Still struggling with white smoke fuel smell from exhaust

[crazzmc]

Hi guys,

Still struggling haven’t shown a mechanic yet. I did a compression test (dry only) 109-119 on each. I did a combustion leak test (no problems at all didn’t change colour). I just plugged in a Vacuum gauge on 2 different ports on my Holley carb, one was reading super low so I did it on the other one at the lower left underneath the front float and these are my results (I couldn’t even see much change when turning the screws an 1/8 at the time cause it was shaking so much):

Idling in Park:

https://youtu.be/PCTuSxt_Jfs

https://youtu.be/PCTuSxt_Jfs[/video]


In Drive:

https://youtu.be/1sG9Kgp3icE

https://youtu.be/1sG9Kgp3icE[/video]


Smoke from exhaust (fully warmed up water on ground cause I hadn’t started it in about 2 months let it idle for 10 mins before the clip was recorded.):

https://youtu.be/u2lWOeCeK18

https://youtu.be/u2lWOeCeK18[/video]

In the video it’s set to 2 turns out.


When I was setting my mixture screws the smoke was pretty consistent (when it forced the idle up it smoked a bit more).


Im at the point where I think I just need to find a good mechanic.


302 with a C4 Automatic

Holley Carb (I think it’s a 750)

Any advice before I throw in the towel? Much appreciated.


Thanks,
-Crazz

[The Bandit]

The white smoke looks to me to just be water vapor left over from the combustion process which is normal for most vehicles.This time of year the cool damp air is going to cause this more often than the dryer air in the summer and fall times.

The fuel smell is probably the carb just loading up from sitting there idling. It happens a lot with our carbs.

[crazzmc]

The white smoke looks to me to just be water vapor left over from the combustion process which is normal for most vehicles.This time of year the cool damp air is going to cause this more often than the dryer air in the summer and fall times.

The fuel smell is probably the carb just loading up from sitting there idling. It happens a lot with our carbs.

Problem is whenever I drive same thing. I stop at a light cloud of smoke. Fuel smell starts seeping in. The only time I can get away with it is on the highway. Whether its idling, a 10 mile drive, or a 50 mile drive every time it smells.

[Ranchero50]

What's the rest of the engine combo? Exhaust note says cammed. 750 cfm on a cammed 302 with a C6 seems way too big, especially if it doesn't have a loose convertor. White smoke shouldn't be a big issue in Connecticut during the winter. Rich smell from the 750 trying to cover a vacuum problem from the cam and low compression. Ditto low vacuum. Cam needs RPM to generate vacuum. Should be idling around 1k out of gear, 800 in gear. If it pulls too hard you have the wrong convertor or engine combo (cam and compression).

Seems to be a classic incorrectly built engine for the rest of the truck.

So, less cam, less carb, for better economy and driveability or more compression with a looser convertor for less economy and driveability but more smiles per mile.

What do you need verses want?

[crazzmc]

What's the rest of the engine combo? Exhaust note says cammed. 750 cfm on a cammed 302 with a C6 seems way too big, especially if it doesn't have a loose convertor. White smoke shouldn't be a big issue in Connecticut during the winter. Rich smell from the 750 trying to cover a vacuum problem from the cam and low compression. Ditto low vacuum. Cam needs RPM to generate vacuum. Should be idling around 1k out of gear, 800 in gear. If it pulls too hard you have the wrong convertor or engine combo (cam and compression).

Seems to be a classic incorrectly built engine for the rest of the truck.

So, less cam, less carb, for better economy and driveability or more compression with a looser convertor for less economy and driveability but more smiles per mile.

What do you need verses want?

So I’m pretty sure it’s tight because it rolls in drive. I never had a tach on the truck until I installed it a few months back. At that point it always idled around 800 ish.

All I know is the previous owner told me that the guy he bought it from wanted to turn it into a “race truck”. Idk why it was an automatic if he wanted it to be a race truck but I guess that’s besides the point. He gave up on the project and sold it to the previous owner exactly the same how I received it.

Honestly right now I want a truck that doesn’t smell of fuel and doesn’t smoke up 24/7. I also am inexperienced with so that’s why I haven’t opened anything up yet.


I can play around more with the air fuel mixture and isle to get it up to 1000/800.

I guess by your recommendation start off with a smaller carb maybe a 650 or a 500 and then work from there? Thanks for the insight.

[sargentrs]

First make sure your carb is set properly. Adjust your air/fuel mix to highest vacuum. When yiu remove the vacuum advance hose always plug/cap the ends. Here's a decent video
https://youtu.be/X0uEMeDVxaA
Next, check your float adjustment.
https://youtu.be/LKEonVeOXco
A 750 cfm carb is way too much for a stock 302. Even if it was a performance built engine. Stock would have been around a 350 cfm. 500 cfm is tapping the hugh side.

[Ranchero50]

Ditto. Also post up some pictures of the engine bay. From the video it looks like you distributor is in wrong and there's probably a couple other little things that will be obvious to those with more experience.

For tuning what you have now, do what's needed to make it run as efficiently as possible. Get a hot spark at the correct time and let it burn as lean as it'll idle well. The problem with the cam and compression combo is you don't have much vacuum at idle so it needs more fuel to idle smoothly, thus the stink.

[71cc]

If you find the list number on the airhorn it will tell you what size carb. The early 1850 iirc are a 600 with leaner calibration. Jet sizes alone will not cure rich idle and transition mixtures. Having a vacuum advance will allow a leaner idle too. That also will help vacuum 1-2" .

