I noticed from some of the replies that folks may not have seen the info below:
With the above work performed, the compression ratio is likely above what was mentioned in a few posts. Would need to know piston-to-deck clearance and head chamber volume to accurately calculate the CR but it could be as much as 10.5:1.

 

Let me clarify: they put them on the decking machine to "clean up the surfaces." Instead of just putting a straight edge on them, he made a pass over them to make sure that the heads and block deck were true and flat. I was worried about changing push rod geometry, but he took so little material off that the original push rods still were within tolerance for length when he did the mock up for me.

 

Ran some tests and am no closer to having an answer. I rerouted the vacuum advance to the manifold and put a piece of timing tape on it to mark 36 degrees. At 2500 rpm, it's now dead on the mark. I put a pressure tester on it and it held 13 psi without leaking down.

I ran it without the cap to try to do the block gas test and the water wouldn't settle down enough to not interfere with the sampler. The water was humming right along, but when I revved it, it became unstable, dumping a bit out of the filler neck.

I put the cap on and ran it at 2500 to see what the temps would do. It slowly climbed past 180 to 190, to 200, 210 and finally crept to 220 when I decided to punt.

After about 15 minutes, I put a big towel over the cap and popped it. When it settled down, I put the gas tester on it and cycled air and steam for 5 minutes without the fluid turning color. It stayed blue, hopefully indicating that it's clean.

The timing marks stay steady at whatever spot they're at for whichever RPM - no dancing or wavering with the light on.

Unless it's the radiator (too small), I'm stumped.

 

Next test: timing at 18 degrees, idling, let it just sit there. It came up to 215 degrees and hovered right there.

New thought: this thing won't idle smoothly. Not like a cam lope but an unsteady surge of about a hundred rpm. Like it's stumbling then good, stumbling, then good. Almost like a blower, but much less pronounced.

Vacuum readings at 800 rpm taken on the manifold are fluttering very rapidly, but by only a fraction - it's just not smooth. As it surges, vacuum goes between 15 and 17 inches.

And the rich fumes are burning my eyes. It won't really react to idle mixture adjustments.

I'm wondering if the push rods aren't too long, causing the bad idle, rich fumes, and overheating.

 

You need to adjust your idle speed back down to where its supposed to be. Make sure the vacuum advance is disconnected. And then try and adjust the carb. Just remember that your distributor timing curve is not set up for that much initial. The engine may ping (a lot).

 

That's no different than what I've done. And it won't refire with that much initial timing. I just wanted to see if the temp would hold steady or just climb no matter what.

 

[QUOTE=Racer24ksi

I ran it without the cap to try to do the block gas test and the water wouldn't settle down enough to not interfere with the sampler. The water was humming right along, but when I revved it, it became unstable, dumping a bit out of the filler neck.



Unless it's the radiator (too small), I'm stumped.[/QUOTE]


It sounds like you seen good flow through the tubes while on high idle if I read this correctly.
It will push coolant out the filler neck when revving and once you let off the high idle with the cap off.
You just neeed to top the rad off and put the cap on after you see coolant flowing good through the tubes on high idle. The over flow will just push out either in a overflow bottle or on the ground,depending if you have a closed or open system once you turn the car off with the cap on tight.
You could try a 3 or 4 row, or an aluminium rad, but at this point I don't think you have any issues with the water pump, t-stat not opening or rad itself.
You could put the heater on defrost and blow heat out, this will help it cool if you feel as thou the rad may still have an airlock or your questioning flow.
I think the guys that are asking about your engine clearances and timing would be more the problem than the rad and cooling system JMO.
I hope this helps
Cheers
Eric

 

I had issues with the Mr Gasket high flow thermostat but it was more at speed. Pull the thermostat, worth a shot.

 

I havent ran a thermostat in years. Car runs nice and cool on hot days on on really hot days it will only hit 210 at lights.

 

My setup isn't much different from yours. I'll be experimenting with a more radical advance curve today - 18 degrees at idle, where the engine is starting to display a little kickback from the starter, 32 degrees total due to relatively high cylinder pressures, and limited vacuum advance as most have way too much.

Manifold vac to the vac unit.

When does your car overheat? Idle or cruising or both? At idle you adjust your mixture to quench the heat, advance the timing to 16-18 BTDC, and switch to manifold vac for the distributor. Combined, that will solve idle boiling.

