Request for tuning advice

[ozconv]

I have a '67 Mustang Convertible with the following build:

-200 six, essentially stock short block rebuild (+0.030) but with ARP fasteners, 0 decked,
double roller timing set, and H264/274 cam with 112 lobe center, advanced 4 degrees.
-Rebuilt OZ-250 head and intake, ported with 1.8" back-cut intake valves and
1.5" exhaust valves, 3 angle valve job, 302 valve springs.
-1.6:1 Adjustable roller tip rockers.
-Classic Inlines header, custom X-pipe, 2" dual exhaust with FlowMaster 40 mufflers.
-Rebuilt post 68 Pre DS1 dizzy with mechanical and vacuum advance, Pertronix Igniter II,
Flame Thrower II coil, Pertronix Wires with 0.045" plug gap (one step colder Autolite 45s).
-Rebuilt 1.02 245cfm Autolite 2100 with manual choke, 53F jets, and throttle plates modified
by drilling 0.040" holes in center of each throttle plate on side of shaft closer to idle screws.
-0.050" compressed Corteco head gasket with 6.5CC stock dished pistons for CR of approximately 9.3:1.
-Higher stall (2800-3000rpm) converter with stock C-4 automatic and trans cooler.
-Stock rear axle with 3.2:1 ratio.

The car idles in gear between 800-900 rpm and about 1400-1500 rpm in park.
Vacuum idling in gear moves between 6-8" and between 14-15" idling in park.
Vacuum when cruising at 45-50 on level surface is about 15".
Under heavy acceleration (close to WOT), vacuum drops to about 3".
When coasting vacuum increases to about 17".

Base timing was set to 18deg at 750 rpm with vacuum advance plugged.
Distributer reluctor set to allow 20deg of mechanical advance max and the lighter spring has been
replaced with the lower tension MR. gasket spring.
Using a dial back timing light with the vacuum still plugged I got the following measurements:

750rpm 18deg
1000rpm 18deg
1500rpm 23deg
2000rpm 28deg
2500rpm 33deg
3000rpm 33deg (not sure why the advance isn't continuing to 38deg max.)

I originally drilled the carb throttle plates to get the engine to stay running below 1200 rpm but I
think it may now be running either too lean at idle or has too much advance at idle (I am using manifold
vacuum since it will stall in gear with only 18deg (best vacuum at 25-30deg). In park with manifold
vacuum the timing is about 40deg at 1500rpm. The balancer is brand new and I have verified TDC.

I suspect a lean or too much timing condition because the engine seems to be running a little hot.
I have a new aluminum water pump, 180deg T-stat, 2-row aluminum radiator with overflow tank, 6 blade mechanical fan,
and a custom aluminum fan shroud fabbed from a universal kit. Fan is about 1" from the radiator and is about
75% of the way into the shroud. Temperatuer measurements with an IR gun are 190-200F taken at various
locations on the cylinder head. One area (topside of #3&4 exhaust port), however, is much hotter.

The head is an OZ 250 2V and the paint on the top side of the siamesed 3&4 exhaust ports has been burning off.
Temperatures at this location are as high as 470F. I don't believe there is any coolant in this area of the
head so I would expect it to be higher but is this too high? I do not have a port divider but do have a CI header.

Plugs still look brand new (white with no coloring or deposits at all making me suspect lean idle).

Driveability isn't too bad with the following exceptions:

1. Idle "hunts" a little bit when stopped at a light for too long. This could just be the cam, or maybe since the vacuum
is fluctuating between 6-8", the power valve might be coming off and on (not sure what PV rating is).
2. Car accelerates well up to about 50mph but seems to run out of steam from there up to 65-70 when trying to
merge on to the highway.
3. At about 2800rpm, the exhaust stops sounding good and starts to sound like a very loud trumpet or kazoo (buzzy).
I'm guessing this might just be the way 6s are but wanted to ask since I am not sure how to recognize "pinging".
Could this also be caused if the timing isn't advancing enough?

