8:36pm
You might get better luck if you pass #2 on to QF.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-22-2019 at 10:56pm
Puzzle #1 sounds like you're hooked up to the wrong port.

You have a full manifold vacuum port and a 2 timed spark ports . Try the manifold vacuum port and your vacuum readings will probably be what you're expecting.

In the link are the illustrated instructions with a good explanation of the ports and their locations.

link

And Holley tech support will be just fine since Orlando 76 doesn't seem to know who owns Quick Fuel these days   

Pictures of the leak and also the vacuum port hookup would be good
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 12:08am
I should mention that the full manifold vacuum port senses vacuum below the throttle plates and the timed spark port senses vacuum above the throttle plates.

At idle with the plates almost completely closed the timed vacuum port is seeing very little vacuum and at idle the full manifold vacuum port sees around 14 to 17 inches or so of vacuum
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Off Trail Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 12:12am
Originally posted by KENO KENO wrote:

Puzzle #1 sounds like you're hooked up to the wrong port.

You have a full manifold vacuum port and a 2 timed spark ports . Try the manifold vacuum port and your vacuum readings will probably be what you're expecting.

In the link are the illustrated instructions with a good explanation of the ports and their locations.

link

And Holley tech support will be just fine since Orlando 76 doesn't seem to know who owns Quick Fuel these days   

Pictures of the leak and also the vacuum port hookup would be good


Man, thanks Keno. I knew I was doing something stupid - thanks for finding it so quickly! I was definitely hooked up to that timed spark port on the side. I looked high and low for the other 2 ports shown in that photo, but didn't find them. I just assumed that since the manual wasn't really for the 600 (it references 4 corner adjustment that is only available in the 650 and up), my 600 must only have the one port.   After seeing your post and taking a harder look, I found the port I should have been on.

I'll test that one and get a photo of the leak tomorrow.

Thank you thank you
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Off Trail Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 12:15am
Originally posted by KENO KENO wrote:

I should mention that the full manifold vacuum port senses vacuum below the throttle plates and the timed spark port senses vacuum above the throttle plates.

At idle with the plates almost completely closed the timed vacuum port is seeing very little vacuum and at idle the full manifold vacuum port sees around 14 to 17 inches or so of vacuum


Got it. That gives me a good target. I've seen a lot of different ways to figure out a target vacuum pressure and wasn't sure what I was going to find. I knew Zero was wrong though.

I'm wondering how much my elevation (8,200ft) will affect the vacuum pressure. My plan is to just tune the idle screws to max vacuum at idle - as long as it is somewhere in the teen's I should be good.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Off Trail Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 12:18am
And while we're solving all my problems - does the tilt of the engine affect the float adjustment?   I have been just using the forward bowl/sight glass for adjustment. The rear, being lower is completely 'full' ie the fuel is above the top of the sight glass. I'm targeting lower middle on the front sight glass and that seems to be working.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 12:35am
Originally posted by Off Trail Off Trail wrote:

Originally posted by KENO KENO wrote:

I should mention that the full manifold vacuum port senses vacuum below the throttle plates and the timed spark port senses vacuum above the throttle plates.

At idle with the plates almost completely closed the timed vacuum port is seeing very little vacuum and at idle the full manifold vacuum port sees around 14 to 17 inches or so of vacuum


Got it. That gives me a good target. I've seen a lot of different ways to figure out a target vacuum pressure and wasn't sure what I was going to find. I knew Zero was wrong though.

I'm wondering how much my elevation (8,200ft) will affect the vacuum pressure. My plan is to just tune the idle screws to max vacuum at idle - as long as it is somewhere in the teen's I should be good.


I knew you were high, just didn't think you were that high

You could be around 11 to 14 or so (kinda a guess here).

General rule of thumb is 1 inch worse per 1000 ft

You'll also want to do final adjustment of the idle mixture in the water idling in gear for the best off idle throttle response.

If the rear bowl is overflowing or seems high , I'd adjust that too
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Orlando76 Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 6:02am
Whoops....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 7:11am
As far as vacuum readings, put the gauge on your Malibu to get an idea what would be a good reading to be looking for.

You'd figure it should be pretty close to that reading
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 7:12am
Originally posted by Orlando76 Orlando76 wrote:

Whoops....


