Life after Holley Sniper - back to Carb

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jakuzzie said:
Totally. Fell for their lies. Nothing on this thing is self adjusting. If you want to do it right you need a dyno and an online course.

The in-tank fuel pump (walbro) was louder than the exhaust.
Pressure regulator failed after a week.
IAC Valve turned it self out a couple of times and left me with idle at 1500.

What a waste of time and money..
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A dyno is always a must for fuel injection
 
RustyRatRod said:
IMO, one of the best for out of the box performance is the Holley Street Demon. The 625 would be right on the money.
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On their website, they offer a factory reconditioned street damon, and when they're not available, you can be put on a list and I did that, and it took two weeks to get the call and I got mine for like two hundred and twenty dollars or something brand new or reconditioned...
 
AJ/FormS said:
As to the carb(s)
I can almost guarantee you that your throttles were too far closed, and the transfer-slots had gone to sleep. This almost always happens when guys try to run too much Idle-Timing.
The cure is embarrassingly simple; just increase the curb idle screw adjustment to open the transfers, set the idle-speed with less timing, then reset the mixture-screws as may be required..
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As to what cam to choose,
well they tell me I'm lousy at that game, so, keep this in mind while I rant.
Here are some things that will help you get started down this road.

1) Budget

2) Application; what do you expect out of this combo?
a) low-speed torque
b) hi-speed Power
c) midrange pull
d) fuel economy
e) long cam-life

3) the Chassis
a) the transmission
b) the stall
c) the rear gear ratio
d) overdrive
e) power to weight ratio

Because you already have a generous compression ratio, alloy heads, and an AG intake, you are way ahead of the game, and cam selection will make or break the smile factor.
Your cam selection will depend on how you answer the big three questions above.

If yur anything at all like me, you want everything! and that's gonna require;
1) a generous budget
2) an overdrive;
3) a race-type rear gear, cuz that will keep your small engine on the pipe
4) a modest but generous stall, to get you launched
5)
as for #1;
cuz there's no sense dreaming if yur broke; save up
As for #2,3,and 4;
the OD is not just for hiway economy, but more; so that you can run appropriate street gears for the modest sized engine.
For a small-engine-streeter, having the right gear at the right time is probably more important than anything. This allows you to choose alternates among the other parameters. For instance; if you can use 4-series gears, you won't need a big stall.
But this goes back to budget. If you need or want to hit the hiway for lotsa miles, but you cannot afford an overdrive, then you have to sacrifice something else, be it gears or stall or both.
I'll tell ya, installing an overdrive is the best move I ever made on my combo. I saved up 4 years to get it, and during that time, there was a lot of stinking parts swapping going on.

So then, say you have no budget for an overdrive, nor for a higher than current factory stall, and are stuck with say 3.23 gears. This is gonna require a hi-torque cam to get off the line, and when she gets into Second, she'll be done early.
But if you can at least afford a higher stall convertor, say going from 2000 to 2400, now you can up-cam maybe two sizes. This will push your powerpeak up a similar 400rpm, which causes a power increase at the top.
But, with 3.23s, now you find out the the powerpeak is at 75 mph, where you almost never drive or don't want to drive. So now you need say at least 3.91s, to bring the powerpeak into a more useable mph range. And thus your long-distance hiway cruising rpm becomes, lets say, "harsh".

So, as you can see, cam selection, with existing chassis limitations, becomes very important.
Now
lets talk about your already existing engine;
With a tight quench design this alloy-headed dream-318 can run 190 psi still on 87E10. As compared to 155psi with iron open chamber heads, the entire low-rpm torque is increased, which is like bolting on a turbo; and this amount of pressure makes a stunning streeter. And it doesn't stop there, that increased torque translates directly to top end power. If you keep the pressure up in that 190 plus range, you can run nearly any modest rear gears, and your engine will feel much bigger than it actually is.

The sad news is that in a given engine, cam selection, pressure, and operating elevation, go hand-in-hand; the later the Intake valve closes, the lower the pressure will be. and the same at higher elevation. So then, to keep the pressure up, with each bigger cam, the Static compression Ratio has to keep up.
Now, in post #1, you say the Scr is 10.5. to be sure, this is a very good number. To achieve that in a 3.94 bore, requires a TOTAL combustion chamber size of 69.6cc. That's pretty small. and that's gonna be hard to get down to with 63cc heads. So I'm assuming your builder actually knew what he was doing, and that 10.5 is real and True. If it is, then any cam with an Ica of 54* is gonna hit the 190 psi mark....... at sealevel.
In Austria, at 3000 ft, the pressure is predicted to drop to 173psi........ So you see where I am going right?
Now, a cam with an Ica of 54* is generally considered a pretty small street cam, like about a stock 360 2bbl cam. Your Lunati at 262/268/114 cam, 220/226@050, in at 110 has an Ica of 61*, which, at 3000 ft is predicted to make just 163 psi. The Scr would have to be pumped up to 11.8, to get to 190 psi.
Here's the part where I tell you to go do a compression test, to see where you currently stand; as others have already suggested. Here's the deal, at 163 psi you could have just run iron heads at 10.5Scr and made more power on them with the same cam. How is that possible? Because the alloy heads suck so much heat out of the chambers that at your power level, you need about an extra point of compression, just to break even.
So, Like I think I said in a previous post, I would throw that heat-sucking, pressure bleeding, power not making 114LSA cam away........ lol.
Of course you see what I did there right?
I assumed that you have a true 10.5 engine and
I assumed the cam was in at 4* advanced, and
I assumed that Jakuzzie lives in Austria, and
that Wiki is correct when it says the average elevation in Austria is about 3000 ft.
if you're at Neusieidler Lake, elevation 377ft, that's gonna be a different calculation.