 

I don't know what's really going on with his car, as I haven't seen it and internet diagnosis is tricky at best, but note that he said earlier that it smells pig-rich, which to me points more to timing than to mixture as the chief driver of overheating.

- Eric

 

I ran two scenarios last night:

The first was at a cruising RPM and 36 degrees total advance. The motor climbed steadily to 220, albeit slowly, but never showed signs of stopping the path to overheating. I didn't want to risk it, so I shut it down.

The second was at idle, sitting at 18 degrees advance at low RPM. The motor climbed to about 215 but stayed there.

My other clue is the fluttering vacuum needle. I could feel the gauge pulsing in my hand when it was doing it.

I'm seriously thinking about looking into valve lash next. The machinist told me before I started it for the first time that loose valve lash will clatter and tight valve lash will give you a poor idle. It might be that it's loose enough to run, but tight enough to keep the valves from seating right.

Any amount of recutting valves, recutting seats, surfacing the block and surfacing the heads will net thousandths that could have made the original push rods a little too long. Even though the one or two that they checked might have been within tolerance, when it all heats up, maybe it's just too close to the outer limit. And now I see that they sell girdle shim kits for $15.

One last thing: I noticed my Chassis Service Manual shows a 3-core for AC applications. I have an A/C, but haven't charged it yet. I probably need a different radiator anyway, but I want everything to be RIGHT.

Bill

 

Do a compression test to see whether you have any signs of valve leakage.



I agree that you will need a bigger radiator, but a 2-row radiator should be adequate to cool your engine at idle or when racing the engine in the driveway.

It would show its inadequacy on the highway or on long uphills.

The particular radiator you have may be conducting heat poorly, or your engine may be making more heat than it should, such as from being too far retarded, or maybe leanness in a few cylinders, say from manifold leaks.

- Eric

 

So how did you guys figure valve lash with the stock rockers ?. Did you check for pushrod length? To make sure that the lash was good.

 

Valve lash is something you check on solid flat tappet cams. With a hydraulic cam you are checking for preload. "Valve lash" indicates clearance, preload indicates no clearance.

For hydraulic lifters and stock rocker applications, I use a wire gauge to measure the distance between the clip in the lifter and the plunger itself. You want to shoot for .020"-.060" if I remember correctly. It's been so long since I did this.

You need the intake off to check this.

Also, as mentioned before.....the speed pro forged piston needs extra clearance. The instructions say one thing, so if they were setup per instructions they are too tight. You should really ask your machinist what he set up the piston to wall clearance at. Just for piece of mind.

 

I corrected myself a couple of times on this - I misstated: they are Sealed Power, not Speed-Pro. I do not think they're hypereutectic and do not require additional clearance due to heat expansion. Regardless, the machine shop had the pistons and specs in their hands when they bored the block. I'm not seeing evidence of anything seizing. The oil is still a pretty golden yellow. And for that I used Comp Cams break-in oil. I wasn't about to melt down a cam lobe during break-in.

I personally did not check the preload (I'm using the term "lash" generically). The machine shop did a mock-up and said that it measured within tolerance. When I did the assembling, I just tightened everything down.

I've read some things about the valve lash being too tight, resulting in backfiring. Even though it's not exhibiting obvious symptoms, the valve train may be too tight anyway. I know on the Chevy's when you overcrank the rocker arm nuts, it will still run but not great. Maybe this Olds is in that zip code - tight enough to be a problem, but not too tight to be ugly.

 

If they are Sealed power, they are not forged and probably big dish cast, which means maybe 8 to 1 compression. Big difference.

 

 

Those are forged flattop pistons I belive the F designation on the piston part number indicates to that. And they are speed pro.

 

From Summit:


Federal Mogul Premium Engine Rebuild Kits CSMHP820-300

Aluminum Forged, about 9.6:1 based on 70cc chambers. I don't know what the 7A's volume is.

 

Yes, those are the pistons.

 

Agreed, L2320F forged pistons.

Sealed Power and Speed Pro are both Federal Mogul companies and the pistons are listed as either one depending upon the retailer's web site.

Here's a picture from the Federal Mogul web site showing both names on the piston box:

 

The side skirts had that same black "paint", which I assume is an anti-galling coating. But, maybe it's nothing more than marketing.

