351C 2V Heads Help

[pjs2pc]

Hi guys, new to the forum so let's see how this goes. Looking for some opinions/advice.

I have a 73 mustang coupe with a 351c that I rebuilt fully about 10 years or so ago on a college student budget--which wasn't much. Since then I haven't even put 3000 miles on the car because it doesn't run the best. It was a stock 351c that I did the following to: bored to 4.030", put speed pro flat top pistons in, put a comp cams 280H (0.530 in/ex lift) 110º lobe separation cam in, edelbrock performer intake, holley 750 carb, msd distributor, and had a machine shop rebuild the open chambered 76cc heads. The rest was typical rebuild items. Rear end is 3.73 posi, transmission is a c4 that was rebuilt with a 3600 stall (I believe--been awhile).

Car just does not run correctly no matter how I change timing or fuel delivery--sometimes I get close depending on the weather, but it's VERY rare. I'm thinking my issues are due to the mismatch with the cam, intake, and heads. The heads seem to really have a detonation/pinging problem. Sometimes you can tune it out, but most of the time the rpm will lag/hesitate especially if you drive the car and give it some fuel.

I've tried everything I can think of with the parts I have. I've thrown the idea of going to aftermarket heads with quenched chambers, but didn't know if that would solve my problem or I really needed to start over.

Again, just looking for advice or if anyone has had similar issues with the 2V heads. I really hate seeing the car sit in my shop :/

 

[Q1SVT]

... how was the MSD setup timing curve? When is it all in by? total timing

What water temp thermostat are you running? Should be 180*

Condition of radiator? correct size?

A/F ratio?

personally I don't think you have enough compression to ping.

Open chamber heads ping more at lower compression... I like to add pop-up pistons. picture is a 72 351c QJ four bolt, 4v OC head motor w/JE pistons... compression set 10.2:1 w/more cam than you.

 

[pjs2pc]

Thanks for the reply!

Pretty sure at one point I tried every single combination on that MSD timing curve. I'd have to double check what I'm currently at. The engine really liked a lot of initial timing with all of it in as fast as possible. Even made a custom bushing at one point for a test. I'll update when I get home what the current timing setup is.

Thermostat is 180.

Radiator is all aluminum aftermarket. Car stays around 200º.

I have no way of measuring A/F ratio. I've had the holley 750 and an edelbrock 600 on. Messed with jets, discharge nozzles, cams etc on the holley all to go back to stock. The edelbrock seemed to be more consistent throughout the rpm range, but felt lean especially when you got on it or were at high rpm for a decent amount of time. Holley has always performed the best, but it's that lag which almost feels like it's dumping too much fuel at a quick full throttle that gets me. Cruising at 2000rpm or so and you hammer the gas, rpm drops, car lags, then picks up for the most part. Sounds fuel related for sure, but I can't figure out what other combination of parts to test.

Maybe I haven't found the right fuel and msd timing curve combo. Just too many combinations to test.

 

[Q1SVT]

Holley has always performed the best, but it's that lag which almost feels like it's dumping too much fuel at a quick full throttle that gets me. Cruising at 2000rpm or so and you hammer the gas, rpm drops, car lags, then picks up. Sounds fuel related for sure, but I can't figure out what other combination of parts to test.

Maybe I haven't found the right fuel and msd timing curve combo. Just too many combinations to test.

The lag could/sounds like an Accelerator Pump matter... A/F is going to be needed sometime, but pull a spark plug from each side and post picture

edited: might sound silly but check to make sure you have the right Firing Order...

 

[Cleveland Crush]

Pulling plugs for an exam (as stated by Q1SVT) is job one, other wise you are flying blind. Also you're heavy on the carb at 750 for your setup. May have to compensate with a bit more timing because that big carb may have a slow/delayed signal. Another request here for a couple spark plug photos.

 

[Sheriff41]

What do you have your base timing set at? If you have it at the factory 6° then you need to advance it 8-10° and tune from there. I agree with @Cleveland Crush on the carburetor sizing.

