Hi guys!
Better bite the bullet and admit that I suck as a mechanic.

I have installed #6 350 heads on my 403 powered Trans Am.
Some basic information on the build:
Heads milled to reach a calculated 9.5:1 static compression.
Untouched stock pistons and rings. Compression test show 170-180 PSI on all cylinders, leak-downtest is also done which show that the cylinders are sealing good.
New Edelbrock Performer 2711 installed with 350 turkey tray gasket and rtv on both sides of ports.
Comp Cams XE262 cam and Magnum roller tip rockers, pushrods lengths matched with adjustable pushrod length checker. Valve lash has been checked at least twice, not tight, 0 lash + 1/4 turn.
Cam was in the engine before the head swap, roller tip rockers are new. Cam is checked with indicator clock, shows .296" lift at lobe, Comp advertise .297", so cam should be fine.
Ignition advance is checked a 1000 times, I have it currently at 18° initial, 10° vacuum advance and 14° centrifugal. Anymore, and it will ping.

It runs fine in idle, vacuum is at 13 in/hg, drops to 10-11 with trans in gear. If I flip the throttle "heavily" when standing still and release it, it will stumble and die coming back to idle. If I drive it in 1500-1900 rpm, it sounds like it has a misfire or a large vacuum leak (can't find any vacuum leaks spraying starter gas around vacuum hoses).
At WOT, it feels weak, lacking something. Definitely not as strong as I expected, actually no improvement from stock. It's much easier to do a burnout from stand still though. Spark plugs are whiteish ash grey. R45S AC Delco
I was pretty sure that it was running lean, so I got hold of #75 and #76 main jets to try to richen up the Q-jet. But that plan died when I took off the carb yesterday and found oil in the intake?
I wiped it clean today, and was going to try running it again, but this time with the PCV hose into a bottle instead of the carb. That's how far I got today, because the old steel fuel line had enough and decided to start leaking.
But what else than PCV can put oil in the intake, right under the carb? Could the Performer intake be bad or cracked, and leak/suck air and some oil from the lifter gallery? That would explain the rough/lean running too?
Doubt it's brake fluid, booster and brake cylinder is new (ish). Oil is not red, so not trans fluid.

If some more background is needed, here's the thread I started about this build: https://classicoldsmobile.com/forums/small-blocks-3/tips-pointers-403-build-6-heads-needed-134173/

 

As I said my 403 carb ran like pure garbage until the retune. It ran fine before bumping the compression from 7.9 to 1 to 9.6 to 1, kept the same cam like you did. It may be a vacuum leak or it may not be. My intake is leaking oil past the gaskets on top of the intake but no vacuum leak.

 

Do you have stock baffled valve covers? Some have found increased oil thru the pvc w no VC baffles

 

Thanks for the reply Olds 307! Yes, I know you said that, I have tried to talk to the guy in Sweden who restored my carb to get some tuning help, but quite frankly, he's an *******. He makes you feel like an idiot on purpose and he blamed the XE cam for all of my problems, and sent me on a wild goose chase with setting the ignition like this and that, and measuring vacuum high and low and never telling me why, just that my cam was ****.

I have also tried calling Cliff Ruggles with no luck.
I have managed to find out that the stock 403 Q-jet has #74 main jets, and 52B primary metering rods? Is this correct? Would it be advisable to enrichen it by putting in larger jets? I have purchased #75 and 76 as I said.

My intake seems tight at the gasket, the oil is collecting inside the plenum/runners (see photo). 1st photo is dark, but you can see the oil. 3rd photo is after I cleaned most of the oil up, but look at the right corner of the runner, looks porous?

 

X2? Was there oil in the port where the PCV connects to the carb? Disconnect your PCV and plug the port.

 

I have stock valve covers. I have put in a new oil pump though, and have a few more psi of oil pressure than before. A Pontiac guy told me that 403s are notorious on pumping a lot of oil up to the heads, and that some people building them put in oil restrictors to reduce the flow to the heads in order to bring more oil to the bearings?

 

No, I didn't notice any oil there, and not a single drop from the hose today, from being disconnected overnight.

 

If you didn't get the turkey tray bosses into the holes they drop in it would create a vacuum leak and a coolant leak. Did you put rtv around the water and intake ports?

 

I'm 99.9% certain it's in place, the heads are milled .055 which made the intake bolts drop in with zero margin. Intake isn't milled, so if the turkey tray wasn't in place, I couldn't have fitted the bolts.
Yes Sir, RTV around coolant and intake holes, on both sides just as the instructions says. I didn't use the rubber end seals towards the block, only a tall bead of RTV.

