SAAC Forum

The Cars => 1965 GT350/R-Model => Topic started by: dockbay on April 05, 2018, 01:19:32 PM

Title: 5S276 Fuel distribution problem?
Post by: dockbay on April 05, 2018, 01:19:32 PM
HI guys!
I have my car back up and running after a fresh engine, tranny and rear end rebuild. Here's the short story. I just pulled off my headers to take them back to Sanderson who did a crappy job ceramic coating them black. What I noticed when I removed them (I have run the car for about 50 miles and it seemed to run great) is that the most rearward cylinder on each header is clearly running ultra lean. There is consistently similar carbon distribution on the first 3 ports and almost NO visible carbon on the last port on each side. The motor seemed to idle fine so I don't suspect that there is a vacuum leak on both sides (I will check)  So I'm thinking that I might have a fuel distribution issue? My thought is to try a phenolic spacer under the carb and see what that does. Any other thoughts you all have would be helpful. Something amiss in the manifold? Anybody running a spacer on an otherwise completely stock setup? Will it fit under the hood? Truth is I'd really like to keep the car completely stock without a spacer but clearly something is amiss....
Cheers and thanks in advance,
John
Title: Re: 5S276 Fuel distribution problem?
Post by: 6s1802 on April 05, 2018, 01:25:30 PM
The rear tubes on 6S1802 run hotter too, especially the right side. I suspect it might be the original intake manifold. I run a 1" phenolic carb spacer and run the PCV hose into the back of the spacer not the rear vacuum port on the manifold.
Title: Re: 5S276 Fuel distribution problem?
Post by: s2ms on April 05, 2018, 01:35:08 PM
+1.

Check your spark plugs, the rear 2 cylinders, especially #4, get the huge bulk of the PCV vapors due to the design of the Cobra intake. I suspect the carbon buildup is from the oil in the PCV vapors and your plugs should reflect that. Running a thin spacer and attached PCV hose, like the Boss 302, will balance out the PCV vapors. But it won't look totally stock...

Dave
Title: Re: 5S276 Fuel distribution problem?
Post by: doublemyv on April 05, 2018, 07:08:20 PM
SFM5s444 has had the 289 completely rebuilt to original specs by Craig Conley @ Paradise Wheels.   One thing he mentioned when we were breaking in the motor on the test stand is that " we put a restrictor inside the pcv line between the pcv valve and the manifold, to prevent the rear cylinders from running too lean, but maintaining a stock look ".   He did not mention the size of the hole drilled in the center of the plug/restrictor, but others on this forum may have some info on that subject.  Good Luck, Mark
Title: Re: 5S276 Fuel distribution problem?
Post by: dockbay on April 05, 2018, 10:07:50 PM
Thanks for the feedback! I just checked in my records to see how old the PCV valve was as I thought it might be involved somehow. It's pretty new. I like the idea of the restrictor in the line as that would be hidden. I'll give Craig a call in the morning to determine the size of the hole in the plug..
Cheers,
John
Title: Re: 5S276 Fuel distribution problem?
Post by: Rickmustang on April 05, 2018, 10:32:02 PM
Please let us know what you find out
Title: Re: 5S276 Fuel distribution problem?
Post by: zray on April 05, 2018, 10:42:46 PM
Yes the rear cylinders will run slightly more lean due to the. PCV intake location. However this is not to be considered extreme or damaging in ANY way., there is absolutely no problem in using the stock Cobra Hi-rise intake with the rear PCV hose location.  Additionally, there is no performance advantage to be changing the stock Shelby arrangement to an under carb spacer for more even distribution. Any theoretical advantage does not translate into actual measurable improvement .  I've experimented with every possible variation in PCV / intake hose plumbing using the the Cobra Hi-Rise manifold and found no benefit to deviating from the stock arrangement.

Z
Title: Re: 5S276 Fuel distribution problem?
Post by: 6s1802 on April 05, 2018, 11:58:25 PM
I also restricted the PCV hose for less flow
Title: Re: 5S276 Fuel distribution problem?
Post by: shelbydoug on April 22, 2018, 07:49:11 AM
A .100" restrictor seems to work better but a lot of the issue is that the pcv valve itself is basically cheap junk and doesn't do what it is supposed to do. They are supposed to completely close but don't.