[crazzmc]

First make sure your carb is set properly. Adjust your air/fuel mix to highest vacuum. When yiu remove the vacuum advance hose always plug/cap the ends. Here's a decent video
https://youtu.be/X0uEMeDVxaA
Next, check your float adjustment.
https://youtu.be/LKEonVeOXco
A 750 cfm carb is way too much for a stock 302. Even if it was a performance built engine. Stock would have been around a 350 cfm. 500 cfm is tapping the hugh side.

I did try and my results are posted in the few video links I posted above. The gauge literally bounces back n forth rapidly and adjusting with 1/8 - 1/2 turns doesn't honestly do much.

Def agree that the 750 is way too big, I think I'm going to look for a 500 cfm to put on and test for a bit.

Ditto. Also post up some pictures of the engine bay. From the video it looks like you distributor is in wrong and there's probably a couple other little things that will be obvious to those with more experience.

For tuning what you have now, do what's needed to make it run as efficiently as possible. Get a hot spark at the correct time and let it burn as lean as it'll idle well. The problem with the cam and compression combo is you don't have much vacuum at idle so it needs more fuel to idle smoothly, thus the stink.

Here's my engine bay I also have more pictures posted at the link below:





http://www.fordification.com/forum/view ... 96#p741196

If you find the list number on the airhorn it will tell you what size carb. The early 1850 iirc are a 600 with leaner calibration. Jet sizes alone will not cure rich idle and transition mixtures. Having a vacuum advance will allow a leaner idle too. That also will help vacuum 1-2" .

https://www.holley.com/products/fuel_sy ... s/0-80508S- This is my carb

[Ranchero50]

Get a working PCV system. Shouldn't make a huge difference but it might.

[sargentrs]

Know if that's the original motor rebuilt or did someone swap in a newer motor? I ask because I noticed your timing is the newer 1981+/351w firing order instead of the original 1968 302 timing.

[RottenAppleRed]

Double check your firing order. It needs to be cam appropriate. The 302HO uses the same order as the 351W/C/M engines. All other 303s are the standard Ford small block order.

What did the plugs look like when you pulled them for the comp. test? Speaking of plugs, are they correct for the HEI unit...and gapped as such?

That carb is WAY too big for your engine. Not to mention the fact that they are prone to internal and external leaks. If there is no power valve protection and you've had a backfire, the power valve diaphragm is likely blown and causes a full rich idle. In this condition, the adjustment screws do nothing.

Your vacuum is very eradic. Start by eliminating any vacuum connections to the engine (brake booster etc.) Then run it with the gauge for results. Based on how it runs while driving down the road, in its current condition, I'm guessing the valves are too tight. I'd like to know what rocker system the engine has.

The fact is...there are so many variables that can cause erratic vacuum. The rich condition can be connected or completely separate.

[crazzmc]

Get a working PCV system. Shouldn't make a huge difference but it might.

Will do sir.

Know if that's the original motor rebuilt or did someone swap in a newer motor? I ask because I noticed your timing is the newer 1981+/351w firing order instead of the original 1968 302 timing.

I believe its a late 70s early 80s motor. It was apparently rebuilt by the owner before the previous. It has ~5300 miles after rebuild. Transmission I'm assuming was also rebuilt or at least assembled by the same person because the crap job done sealing the valve covers is the same on the trans pan gasket.

Double check your firing order. It needs to be cam appropriate. The 302HO uses the same order as the 351W/C/M engines. All other 303s are the standard Ford small block order.

What did the plugs look like when you pulled them for the comp. test? Speaking of plugs, are they correct for the HEI unit...and gapped as such?

That carb is WAY too big for your engine. Not to mention the fact that they are prone to internal and external leaks. If there is no power valve protection and you've had a backfire, the power valve diaphragm is likely blown and causes a full rich idle. In this condition, the adjustment screws do nothing.

Your vacuum is very eradic. Start by eliminating any vacuum connections to the engine (brake booster etc.) Then run it with the gauge for results. Based on how it runs while driving down the road, in its current condition, I'm guessing the valves are too tight. I'd like to know what rocker system the engine has.

The fact is...there are so many variables that can cause erratic vacuum. The rich condition can be connected or completely separate.

Some plugs were sooty and some were oily. But honestly I don't remember what I gapped them at but I believe it was around ~.32. I did a bunch of research and the previous plugs were gapped the same. I'll double check tomorrow. I'll also pop open the valve covers and take some pics for you guys.

[Ranchero50]

Yeah, there's a lot of wonky going on there but we'll figure it out. Wonder why the starter solenoid is back on the firewall? I assume so the starter wire is run behind the headers instead of under them. Just kind of wonky.

Sarge, good eye on the firing order. Dizzy needs clocked but that's not a horrible issue unless they can't get the timing correct.

Rotten, forgot about the PV issues on the Holley's. Thought they put the blowback prevention valve in the newer ones.

Spark plugs should be evenly colored. Oily is an issue. PCV system should help the crankcase run cleaner.

[RottenAppleRed]

After my post, I saw that you have a newer Holley with power valve protection. Either way, the carb is too big.

When GM switched from points ignition to the HEI (high energy ignition) unit, they also changed the spark plug resistance and gap. HEI plug gap should be around .045", while points are typically around .035". You might look into plugs for a '78 302. Ford used the duraspark ignition...which is similar to the HEI. You may have to go up or down in heat range, based on compression ratio. The stock plug would be a good starting point. This all depends on your heads. If they have the gasket type plugs or tapered seat plugs.