4eighteener
Well-Known Member
I can't wait to follow the transformation !
Engine is pulled - 273 rebuild or replacement 360 crate?
- Thread starter brodphish
- Start date
-
4eighteener
Well-Known Member
I hear what you are saying. Once I read the op would run some of our ideas by his mechanic, I knew I was not offering suggestions to a home builder. I think blueprint engine has a well sorted out 408 enginepackage at a reasonable price. I am sure you and others on this site could supply something comparable that he could basically drop in.
My suggestion was for a backyard rebuild, ala' UTG with a harbor freight hone. Since it has been previously bored, I suspect many times, I would gamble one of the times the bores were straight and just might need a crosshatch.
I guess the question is iif it would even clean up with a hone since no measurements of the bore size overage was ever given.
Since people were originally suggesting $100 a hole sleeves, I thought the line to line was about 1/3 the cost, and not deal with a machine shop, and getting a block there, at all.
And yes, line 2 line does say approximately 3 weeks turn around, but that is golden compared to the time frame for machine shop work here in south Florida, which is measured in seasons. Wisconsin may be better.
Anyway, I should just put up the popcorn emoji and follow.
Btw, I had hoped that your love of movie quotes would draw you back in
That could actually work, depending on the wear on the cylinders. 2 barrel pistons are not a problem with a 273, they can easily run 9+ compression ratio with 64-67 heads. Rings are easy, just call Total Seal. They will make rings for any bore size you want. If the cylinders have very little wear, you could just hone with torque plates and be very good to go. Just don't order any parts till you know if the block will clean up with a minimum hone. As for vastly bigger engines, once you start down that road, you are talking about replacing the whole drive train. Starting with the bell housing and ending up at the 7 1/4 rear. The trans should be good and the headers may have to go if you run large exhaust ports on the early 340 or 360 heads. Barracudas only need Formula S badges.
So today we picked up a 5.2 Magnum from a late 90s Dakota. $300 from the local pick & pull. Also scored a brand new Milodon SBM timing gear set for $50 from the machine shop that’s going to do our work.
So that brings up the 273 block is going to the machine shop to be assessed for the extent of clean up it needs. If it’s minor maybe we can use the 273 block with Egge .060 over pistons and Total seal rings?
One thing we discussed is boring the 273 block out to 3.91 like a 318. The machine shop says it can be done and the block integrity tested before and further work / build is done. I’ve often wondered why these small motors can’t be bored out to 318/340/360 since it’s the same block, it’s all metal, right?
If we go this route can we use the 5.2 heads? Clean & port em’? Will the TTI headers bolt right up?
The advantage to this route is the engine would slide right back into place, tranny, mounts, etc. Keep the bell housing and 7 1/4 at least for now.
Or we could rebuild the 5.2 with performance parts and make the minor modifications necessary.
So that brings up the 273 block is going to the machine shop to be assessed for the extent of clean up it needs. If it’s minor maybe we can use the 273 block with Egge .060 over pistons and Total seal rings?
One thing we discussed is boring the 273 block out to 3.91 like a 318. The machine shop says it can be done and the block integrity tested before and further work / build is done. I’ve often wondered why these small motors can’t be bored out to 318/340/360 since it’s the same block, it’s all metal, right?
If we go this route can we use the 5.2 heads? Clean & port em’? Will the TTI headers bolt right up?
The advantage to this route is the engine would slide right back into place, tranny, mounts, etc. Keep the bell housing and 7 1/4 at least for now.
Or we could rebuild the 5.2 with performance parts and make the minor modifications necessary.
NC Engine Builder
Grumpy Old Man
- Joined
- Oct 10, 2008
- Messages
- 7,244
- Reaction score
- 12,239
Strip the parts off the 273 and throw the block in the scrap bin. The 5.2 magnum is superior in every way.
Will the TTI headers bolt to the Magnum heads? The headers look to be standard SBM, the ports are larger than the 273 head exhaust ports. What mating the 5.2 to the A833? I heard it’s not difficult but don’t know exactly….
Nice score!
NC Engine Builder
Grumpy Old Man
- Joined
- Oct 10, 2008
- Messages
- 7,244
- Reaction score
- 12,239
The headers will bolt right up to the magnum heads, and the flywheel, bellhousing and all is a direct bolt up as well to the 5.2 magnum
this. this is the way.
5.2 dressed up like a commando. use the 273 tins & accessory stuff and nobody will ever know (unless they look at the intake bolts).
that 273 is a loser in every possible, conceivable way.
the 5.2 will make more, and better power, be loads cheaper and stone reliable with TONS of parts available for it should something catastrophic happen. the heads are eons better than what you've got on there and it's got a roller cam as well.
i'm sorry but i wouldn't give a machine shop dime one to tell me my wheezy 273 was slap *** wore out and then let them try and juice me for some build they think would be neat.
a 5.2 will drop right in and attach to everything that's there already.
it can't be bore out to a 318 bore, that's massive overbore.
cudamark
Well-Known Member
Boring out the cylinders is always dependent on the wall thickness and core shift, if any. You get too close to the water jackets and it will overheat regardless of how good your cooling system is. Getting custom pistons can be very expensive too.
Call @Johnny Mac and get you a Blueprint 408.