I have the following questions:

1. Do these head temperatures seem too high?
2. Could the flattness at 50mph (approx.2700rpm) be do to timing. Should I bend the larger spring tab on the distributer
to bring the mechanical advance in sooner?
3. Should I go to a bigger carb? (1.14 or 1.23 I have both available). I have read that the larger throttle
plates of the 1.23 may allow me to get a better idle without drilling since they don't need to be open as much at idle
and I may not have to open into the transfer slots or drill.
4. What kind of performance should I expect from this build? Is it even possible for this build to spin the tires at a light
(tires are P235/60 R14)? The cam is rated from 2400-6200 so the reduction/loss of acceleration/power above 50 (2700rpm)
is troubling. When I started the engine for the first time (winter), it seemed to be too rich (fouled plugs). Now it
seems lean (summer). Changes (not all at once but in this order) since then included adding the exhaust, removal and
reinstall of head to have checked for cracks (slightly thicker Corteco gasket used instead of Felpro when reinstalled), retarding cam
from 6 degrees advanced (106) to 4 degrees advanced (108), drilling of throttle plates, changing jets (48F to 53F), and
colder Autolite 45 plugs.

Any help/advice would be greatly appreciated.

 

[CZLN6]

Howdy Ozcon:

Sounds like a nice build. Off the top of my head I will offer a few observations. First, a 1.02 is probably a little small for the Higher rpm end of your build. That includes total cfm, as well as a leaner K-cluster. The K-cluster functions like the metering plate in a Holley, but less is known about their markings. The idle circuit is a channel restriction built into the K-cluster, which is not easy to change. You could try increasing the main jets to 55 to 58 range, but that will only help on WOT- not the idle circuit.

Also you will likely need to start collecting Holley Power Valves. They are rated in one inch increments. Given your stated vacuum readings you will likely need a PV rated at 4.5 or 5.5. Your head and cam should favor higher rpms. Autolite PVs are not rated, but color coded- red or green for elevations blow 5,000 ft. Yellow or plain indicates elevations above 5,000 ft. Unfortunately, many rebuild kit PV are not color coded or marked at all. For stock applications they are usually close, but that won't apply to you.

IIWIYS, I'd be inclined to go with a 1.23. You will likely loose some low end crispness in favor of a better idle and top end. By changing to the 1.23 carb you will get a K-cluster engineered for a 351 engine. The 1.02 you're now using was designed with 260 V8. In theory, a 1.02 should be just about right for a mild 200. Your engine is beyond that.

I'd suggest that you don't do any more changes with timing until you zero in the carb closer. A lean carb and too much timing are not a friendly combo. Heat is a very likely result.

What is your elevation? I'm hoping this is helpful. Keep us posted on your progress.

Adios, David

 

[66200i6]

I haven't heard of anyone drilling a hole in the throttle plate in quite some time. This practice was used by Audi as a matter of tuning their carbs due to the use of smaller than normal Ventures. This was needed because the amount of air being pumped by the cylinder was more than the carb would allow if the throttle plates were in the proper position (dimension from face of venture) to engage the idle circuit. The throttle plate would have to be opened beyond this ideal point just to get enough air for the engine to run. At this point you would end up running the Main Circuit at idle.

The hole were drilled to allow additional air to pass through the carb while also allowing the throttle plate to be adjusted (closed) back to the correct dimension from the wall of the venture to engage the idle circuit. This practice also, usually, included two holes as well, one either side of the throttle plate centerline.

Is there a reason why the hole was drilled in your application?

Ric.

 

[66200i6]

I think David just answered my question.

 

[FalconSedanDelivery]

Ok here I go again , almost any cam over stock in a 200 without a very loose converter will be a DOG , you mention a converter change but it obviously is not what you state/need ,You should not of drilled your carb butterflies , you have 2 choices , less cam or more converter , until that is corected all the adjusting in the world will not fix it, after re reading your post I am also skeptical on the compression , have you done a cranking compession check if so at 9.3 you should be at aprox , I'm betting its much lower , based on your vacuum readings

 

[ozconv]

Elevation here is about 800-1000 feet above sea level. I will order some PVs from holley. I see they have 2 stage PVs. Has anyone ever used those with an Autolite? In addition to the 1.02, I have a 1.08,1.14, and the 1.23. If the 1.23 is too big, would it be possible to use the K-cluster from the 1.23 in one of the smaller carbs to get a better idle??