 

That does sound like a stock 403 carb. I think it is more the super lean idle calibration on these carbs that was the main issue. Ken at Everyday Performance did a minor rod change but I had changed the jets to 72 from 73 and it had 44K primary rods, he changed it to smaller rods. The richer jetting may help but unless the idle circuits were modified, it will still run terrible. The bog could be the secondary air door set too loose. It does sound like a lean misfire or pinging. How old are your ignition parts? That amount of oil is minor in my books.

 

Buy a wideband and stop guessing.
Your Intake should be cut as needed, and squared up at the same time. That will alleviate that variable.
Next would be to verify the oil, is there any on the back of the valves? You can check that when you remove the intake to check alignment etc.

 

I will try the richer jets, I would be happy if it ran fairly okay, just so I could be sure it doesn't run so lean that I get damages from it. The Swedish guy who did my carb said though that the idle circuit was "generously calibrated", don't know what he meant by it though,
I did one change when we did the leak-downtest, spark plug gaps was very tight, only .030, so I opened up them to .045. I do think it sounded a little better after that, but I didn't have time to do any more testing that day. I have been thinking about buying a wideband afr gauge as cutlassefi suggests.
I don't want to say I have a "bog", it does respond to the pedal and doesn't fall on it's face, it's more like it's sucking a lot of air (air inhaling sound is significantly more noticeable) but engine performance doesn't correspond.

My distributor is *probably* the stock one, it has an Accel performance coil, you know, the grey round type on top of the distributor lid, and Accel ignition module, I have no idea how old the Accel parts are since they were on the car when I bought it 9 years ago. Weights and springs are new, so is the vacuum can. Spark plug wires are maybe 5-6 years old, so is the dist lid. No arcing inside the lid, no visible arcing under the hood either.
I have checked ignition function over and over with an dial back induction gun, and it is consistent, full centrifugal advance comes in at 3200 rpm.

 

Thanks for your input cutlassefi! I have been looking at wideband lambda gauges actually, but was thinking it was an unnecessary expense since I'm planning for an Holley Sniper setup this winter. Maybe I should just do it and then sell the afr gauge setup used when I get the EFI...
I'm not sure what you mean by "is there any oil on the BACK of the valves"? By "back", do you mean looking at the stem of the valve through the intake ports on the heads, or under the valve cover where the valve springs sits? I can tell you that the valves looking through the intake ports on the old 4A heads was very greasy, but that is maybe normal?

How do I determine how much is needed to mill off the intake? Or is it just "take a little, test fit, and take more if not enough? By" square up", do you mean aligning the sides so they are parallel and in 45 degrees angle?

 

Thanks for all the replies guys! I appreciate it! Hope you don't think I talk too much, just trying to provide as much information as possible.

 

A lot of out of box Edelbrock intakes are not straight, it may need cut. The Sniper sounds like a timely upgrade.

 

Hi again!
Well, after having put the #76 main jets in the Q-jet, it finally seems like the engine is happy! Sounds and run a lot better. It finally even reacts like a normal engine if you pull off a vacuum hose, and raises idle! The stumble when it comes back to idle from a Rev-up is still there, but not as significant.
I have ordered a wideband lambda, hopefully it will arrive by Friday, and I will start finetuning. Should I put the sensor in the X-section on my exhaust, so it picks up both cylinder banks, or doesn't it matter?
Took off the PCV hose to the carb and put a breather filter instead. The other side is still connected to the air filter housing, it has some visible fumes coming out of it, looks kinda like a humidifier on low setting. Does not seem to be excessive pressure. Should I install a PCV breather with a catch tank, or just put a breather filter on drivers side too?

 

Oh, forgot to mention, I broke the fuel line last time I wrenched on it, been struggling to get couplings for a steel braided fuel line with AN-couplings to replace it. That damn thermostat housing is in the way! Ordered the shorter fuel filter housing today from a carb company in Stockholm, that will solve the problem. Does that pose any problem, with a shorter fuel filter?

 

The wideband kit:

 

Are you running the filter in the housing? If so, those are restrictive, replace it was a 3/8" inline filter.

 

Isn't the filter supposed to be there, to act like a check valve?

 

Eh, I removed the in-carb fuel filter on my car back in the 1980s and installed an inline fuel filter. No issues, so I suspect it's not really necessary.

 

You're right, I was thinking backwards because of the spring and gasket on the filter. I understand now that the spring is there to allow the filter to move off the seal and let fuel in, even if the filter is clodded.

 

Use a bit of rtv at the water ports, but not at the fuel/air ports. Gasoline eats rtv.

 

I use Permatex Aviation sealant around the intake ports.