I ordered shims today to have for the weekend. They're inexpensive enough and I'd rather have them in my hand in case I have to go that route. I'm also looking into radiator options for either a 3-row repro unit or recoring mine locally. I believe this 2-row should be keeping up with me in the garage, so I'm still looking for the bigger problem, but when I DO get it fixed, the A/C and Louisiana heat and humidity is going to mandate that 3-row unit.

 

I agree with the 3 row once you get it up running with A/C . You could also go with a 2 row 1" tube Be-Cool rad , they are a little pricey but very good flow.
I have one in my 76 cutlass supreme and I'm more than happy with it.
You have lots of help here and suggestions to get you going with your engine tweaks, I'm learning a lot from your thread.
Its never easy diagnosing engine issues over the web!!
I still shake my head in awe, how these guys always come through and help out here in an instant.
Cheers to all!!
Eric

 

Won't the increased thickness of the felpro head gasket make up for the slight milling of the head and deck as well as cutting the valves?

 

That was my thought.

 

Generally, yes, but it sounds like in this case very little material was milled off, so the head is probably sitting slightly higher than its original position.

That being said, the acceptable lifter preload range is quite wide, and it is very unlikely that the ~0.010"-0.020" height change would make a functional difference.

Even if it did, the difference would be one of the valves not opening wide enough, thus not allowing as much mixture into the cylinders, thus creating less heat.

- Eric

 

Just get a set of adjustable rocker arms. A kit like this will resolve all your geometry issues:
https://www.summitracing.com/parts/c...ake/oldsmobile

Shims will only work as well as the valve job was done. If all the seats were cut to different depths, you'll never get it right without adjustable rockers.

 

Just the opposite of what the OP was suspecting.
Is the air flow though the rad good or is it restricted due to dirt or bent fines or??

 

Everything on the car is essentially new, refurbished or rebuilt. The radiator was tanked and pressure tested. If there are any clogs, they managed to escape the process and would have to be on the bottom of the core because I can see strong flow on the top. The fins aren't mangled and the few flaws that are there are much less than I've seen and lived with before.

So we know that the water pump is pumping, the thermostat is opening and allowing good flow, I've got no pressure losses in the cooling system, no detectible exhaust gasses in the coolant, and the timing isn't retarded. I've adjusted the idle mixture screws from one end to the other, same result.

In case anyone is interested and is on Facebook, I have a page for the project here:

https://www.facebook.com/Dream-On-71...?ref=bookmarks

There's a video of the ignition test before we started it the first time and then another video once we started it for break-in.

Bill

 

You have forged speed pro flat top pistons. Ask your builder what he set the piston to wall clearance at. It is a mistake that happens with shops that have been in business for 4 years or 104 years. Once you know, and it is within acceptable tolerance, we can move on.

 

Yes, this question has been waiting to be answered since the beginning of this thread...

- Eric

 

I will ask. In fact, I saw him walking his dogs last night and chatted with him about the whole deal. He has some intel on the radiator shop that I used and it doesn't sound good. I may not have got what I bargained for through them. He referred me to another shop that I spoke to yesterday and they said that if the radiator wasn't disassembled, then there really isn't a sure fire way to clear out any mineral build ups that may be within the core. He quoted me $325 for a brand-new 3-row brass and copper unit that has the correct size tanks. Knowing that I need that for A/C, I'm going to order it. It may be all of my problem or not.

Regarding the pistons:

When I received the block after machining, I checked every bore for ring gap. I inserted compression rings in every bore and measured the end gap with feeler gauges. Every cylinder was right on the money for what the piston's papers said they should be.

I think this should satisfy the questions about piston-wall clearance if everything came as a kit and the ring end-gap was measured to be correct.

 

I'm not an engine builder but I see a problem with your assumption that everything is correct.

You need to know what the piston wall clearance is by direct measurement.

 

Piston to wall clearance is measured by first measuring the piston with a micrometer on the appropriate spot depending on the piston. Once you have that measurement you set up a bore gauge to the size you have on the micrometer. The bore gauge will then let you know how much actual clearance you have between the cylinder wall and piston itself.

This is very important with speed pro flat top pistons for Oldsmobile because they list the piston to wall clearance on the box at .002-.0025" (I forget exactly, but it is too tight).

So, your machinist could be the very best, but if he set it up as to what speed pro recommends, you will have issues. This is very common with Oldsmobiles, and I cannot figure out why Speed Pro won't change that spec in their instructions.

