To rebuild or not to rebuilt... it is the (expensive) question...

Hey everyone!

So we've been having a lot of issues in getting our engine to idle nicely. It's a 273 V8 in a '67 A100.

I did a compression test today, and two of the cylinders were a bit weak. I was getting about 90 psi max out of two of them, the rest were solid at 110-140. One of them would pump up to 90 @ WOT, but otherwise was even a touch lower at 75-80. boo!

The specs call for 120, +/- 10 or something along those lines.

So now I'm thinking: should I even put money into a rebuilt/new carb and other things to get it to idle and run better, or is the engine even worth it at this point? Should I just throw in the towel and throw in a rebuilt engine?

So then you don't think the compression is too low? This is OK?

I know the carb has some issues and could use a rebuild, and then I also think that the manifold is full of carbon for the heat riser choke doesn't work very well. My van is weird, it's a '67 but a very early '67, so it's more a '66 1/2 or something, hence the stock 273 in it. I've got a '67 shop manual, and it doesn't have the carb that's on the Van in it, but I don't know if that's due to it's early build or if the carb isn't original. It's still a 2-bbl, and it looks like a Stromberg-style, similar to what's shown in the '67 shop manual I have but mine's different. So if it's the carb I'm thinking I'll just replace the carb altogether with something else, and maybe the intake too.

I did the cylinder balance test today too, actually, and it had the same drop all around.

I didn't do a vacuum test today, I will tomorrow, but last time I did two months ago it was fine.

I replaced the ignition with the Mopar electronic kit about a year ago. So it's got a new distributor. Hasn't been driven too much, so it should still be fine. I also replaced the alternator with a better one, and re-wired everything and get a very steady charge.

So I think it's the carb and intake, which I'll replace if y'all think the compression is decent enough. Otherwise I'm thinking I'll swap in a rebuilt 318 with an automatic and ditch the three-on-the-tree. Which, while it has it's charm, is a bit of a pain...

Cool, thanks for the tips on the valves. I was thinking that the lower compression there might just be from carbon build-up, but I wasn't sure.

How hard and with what should I pound on the valves with?

I should take a look at the cam. It's always been lopey, so I'm pretty certain it's not stock, but again I have no idea what it is or what shape it's in.

As for the idle, I think it's all in the choke. If I force it open once the engine is even a little warm it smooths out the idle quite a bit. However, the engine always has had to be set with a much faster idle than I'm used to, otherwise it stalls. The carb seems to have some other issues as well, so I think I'm going to just replace it.

I'm also getting a bit of a miss at idle, which I'm still sorting out. The electrical system in the van isn't great at all, so again I'm thinking I might just bite the bullet and rewire the thing here soon.

For what it's worth:

Do you have an electronic voltage regulator in there or the points type mechanical VR? The Ampmeter should fluctuate if it's mechanical. From what I remember, the electronic ignition likes a steady 13.8 volts. It's a cheap easy upgrade that will prevent the frying of your van's wiring.

You may want to see if the compression goes up any with a squirt of oil in the cylinder. If does go up, you probably have bad rings.

I was able to get a carb kit for around $25 for the Stromberg on my '65. Be sure to douse those little vents with carb spray. Nate says you can bolt on the latter style carb (Carter?) if need be. I do believe that a lot of people are having problems with the rebuilt carbs currently out there (worn shafts, etc).

IMO the 318 is better than the 273. Hydraulic lifters, new one should have harderned valve guides, etc.

If you have the 90" wb A100, you'll need the short tailshaft on the automatic trans + maybe the dash shifter with a cut-out templet + the kickdown linkage.
This is where a donor van comes in handy. I love my automatic.

