[steve25]

The block parameter's of the 403 are great, the dam heads flat out suck!
Believe me your comment on feeling like 360 hp is way generous!

[Mr Anonymous]

Pull the 4A heads and set them aside. Dead head gasket is not uncommon. Use a pair of #5, 6, 7, or 7a head (68-72 350 SBO), have the holes for the head bolts clearanced for the 1/2" 403 head bolts (350 are 7/16). You end up going from 7.9 to 9.5:1 compression. Bonus points if you install a 2.00 or 2.07 intake valve. It will run good, esp with a cam swap. They can run really well, just keep RPM down below 6000.

[STEELCITYFIREBIRD]

I would think diagnosing this engine would be first order of business

Inspecting valve train would be next up. IIRC broken pivot bridges are an obvious dead give away of trouble?

A relatively new rebuild, you may find unmatched parts were reused and wore rapidly on rockers, came loose, etc.

Once rockers are off for inspection and air test into each cylinder with thermostat housing removed to watch for air(cylinder pressure) going to cooling system would be up next.

Did this problem begin all at once?
Rapidly or slowly deteriorate?


Luke

[i4abuygto]

Pulled the valve cover - all inspected good so I ran the engine and all valves seem to be open and closing with proper tension on the rocker arms (none are loose). Aluminum rocker arm stands look good.
I think I can pull the head rather easily in the chassis after removing the header which is a PITA. I just replaced the exhaust gasket on that side a few weeks ago, so I should be good at it.

The Pontiac 400 engine I have on the stand should be a better performer (approx 425hp) so, I guess it is decision time on just doing the head work or swapping engines. I appreciate all of your advice. I think I have double and triple sets of brackets around here but I am not sure exactly what I have for brackets. My 67 WS engine is also out of my GTO as I am currently doing a frame off on that car. I should have plenty of parts to do the swap if the 403 torque converter, flex plate and 400 transmission will interchange as my GTO is a 4 speed.

I think what I will do is pull the head this week at some point and find out what is going on and see if I can just do the head work while engine is still in the chassis. If I have to pull the engine - I will probably do the swap.

Let me know your thoughts. - Thanks guys

[i4abuygto]

Here are photos of the valve train with cover off.

I will check the compression again before I start the work.

Any shortcuts or advice to pulling the head- I know I have to keep rockers and push rods in order and labeled. I will reference bolt and locations too.

[Schurkey]

Originally Posted by i4abuygto

Any shortcuts or advice to pulling the head-

Do all your diagnosis BEFORE you rip the head(s) off. Leakdown tests, cylinder-balance test, anything you'd want to know needs to happen before disassembly. I'm thinking in terms of the cylinders that run, but have low compression.

Originally Posted by i4abuygto

I know I have to keep rockers and push rods in order and labeled. I will reference bolt and locations too.

Wild Guess: The rockers and rocker stands won't be re-usable due to excess wear. Inspect a few, if they're crap...just scrap the whole bunch. Replacement "standard" rockers are readily available and not horribly expensive. Aftermarket roller, or roller-tip rockers are similarly available, expensive or VERY expensive or VERY Junk Chinese. When I wanted a set of stock rocker arms, I needed three sets of used arms to find enough good ones to make one full set.

Pushrods are more likely to be re-usable, but still need to be inspected at both ends, and checked for straightness, and to be sure the hollow center is not plugged.

Clean the bolts, use the proper lube and torque when reinstalling. Nothing wrong with the OEM bolts IF (big IF) they're in good condition.

Whatever heads you reinstall--make sure you have a GOOD valve job, and that all the valve tips are at the same height. Cheap valve jobs will have the tip heights all over the place.

When it was me, I had hardened exhaust seats installed. Others will disagree. I say that if your machinist can't install hardened seats properly, you need a different machinist.

Valve springs as appropriate for the cam. Valve seals installed properly. I don't have much use for valve rotators especially with aftermarket springs. You may need new spring retainers (if your heads even have them. Not all do.) The Olds heads I've seen have the rotator on TOP of the valve spring, which is bat-shiit crazy; the last thing you want is all that weight jumping up and down with the valve motion. Chevy puts the rotator under the spring, where the rotator weight doesn't matter.

Or just buy Edelbrock aluminum Olds heads, and have fun.