I am not speaking from hear say either, I have seen the first hand results from two Oldsmobile engines set up too tight, and had the exact symptoms you are describing. One of the engines came from a shop that is well known locally with decades of experience.

Measuring ring end gap does not give you the piston to wall clearance. If the rings are perfect in a 4.087" bore (.030 over 350 size) and the piston skirt measures 4.085" you have .002" clearance. Now, the same situation but the piston measures 4.083" you now have .004" clearance and the ring end gap is exactly the same. Heck, take it to the extreme.....put a 4.055" piston in there and now you have .032" clearance but your ring end gap is still perfect.

 

[QUOTE=Racer24ksi;965958] He quoted me $325 for a brand-new 3-row brass and copper unit that has the correct size tanks. Knowing that I need that for A/C, I'm going to order it.

That sounds like a decent price for a 3 row copper re-core. I really don't think its your rad though, TBH.
If you don't see any build up on the tubes looking down inside the filler neck then the rad is good. Other than loose/bent fins that can cause your overheating problem.
I guess you'll know once you get your new rad in and running.
I hope you get the issues sorted out soon.
Cheers
Eric

 

Pulled the plugs and took some compression readings. Every cylinder is between 145 and 150.

A couple of the plugs look lean, the #6 being the most obvious. None were wet and none had any particles on them.

 

Those plugs look pretty normal to me (a little leaner here and there is common, and they don't look dangerously lean), and your compression sounds good, so that's two things off your list.

This is getting tough, because you keep ruling things out, but not finding the cause.

You'll figure it out.

- Eric

 

I just checked the pre-load on all of the valves. I made up my own method because all of the official ways require either 1) an adjustable push rod, or 2) a Sharpie, two marks and math to calculate difference in thousandths. Blech.

I brought the #1 to TDC and loosened the girdle over the intake and exhaust. I tightened the bolt over the intake until I took out all of the play, jiggling the rocker and push rod as I slowly brought it finger tight. I did the same on the exhaust and made sure that both valves were right at zero lash in case the girdle was affecting the other rocker.

I then took my feeler gauges and measured the clearance between the bottom of the girdle and the top of the head at each valve. When tightened, the pivot point is actually the top of the closed valve. The valve-to-girdle distance is 1.5" and the valve-to-push rod distance is 2.5". So, the preload on the pushrod and lifter would be (2.5/1.5) x (gap beneath the girdle).

According to Comp, 0.030" is ideal with 0.060" being the max recommended. Based on the geometry, that would mean that there should be about 18 thousandths (0.018") at the girdle to get the ideal 0.030" preload. The max shouldn't exceed 0.036" at the girdle.

My least measurement was 0.019" on one valve. (3) were in the 20's, (8) were in the 30's, (3) were in the 40's and (1) was at 0.050".

This confirms my belief that most of the valves are lashed TIGHT. I can't say that that's the problem, but that could be why it won't idle worth a damn.

I have 20-thousandth shims that I just got yesterday from Summit. I'm going to insert shims where needed to get the girdle gap between 0.018" and 0.036" at zero lash. That will tighten down to provide the proper preload. But with only 20-thousandths available, some are going to have to live outside of that range by a hair.

 

UPDATE: I ended up shimming 7 valves, 5 intakes and 2 exhausts. It might have run a little bit better when I first started it, but not appreciably. I ran it at 1500 RPMs for a little while and watched the temperature come up very slowly but surely all the way up to 225. It's only willing to idle, albeit poorly, when cold. Once it gets up to operating temps, it just does not want to slow idle. It will rest at about 1000 and if it dips below that, it heads off to die. But if I rev it, it responds crisply.

This 2-row radiator ought to be keeping up. I can't see that its the problem.

I hate to say it, but I'm running out of options that aren't the "pistons are too tight" theory. That means pulling the motor out of the car and tearing it completely down. Believe me, I want to exhaust all other options before resorting to something so absolute and extreme. And then if I do, imagine it from my perspective: the manufacturer and the machinist are surely experts compared to me. Who am I to say, "hone it PAST the spec."? So what if that's NOT it and I do it? Am I ruining my block??? I've got $4000 in this motor, more than I could have spent on a GM crate engine, but this is what I want - original.

Thanks for all of the help and feedback.

Bill