273's also came with a mechanical camshaft and adjustable rockers. not saying you have one but a tight valve will also cause a poor compression test. easy to tell if it is... there will be an adjuster bolt at the pushrod end of your rocker arm. remove the valve cover to see or look in the oil cap hole.hydraulic cams were easier to maintain but mechanical ones were better horsepower and constantly needing adjustment.
just for giggles take your compression test again on the cylinders in question and then add two good squirts of engine oil into the spark plug hole and do it again. after that loosen the rocker shaft to remove the push rods from the two cylinders and do it again. tighten down the rocker shaft with push rods out because the oil will pump out where the shafts mount to the head. compare the three numbers or post them here. if i had my choice a well tuned mechanical cam 273 would be in my truck if i could have found one to do. 273's a better engine than the 9:5-1 360 i got in it now. just my two cents worth.........................jeff

I do like the 273, well, just because it's different and original. It's a pain that not as much is out there for it ala the 318, but it's not a racer anyways. ;-)

However, if I was going to replace the engine, a newer 318 with hydraulic lifters and such I think would be a better way to go. If we do go with the 318 / Auto, I'll need a driveshaft certainly but I don't want to cut my pristine dash and so I was thinking of making a cool mount for a new cable shifter that mounts to the front of the doghouse or something (I've got a CNC machine so I can pretty much make anything, even stupid things for the van).

As for the mechanical lifters, man, that's good to know. Along with the oil-in-the-cylinder trick. I'll pull the valve covers and check. They are old M/T aluminum finned ones (hence how I know someone at some point loved this van) and I was looking for an excuse to pull them off and repaint them anyways!

As for the carb, I'm actually leaning towards maybe replacing the intake manifold (to cure my carbon plugging) and putting on a smaller 4-bbl carb. The van has headers on it already, I might as well go the rest of the way. I'm also looking at CNG setups to run it off of 'alternative fuel' being a stupid Californian who runs a business that does a lot of 'green' stuff.

As for the voltage regulator, I went with a one-wire high amp alternator and re-wired the system to be able to take the increased load, and added a volt meter to the system. It holds at a very steady and happy 13.8 or thereabouts. However, some of the existing wiring is still being used (I didn't rewire everything, just the bits for the electronic ignition and the alternator) and so I'm also wondering if a lead from the coil is bad or something. I should just rewire it all at some point...

Thanks for all the great advice, I'll get back to y'all soon.

don't kid yourself.....there is still a lot of aftermarket parts out there for a 273. memory serves me correct a 1967 273 made about 230 horse power with a soild or mechanical cam and 10:5 - 1 domed pistons that are still availible today. egge machine in california has them and k-b pistons has them too. more aftermarket high performance parts for 273's than 318's. go to a local drag strip and talk to some owners with small block mopars. get informed.

If the motor is dead, I wouldn't even hesitate to find a 318 and put it in. You can find 318's cheap and plentiful. You can put the original motor in the garage for later if you really want to save it for originality.

I put a free 318 in my Barracuda and have never looked back. I would never spend money on a 273, only because for the same money or less you can spend the money on a 318 or 340 or 360 and get so much more reliability and horsepower.

Speaking of 273's...wasn't there a Hi-Po version rated at like 275 HP? I know the 340 was supposedly rated at this HP, but I swear I remember reading about an early 273 package that was high HP.

yes there was a hypo 273 , i dont remember what they came in, mabee baracudas? i have an extra 273 crank -was thinking of building a stroker 318 someday, mabee replace the slant 6 in my 41 ih streetrod

i heard the 273 4 bl or even 2 bl intakes dont interchange with 318, 340 and vice versa is this true?

For 1965, 66 and 67, available in Darts, Valiants and Barracudas there was a 273 Commando (that's what came in my Barracuda Formula S). It was a 273 with a 4-barrel intake, Carter AFB, dome top pistons, chrome air breather, chrome pcv, black crinkle valve covers and that's it. It was rated at 235 horsepower as opposed to the 180 of a regular 273. They kind of copied some of the Hemi stuff (dome top pistons, chrome PCV same as hemi cars, black crinkle valve covers like hemi ones) In fact, the PCV and ignition wire grommets are the same ones as hemi cars and tend to be expensive because of this. If you got the Commando motor in your car (you could order the Commando motor in a regular Barracuda, not just a Formula S) you also go the commando exhaust which consisted of a straight through glasspack muffler and a canister resonator with a rectangular tip out back.

