A 273 Build (aka Barracuda engine 4.0)

[MrMoparCHP]

Now that the CHP car is done I'm building a new engine for my 1967 Barracuda.

Not necessarily a C-Body engine but the thought that goes into this is just what we did on my 440. The 273 has some unique challenges as parts availability just isn't there.

The car for those who may not have seen it here, a 1967 Barracuda Fastback 273 2-bbl Console Automatic. My grandparents purchased it new in 1966, I got it in 1985 and restored in 2008. At the time of the restoration I chose to cleanup the original engine as it only had 1500 miles or so on the rebuild.

Same engine in the middle of being torn down for cleaning and new paint.

Cleaned, new gaskets, painted.

Repainted correct red and ready to install.

In the car, in a few months it would be one the road for the first time in 18 years.

That was July 2008, October 6, 2008 It was on the road.
Instantly I had overheating problems, bad, blowing off bad.
First up I found the thermostat upside down, oops.

Fixing it didn't make a difference a day or so later I put the hose in to top it off and cool it down while it was running. I had the hose on a trickle and a few minutes later the car started to shake real bad, I shut it down and checked the oil, milk shake, engine is now full of water.

I didn't finish the car and get this close to the first show not to have it there, I have a few days to do a swap. At the time I had a 67 Valiant with a 273 also so the plan was to pull it and put it in the Barracuda. Day 1 after work I prep the engine to pull, day 2 after work I pull the engine out of the Barracuda, day 3 I prep the Valiant engine to pull, day 4 I take off work to do the swap the day before the show.

An attempt to clean it first was going to be more a waste of time.

Minutes later I was putting the engine in the Barracuda, a couple hours later a friend showed up and we buttoned it up and hit the road. I saw that as a temporary engine although it was a very strong runner. Just a month earlier I acquired Commando 273 that was a good runner that I was going to clean up, paint and use.

A little more background and I'll get into the new build.


Alan

 

[MrMoparCHP]

While Restoring the Barracuda I acquired another 273, this one had the domed Commando pistons.

Like the other one the intake and heads were pulled, new gaskets were installed and the engine reassembled and painted.

That engine was put in a few months later and ran great, noticeable difference in power. The car went on to take second place A-Body stock in its first show, a year later the car was taken on a 2000 mile road trip up to Oregon but over the next few year the power started to fade but I was now fully vested into the CHP restoration so I just kept the car local as it just wouldn't climb the hills needed to get back.

Once the CHP car was done I felt like I could now look at doing the engine on the Barracuda, I talked with my friend about options. Do we just get a parts store rebuilt long block 318, we have heard too many bad things about those so that was ruled out. The next option was to get a 318 core and rebuild it ourselves but at that point we felt option three to rebuild a 273. I had five to pick from counting the one that I had issues with at first. The decision was to go with the one that was a known strong engine, the one that was taken from the Valiant and used temporally in the Barracuda.

The engine was opened and a preinspection was done.

The plan is a basically stock and back to its original 2-bbl setup. At this time we are still looking into what parts are available to do a better than stock build, essentially blueprinting a 273. We have a very limited selection of pistons and right now we're looking into sourcing quality head gaskets, the 273 has never actually used a 273 gasket. When the 273 was introduced it used a 318 head gasket with a void and again later modified the 340, the over sized bore is not desirable when trying to blueprint an engine. Checking with Cometic it looks like we can get a gasket with the bore we are looking for.

Again I never covered this stuff on my 440 but we went through this and felt that this would be a good opportunity to show what goes into doing an engine, this will be my second engine and myself will be learning.


Alan

 

[1978 NYB]

My neighbors would kill me if I had a cherry picker in front of my house. LOL!

 

[63Fun]

Looks like an interesting project. Keep that 273 for sure!

 

[Samplingman]

I love the 273. Out of all my cars, the '67 Belvedere with the 273 was the most durable.

 

[MarPar]

Cant wait to see it all come together, Alan...

 

[commando1]

I cut my teeth on the 273 back in the day. Wasn't a nut, bolt, or washer I didn't tangle with six times over. Watching this with most intense interest!!

If I had to do it all over, I know what I would do now.

