Need some help....

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Need some help....

Post  XF-66 on February 22nd 2017, 5:48 pm

Hey guys I need some help with my Weiand tunnel ram, 532 Ford. 10:1, SCJ heads, SFT cam Int 266/.658 Exh 272/.678 110 LSA, pump gas engine build.
On my build I cut corners with my Carburetors. I was low on funds (Doctor bills) and talked myself into two 750 cfm QF Slayer Carbs. At the time I wanted to use these carbs to limit or tame the horsepower in the Dragboat/Lake Hotrod the motor is going in. I figured that later on I swing for a couple of Dominators down the road when I won the lotto! Lol. Really in all honesty until my old ass caught up with the program!

I left the carburetors jetting stock with 76 Pri jets and 80's jets in a metering plate. I bumped the shooters to .037 from .033's along with adding 50cc pumps to help with the lack of secondary accelerator pumps. The shooters squirt about 3/4 of the throttle blades rotation. The carbs are vacuum secondaries. I changed out the power valves to 4.5 from 6.5. The Carbs have changeable air bleeds, on a tunnel ram or dual carb setup should the air bleeds be changed out for more air/less fuel as a rule of thumb?

The plugs in the motor are 3911 and are fouling out now, I took what the parts guy had to fire the motor, it hasn't been on the water yet! What would be the right heat range for a setup like this? I think the fueling a tad fat by the looks of the plugs. I run a Joe Hunt Mag (20 built in it and set 8 on the dampener) and I know the spark isn't as hot at idle when compared to the modern CD boxes of today. So the magneto isn't helping.  

I've setup and ran dual carbs years ago (40 or so) on an old FE Crossram intake and had great success. Back then there wasn't much adjustability. Today with the adjustability and the larger engines sizes I find myself a little lost and hunting for a starting place to shoot from. The motor as a whole seems to be operating correctly I'm the one who is the weak link in the setup.

Any advice would be welcomed. TIA

Art


Last edited by XF-66 on February 22nd 2017, 9:56 pm; edited 1 time in total

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Re: Need some help....

Post  Scott Foxwell on February 22nd 2017, 7:28 pm

Do the carbs have four corner idle? Part of the problem may be that the carbs aren't set up for a TR/dual carbs. Since the carbs are basically running on half the signal, sometimes you have to open the throttle blades further at idle in order to get enough air flow, and then they end up exposing the transfer slots and will idle fat. You might try cracking the secondary throttle blades open a little more and see if that helps, or just try a couple size bigger idle air bleed -or both.
The other thing that would help is to run teh dist. locked out. The more timing you can run at idle, the happier the engine will be. It will idle a LOT cleaner and have a LOT better throttle response. If you can't lock it out, put as much initial as possible in it. From the sounds of it you're only running 28 total and that doesn't sound like enough so maybe just bump the timing up some.
I also wouldn't just automatically run bigger squirters. Did you try the stock squirters? The bigger pumps will help extend the duration of the squirt and so will a smaller squirter.
I would take the boat out and see what the vacuum is at your most typical cruise rpm, then run one or two size smaller power valve but get the timing issue squared away first. I think you'll end up with more vacuum than you have now.

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Re: Need some help....

Post  Lem Evans on February 22nd 2017, 8:43 pm

Loose the tunnel ram and two carbs. Easier on the budget.

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Re: Need some help....

Post  XF-66 on February 22nd 2017, 10:43 pm

Scott Foxwell wrote:Do the carbs have four corner idle? Part of the problem may be that the carbs aren't set up for a TR/dual carbs. Since the carbs are basically running on half the signal, sometimes you have to open the throttle blades further at idle in order to get enough air flow, and then they end up exposing the transfer slots and will idle fat. You might try cracking the secondary throttle blades open a little more and see if that helps, or just try a couple size bigger idle air bleed -or both.
The other thing that would help is to run teh dist. locked out. The more timing you can run at idle, the happier the engine will be. It will idle a LOT cleaner and have a LOT better throttle response. If you can't lock it out, put as much initial as possible in it. From the sounds of it you're only running 28 total and that doesn't sound like enough so maybe just bump the timing up some.
I also wouldn't just automatically run bigger squirters. Did you try the stock squirters? The bigger pumps will help extend the duration of the squirt and so will a smaller squirter.
I would take the boat out and see what the vacuum is at your most typical cruise rpm, then run one or two size smaller power valve but get the timing issue squared away first. I think you'll end up with more vacuum than you have now.