There was also a 273 D/Dart motor rated at 275 horsepower but they are very rare, made only for race applications I believe. I think they were put in some racing Darts in 1967.

The commando 4-barrel intake manifold will fit on any 273/318/340/360 with the following exceptions. In 1965 (the first year of it) the angle of the bolt holes is different so you can only put a '65 intake on a '65 motor. Unless you drill the holes bigger and at a different angle and beef up your gasket. The '66/67 4 barrel intake will fit any subsequent small block.

I have a 318 with a '66/67 commando intake, '67 4-barrel carb and all the Commando dress up stuff in my '65 Barracuda Formula S. I have no interest in getting an original motor, I prefer a later motor with the dress up stuff added.

Cool...thanks for the lesson there. Did the early intake bolts go straight in or am I thinking of the early Max Wedge motors?

thanks enbro, i like my 273 in my 65, good lil engine. id like to warm it up a little but it runs so good i dont want to mess with it.

You know, I didn't mean to offend with the comment about the 273. What I was getting at is that I'm having a hard time finding anything used, i.e. off of Craigslist or Moparts, that are 'speed parts' if you will for a 273.

Summit has tons of different new intakes for a 273, for example, that all look awesome. But they are all $300+. For my old Dodge Coronet I used to have, I got a used Wieland dual-plane aluminum intake in great shape used at a swap meet for cheap, and some other parts I needed off of the local craig's list no problem.

I was considering replacing the intake, because I think the old one is full of carbon and if I've got to pull it off anyways to clear it out and clean it up, and if I'm also at this point rebuilding or getting a rebuilt carb for it, well, why not spend a little more. Get a used aluminum intake and a rebuilt 4bbl carb and swap up to that. But now i'm having a hard time finding an intake for less than what I can locally buy a whole running 318 for, so... what to do?

I don't know what angle the intake bolts go in on a '65 273 Commando, I only have the '66/'67 one here, and they're on an angle.

Toast, if your 273 is a '67, any 318/340 intake should work on it...but the intake ports where they meet the heads will be mismatched. I used to have a '69 273 with a 340 intake on it and that was an issue, but it did run. A 318 intake should be okay.

So I snuck in a second to look at the Van again today, and here's what I found:

1. Plenty of vacuum. Lots of it, in fact. And no leaks.

2. No leaks around the manifold or anything like that.

3. The heat riser isn't I think. I let it warm up while I watch it (oh the beauty of the forward control design!) and it doesn't move once the engine heats up.

4. The idle is still really rough at lower RPMS, and it occasionally misses a little. I'm going to put a new coil on it, as well as re-do the timing, and see if that makes any difference at all.

5. I think I'm hearing a very slight knocking as well, now that I've paid more attention to it. Not 100% certain, and I don't have tons of experience, but it doesn't sound 'right' to me. Hard to tell over the fixed fan noise, so maybe I should take that off and run it again and see if I can narrow it down. Boo!

Haven't had time to pull the valve covers off and see if I've got mechanical lifters or not. I was hoping to do that today, got to the shop too late to do it...

nate the skate wrote:Cool...thanks for the lesson there. Did the early intake bolts go straight in or am I thinking of the early Max Wedge motors?

It was the difference between the Late '64 - '65 and '66 to '69 273 intakes.
Earliest intake bolts went in at a slightly different, shallower angle. Remember this new LA Small Block was eventually become the new '67 318, '68 340 and finally the 360 LA's. Oil leak problems at the front and rear of the intakes made them change to the steeper angle for better clamping/sealing.
HEADS? The later 318, the 340 and the 360 intakes and heads will only interchange with the early 273 and 318 if used TOGETHER. Smaller ports on the 273 and first LA 318s are way too small to match up with these later intakes.
Ter'