My calculated static compression ratio is 9.3:1. With this cam, my dynamic compression ratio is lower. I've run a compression check and 5 out of 6 cylinders are in the 170-178 psi range. Number 4 is higher at about 185 psi. When assembling the engine, I CC'd the chambers they varied from 50-51.5 CCs. Block is 0 decked, pistons are the standard 6.5cc dish, head gasket is the Corteco that Mike sells.

Do the temperature measurements seem high? If 4 has slightly higher compression, I am thinking that might contribute to the higher temperature measurements on the outside of the siamesed exhaust port.

 

[CZLN6]

Howdy Back OzCon and all:

The two stage PV was designed for RVs and trucks with heavy loads. I'd be inclined to NOT go with a two stage PV as it complicates tuning issues. And given your engines state of tune and your pretty ideal gearing a two stage PV wouldn't help anything and it may complicated things.

The 1.14 and the 1.23 are earlier versions of the 1.08 and the 1.21. They, generally, are built with richer internal orifices. As far as swapping the K-cluster, I could not recommend it. As I said earlier I know of no known decipher of how to read the internals of the various clusters. There are, at least, two variables built into each cluster; internal orifice restrictions and air bleeds, both high speed and low speed. I'd be inclined to try either your 1.14 or 1.23, as is, and tune from there. I try to minimize variables when adapting a new carb to an engine. I try to make one change at a time, analyse, assess and then make a change if needed.

As far as the idle goes, that may be a result of your cam timing. You may have to hole the t-plates of the bigger carb too. But try it first and then assess.

I don't know about your gun reading on exhaust temp. It sounds high to me, but I've never used the gun approach. Your plugs sound lean, but not hot. Do they show any signs of peppering or glazing? A slight variance in chamber dish won't matter much. What is your water temp?

Keep it coming.

Adios, David

 

[wsa111]

First off get rid of the pertronix II. Either install a pertronix I or get a duraspark 11 & a msd box.

Pull the distributor & get it on a sun distributor machine so the centrifigul advance can be properly dialed in. 20 degrees @ 2700 rpm would do the job.

Check the vacuum advance for proper vacuum settings using a hand held pump or on the sun machine.

Hook up the vacuum advance to manifold vacuum.

That cam is not that radical. If all of the above do not fix the problem then concentrate on the carburetor.

A victor head gasket is .006" thinner & would have given you a little more compression.

Do the above & then go the carb route. Bill

 

[Frankenstang]

Okay, you’ve got folks with tons more experience and knowledge responding here than myself, so I hesitate to post this (don’t want to add to any confusion or the number of targets)…

BUT, did you ever get your cam degreed properly. Based on this thread (and I really mean no offense)
viewtopic.php?f=1&t=60723&p=467374#p467374
I do not get the impression you got a ‘good’ handle on it, again no offense.

This may be a really simple and stupid question, but could your cam be too far advanced for your current setup?

From your degreeing thread the only thing that seams ‘relatively’ sure is that measured straight up you believed you had more advanced phasing than it should (measuring a 108* intake center line)….so here’s the dumb question part B

Have you tried running it with the cam straight up? Or is that where you're at now when you mentioned above...

retarding cam
from 6 degrees advanced (106) to 4 degrees advanced (108)

Again, no offense but given you degreed the cam with the head on (not recommended as I understand), it just seems like proper degreeing of the cam may still be in question here, and if it is (or if I were in your shoes)…I’d probably sooner run it straight up and see what it does (realizing it’s better to properly degree), but at least that would give you an idea if this is part of the issue.

I realize you’ve been at this build for some time looking at your old posts (looks like going back to the first part of 2010), so I don’t envy your situation (except for the oz head and rag top ), and don’t mean to add to any tensions or headaches by inserting this ‘simplistic’ analysis.

Looks like you went to a higher stall converter after this thread and based on what you said above, …
viewtopic.php?f=1&t=65649&p=502763#p502763
… also sounds like you went back to points at some time to cure a fried coil.

So if my idea is way off base, it won’t bother me a bit if someone says so…not trying to add to the number of targets…just spit ballin. Good luck!