No Scott, they are not 4 corner idle. So the secondary side of the engine should show leaner plugs than the primary side plugs in theory. I have never messed with or tweaked the secondary throttle blades. I'll give the idle air bleed jets a shot first then tweak with the secondary throttle blades a go if I see no changes.

On the timing because it's been awhile since I've done any real old school tuning, I followed the forum here and hung with the 28* that these SCJ heads like from the general consensus of those here on the board. Of course I'll give the engine what it needs or likes. I'll also give my Mag guy a ring and have him lock out the mag. I originally wanted to lock out the mag but was worried about the engine eating starters. I do have the starter wired for a push button so I can spin the motor and then unground the mag with a toggle switch to fire the engine.

On the squirters I misquoted the size of the stock squirters, they were .033's not .031's. No, I never used them. I'll drop them back in. Being smaller can only help lean things out. I knew that I'd needed a longer fuel shot being that these were vac secondary carbs, then I thought of the cubic inches and went with the .037 shooter.

Thanks for letting me bounce some of this off of your head. As you can read it seems I got a bit ahead of myself trying to anticipate the fuel requirements of my motor.


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Re: Need some help....

Post  XF-66 on February 22nd 2017, 10:52 pm

Lem Evans wrote:Loose the tunnel ram and two carbs. Easier on the budget.

I have a 501 short block sitting in a plastic bag for another project. If I can get past this 532, which I will, the 501 is getting a single 4.
The 532 will get it's Dominators by the end of the year. For now......

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Re: Need some help....

Post  Scott Foxwell on February 23rd 2017, 9:29 am

XF-66 wrote:
Lem Evans wrote:Loose the tunnel ram and two carbs. Easier on the budget.

I have a 501 short block sitting in a plastic bag for another project. If I can get past this 532, which I will, the 501 is getting a single 4.
The 532 will get it's Dominators by the end of the year. For now......
Just FYI, we've made 920hp on pump gas 540 with a pair of 750's and over 900 on a compression 496. (Both marine engines). Not sure how much power you're wanting to make but unless you're just wanting Dominators, the 750's might be a better ticket. I also think you'd be better off with a pair of DP's, but you have what you have.
Are these sideways mounted?

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Re: Need some help....

Post  DanH on February 23rd 2017, 1:23 pm

6.5 of from 4.5 .good reason for a richer idle

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Re: Need some help....

Post  Scott Foxwell on February 23rd 2017, 2:06 pm

DanH wrote:6.5 of from 4.5 .good reason for a richer idle
Power valve has nothing to do with idle. Two completely different circuits in the carb.

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Re: Need some help....

Post  DeepRoots on February 23rd 2017, 3:14 pm

What if the intake vacuum at idle was 6in tho? would that not open the power valve?

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Re: Need some help....

Post  XF-66 on February 23rd 2017, 3:49 pm

DanH wrote:6.5 of from 4.5 .good reason for a richer idle

Scott Foxwell wrote:
DanH wrote:6.5 of from 4.5 .good reason for a richer idle
Power valve has nothing to do with idle. Two completely different circuits in the carb.

DeepRoots wrote:What if the intake vacuum at idle was 6in tho?  would that not open the power valve?

All good point!
Rather than debate this, I'll pull the power valves and reinstall the stock 6.5's and see how it turns out. Simple to do. I'll also find some hose for my 40 year old vacuum gauge and see what the motor is doing. These are all things that I should have done to begin with.

Yes the carbs sit sideways, and I'm not stuck on the Dominators. I just thought they would work better when I added a little spray. No more than a 200Hp hit. Thought I read that given the same size CFM rating the Dominators were better at making horsepower than a 4150 style carb?

Anyway let me get things swapped out and some new plugs in it and go from there. I'm thinking I got ahead of myself on some of the changes I made to the carbs. I'll get back to you all in a day or so with my results.

Art

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Re: Need some help....

Post  Scott Foxwell on February 23rd 2017, 4:12 pm

DeepRoots wrote:What if the intake vacuum at idle was 6in tho?  would that not open the power valve?
It might but they work through the main circuit, not the idle circuit. Not enough air flowing through the carb at idle to pull fuel through the main circuit. If there was, it wouldn't matter if the PV was open or not. If a PV is blown, then it might leak fuel around the diaphragm and that's about the only way a PV will affect idle.