 

[BeatersRus]

scott harvey used to tear up the competition with a 273.
i went looking for specifics of his motor build but couldnt find it.
also we have a sweet hydraulic lifter version/68 in a coronet.

heres some other random stuff for 273-s.
factory tweaking -bitd
Enhancements included a four-barrel carburetor and intake manifold, hotter cam, dual-point distributor, higher compression and a larger-diameter single-exhaust system with a low-restriction muffler and a tailpipe resonator.
The Carter AFB featured 1.437-inch primaries and 1.562-inch secondaries and the solid-lifter camshaft sported 248/248 degrees advertised duration and .415/.425-inch lift, compared to the two-barrel engine's solid-lifter cam with 240/240-degrees duration and .395/.405-inch lift. Valve-spring pressure was increased and new lightweight, aluminum alloy, domed pistons squeezed the compression ratio to 10.5:1.from 8.8:1.

site that had a good read.
The Mopar 273 Small Block
interesting idea he mentions about swirl heads on the 273??
which would also open up intake selection?

 

[moper]

The 273 is equal to the 383 in terms of blueprinting. You will need the Cometic gaskets, plus custom pistons if you want anything of quality. Egge makes the factory types I think to order, but these leave a bit to be desired if more power is in the cards. For a little more have a set made by a reputable manufacturer like Diamond, J&E, or someone like that.

 

[MrMoparCHP]

On to the engine, just a reminder, this is basically a stock rebuild and it is going back to a 2-bbl. A standard block was selected and was machined to 0.030 over.

Day 1

Once the machine work was done the first thing was to clean the inside of the water jacket, something that should have been done prior to sending it out. Bristle brushes and coat hangers were used in every conceivable angle in every opening in the block, some of the brushes were bent in a curve and worked around the back of the cylinders. This was done multiple time with the block rolled at different angles constantly rinsing with high pressure water. Once that was done the outside of the block was washed with soap and water, then blown off with air to dry.

With the block clean the heads, intake, valve covers, oil pan, oil adapter, and timing cover were put together. The other parts were cleaned and the assembly was painted. My engine guy prefers the block to be painted first to prevent the cast iron from soaking up oil, it will get painted again once it is together.

All the parts were removed and the inside was sprayed down with WD-40 and wiped down to clean any machining dust that may still be there. Once clean the inside was sprayed again to protect it.


Day 2

With the rough cleaning and prep done the detail cleaning could start. Some small (long) soft bristle brushes were run through all the different oil passages, cleaning the brush before pulling it back out.

With the block thoroughly clean the first thing was to check all the machining, the main bearings were fitted and the caps bolted and torqued down. Multiple measurements were taken and compared to the crank (this block was aligned bored). Each of the pistons were measured and compared to the bore to verify the piston to wall clearance.

With all the numbers checking out the distributor bushing was knocked in with an old distributor drive gear. Then the cam was installed (with assembly lube) to verify that the bearing were installed correctly (wouldn’t want to figure that out with the engine all together), along with the thrust plate (blue Loctite on the bolts, all 4 were used).

Day 3

Good to go the various oil plugs were installed, all with sealant.

From there the crank was inspected for flaws and the oil passages cleaned. Main bearing installed and the crank (with assembly lube) and caps, all torqued, check rotation. Next was to fit the timing chain and check the slack. The chain was looser than desired because the engine was align bored, something I didn't think about when I ordered the chain. My friend that is helping me with the assembly said to get the 0.010 under chain, well that one came in and he felt it was a little on the tight side so a new one was ordered (a 0.005 under).

0.010 under

0.005 under

Alan

 

[MrMoparCHP]

Day 4

The new timing chain arrived and was installed, perfect tension. Happy with the timing chain the work moved to the heads, my builder chose to go with new springs, retainers and locks, the machine shop used the originals. One by one the parts were replaced, pretty easy with two people. While at it the heads were blown out to clean all the machining dust. The day was wrapped up with fitting all the rings on the pistons, he chose to use a current chart for clocking the rings from what is in the service manual.


Day 5

New day, one by one the pistons were coated inside with oil to get the wrist pins and then oil was liberally poured over the outside and worked into the rings. As each piston was done it was inserted and bolted in, torque would be done later. Each bank was done separately, 1 - 3 - 5 - 7 then 2 - 4 - 6 - 8 to keep from having to rotate the engine back and forth. Sections of tubing were used to guide the rods in and protect the crank from being scared.

Once all the pistons were in the assembly was rotated once again this time to facilitate torquing each of the nuts. Afterwards each of the rods were checked at the crank for binding. Still time available a new high volume oil pump and pickup were installed followed with the windage tray. We needed to play with the shape of the windage tray to get it to clear the oil pan (Blue Loctite was used on the windage tray bolts).