Magnum exhaust ports are small like your 273 heads. Make sure the crank is drilled for a 4 speed and will accept a pilot bushing. Or use the newer bearing, but I'd have the crank drilled so you don't have to cut the 4 speed input shaft. Since you now have a magnum, I'd go with that. Use the 273 front cover, damper, and pulleys. Just get an intake that will work, have the cam reground and get valve springs to match, and keep everything else. You can keep the 9 1/2"/10" bell housing and 7 1/4 at least for now, but you may have to upgrade the bellhousing, to the 10.5"/10.95" bell housing and clutch assy. The small clutch or the 10.5 would not even hold my 273 for more than a month. Nothing wrong with early 273 heads or making good power with a 273, but +.06 is probably as far as I would go without having the bores checked for thickness. Not worth mixing and matching 273 and 5.2 parts other than discussed.
MopaR&D
Nerd Member
Smart move on getting the 5.2 Mag. Only possible issues to check for are cracks in the heads between the valve seats and cam bearings. Cylinders and pistons shouldn't need to be touched unless it was severely abused. Stock roller cam can be reground and stock roller lifters can be reused. If heads are cracked (likely) there are a couple routes to go, I lean towards cheap aluminum heads (Speedmaster) checked over by a good machine shop and oil-through-pushrod rockers unless your Magnum block still has the holes drilled for LA-style rocker shaft oiling. Aftermarket LA-based heads also open up many more options for intake manifolds.
You can't just bore a 273 out to 340 size because the cylinders are cast different with generally the same thickness; it's not like they're all cast to the same OD and just bored out different sizes from the factory. You might get lucky with a block that has unusually thick cylinders or core shift in a desirable direction but that's not common and needs to be sonic checked to know for sure.
I prefer the ceramic-metallic lining for a clutch disc. Most commercial relining outfits will build one for you. Considering the O.P.'s OEM bellhousing diameter, this set up may handle 300 hp with 9.5" disc and live.
Last edited:
Brewer Performance has 9.5" clutches to hold hundreds of horsepower. Select by Category - Mopar A833 4-Speed Transmission & Component Specialists
I have tried most every type of clutch. The very best was an original 10.95 440 clutch and pressure plate, but it was too stiff and broke things. I'm afraid my best 273 iteration was way over 300 hp at 6,500 rpm. I do have a McLeod 105 BB/Long setup to try with next engine. Not a fan of ceramic metallic clutches or diaphragm pressure plates and have tried them.
Last edited:
My engine builder is going out of State for two weeks to rebuild some diesel in a big commercial truck. The disassembled 273 is sitting in his shop next to the 5.2.
Once the 273 block has been evaluated by the machine shop we will see if a light clean up would let us use it (with the Magnum heads). Keep the old school uncluttered look. If not then the 5.2 gets built.
Definitely need an upgraded clutch, I’m gonna read through all these posts and develop the road map towards completion.
One thing I’m considering is a Moser rear end and 4 wheel disc conversion. That way it’s ready for a 408 if my plan “blows up.”
My hesitancy to do go this last route is 1) I like this CC1 blue car the way it is/was and 2) I have a very nice, clean 1966 2 BBl car Iwas slating for a 408 conversion in 2027. But for reasons I won’t get into now this blue car is a better candidate.
At any rate I’ll post pics and comments as the project moves forward. Plan to finish by March at the latest.
Thanks again, FABO.
Once the 273 block has been evaluated by the machine shop we will see if a light clean up would let us use it (with the Magnum heads). Keep the old school uncluttered look. If not then the 5.2 gets built.
Definitely need an upgraded clutch, I’m gonna read through all these posts and develop the road map towards completion.
One thing I’m considering is a Moser rear end and 4 wheel disc conversion. That way it’s ready for a 408 if my plan “blows up.”
My hesitancy to do go this last route is 1) I like this CC1 blue car the way it is/was and 2) I have a very nice, clean 1966 2 BBl car Iwas slating for a 408 conversion in 2027. But for reasons I won’t get into now this blue car is a better candidate.
At any rate I’ll post pics and comments as the project moves forward. Plan to finish by March at the latest.
Thanks again, FABO.
Go 273 or 5.2. Magnum intake valves are too large for a 273. Nothing wrong with early 273 heads, with port and bowl clean up they can flow about like small valve "J" heads and are closed chambers so you can get quench.
JDMopar
Well-Known Member
I would be leery of the Moser 8 3/4 for an early A body. A factory 8 3/4 has minimal clearance between the back of the housing and the gas tank. That Mad Maxx looking Moser housing may be too big in an Early A.
I had an 8 inch Ford with 3.55:1 in a 64 falcon that took a lot of abuse from a SFT 289. That may be another way to go.
what makes you think the 5.2 will look "cluttered"?
dressed up with the LA/273 front cover and accessories it'd be nearly indistinguishable.
JDMopar
Well-Known Member
The differences in the valve cover bolt pattern trick a lot of people. Some people will look at you like you've got two heads if you tell them LA valve covers will bolt right on a Magnum head. To change an old saying, "Valve covers and paint make it what it ain't!"
Well right now the Magnum has all kinds of wires and hoses hanging off it, plus plug proctector tubes that make it look like a rusty porcupine.
I’ll hold off judging until we clean it up a bit.
I’ll hold off judging until we clean it up a bit.
-
Similar threads