[Edit: Edelbrock heads don't fit small-blocks if you still have an engine-driven fuel pump. If you've got an electric pump, and the chamber CC is adequate for your compression...go for it.[/Edit]

[i4abuygto]

Schurkey,

Thank you for the great post and advice. I thought I would tell you what I know about the engine to help better diagnose the potential problems.

I appreciate all of you guys and your advice -
The previous owner did a performance upgrade to the 403 Olds, done by a known 403 specialist. Performance modifications to the heads, block and added performance cam and a rear end upgrade to 3.43 gears (or between 3.25 and 3.5). The engine ran strong when I purchased it and I was told that it was around 400hp but he had no paperwork to back it up.

This work was done many years ago but I was told it was driven every year but very little per year with an annual oil change and that he thought approx 15000 miles on the rebuild.

Did this problem begin all at once?
Rapidly or slowly deteriorate?

The engine seemed to run great when I purchased it.

Shortly after I purchased it the car started flooding badly (750 Holley carb). Seal went out on the primary needle / seat and flooded the engine. While I was diagnosing the flooding issue I dumped enough fuel into the intake to hydra lock the "now bad" cylinder with fuel. It didnt lock up while running - only while cranking with the starter. After pulling the plugs - that cylinder was full of fuel. I spun the engine over with all the plugs out, sprayed fogging oil in all cylinders to lube the cylinder walls and spun it over again. I than changed the oil - drove it approx. 25 miles and changed the oil again.

When filling with oil it took 8 quarts to get to the full line - stupid me thought the previous owner put an oversized oil pan in. I think I was running with 3 quarts too much oil for about 50 miles until I realized that it was blowing oil out the breather and burning off on the exhaust - alot of smoke.
So could the fuel hydra lock or the too much oil be what caused this?

I am hoping when I get in there that not too much damage has been done.

All cylinders have between 125 - 130 lbs except the two middle on the passenger side 0 lbs - last one on passenger side nearest fire wall 75 lbs - last one on driver side nearest fire wall 115 lbs

Once rockers are off for inspection and air test into each cylinder with thermostat housing removed to watch for air(cylinder pressure) going to cooling system would be up next.

What is the process with this - just spray compressed air into the plug hole with rockers off and see if I get air out the thermostat hole?

You all recommend different heads- I dont want to go big buck but better performance would be good.

Thanks guys - let me know your thoughts.

[i4abuygto]

Do all your diagnosis BEFORE you rip the head(s) off. Leakdown tests, cylinder-balance test, anything you'd want to know needs to happen before disassembly. I'm thinking in terms of the cylinders that run, but have low compression.

Is it easy to to a leakdown and balance test - is it done by pressurizing the cylinder?

[Mr Anonymous]

here's a tip for removing the head. leave the valvetrain intact, since you have stock stuff. The socket for the head bolts should be able to take the head bolts loose without removing the rockers. This way, when the last bolt comes out, the spring pressure and leverage will help push the head loose from the block.

[Schurkey]

Originally Posted by i4abuygto

Is it easy to to a leakdown and balance test - is it done by pressurizing the cylinder?

Leakdown test requires a moderate-to-large air compressor, and specialized equipment--the cylinder leakdown tester. Typically--but this depends upon the leakdown tester used--you'd push compressed air, regulated to 100 psi (static) into the cylinder. The tester measures the pressure (dynamic) and the difference is the indicated cylinder leakage.

At the same time, the operator is listening for the hiss of escaping pressure at the carb/throttle body (intake valve leakage), with NO indication permissible. Also at the tailpipe, (exhaust valve) with NO indication permissible. Inspect the coolant under the rad cap--NO bubbles or other indication of leakage permissible. Therefore, the only remaining leakage is past the rings, there will always be "some". You need the gauge of the leakdown tester to decide if the leakage is low, acceptable, or excessive.

Interpreting the indicated leakage is an easily-learned art form that requires some experience with the leakdown tester used; by testing similar known-good engines and comparing the indicated leakage. Anywhere from 2% to 40% can be "normal".

Given a choice, you want a leakdown tester intended for aircraft engines having a bore diameter of less than 5 inches. "Automotive" leakdown testers have no legal or "industry" standards to regulate the mechanism. Results, therefore, vary greatly.