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Re: Need some help....

Post  DanH on February 23rd 2017, 6:12 pm

Blown valve open due to lower vacuum is the same.

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Re: Need some help....

Post  Scott Foxwell on February 23rd 2017, 7:41 pm

XF-66 wrote:
DanH wrote:6.5 of from 4.5 .good reason for a richer idle

Scott Foxwell wrote:
DanH wrote:6.5 of from 4.5 .good reason for a richer idle
Power valve has nothing to do with idle. Two completely different circuits in the carb.

DeepRoots wrote:What if the intake vacuum at idle was 6in tho?  would that not open the power valve?

All good point!
Rather than debate this, I'll pull the power valves and reinstall the stock 6.5's and see how it turns out. Simple to do. I'll also find some hose for my 40 year old vacuum gauge and see what the motor is doing. These are all things that I should have done to begin with.

Yes the carbs sit sideways, and I'm not stuck on the Dominators. I just thought they would work better when I added a little spray. No more than a 200Hp hit. Thought I read that given the same size CFM rating the Dominators were better at making horsepower than a 4150 style carb?

Anyway let me get things swapped out and some new plugs in it and go from there. I'm thinking I got ahead of myself on some of the changes I made to the carbs. I'll get back to you all in a day or so with my results.

Art
Art, just food for thought; with the carbs mounted sideways and no secondary idle circuit, you're going to really struggle with idle quality. One side of the motor will be completely different than the other. I don't even like progressive linkage on sideways mounted carbs because of part throttle conditions especially on a blower, but guys seem to get away with it.
As fr as Dom's with spray, the spray is after the carb and basically provides it's own atmosphere. Personally, I'd find a set of 750DP's with 4 corner idle and set them up (or have them set up) for a TR. If you want bigger carbs then look at some of the 1000hp's. That will be more carb than you''ll need and 4150's usually drive better and even run better than Dom's.

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Re: Need some help....

Post  Scott Foxwell on February 23rd 2017, 7:42 pm

DanH wrote:Blown valve open due to lower vacuum is the same.
No, it's not the same.

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Re: Need some help....

Post  DanH on February 23rd 2017, 7:50 pm

Blown valve open due to lower vacuum is the same.

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Re: Need some help....

Post  XF-66 on February 23rd 2017, 11:32 pm

Scott Foxwell wrote:
XF-66 wrote:
DanH wrote:6.5 of from 4.5 .good reason for a richer idle

Scott Foxwell wrote:
DanH wrote:6.5 of from 4.5 .good reason for a richer idle
Power valve has nothing to do with idle. Two completely different circuits in the carb.

DeepRoots wrote:What if the intake vacuum at idle was 6in tho?  would that not open the power valve?

All good point!
Rather than debate this, I'll pull the power valves and reinstall the stock 6.5's and see how it turns out. Simple to do. I'll also find some hose for my 40 year old vacuum gauge and see what the motor is doing. These are all things that I should have done to begin with.

Yes the carbs sit sideways, and I'm not stuck on the Dominators. I just thought they would work better when I added a little spray. No more than a 200Hp hit. Thought I read that given the same size CFM rating the Dominators were better at making horsepower than a 4150 style carb?

Anyway let me get things swapped out and some new plugs in it and go from there. I'm thinking I got ahead of myself on some of the changes I made to the carbs. I'll get back to you all in a day or so with my results.

Art
Art, just food for thought; with the carbs mounted sideways and no secondary idle circuit, you're going to really struggle with idle quality. One side of the motor will be completely different than the other. I don't even like progressive linkage on sideways mounted carbs because of part throttle conditions especially on a blower, but guys seem to get away with it.
As fr as Dom's with spray, the spray is after the carb and basically provides it's own atmosphere. Personally, I'd find a set of 750DP's with 4 corner idle and set them up (or have them set up) for a TR. If you want bigger carbs then look at some of the 1000hp's. That will be more carb than you''ll need and 4150's usually drive better and even run better than Dom's.