Ok now lets talk a lil bit about cams. I have a rudimentary understanding of cams, and experience with only a few of them , so here's what I have found;
1) for gas mileage
you need about 108 or more degrees of Power Extraction, the more the better. Going down to 100 degrees the cam will suck dry every gas pump in your neighborhood. By 112*, it is steeling degrees from somewhere else. Is that bad? Not every time.
2) as for compression, you need about 120*s. This will vary with the desired cylinder pressure
3) as for over the nose power, you need a bunch of overlap, 60* is good, 66 is better 72 or more is getting to the limit of streetability. A reasonable compromise would be 62*.
4) ok lets add up what we got so far. This is an exercise.
120+108+say 62=290. We only have two full revolutions plus the overlap in the which we can make this work, so, in this case; 720+62=782 degrees. Subtracting the 290 leaves 492 for intake plus exhaust. Now adding back the overlap of 62= 554 total, and dividing by 2=277 degrees to be allocated to each of intake and exhaust durations.
However, for flexibility in setting the installed center line, and maintaining a decent overlap, I'm gonna give 4* from the intake, to the exhaust, making it 273 intake/281 to the exhaust. Next I'm gonna take these numbers and calculate the Lsa, like this
(intake plus exhaust) less overlap, divided by two, and I get 107.5.
Next, I'm gonna gather up all those numbers and get;
273 intake/120 comp/108 Power/281 exhaust/on a 107.5/ in at 103.5
Next I'm gonna see what might be commonly available. And I see;
272/280/108 which, installed at 104, at 3000 ft is predicted to make just 163 psi
272 intake/120 comp/108 Power/280 exhaust/on a 108/ installed at 104.
Compare that to your Lunati cam
262 intake/119 comp/108 power/268 exhaust/on a 114/installed at 110
Easy peasy. Is this (the one in Blue) the cam you should get?
Answer ; NO!,
the Ica is too late! with only 120 degrees of compression, the cylinder pressure is predicted to be just 164@[email protected] Scr. This would be fine for an iron-headed 318, great actually, but with alloy heads, it will be down on power/torque, as compared to what it could be, cuz the alloys with a tight Q can easily support 190 psi, which I previously mentioned, would take an Ica of 54 degrees@3000ft.
So I gotta stop talking here, cuz all this talk is based on assumptions of elevation and true Scrs, and the total lack of hard data, lol. At this point, it is all just parlor talk, designed to get you thinking.
Happy HotRodding
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Thanks a lot! I will print this and think of everything you mentioned. I appreciate this.
 
Died in winter, ok in summer? Might just be a simple choke adjustment. They do have W & S settings.
 
jakuzzie said:
After a couple of years with the Holley Sniper EFI and it’s problems I now decided to go back to carb.
I need some suggestions, so I buy one I can work with.
I tried Edelbrock 1405 and 1406 before the Sniper, was never happy with.

318 with 904.
Edelbrock RPM Airgap intake
Edelbrock RPM Aluminium heads
Zero deck (10.5:1)
I beam rods + KB Pistons
Lunati Cam 10200702

Thanks!
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I have had a 650 Mighty Demon on my 71 340. Fantastic, problem free
 
Eddy AVS2 650cfm gets my vote too. The off idle, part throttle responsiveness is much improved over the previous generation. Annular boosters must be part of the reason. The low load WOT bog still has to be accepted or tuned-out. The eddy VRS looks very interesting but a whole different price level than AVS2.
 
750 street demon works well on my 340 no problems in3 years use
 
Ricks70Duster340 said:
The Edelbrock AVS2 1906 (650 CFM) would do well for you. With its annular boosters you'll get superior throttle response. I too, like you, tried the earlier model without success. If you go with a 1906 I encourage you to also get the tuning kit so you can zero in on just what the engine wants.
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I second the AVS2. I would say that it's the best street carb out there. Also agree with the tuning kit. They're very easy carbs and the throttle response is great. I had an issue with boiling fuel, but a spacer cured that 100%.
 
510Mopar said:
Eddy AVS2 650cfm gets my vote too. The off idle, part throttle responsiveness is much improved over the previous generation. Annular boosters must be part of the reason. The low load WOT bog still has to be accepted or tuned-out. The eddy VRS looks very interesting but a whole different price level than AVS2.
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The VRS is advertised as race carb without choke. I think it would be overkill to my little 318. Although it looks so god damn good. It is superior to the holley 4150 according to rumors. Haven’t seen one my self in reality so far..
 