If you decide to try to re-engineer the mess, go immediately to the ME Wagner unit. It is about 95% efficient rather then 5% like an over the counter Chinese valve is.

It's the best that you can do at this time.
Title: Re: 5S276 Fuel distribution problem?
Post by: zray on April 22, 2018, 11:42:28 AM
".........What I noticed when I removed them (I have run the car for about 50 miles and it seemed to run great) is that the most rearward cylinder on each header is clearly running ultra lean. ...."


"...... The motor seemed to idle fine......."


OK, so the car is running "great". as described by the OP

additionally, it "....idles fine..."

You don't have a problem. If there was a lean condition so bad it was causing engine damage, the car wouldn't be running great and idling fine. With two cylinders REALLY running extremely lean the idle would be hunting all over the map,  and you would be down on power. Just because the carbon residue is lighter colored in the two rear cylinders is not reason to think the sky is falling and something must be done.

You will never get all the cylinders to show the same exact burn color with a Cobra Hi-rise manifold.

 So put on your headers when they are done (again) and drive the car. When you have a problem you won't need to be analyzing the inside of the headers to discover it. It will be obvious and manifest itself by an unstable idle, massive bog off idle, and poor acceleration.  Until you have those symptoms, you don't have a problem.

Z
Title: Re: 5S276 Fuel distribution problem?
Post by: 2112 on April 22, 2018, 04:52:15 PM
Yeah, lean cylinders are not a problem.........until they are.

Ever blow an engine up on a few lean cylinders? I have. It sucks.

It was the non-tunnel ram, un-corrected intake that caused my meltdown.

I can understand not wanting to touch an original intake (equalizing flow) but if you want to run the engine hard on a regular basis, an option would be a flow equalized repro (Art Francis) intake manifold.

Easy bolt-on/bolt-off proposition.
Title: Re: 5S276 Fuel distribution problem?
Post by: zray on April 22, 2018, 05:46:20 PM
".......Ever blow an engine up on a few lean cylinders? ......."


No I haven't . Either I've been lucky for 55 years, or I know better. You decide.

I'm just some guy that cleans up the mistakes of others. A nobody.

There's a difference between inconsequential lean, and lean that matters.  A Cobra Hi-rise manifold is the former.

Z
Title: Re: 5S276 Fuel distribution problem?
Post by: 2112 on April 22, 2018, 09:19:11 PM
Until it has been singing at 6,700-7,000 rpm for a while.

Not my engine, go for it, right?
Title: Re: 5S276 Fuel distribution problem?
Post by: 2112 on April 22, 2018, 09:50:29 PM
If intake modification or swapping intakes isn't desirable, at the very least, I would retard the timing and/or jet the secondaries to richen the leanest cylinders.

IMO, all non-tunnel ram/Webber intakes have a lean runner(s) somewhere. If you run hard, you will find out which one eventually.
Title: Re: 5S276 Fuel distribution problem?
Post by: zray on April 22, 2018, 10:33:23 PM
Until it has been singing at 6,700-7,000 rpm for a while.

Not my engine, go for it, right?

I think the OP has a more or less stock engine, right ?   And it runs great and idles fine, no lean hunting at all.   Doesn't sound like a problem to me. For example, with a vintage Paxton sitting on top of the Hi -Rise manifold in my old '66 GT350, I ran the course of the BBORR many many times (off season) at full throttle for the entire 69 miles. The rear cylinders always showed a little lean, but nary a sign of  damage.  If a 289 w/ a Paxton and the suspect Hi-rise manifold can make the Big Bend course look like a walk in the park, over and over, again, then I'm not worried about telling someone they don't have a problem with a well known minor lean issue on the rear cylinders.  After all, this issue isn't something new. It's been observed since these cars were new, and Hasn't been the cause of engine failure yet.  I fussed with it myself for a couple a years, and never found a way to eliminate the anomaly without creating other problems. Eventually coming to the same conclusion everyone else has since the days of the '65 championship season; minor lean running can be tolerated in the rear cylinders without causing damage

As pointed out, most dual plane manifolds have some irregularities in fuel charge distribution. If that's worrisome, just put on a nice set of 48 IDA Webers and problem solved.
Title: Re: 5S276 Fuel distribution problem?
Post by: 2112 on April 23, 2018, 01:02:05 AM
I would not argue with any of that. I believe that is exactly what you experienced.