I think you knew and just forgot
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GottaSki Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 7:38am
Very good to hear you have it sorted and running!

Originally posted by Off Trail Off Trail wrote:

My plan is to just tune the idle screws to max vacuum at idle - as long as it is somewhere in the teen's I should be good.


Consider this idle mix procedure - set for max vacuum when in gear and in the water for best results, else it will be on the too-lean side and be a little dull off-idle, plus other issues will manifest.

After this it will be an off-idle beast with lots of snap, no hesitation.
This will also provide best conditions for no-throttle starting

This simulates the auto-trans carb setup procedure (in gear - wheels chocked) of yesteryears.

Will also minimize the delta-rpm   from in-gear to out-of-gear because your are setting for best idle torque, not just raw rpm



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Off Trail Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 8:47am
Originally posted by KENO KENO wrote:

As far as vacuum readings, put the gauge on your Malibu to get an idea what would be a good reading to be looking for.

You'd figure it should be pretty close to that reading


I'll check that out when the Malibu re-emerges from hibernation. I didn't know if fuel injection and different brand motor would be representative, but now that you say it it makes sense. It was snowing while I was messing with the Nautique yesterday, so not sure when I'll pull the Malibu out.....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Duane in Indy Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 8:50am

For "Optimum" performance the carb should be level as poss. With all your plates under the carb it seems as though you should get it a little more level with some work.

First pic shows my wedge plate. Pic #2 shows the carb level and the engine at normal angle.
You are going to really like the QF/Holley carb.
ps.   Follow KENO's directions. He will steer you straight!


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Off Trail Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 8:51am
Originally posted by GottaSki GottaSki wrote:

Very good to hear you have it sorted and running!

Originally posted by Off Trail Off Trail wrote:

My plan is to just tune the idle screws to max vacuum at idle - as long as it is somewhere in the teen's I should be good.


Consider this idle mix procedure - set for max vacuum when in gear and in the water for best results, else it will be on the too-lean side and be a little dull off-idle, plus other issues will manifest.

After this it will be an off-idle beast with lots of snap, no hesitation.
This will also provide best conditions for no-throttle starting

This simulates the auto-trans carb setup procedure (in gear - wheels chocked) of yesteryears.

Will also minimize the delta-rpm   from in-gear to out-of-gear because your are setting for best idle torque, not just raw rpm





Thanks Gottaski and Keno - I read about tuning at idle under load and planned to do this when it stops snowing and I get out on the water.    Ahh, heck, why wait.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Off Trail Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 9:04am
Originally posted by KENO KENO wrote:





If the rear bowl is overflowing or seems high , I'd adjust that too


What a novel idea, a separate adjustment for the rear bowl. How did I miss that??    I swear I looked, but it was partially hidden under the spark arrestor and I didn't give it another thought.

This is becoming the 'stupid questions about carbs by a newb' thread. Sorry.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Off Trail Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 9:06am
Originally posted by Duane in Indy Duane in Indy wrote:


For "Optimum" performance the carb should be level as poss. With all your plates under the carb it seems as though you should get it a little more level with some work.

First pic shows my wedge plate. Pic #2 shows the carb level and the engine at normal angle.
You are going to really like the QF/Holley carb.
ps.   Follow KENO's directions. He will steer you straight!



Looks like I need to buy me a wedge plate. I've already got the extra long carb studs I bought maxed out with all the other nonsense, so I may ditch the factory 1" spacer and replace it with the wedge.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote phatsat67 Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 9:33am
You will have no problem running that carb without a wedge plate. Edelbrock/Carter style carbs are much more sensitive to angle of the engine.

On a 4160 style carb you run the front bowl pretty low and the rear bowl a little higher than normal to compensate for the rearward angle. While a wedge may be the best possible setup for a carb to be level it's certainly not necessary.

Get the bowls adjusted exactly where you want them before messing around much with idle settings. The rear has no idle settings and differences in bowl level will cause slight idle changes.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 9:51am
Originally posted by Off Trail Off Trail wrote:

Originally posted by Duane in Indy Duane in Indy wrote:


For "Optimum" performance the carb should be level as poss. With all your plates under the carb it seems as though you should get it a little more level with some work.