Pulled the plugs.
All were equally black and wet, surprisingly consistence between each other. So it's not the idle circuit, if so I'd see a difference in color and heat between the two banks. I dropped my Mag off to be locked out, should have it back soon. Tomorrow I'll change the shooters back to the stock 33's, hell they might even be too big I'm thinking now. There is some form of an idle circuit in the rear of the carburetor. I've been told this by a QF tech. I've seen what happens when you withhold fuel from rear float bowl and run the engine at idle. It makes a big difference in engine tone. It is non adjustable, sort of a passive circuit I guess.

I understand the No2 better now, I was thinking bigger the opening better the flow. You are right it does make it's own atmosphere.
I see the bigger picture now!! Thanks!

Cool I'll pass on the Dominators, that will save me some frogskins. I do have a couple brand new Holley 600 DP'ers in boxes here at the house.
They were slated for a FE Ford project that fell through. Maybe I can turn these carbs into 750's or 850's. All I'll need is main bodies and base plates. I'll have to check on the metering block differences.

I'd like to source a O2 sniffer, but I hear they don't play well with EMF and RFI from the Mag. Any thoughts or experience with this.

Again thanks for your input..



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Re: Need some help....

Post  Scott Foxwell on February 24th 2017, 9:50 am

I don't have any input or experience with 02's and a mag.

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Re: Need some help....

Post  DanH on February 24th 2017, 2:12 pm

Xf-66, lot of. Questions have"by been ask. BTW both Fox andI are right.there a reason why.- can be what you are doing

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Re: Need some help....

Post  Scott Foxwell on February 24th 2017, 2:42 pm

DanH wrote:Blown valve open due to lower vacuum is the same.
You can repeat this a hundred times, it's not the same or even close.

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Re: Need some help....

Post  Scott Foxwell on February 24th 2017, 2:43 pm

DanH wrote:Xf-66, lot of. Questions have"by been ask.          BTW both Fox andI are right.there a reason why.- can be what you are doing
Huh? English?

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Re: Need some help....

Post  rmcomprandy on February 24th 2017, 7:27 pm

DeepRoots wrote:What if the intake vacuum at idle was 6in tho?  would that not open the power valve?

Even if it does open ... so what.
The power valve channels open into the MAIN circuit NOT the idle circuit so, unless there is fuel coming out of the booster at idle, it will make absolutely NO difference.

A "blown" power valve will allow fuel to transfer to the manifold vacuum side of the power valve which is completely a different situation.

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Re: Need some help....

Post  DeepRoots on February 24th 2017, 8:47 pm

Thanks for clearing that up Scott... dunno what I was thinking, I knew it before I hit *send*

Randy, you really need a PR guy.

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Re: Need some help....

Post  supervel45 on February 25th 2017, 1:00 am

Scott Foxwell wrote:
XF-66 wrote:
DanH wrote:6.5 of from 4.5 .good reason for a richer idle

Scott Foxwell wrote:
DanH wrote:6.5 of from 4.5 .good reason for a richer idle
Power valve has nothing to do with idle. Two completely different circuits in the carb.

DeepRoots wrote:What if the intake vacuum at idle was 6in tho?  would that not open the power valve?

All good point!
Rather than debate this, I'll pull the power valves and reinstall the stock 6.5's and see how it turns out. Simple to do. I'll also find some hose for my 40 year old vacuum gauge and see what the motor is doing. These are all things that I should have done to begin with.

Yes the carbs sit sideways, and I'm not stuck on the Dominators. I just thought they would work better when I added a little spray. No more than a 200Hp hit. Thought I read that given the same size CFM rating the Dominators were better at making horsepower than a 4150 style carb?

Anyway let me get things swapped out and some new plugs in it and go from there. I'm thinking I got ahead of myself on some of the changes I made to the carbs. I'll get back to you all in a day or so with my results.

Art
Art, just food for thought; with the carbs mounted sideways and no secondary idle circuit, you're going to really struggle with idle quality. One side of the motor will be completely different than the other. I don't even like progressive linkage on sideways mounted carbs because of part throttle conditions especially on a blower, but guys seem to get away with it.
As fr as Dom's with spray, the spray is after the carb and basically provides it's own atmosphere. Personally, I'd find a set of 750DP's with 4 corner idle and set them up (or have them set up) for a TR. If you want bigger carbs then look at some of the 1000hp's. That will be more carb than you''ll need and 4150's usually drive better and even run better than Dom's.

I agree with Scot on a tunnel ram with side mounted Holley's and even inlines to a lesser extent. Double Pumper 4150's with 4 corner idle would make life a lot easier.