 

[wsa111]

I believe the cam timing is pretty close. With 4 degrees advance that would close the intake valve a little sooner than being straight up. 175# with 9.3 compression & that camshaft are in the ballpark.

Like i said before you need to get the ignition straightened out first & then go to the carburation.

From what i read its a nice build, this fellow spent a lot of money to get what he has. It just needs the right parts & fine tuning to get it right.

If it gets down to carburetion just borrow a holley 7448-350 carb & bolt it on. Even out of the box it will be close enough to fix a carb problem. This engine needs more than a 350, but thats a starting point

The holley has 400% more adjustability than the autolite if a carbutetor expert is designing it for his application.

The only way to finalize carb calibrations is via a wideband A/F tester & then to strip test it from there.

If your spark plug insulator is white & you are running autolites, switch to NGK iridium WR51X stock # 7510

& gap them at .050" if running a stout ignition system. Bill

 

[MustangSix]

I've drilled Holley throttle plates before to get more air at idle. Without the hole, I would have to open the throttle to a position that was past the idle transition slot which screwed up both idle mixture and ported vacuum. With the holes I could keep the idle up and still have the vacuum transition slot closed and the idle mixture slot open.

But this was on cars that had BIG cams and idled at 1200-1500 rpm. If you drill the throttle plates on a car that really doesn't need the fix, you have basically introduced a vacuum leak and you might have created some idle problems. I know that will happen on a Holley, but I'm not sure of the effect on an Autolite.

 

[ozconv]

CZLN6 - Not sure what the actual water temperature is. For what it is worth, the factory temp gage tends to stay within just under half way to half way except when the car is restarted hot. When restarted hot the gage will peg all the way to the hot side and then slowly come back down to about half way though the gage tends to stick and I have to tap it to get it to keep moving. Since the accuracy of factory gages is hit and miss, I used the IR gun to get actual temps from the cylinder head surface. As I stated the outside surface of the head runs between 190F and 200F everywhere except the siamesed exhaust port where it is much hotter (400F to 470F). This higher measurement along with the white plugs had me concerned about a lean/hot condition. I haven't noticed any deposits on the plugs, they essentially look like they just came out of the box.

As far as the cam indexing, I took measurements with the cam straight up (0 keyway on crank sprocket), 2 degrees advanced (+2 on crank sprocket) and 4 degrees advanced (+4 on crank sprocket). For the straight up position, my intake centerline was 108, and for the other two locations it was 106 and 104 respectively. For duration at 0.050" lift I got 212 for the intake and 222 for the exhaust. I should have gotten 214 and 224 so I know my measurements were off a little. Total lift with 1.6 roller rockers was around 0.470".

What confused me when degreeing the cam were my exhaust valve measurements. My understanding is that a H264/274 112 cam which mine is marked as should measure 112 for the intake and 112 for the exhaust when degreed straight up. If advanced 4 degrees the measurements should then be 108 for the intake and 116 for the exhaust. My measurements for +2 and +4 came out 106/114 and 104/116. This made me wonder if my cam wasn't actually an H264/274 110. I originally left it on the +2 keyway (106/114) figuring my measurements had a couple of degrees of error in them and I would split the difference. At initial start the car was running very rich (pre throttle plate drilling) and backfiring through the carb. I thought that perhaps the cam was advanced too far and the intake valve was opening too early so I re-indexed the cam to the straight up position (108/112).

The torque converter that I recently installed was a custom built 9" converter from Phoenix Transmissions as recommended and I was told the stall would be in the 2800-3000 range although it did not have any confirming paper work with it when it showed up. It did help (car doesn't stall in gear), however, the idle still drops from 1500 in park to about 900 in gear.

I installed the 1.23 with 59F jets yesterday and was able to start the car, however, the throttle linkage was not adjusted properly so I couldn't drive it. There was no backfiring through the carb, however, the engine was back to the pre-throttle plate drilling condition where it wouldn't idle in park below about 1300. I did pull the number one plug and it was black though I didn't run the car long enough to reach operating temperature. I will try to get the throttle linkage worked out tomorrow so I can take it around the block to get it warmed up and then hook up the tach, vacuum gage, and timing light to see what is going on. I suspect, however, that I will have the same condition as with the 1.02 where it wouldn't run with the throttle plates closed unless drilled. The smallest bit I could find was 0.040" and that's what I used on the 1.02. Afterwards, I could lower the idle from 1300 in park to as low as about 700 before it would threaten to stall. The side-effect, however, seemed to be that the carb went from way rich to somewhat lean, atleast at idle.