First pic shows my wedge plate. Pic #2 shows the carb level and the engine at normal angle.
You are going to really like the QF/Holley carb.
ps.   Follow KENO's directions. He will steer you straight!



Looks like I need to buy me a wedge plate. I've already got the extra long carb studs I bought maxed out with all the other nonsense, so I may ditch the factory 1" spacer and replace it with the wedge.


Like Zach said, you don't really have to worry about the wedge plate. All those PCM 351's over the years ran fine without them

Duane's kinda like a mad scientist. Word on the street is that he built himself a gyroscopic carb levelizer (GCL for short) to automatically keep the carb level at all angles of pitch and yaw and whatever terms might apply. It's kinda complicated   

He was too cheap to buy some raw water pump parts, so he got a big ol' chunk of metal and made them himself
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Duane in Indy Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 10:10am
Originally posted by KENO KENO wrote:

Duane's kinda like a mad scientist.

He was too cheap to buy some raw water pump parts, so he got a big ol' chunk of metal and made them himself


Aw come on Ken, which pump???





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Post Options Post Options   Thanks (0) Thanks(0)   Quote phatsat67 Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 10:14am
Ken's pump service, if it's liquid we move it. How can we help you?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 10:52am
Did you change your jet sizes to match the altitude? I've had 2 QuickFuel carbs running at 4,400+ feet of elevation in the Salt Lake City area. Both carbs ran rich with the stock jet settings (sea-level is stock). I went 2 sizes smaller for jets in both the primary and secondary metering blocks. That solved the "too rich" condition.

Checking the float level is critical -- as mentioned above. the QF carbs should come from the factory with pre-set float levels, but my M-650 came from the factory with the secondary float out of adjustment -- waaaay too high of fuel level in the bowl. The only real problem I've had with QF is that the primary bowl needle/seat assembly had a small piece of brass / metal shaving that somehow became lodged and prevented the needle from closing. QF sent me a needle/seat assembly. Super easy fix. No problems since, only high performance.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Off Trail Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 10:18pm
Originally posted by Jonny Quest Jonny Quest wrote:

Did you change your jet sizes to match the altitude? I've had 2 QuickFuel carbs running at 4,400+ feet of elevation in the Salt Lake City area. Both carbs ran rich with the stock jet settings (sea-level is stock). I went 2 sizes smaller for jets in both the primary and secondary metering blocks. That solved the "too rich" condition.

Checking the float level is critical -- as mentioned above. the QF carbs should come from the factory with pre-set float levels, but my M-650 came from the factory with the secondary float out of adjustment -- waaaay too high of fuel level in the bowl. The only real problem I've had with QF is that the primary bowl needle/seat assembly had a small piece of brass / metal shaving that somehow became lodged and prevented the needle from closing. QF sent me a needle/seat assembly. Super easy fix. No problems since, only high performance.

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That is the one thing I was ahead of and got right (it seems). Bought a good array of jets and installed the recommended size for my altitude before I put the carb in the boat. I'll check the plugs after a couple good runs. Thanks for the reminder though.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Off Trail Quote  Post ReplyReply Direct Link To This Post Posted: May-23-2019 at 10:22pm
Thanks to all the rest!    I'll get my float levels dialed before I go to the lake and will worry about the wedge plate if I get bored this summer.

Mounted the Alloy Marine platform mounts, and put a drain plug in the rear this afternoon....since it was snowing again and I had a nice fire going in the barn.   Might put the replacement hour meter and depth/water temp gauge in tomorrow evening.

Will get back to motor tuning when spring hits. Maybe July this year?
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I believe at your altitude you can benefit from a little more timing in your engine.
This adjustment can be dangerous if you happen to take this engine to low altitude and fail to adjust back to low altitude settings. I am thinking 2 degrees but maybe some with more experience at altitude can chime in. You have less air/oxygen for the engine to compress so your tune will be very unique.
A supercharger or Turbo could really help at your altitude.
I took my 78 Nautique up to Lake Tahoe, 6,200 ft and it only had about 2/3 it's normal power and I was modified with performance heads and more compression than stock.. I can only imagine how much 8,200 ft will hurt your performance.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-24-2019 at 7:02am
Now you don't have to imagine.