 

[boilermaster]

pjs2pc,
Agree 100% with what has been recommended here so far.
I would add, don't chase numbers on a timing curve unless you 100% know where TRUE TDC is, Ford balancers can and will slip as well as the pointer can be manipulated keep retarding timing until the detonation is gone (that will save your engine.
check your PCV system for proper operation and make sure that it is not sucking a bunch of oil causing the detonation, a leaking intake manifold gasket can cause the same, pulling in oil from the lifter valley.
You did not state vacuum or mechanical on the Holley, if vacuum, I like to know exactly what rpm the secondary's are just starting to open, too soon and you will get a lean bog, and if you are (all in on timing) possibly lean detonation.
I have found a hitch pin clip works well, placed between the stem of the diaphragm rod and the housing, just snug up the clip and start making passes, might be helpful to know what color spring you have .in there too.
You might be surprised what opening too soon adversely effects performance, if you hear the secondary's open, that is too soon.
Boilermaster

 

[boilermaster]

p3js2pc,
If you post a picture of your spark plugs, you might as well post one of your carb. list # from the choke air horn.
Current jet sizes and accelerator pump nozzle size and pump cam color
too please.
Boilermaster

 

[Hemikiller]

Pull the plugs and post some good pics. If they show signs of oil fouling, it could be a as simple as an intake gasket like Boilermaster suggested. I've had a leaking intake on a couple Cleveland engines, and it will cause detonation. Some aftermarket valve covers have no baffle below the PCV. Pull the hose from the carb and check for oil inside.

 

[steves73]

Have you tried octane booster just to see how it runs with the ping taken away? I have about 9.5 to 1 compression with my pistons and 2V heads, but have my advance less than I would like. I used to be able to get 94 octane, but sometimes only 91 is available (in Canada).

 

[boilermaster]

pjs2pc,
you state (cruising @ 2000 rpms} when you mash on the gas,
are you in high gear ? and if so does the transmission downshift ?
how does the engine perform in 1st and 2nd gears ?
Boilermaster

 

[pjs2pc]

First off thanks for all the advice, everyone. I'll try and get as much info as I can this weekend sometime. Kids and work interfere quite a bit.

Starting to lean towards a fuel delivery issue. The holley I have is a 750 double pumper 4779C. Memory fades why I bought that size. I did have a edelbrock 1405 600cfm carb on it prior. The edelbrock idles nicely, but if I remember right felt lean on the top end and maybe just through out rpm range. I still have it and will probably put it back on to confirm some things.

So the move was to the holley (probably should have went lower on the cfm). Holley was night and day when it came to power, but now it does have the hesitation.

With the holley, car will start and eventually idle on it's own. You can drive down the road and gradually increase throttle and no big deal. If you go full throttle (regardless of whether you're driving or the car is in park) it will hesitate/bog and then pick back up. Like I'm drowning it with fuel until it can catch its breath again. Top end loves the fuel (once it gets over its hesitation. This is where I messed with accelerator pump cams, discharge nozzles, jets, etc.

Anyway, I will check where I'm at now on terms of all settings and pull some plugs.

I manually shift the car and with 3.73s and the c4 first isn't much. So most of the time I'm in second gear and move to third when I need to. I can duplicate the bog in park in my shop, load on the road just makes it really noticeable.

 

[Q1SVT]

"Holley was night and day when it came to power, but now it does have the hesitation." psj2c...

With your build cam, 373 gears, high stall, I would keep a 750 carb. Either fix the one you have [accelerator pump?, couple of dollars] jets...

Let us know when you get time to check the other items.

 

[boilermaster]

pjs2pc,
Just looked up your carb o the Holley web site,
pri. jet 70, .028 pri. squirter 6.5 pv.
sec. jet 80 and .031 sec. squirter.
While I speak holley l prefer vacuum secondary's and don't know double pumpers very often.
both the jetting and power valve seem fine to me as a starting point but I find it alarming that Holley states that you have a .028'' primary and .031'' secondary squirters, this seems backwards to me.
I would suggest that (AFTER) you get your detonation under control,
that you recheck accelerator pump clearance at WOT for .015'' clearance with the pump lever fully depressed.
please check and verify the size and location of the squirters.
Someone may knock me here, but I think you need the .031'' in the front and the .028'' in the REAR !
If I am correct, this will at least get you going in the right direction.
my cleveland , 408 4 v needs .035'' primary with 370 rear gears and 5 speed manual.
you also need both cams in the # 1 position IMHO.
Boilermaster

 

[Don C]

With that camshaft your dynamic compression ratio is probably around 8:1, so that shouldn't be causing pinging. I don't have the cam specs, so this is a guess. I agree with the others, read your spark plugs, check for intake manifold leaks and other vacuum leaks. Make sure your carburetor isn't plugged up someplace. Make sure your power valve matches your intake vacuum. In other words, check all of the basics, then check them again.