I'm still hoping that maybe a base timing adjustment or idle mixture screw adjustment (I think I bench set them to 2 turns out) will work so I plan to try since I would rather not drill another set of throttle plates. I am also not sure of the PV rating so I will probably take the carb back off and swap in the 4.5" PV when I get it. Do the Holley 350s allow you to adjust the idle air bleed? I don't want to drop another $300 on a carb if I am going to have to drill those plates as well. The OZ head and intake were an eBay purchase and the head has definitely had a fair amount of porting done to it. It has never been flow tested but I wonder if they may have screwed it up (uneven flow from cylinder to cylinder or too much porting) and maybe that is why the idle is so bad without drilled throttle plates.

 

[wsa111]

As i said before, the cam you have is mild. It should not require drilling the throttle blades to get more air.

You need to fix your ignition first & then you can move on to the carburation.

The throttle blades should be no more than 1/3 rd up the transistion slot in the base of the carburetor.

On most of my carbs i run a 8.5-7.5 power valve to cover up the transistion period from idle to the main nozzles.

The 350 carb does not come with adjustable bleeds, air & fuel. You can purchase a carb that already is modified with screw in bleeds from a carb specialty shop or get your carb modified for adjustable bleeds.

You need to fix either a vacuum leak & or an ignition problem first before blaming the idle problem on carburation.

With your mild cam you should not need to drill holes in the throttle blades on a 350 or 500 carb.

In fact i braze the hole shut already drilled in the 500 carb. Bill

 

[Frankenstang]

Well I'm not going to suggest (or try to suggest) that you don't have ignition/dizzy out of whack and/or a vacuum leak...I'm sure all are quite possible. Especially given these two seemingly, wildly inconsistent measures...

Using a dial back timing light with the vacuum still plugged I got the following measurements:

750rpm 18deg
1000rpm 18deg
1500rpm 23deg...

...In park with manifold vacuum the timing is about 40deg at 1500rpm.

However, I will throw out the idea that it is still possible there is a fuel delivery issue mainly because of the "white" plugs and the fact it 'hits a wall' at higher speed/rpm...based on this...

....Plugs still look brand new (white with no coloring or deposits at all making me suspect lean idle)....
2. Car accelerates well up to about 50mph but seems to run out of steam from there up to 65-70 when trying to
merge on to the highway.

Might be worth checking fuel pump pressure and fuel volume delivery rate, which pump are you using?...leaning out along with excessive amounts of advance can both cause overheating (although granted retarded timing generally causes excessive heat issues more quickly noticeable).

I guess my point is, yes your ignition may still have issues and curve may be way off (ie needing 18* advance to stay running doesn't seem right), vacuum leaks also possible (do you have power brakes? leaks there?)
...but the "hitting a wall" under acceleration more than anything else would have me wondering about fuel deivery...and it can be a 'before the carb' issue.

 

[MPGmustang]

a trick to try for the 1500rpm park idle to 900rpm gear idle:
set the ignition timing to 8*, then retune, if it doesn't jump as far I suspect the cam timing is still too far advanced. try drving it around if it has more pep then you might want to redegree the cam, I recently did on my engine and must confess much smoother running.

IMO, you'll want the 1.23 or bigger, and don't drill the holes in the butterfly plate...

in comparison, IMO you want to re-tune your dizzy, My DUI is set to 12* static, it has 24* centrifugal advance @ 3000 rpm, total timing is 36*, with the vacuum advance it's close to ~53* (hard to tell as I have a 1984 sears timing light...)

Good luck!
Richard

 

[ozconv]

Fuel pump is a stock replacement mechanical pump.

I will try to lower the initial timing and re-tune but I will probably have to find some way to lock out the mechanical advance along with the vaccum advance since at 8 degrees I doubt it will run unless the idle is raised to where the mechanical has already started to come in.