Here's what he said last fall

Originally posted by Off Trail Off Trail wrote:



Thanks for the feedback.   Based on my experience with other boats at this elevation, I really think this thing is doing great and probably about as dialed as it could get (prop-wise) at stock horsepower (minus elevation penalty). As I mentioned, my '99 Malibu Response LX (325hp monsoon) with 600 well-maintained hours, and the perfect acme prop got that boat to 42 mph after a bunch of prop swapping, re-cupping etc. And that diamond hull was a fast hull - 49-50mph at sea level. I'm impressed the '79 will hit 40 mph.   I WILL pull the nut off and report back on what prop it has when I get the boat to my house.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GottaSki Quote  Post ReplyReply Direct Link To This Post Posted: May-24-2019 at 8:04am
Originally posted by MrMcD MrMcD wrote:

I believe at your altitude you can benefit from a little more timing in your engine.
This adjustment can be dangerous if you happen to take this engine to low altitude and fail to adjust back to low altitude settings. I am thinking 2 degrees but maybe some with more experience at altitude can chime in. You have less air/oxygen for the engine to compress so your tune will be very unique.
A supercharger or Turbo could really help at your altitude.
I took my 78 Nautique up to Lake Tahoe, 6,200 ft and it only had about 2/3 it's normal power and I was modified with performance heads and more compression than stock.. I can only imagine how much 8,200 ft will hurt your performance.


Good point. Very much the opposite scenario of pulling back advance when increasing compression

Altitude = Less dense charge, slower flame , later peak pressure - wold benefit from advance
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Originally posted by MrMcD MrMcD wrote:

I believe at your altitude you can benefit from a little more timing in your engine.
This adjustment can be dangerous if you happen to take this engine to low altitude and fail to adjust back to low altitude settings. I am thinking 2 degrees but maybe some with more experience at altitude can chime in. You have less air/oxygen for the engine to compress so your tune will be very unique.
A supercharger or Turbo could really help at your altitude.
I took my 78 Nautique up to Lake Tahoe, 6,200 ft and it only had about 2/3 it's normal power and I was modified with performance heads and more compression than stock.. I can only imagine how much 8,200 ft will hurt your performance.


I've thought about that..... But the boat may end up living at my parents place in Wisconsin...so I don't think I'll adjust timing until I make that decision. As far as I can tell timing is a whole new realm to figure out and I don't have the tools or knowledge to mess with it yet. If I keep it here in the mountains, it will be worth figuring out though.
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Originally posted by Off Trail Off Trail wrote:



As far as I can tell timing is a whole new realm to figure out and I don't have the tools or knowledge to mess with it yet. If I keep it here in the mountains, it will be worth figuring out though.


Does this mean that you left the distributor in place during the head and manifold job and that you don't know what the timing is set at right now?

If so, I think I'd get a timing light and at least check the timing to see what it is at idle and watch it advance with RPM's so you'll know initial and total advance for future reference

You have a Prestolite with a clip down cap and on those full advance isn't usually in till about 4000 rpm, so don't stop checking till you're at 4000. to see your full advance.

You can check the timing in neutral with no problem. The engine doesn't need to be running under load.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Off Trail Quote  Post ReplyReply Direct Link To This Post Posted: May-24-2019 at 8:11pm
Originally posted by KENO KENO wrote:

Originally posted by Off Trail Off Trail wrote:



As far as I can tell timing is a whole new realm to figure out and I don't have the tools or knowledge to mess with it yet. If I keep it here in the mountains, it will be worth figuring out though.


Does this mean that you left the distributor in place during the head and manifold job and that you don't know what the timing is set at right now?

If so, I think I'd get a timing light and at least check the timing to see what it is at idle and watch it advance with RPM's so you'll know initial and total advance for future reference

You have a Prestolite with a clip down cap and on those full advance isn't usually in till about 4000 rpm, so don't stop checking till you're at 4000. to see your full advance.

You can check the timing in neutral with no problem. The engine doesn't need to be running under load.



That is correct. I'll look into it. Wouldn't there be some outward signs of a timing issue (not running stronger than it did before the head swap, detonation etc.)?
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