33 shooters and a yellow or brown pump cam will give you a full pump shot and should extend it nicely. Pump cams control the volume of the shot and the timing of it, shooter size does not affect fuel volume, a smaller shooter extend's the duration of the shot.

PS: I have gotten a few brand new power valves that were leaky, Not QFT's though. A small leak is not good at all. You might want to get it idling as best as you can timing and idle screw setting's, then pull the carb's and see where you are at on the primary transition slot, and go from there on adjusting the secondaries.

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Re: Need some help....

Post  supervel45 on February 25th 2017, 1:44 am

Scott Foxwell wrote:I don't have any input or experience with 02's and a mag.

I don't either but, since I believe it is just reading a voltage from a thermocoupling more or less, if a digital volt meter gives an accurate reading off a battery or something next to the running engine with a mag then it should be ok? I would use a very cheap meter for the test LoL.

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Re: Need some help....

Post  supervel45 on February 25th 2017, 2:10 am

XF-66 wrote:
Scott Foxwell wrote:
XF-66 wrote:
DanH wrote:6.5 of from 4.5 .good reason for a richer idle

Scott Foxwell wrote:
DanH wrote:6.5 of from 4.5 .good reason for a richer idle
Power valve has nothing to do with idle. Two completely different circuits in the carb.

DeepRoots wrote:What if the intake vacuum at idle was 6in tho?  would that not open the power valve?

All good point!
Rather than debate this, I'll pull the power valves and reinstall the stock 6.5's and see how it turns out. Simple to do. I'll also find some hose for my 40 year old vacuum gauge and see what the motor is doing. These are all things that I should have done to begin with.

Yes the carbs sit sideways, and I'm not stuck on the Dominators. I just thought they would work better when I added a little spray. No more than a 200Hp hit. Thought I read that given the same size CFM rating the Dominators were better at making horsepower than a 4150 style carb?

Anyway let me get things swapped out and some new plugs in it and go from there. I'm thinking I got ahead of myself on some of the changes I made to the carbs. I'll get back to you all in a day or so with my results.

Art
Art, just food for thought; with the carbs mounted sideways and no secondary idle circuit, you're going to really struggle with idle quality. One side of the motor will be completely different than the other. I don't even like progressive linkage on sideways mounted carbs because of part throttle conditions especially on a blower, but guys seem to get away with it.
As fr as Dom's with spray, the spray is after the carb and basically provides it's own atmosphere. Personally, I'd find a set of 750DP's with 4 corner idle and set them up (or have them set up) for a TR. If you want bigger carbs then look at some of the 1000hp's. That will be more carb than you''ll need and 4150's usually drive better and even run better than Dom's.

Pulled the plugs.
All were equally black and wet, surprisingly consistence between each other. So it's not the idle circuit, if so I'd see a difference in color and heat between the two banks. I dropped my Mag off to be locked out, should have it back soon. Tomorrow I'll change the shooters back to the stock 33's, hell they might even be too big I'm thinking now. There is some form of an idle circuit in the rear of the carburetor. I've been told this by a QF tech. I've seen what happens when you withhold fuel from rear float bowl and run the engine at idle. It makes a big difference in engine tone. It is non adjustable, sort of a passive circuit I guess.

I understand the No2 better now, I was thinking bigger the opening better the flow. You are right it does make it's own atmosphere.
I see the bigger picture now!! Thanks!

Cool I'll pass on the Dominators, that will save me some frogskins. I do have a couple brand new Holley 600 DP'ers in boxes here at the house.
They were slated for a FE Ford project that fell through. Maybe I can turn these carbs into 750's or 850's. All I'll need is main bodies and base plates. I'll have to check on the metering block differences.

I'd like to source a O2 sniffer, but I hear they don't play well with EMF and RFI from the Mag. Any thoughts or experience with this.

Again thanks for your input..


       
You would be better off cost wise selling the new 600's and buying the carbs. you want. Around 660cfm with a 750 base plate and a little more with an 850 base plate but probably not 750, plus they will not have down leg boosters like real 750's and 850's. You will have to chamfer the main body and they will still be two corner idle unless you do the 4 corner conversion. I really don't see it being cost effective, since they are new and I see them sell for 300 plus on Ebay regularly. Don't bother changing main bodies and using the 600 metering blocks and bowls, it's just a lose lose deal.

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