As far as a vacuum leak, I suppose it is possible but I normally plug my vacuum gage into the manifold port so everything else (power brakes, transmission vaccum modulator, vacuum advance) are temporarily disconnected and there is no change to how the engine runs.

The intake manifold has been off and on several times with no change. The gaskets were not available anymore from Mike so I had to make my own. Last time I installed it I put steel inserts in the 4 upper holes (the bottom 4 are through holes that are for studs that are installed in the head) since it is aluminum and the threads were well worn. I also used the high temp, fuel resistant permatex aviation gasket sealer on both sides of the intake gasket. I also used the same sealer along with a gasket on the carb adaptor to intake joint. The adapter I am using is made from a 1/2" autolite spacer and has 2 separate holes rather than the single oval slot. I modified it by installing a PCV fitting on the back and installed steel inserts and carb studs along with drilling and counterboring the 4 mounting holes. Originally I used Mike's with the slot but it had no provision for a pcv hose and neither did any of my carbs so I made my own thinking not having a PCV might have been an issue. Changing spacer's had no discernable effect.

If I creat a vacuum leak on purpose, the engine runs better.

The carbs have been off and on multiple times with new gaskets intalled every time.

 

[Frankenstang]

Fuel pump is a stock replacement mechanical pump.

You can verify pressure with a gauge after the pump, and volume by taking line loose before the carb and feeding it into a container (ign disabled of course). Stock fuel volume is 1pint/30secs. You could also try a different mechanical pump or electric, but it still bothers me that what you describe is it falling on it's face at higher rpms...may be fuel flow not keeping up at high rpms, could the float setting be too lean again affecting high revs : ...still thinking about your white plugs.
EDIT: I imagine a fuel pump gauge rigged to read while running could also answer this question.

If I creat a vacuum leak on purpose, the engine runs better.

That's odd, but sounds a bit like too rich at idle IMO...you just may have opposite situation at higher rpm. Are you limited on rpm revs in neutral/parked as well, or just when merging on the freeway (ie under load)? How's it act when revving to 3-4k?

As Bill mentioned, you have to be cautious/careful with the pertronix. Have heard more than a couple (more than 2 or 3 in fact) situations where the magnets come loose from the unit or end up in the wrong location. IIRC Pertronix uses 'pieces of tape' to keep them in place.

I wouldn't make this offer to necessarily anyone, but given your stituation...I've got a totally mechanical advance Mallory Dual Point I removed when I went electronic. Was funtioning like a top...so much so I barely noticed the upgrade to electronic. I'd be willing to 'loan' it to you (cause I'd definitely want to get it back), but it might be an option to eliminate the wierd advance issues, or isolate other issues. It's got a good stock curve already set in it (36* total advance IIRC and the engine pulled hard with it) so it should not hurt your performance drastically, but may help you solve this riddle(s)...cause you could have more than one thing going on here...just a thought, and you can PM me if interested. (I'd need to clean it up, but has good points &condensor on it, would just need to be run with orig inline resistor wire, or an added balast resistor to be sure to protect points...a correct style coil is required for that matter too, but have one of those as well...neither is much to look at because of age, but know they work right). Just a thought since AFAIK manifold vacuum can become unreliable as an advance system once you cam up the engine, and although your cam is mild, you factor in the high ratio rockers and..., just not sure how that might be affecting things. Good luck!

 

[69.5Mav]

I did pull the number one plug and it was blac

If I creat a vacuum leak on purpose, the engine runs better.

You are getting to much gas at idle. Fix this and your other problems should be more solvable.
Check the power valve.
Check the idle circuit
Take the carb off and hold it up with gas in the fuel bowl and see if it drips gas.

My son had some body rebuild his 2V autolight carb and it would not run right. The next day while investigating I had the top off the carb and noticed the fuel bowl was empty so I filled it and turned around to work on something else. When I turned back to my sons car the fuel bowl was again empty so I removed the carb filled the fuel bowl again and held the carb up only to find the fuel fast dripping from the brand new power valve. I reinstalled the old one and rassembled everything and the car ran like a champ.

Any way thats my two cents