That done we wrapped it up for the day, literally. A trash bag is put over it and tied closed. Another thing of note was the use of extra washers on the balancer bolt to lessen the stress on the threads (although this is a spare bolt).

Alan

 

[mr. fix it]

Now that the CHP car is done I'm building a new engine for my 1967 Barracuda.

Not necessarily a C-Body engine but the thought that goes into this is just what we did on my 440. The 273 has some unique challenges as parts availability just isn't there.

View attachment 125742

The car for those who may not have seen it here, a 1967 Barracuda Fastback 273 2-bbl Console Automatic. My grandparents purchased it new in 1966, I got it in 1985 and restored in 2008. At the time of the restoration I chose to cleanup the original engine as it only had 1500 miles or so on the rebuild.

View attachment 125743

Same engine in the middle of being torn down for cleaning and new paint.
View attachment 125744

Cleaned, new gaskets, painted.
View attachment 125745

Repainted correct red and ready to install.
View attachment 125746

In the car, in a few months it would be one the road for the first time in 18 years.
View attachment 125747

That was July 2008, October 6, 2008 It was on the road.
Instantly I had overheating problems, bad, blowing off bad.
First up I found the thermostat upside down, oops.
View attachment 125748

Fixing it didn't make a difference a day or so later I put the hose in to top it off and cool it down while it was running. I had the hose on a trickle and a few minutes later the car started to shake real bad, I shut it down and checked the oil, milk shake, engine is now full of water.

View attachment 125749

I didn't finish the car and get this close to the first show not to have it there, I have a few days to do a swap. At the time I had a 67 Valiant with a 273 also so the plan was to pull it and put it in the Barracuda. Day 1 after work I prep the engine to pull, day 2 after work I pull the engine out of the Barracuda, day 3 I prep the Valiant engine to pull, day 4 I take off work to do the swap the day before the show.
View attachment 125750

An attempt to clean it first was going to be more a waste of time.
View attachment 125751

Minutes later I was putting the engine in the Barracuda, a couple hours later a friend showed up and we buttoned it up and hit the road. I saw that as a temporary engine although it was a very strong runner. Just a month earlier I acquired Commando 273 that was a good runner that I was going to clean up, paint and use.

A little more background and I'll get into the new build.


Alan

Hi Alan, I've always been an avid fan of the small blocks regardless of CID or manufacturer.
Taking a small block and being able to keep up with some of these BB weekend warriors has always made me laugh provided the power to weight ratios are right.

Best of all, I can pass many gas stations while the BB's have to stop at almost every one on the road! LOL!

 

[PontiacJim]

Day 4

The new timing chain arrived and was installed, perfect tension. Happy with the timing chain the work moved to the heads, my builder chose to go with new springs, retainers and locks, the machine shop used the originals. One by one the parts were replaced, pretty easy with two people. While at it the heads were blown out to clean all the machining dust. The day was wrapped up with fitting all the rings on the pistons, he chose to use a current chart for clocking the rings from what is in the service manual.


Day 5

New day, one by one the pistons were coated inside with oil to get the wrist pins and then oil was liberally poured over the outside and worked into the rings. As each piston was done it was inserted and bolted in, torque would be done later. Each bank was done separately, 1 - 3 - 5 - 7 then 2 - 4 - 6 - 8 to keep from having to rotate the engine back and forth. Sections of tubing were used to guide the rods in and protect the crank from being scared.
View attachment 183007
Once all the pistons were in the assembly was rotated once again this time to facilitate torquing each of the nuts. Afterwards each of the rods were checked at the crank for binding. Still time available a new high volume oil pump and pickup were installed followed with the windage tray. We needed to play with the shape of the windage tray to get it to clear the oil pan (Blue Loctite was used on the windage tray bolts).
View attachment 183008
That done we wrapped it up for the day, literally. A trash bag is put over it and tied closed. Another thing of note was the use of extra washers on the balancer bolt to lessen the stress on the threads (although this is a spare bolt).
View attachment 183009