By comparison, a cylinder-balance test is easier to do, requires common/inexpensive equipment, and is easier to interpret. Connect a vacuum gauge to manifold vacuum, or connect a tachometer, or both. Idle the engine. Take a 12-volt test light, and connect the lead to ground. The pointy end gets a dab of silicone grease, and is then slid BETWEEN the plug wire and the plug wire boot at the distributor end. (Not "into" the plug wire, creating a puncture) As the pointy probe connects to the metal terminal of the plug wire end, it grounds the spark to an individual cylinder. Note how much the vacuum or the RPM drops when that cylinder is disabled. Repeat for all the other cylinders. Any cylinder that DOESN'T drop the vacuum or RPM as much as the others is weak. Any cylinder that DOESN'T drop the vac or RPM at all is dead.

[STEELCITYFIREBIRD]

Originally Posted by i4abuygto

What is the process with this - just spray compressed air into the plug hole with rockers off and see if I get air out the thermostat hole?

You can do a full leakdown test if you have or can get the equipment and an adequate air supply volume available.

If your compression tester has a quick disconnect you can use that hose or modify plumbing to connect shop air to each cylinder, and listen for where it escapes. The water neck off will allow you to see the slightest amount of leakage(bubbling) to cooling system very quickly and accurately.

The fuel dumping adds a new possibilities as to possible problemS..

When did the misfire ( or any other problem )start?
Right after fuel dumping or after oil overfill, or a while later after driving etc..??

["QUICK-SILVER"]

Originally Posted by STEELCITYFIREBIRD

The fuel dumping adds a new possibilities as to possible problemS..

I've repaired Olds engines that had bent rods and broke pistons from hydrolock. And they all were from cranking with the starter

If that wet plug is soaked with oil instead of gas....

I would drain water out of the block, before pulling the head, to cut down on the mess that might interfere with seeing what's going on.

Clay

[STEELCITYFIREBIRD]

Originally Posted by "QUICK-SILVER"

I've repaired Olds engines that had bent rods and broke pistons from hydrolock. And they all were from cranking with the starter

If that wet plug is soaked with oil instead of gas....

I would drain water out of the block, before pulling the head, to cut down on the mess that might interfere with seeing what's going on.

Clay

I question was hydro lock from fuel, coolant... or both.
Verify if their is a breech from :
cylinders to cooling system.
cylinder to cylinder
major leaking to crankcase
rings to cylinder
( this may have been a rering... std bore)
I would always advise to drain the block when pulling heads too.

I go into an engine knowing exactly what I found thru testing, then look to verify of discount the diagnosis. Multiple problems not diagnosed make for comebacks. Ain't nobody got time for that!

[Sirrotica]

Now that the whole story comes out it throws a completely different scenario on what may have happened, and how.

If it were possible to dump enough fuel from a flooding carb to to hydro lock the engine, that may explaining the blown head gasket between 4 and 6, but because it's possibly blown just between cylinders no coolant is leaking. The low compression in 8 could still be a partially blown headgasket if 6 was the cylinder that hydro locked. Conceivably blown the gasket to 8, and 4.

Yes, a leakdown test will be invaluable before disassembly for diagnosis.

Thing being if in fact the engine hydro locked there could be a multitude of other problem, from bent connecting rods to fractured pistons and broken rings. The crank could even be fractured as well as flattened bearings. At this point no idea if the smoke was antifreeze, or oil.

Running the oil over full for any length of time could have a negative effect on the engine bearings too, as air is a damn poor lubricant. All depends upon how long the engine was run overfilled and what RPM was reached.

If it were me I'd be at the very least disassembling the complete engine and it might require a major overhaul if there was hydro lock involved, along with aerating the oil by the overfilling.

In the light of all the factors, the OP might save himself money and grief by swapping in a known good Pontiac engine.

If he were lucky and nothing major was damaged, it could be feasible to keep the olds engine, but I would want to completely disassemble the olds to ensure there aren't hidden damage that just a visual inspection might miss, I.E. bent rods, crankshaft fractures, along with block fracture as the bottom end of 403s aren't extremely strong to begin with. Magnafluxing the block and crank would be a good idea over just a visual inspection, but there is extra cost involved.

If it were my car, and my money, I'd go for the Pontiac transplant.