OP mentioned an "ultra" lean condition on #4 & #8, lean enough to burn ceramic coating (even if crappy) off the headers. That sounds pretty lean to me.

I wish I paid attention to my lean #5 & #6 (common on BBF SVO spider manifolds) cylinders, but it was running so good................ ::)

Title: Re: 5S276 Fuel distribution problem?
Post by: shelbydoug on April 23, 2018, 07:14:27 AM
Here's my view.

This depends on which carb you are running. IF you are running the Shelby 715 Holley, that thing is so rich at WOT there is no way that you are going to run lean.

It is one of the reasons that it was selected to begin with by the Shelby people.


IF you are running a stock 1848 Holley, it will run lean at WOT BUT you won't have enough capacity to run much over 5,000 rpm. In effect, it is a rpm limiter.


If you are running  an 1850 Holley, it tends to idle a little rich but will have the same effect on the top end, but with about  500 to 600 rpm more rpm.


Webers will not run lean. Period.


If you are running two 1850 Holleys stock, you are right on the T/A designed mixture.

Dual AFB's...don't know.



There is talk of the headers showing lean. The only place that reading can be coming from is the silver ceramic coating loosing it's shine near the flanges. That's not lean, that's the correct exhaust temps and how the ceramic coating reacts to that temp when the engine is working right.


With the last Holley "Motorcraft" carbs on whatever year that was, 84, 85, 86 Mustang GT, the carbs were set to idle at stoichemic ratio of 14.6:1 AT IDLE. That setting is within the DESIGNED running capabilities of the original Ford valve train and the only thing that it does is turn the TUBE "headers" all sorts of interesting colors on the primary tubes.


You CAN'T blow up an engine by suddenly running lean UNLESS you instantaneously lost fuel delivery (fuel pump failure) at WOT OR it would have to be a massive vacuum lean at maximum load.

When this happens you will backfire through the exhaust and you will blow the mufflers out or up. That I personally can attest to. I did that twice and now always run with an electric pump in the system to reduce the possibility of this happening again. So far, so good.


The intake manifold design HAD NOTHING TO DO WITH ANY OF THIS. Ignorance on my part did.

Just the mufflers blew up. The engine was fine both times.

It will backfire like the "rice rocket bikes" do that have had the mufflers removed when the rider suddenly closes the the throttle from WOT in gear, i.e., a BIG firecracker.


Incidentally the Webers will do this EXHAUST BURBLING to a lesser extent when you decelerate with the car in gear. There it tends to be the overlap timing in the cam scavenging a reverse flow of cold air through the exhaust.


...anyway, I tend to agree with Zray here, all "normal" operation and is expected to cause reading of plugs and exhausts just like this. Drive the car. You worry too much.  ;)
Title: Re: 5S276 Fuel distribution problem?
Post by: kram350 on June 23, 2018, 08:57:53 AM
Just an observation; In trying to correct lean cylinders for years in a road racing environment, many different intakes tried, about 15 years ago I built a set of equal length (EL) headers. Boy did that ever make the plugs color even and yielded pipe temps all within 25 degrees. Water temps came down and even with huge overlap in the cam, idled better. To say the least I was astonished at the results. The variance in cylinder temps varied little whether a dual plane, single spider or the ram box I currently run. Staggered jetting and 4 corner mixture screws helped,  but did not come close to EL headers. I had the lean issue with hooker super comps and the stock try-wye's, all with the same intake manifolds. I spoke with Ed of Headers by Ed quite a bit and he convinced me of the advantage of equal length and really equal flow that will produce the best power. It was a lot of work to build the things, but it would seem the end result was justified. My next car will get EL's, worth the effort to me. For the street, don't know if it is worth the cost and work involved. I would think just converting to 4 corner idle would help on a stock dual plane on the street .