I use a TQ with great success on my '68 Cuda. Once fuel is in the bowls (after sitting for a week or so), it starts instantly and idles at 500-700 RPM even 30 seconds after a cold start (well, cold start in summer isn't quite as cold as other times of the year!). What I found makes carbs work wonderfully is have sufficient initial advance, say 12-15° initial and 34° total. I am toying with the David Vizard approach of using manifold vacuum for the vacuum advance, but that requires more work with the distributor than I have stomach for. Right now, I use a 11° advance (distributor advance) plate (from a mid-70's motorhome or something) which gives 22° total timing in the distributor coupled with 12° initial timing for a total engine timing of 34°. This gives a plug reading for advance right one the ground electrode just above the plug base.

Stock advance of 0-5° initial timing usually leads to longer crank time compared to more advance. IMO at least.
 
RLF Cuda said:
I use a TQ with great success on my '68 Cuda. Once fuel is in the bowls (after sitting for a week or so), it starts instantly and idles at 500-700 RPM even 30 seconds after a cold start (well, cold start in summer isn't quite as cold as other times of the year!). What I found makes carbs work wonderfully is have sufficient initial advance, say 12-15° initial and 34° total. I am toying with the David Vizard approach of using manifold vacuum for the vacuum advance, but that requires more work with the distributor than I have stomach for. Right now, I use a 11° advance (distributor advance) plate (from a mid-70's motorhome or something) which gives 22° total timing in the distributor coupled with 12° initial timing for a total engine timing of 34°. This gives a plug reading for advance right one the ground electrode just above the plug base.

Stock advance of 0-5° initial timing usually leads to longer crank time compared to more advance. IMO at least.
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34 degrees total timing [VA disconnected] is very close to the "magic number". My 340 initial timing is set at 10 degrees, which gets there. I guess every distributor mechanical advance must be somewhat different, so you might want to play with initial a bit.
 
jakuzzie said:
After a couple of years with the Holley Sniper EFI and it’s problems I now decided to go back to carb.
I need some suggestions, so I buy one I can work with.
I tried Edelbrock 1405 and 1406 before the Sniper, was never happy with.

318 with 904.
Edelbrock RPM Airgap intake
Edelbrock RPM Aluminium heads
Zero deck (10.5:1)
I beam rods + KB Pistons
Lunati Cam 10200702

Thanks!
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I built a 383 stroker for my C10 and was talked into going with a Sniper. Worst mistake I ever made. It complicated the whole system because it wants to control everything including the fans, a/c, gauges, and it’s still not tuned properly after taking it to three different professionals. I’m in the same boat as you with that one and am seriously thinking about going to a carb. It was dyno’d with a 750 Brawler, so I’ll probably go with that.
 
jakuzzie said:
The VRS is advertised as race carb without choke. I think it would be overkill to my little 318. Although it looks so god damn good. It is superior to the holley 4150 according to rumors. Haven’t seen one my self in reality so far..
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Don’t believe the rumors.

I’m waiting for someone to bring one in so I can get it on the dyno and work with it.

I doubt it’s all it’s cracked up to be.
 
Newbomb Turk said:
Don’t believe the rumors.

I’m waiting for someone to bring one in so I can get it on the dyno and work with it.

I doubt it’s all it’s cracked up to be.
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Agree 100%
I recently bought a carb from ATM. They are very resonably priced, and I couldn’t be happier with the quality.
I suspect that new Eddy carb is more voodoo than anything else.
 
I recently bought a car that someone had hot rodded by adding electronic TBI, electric fans, electric fuel pump, moving the battery to the trunk, wild MSD ignition etc...
They burnt the fusible link, it scared them and they gave up.
I got the car and I've gone back to stock with everything I can, carb (Demon 625), viscous fan, mechanical fuel pump,, battery in stock location, Chrysler electronic ignition, etc...
Starts, runs, fun to drive, low maintenance.

I have found that no matter what you do to these old cars, they will never drive like a modern car. The technology has changed so much.
In my humble opinion, that is why I am attracted to them.
My kids don't understand setting the choke on the carb before starting.
They don't know setting points, dwell or what a timing light is for.
Some of them don't want to learn a manual transmission.
That's ok, I'll keep that just for me.
 
Edelbrock AVS2 + MaxFire Ready to run it shall be.

Out of the box better performance than the Sniper. I literally took it out of the box and installed it without any adjustments except the idle screws. The engine vibration is finally gone. Runs so much smoother and way faster star up. Drove it 75 miles and even fuel economy is not even worse?!?!

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A few years back I was thinking about taking a part time wrenching job, I asked what would I be working on, he said I have 4 cars with Snipers and not a single car could pull out of the shop
 
Brooks James said:
A few years back I was thinking about taking a part time wrenching job, I asked what would I be working on, he said I have 4 cars with Snipers and not a single car could pull out of the shop
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Wow
 
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