If memory serves me the frame mounts for a 403 and a Pontiac match up, you just need metal engine mounts for an Pontiac powered F body. A friend of mine swapped a 400 Pontiac into a 75 originally olds powered Omega, which has the same sub frame as a late T/A has. The frame mounts were in the same position for both engines. He said it dropped right on the frame mounts. I was pretty astounded that they were in the same position, but he said that it required nothing other than the proper steel brackets on the Pontiac engine. This is second hand information, so it may be correct, or it could be wrong, I've never verified it myself.

[i4abuygto]

All of you have been very helpful, thank you.
The hydro lock was fuel only- It was a surprise to me as the engine was running rough- seemingly burning off the excess fuel while running. At one point in doing adjustments on the needle / seat / float level I had the electric fuel pump on for just a few seconds and noticed the fuel running out the carb bowl vent tube flooding the carb. When attempting to start the engine turned 1/2 revolution and locked. I knew immediately what it was so I pulled the plugs to relieve pressure.

I had a 2004 3.8 engine in a Grand Prix hydro lock from antifreeze so I was familiar with the feel. That engine was fine with no internal issues after the install of a new intake gasket the 3.8 is still running good today

When did the misfire ( or any other problem )start?
Right after fuel dumping or after oil overfill, or a while later after driving etc..??

.

After flushing the engine with oil after the fuel hydro lock, the engine 403 ran strong, with no vibration or apparent misfire. The smoking started right after the oil overfill - approximately 50 miles driving with to much oil.

The hydro lock was in the second cylinder in from front passenger side which now has 0 compression.

I am working on getting the equipment to do a leakdown test.

[i4abuygto]

Verify if their is a breech from :
cylinders to cooling system.
cylinder to cylinder
major leaking to crankcase
rings to cylinder
( this may have been a rering... std bore)

Started to do leakdown test tonight and the gauge was not working correctly. I will recalibrate the gauges and attempt again later. When applying the air to the gauge and into the cylinder, it was hard to tell where the air was leaking to.

Pull the 4A heads and set them aside. Dead head gasket is not uncommon. Use a pair of #5, 6, 7, or 7a head (68-72 350 SBO), have the holes for the head bolts clearanced for the 1/2" 403 head bolts (350 are 7/16). You end up going from 7.9 to 9.5:1 compression. Bonus points if you install a 2.00 or 2.07 intake valve. It will run good, esp with a cam swap. They can run really well, just keep RPM down below 6000.

Where could one find a set of these heads - If I have to replace the heads 9.5:1 sounds alot better.

[Mr Anonymous]

Originally Posted by i4abuygto

Where could one find a set of these heads - If I have to replace the heads 9.5:1 sounds alot better.

they are not hard to come up with, Ive seen whole 68-72 350 Olds engines for as little as $250, but no idea on condition. Where are you located? I might be able to help.

[i4abuygto]

Mr Anonymous,
I am located Blaine, Mn - Northern suburb of Minneapolis, MN

[i4abuygto]

I did a leak down test tonight. The rear three cylinders on the passenger side are communicating, I believe thru the blown head gasket. The rear cylinder had approximately 80% leak down. The other 2 were 100% bad.

Front cylinder on passenger side- and front 3 on driver side all were within 10-15% leak down - I believe thru the intake but it was hard to tell. No bubbles in the water. The rear cylinder on drivers side had approximately 70% leak thru the exhaust- I would expect that is an exhaust valve issue. It didnt sound like any of the leakage was into the crankcase.

The other 4 cylinders (with good compression) I could not identify where the 10-15% leakage went- I believe intake.

I will start by pulling the passenger side head next week at some point and see what I have.

Thanks guys

Mark

[Schurkey]

Originally Posted by i4abuygto

The rear three cylinders on the passenger side are communicating...
...Front cylinder on passenger side- and front 3 on driver side all were within 10-15% leak down - I believe thru the intake but it was hard to tell. No bubbles in the water. The rear cylinder on drivers side had approximately 70% leak thru the exhaust...

...I will start by pulling the passenger side head next week at some point and see what I have.

If you're sure about all this, you need to pull both heads.

If you've got leakage through either the intake or the exhaust valve, you need valve/guide work.

There is ALWAYS some leakage past the rings. Surprised you didn't hear that at the oil fill opening or other crankcase vent.