Alan

Looking great. I like the windage tray BUT....... In rebuilding my Pontiac 455, the Pontiac engines also used a windage tray. I elected not to install one, either factory or aftermarket. My reasoning, yet unproven, is that with the oils of today (even if adding an additive for older engines) supposedly don't lubricate as they did and one of the things I often read of is the accelerated wear or even failures of the flat tappet cam & lifters because of modern oils. The cam lobes/lifters are aided by the oil being thrown about by the crankshaft as it rotates. I know you can cut a slot in the lifter bores for more oil or get lifters with the EDM holes lasered into the bottoms, but I did not opt for either. Instead, I chose to keep the windage tray off and use a crank scraper to pull off excess oil from the crank but still allow some of it to whip about (may also benefit the cylinder walls a bit as well?). The later Pontiac oil pan I am using has a factory baffle in it to aid in preventing oil slosh under hard acceleration. I will probably add my own oil "trap door" to prevent oil slosh on hard decelerations. I don't think the amount of HP lost by not using the windage tray and adding the crank scraper in its place will be enough to be noticed in a street engine in my opinion.

Don't know if this is anything anyone has considered when building an engine with a flat tappet camshaft. Again, you can buy lifters with the small holes in the bottom faces, but they cost more and my thinking is that they could get plugged up and rendered useless.

Keep posting the build.

 

[MrMoparCHP]

We used the Mopar purple cam, so it will have hydraulic lifters and we’re keeping the adjustable rockers.


Alan

 

[vdk2010]

Pretty nice work Alan! Looks great!

Is there a specific reason why you haven't painted the inside on the valley on the second engine?

 

[commando1]

it will have hydraulic lifters and we’re keeping the adjustable rockers.

I don't understand the thinking here, Alan.

 

[70bigblockdodge]

My only thought would be 302 casting high swirl combustion chamber from mid eighties. Hardened valve seats and a closed chamber design to reduce detonation tendencies and promote complete burn, all without big ports to kill torque on such a small cid.

 

[MrMoparCHP]

Pretty nice work Alan! Looks great!

Is there a specific reason why you haven't painted the inside on the valley on the second engine?

The red you see on the first engine is a special coating that some engine builders like to use, I believe it is designed to help the oil drain better.
My friend basically said paint doesn't belong on the inside of an engine.

I don't understand the thinking here, Alan.

Don't recall the specifics, something to do with the geometry, or maybe it's just the cool factor. He did say they will not need to be adjusted again as with solid lifters.

My only thought would be 302 casting high swirl combustion chamber from mid eighties. Hardened valve seats and a closed chamber design to reduce detonation tendencies and promote complete burn, all without big ports to kill torque on such a small cid.

These are the early 273 heads that are closed chamber. As for the difference in ports? I think we chose to keep with what I already had, I'll have to check on that along with the rockers.


Alan

 

[70bigblockdodge]

The red you see on the first engine is a special coating that some engine builders like to use, I believe it is designed to help the oil drain better.
My friend basically said paint doesn't belong on the inside of an engine.

It is to aid oil drain back, I believe it is a crutch to fill in rough casting spots easily that you could sand /grind out for same basic result and never have a paint flake get between cam and lifters. Also really only a benefit at very high RPM.


Don't recall the specifics, something to do with the geometry, or maybe it's just the cool factor. He did say they will not need to be adjusted again as with solid lifters.

Reduces lifter preload to allow higher revving, also said to be closer to 1.5:1 ratio than stamped rockers. You decide.


These are the early 273 heads that are closed chamber. As for the difference in ports? I think we chose to keep with what I already had, I'll have to check on that along with the rockers.


Alan

I do not know. My small block IQ is low. I know the 302s are the small port 318 version and the 308 are the 360 version. Both are bolt on with no valve gear and special manifolds. I do believe the 273 has different angle on center intake bolts so you would need to straighten or realign the bolt holes in intake (a mostly hidden modification) by a slightly larger washer. The Magnum chain tensioner is not a bad idea either. I do think you have to drill and tap a hole so ideally before you got short block together. Still can be done just carefully.

 

[MrMoparCHP]

I do not know. My small block IQ is low. I know the 302s are the small port 318 version and the 308 are the 360 version. Both are bolt on with no valve gear and special manifolds. I do believe the 273 has different angle on center intake bolts so you would need to straighten or realign the bolt holes in intake (a mostly hidden modification) by a slightly larger washer. The Magnum chain tensioner is not a bad idea either. I do think you have to drill and tap a hole so ideally before you got short block together. Still can be done just carefully.

The 65 and earlier 273 have the different bolt angle, the 66+ use the same heads as the 318. All moot point as long as you pair up the intake. The later heads will bolt up to the earlier block, intakes can be redrilled to match heads so the combinations are open.

Alan