 

[c9zx]

What Boilermaster said. Chuck "I would add, don't chase numbers on a timing curve unless you 100% know where TRUE TDC is, Ford balancers can and will slip as well as the pointer can be manipulated keep retarding timing until the detonation is gone (that will save your engine."

 

[will e]

While not crazy that's a fairly stout cam. And the rest of your build, including tranny/converter/gears, would indicate the college student you was after quick off the line performance. You mention it doesn't run correctly focusing on performance. How does it idle and cruise? What is your 'use case' for the car now? Are you looking for a daily driver, weekend fun, run what you brung or ??

Have you tossed a vacuum gauge on it to see what you are pulling? I don't know jack about edelbrocks and am barely a rank Amature on Holly's but you'll want to make sure your power valve is matched for your vacuum. Also, if it's been sitting a while you'll want to check that the power valve(s) are still good. I don't fiddle much with the double pumper but I think some have two power valves?

IMHO buying aftermarket heads is tossing a lot of money and an unknown issue. There isn't any reason why you can't get it to run pretty darn good with the current heads. Once you get to that point then consider if after market heads will buy you extra performance, not if they will solve your current problem.

 

[pjs2pc]

Alright guys, today was pull some info day. I didn’t test anything, but you’ll obviously see I was testing in the past. This info is how the car sits today.

Plugs were all pulled before I started the car up today so it’s what they looked like last time I ran the car. Let’s just say it’s not pretty. Pulled cylinder 1 plug. Fouled. Pulled cylinder 8 and it looked much better. So then I pulled more only to find more fouled plugs and also another one or two good ones. This is odd—makes me believe there is an intake issue or something.

Firing order is correct timing is around 15 degrees advanced at around 850rpm. I apparently have two different springs for the advance rate in the distributor—I was obviously testing everything at one point. The advance stop bushing is 0.350” OD. Not sure which color this is as the color is gone.

Now for the carb. Sorry, but I lied. Checked the jets I have and they are 64, 65, 66, and 67. 66s are in the carb. Which got me thinking so I doubled checked the list stamped on the carb. It is a 4777-7 which is a 650cfm double pumper, not 750. Which makes me feel better. I need to double check the power valve installed, but pretty sure it is a 2.5. I know I’ve messed with this before because I couldn’t get the car to idle. Vacuum with this cam is not very consistent at low rpm. Vacuum is about 10.5” at 850rpm. Might have to put the 5 power valve back in based on that. Discharge nozzles installed are both 31s. 28 seems to be stock as those are the other set I have.

I attached pictures and will post again with a video.

 

[pjs2pc]

Alright guys, today was pull some info day. I didn’t test anything, but you’ll obviously see I was testing in the past. This info is how the car sits today.

Plugs were all pulled before I started the car up today so it’s what they looked like last time I ran the car. Let’s just say it’s not pretty. Pulled cylinder 1 plug. Fouled. Pulled cylinder 8 and it looked much better. So then I pulled more only to find more fouled plugs and also another one or two good ones. This is odd—makes me believe there is an intake issue or something.

Firing order is correct timing is around 15 degrees advanced at around 850rpm. I apparently have two different springs for the advance rate in the distributor—I was obviously testing everything at one point. The advance stop bushing is 0.350” OD. Not sure which color this is as the color is gone.

Now for the carb. Sorry, but I lied. Checked the jets I have and they are 64, 65, 66, and 67. 66s are in the carb. Which got me thinking so I doubled checked the list stamped on the carb. It is a 4777-7 which is a 650cfm double pumper, not 750. Which makes me feel better. I need to double check the power valve installed, but pretty sure it is a 2.5. I know I’ve messed with this before because I couldn’t get the car to idle. Vacuum with this cam is not very consistent at low rpm. Vacuum is about 10.5” at 850rpm. Might have to put the 5 power valve back in

 

[pjs2pc]

Posting via your phone is not the easiest. The two videos before are in park, no load. But these issues I’m about to talk about are worse on the road. Might be hard to tell or see/hear, but there is off idle stumble--you can see it in both the videos giving light throttle to go from 1000-2000 rpms or so. I then give about half throttle pretty quick. This is when the engine hesitates then picks up and goes. If I were to give full throttle fairly fast and not let off, it would kill the engine. For example, I let off the throttle a little if I do a quick ramp up.

@will e The car has been like it is for awhile now. I just want to be able to enjoy driving it. The way it is not is not enjoyable.

Anyway, I enjoy the conversation and hopefully can figure this out sometime.