again 273 wanna hear your opinions ...

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lilredridinghoo

lilredridinghoo

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again i´m into throwing a 273 together (as my wife complained that the fish was to rude and not really driveable in normal traffic with the beefed up Magnum motor)
so decision were made the Magnum has to go and i will stick it into my Dodge D100 Truck next year.

so here are my plans i wanted to hear your opinions on that

this is given and it should stay as it is (money wise)

273 .040over
318 Heads with compcams Springs 901-16, bowl blended, opened intake runners to 340size, bit of portwork, polished chamber and polished exhaust runners.
Stock converter, 904er with shift kit, 3,91 rear with 26inch tall tires
600 cfm Holley with Vac.Sec.
longetube headers unrestricted mufflers 2,5inch dual exhaust

oil pan - windage tray:

standard oil pan + windage tray
deep 8quart pan without windage tray
or deep 8quart pan + windage tray

camshaft - 340 HPstock cam: should i go 4 degrees advanced or not ? think it could/would give me a bit more fun on the low end

intake: i do have an 360° offenhauser single plane and i also have a stock 340 4bbl-iron beast i would tend to use the offy, as it was on the motor when i bought the Barracuda years ago, but the runners are 318 size, which will be fine for the small motor (but the heads are allready opened up to match 340 gaskets, will it hurt too much using smaller intake on wider heads ? Guess the otherway around would create more turbolences ??)

thanks
 
So the "beefed up" magnum motor doesn't work for her... and you think a beefed up 273 will?
Good luck with that
 
I would de-tune and change gears and TQ converter , that is a big under taking..
 
Love MoPars and the CONCEPT of 273's, but I scrap them (after getting the heads/rockers/rods/crank) for 318's every time. It's like building a 318 when you have 5 340 engines laying around. Especially for the cost (pistons and oddball intake bolt angle on some), why give up the bore size and CID? In the BB world, it's like building a 361 or 413, cool but why? BTW, good luck and go for it!!!
 
one of the reasons is also the legal aspect here in Germany - the Barracuda is registered as an "historical vehicle" which gives special permissions like driving in restricted areas (emission control, pollution etc) and also we will have a significant advantage when it comes to taxes - 192 EUR vs 1133 EUR. My registration sheet reads 4473 ccm (= 273 cui) ... similar for the car insurance...
that´s why i want to go back to the "original" engine.

the magnum was to tricky to drive for her. Wet pavement and a bit to heavy on the go-pedal and it will just go sideways

and yes i do know - the more cubes from the magnum... 360 is the way to go... 318 before 273 ..etc etc... heard that all before...

but it would be nice if someone cld throw in his opinions with the parts/frame given.

at the end it´s also a question of money and time
 
If you have some time, check out what I did with my 273. It's no race engine and I didn't build it for maximum horsepower but it is fun to drive, very dependable, and is fairly economical. 273 Build
 
Build it to stock 4V commando specs, 235 HP and well mannered. Just like the previous poster did his.
The rest of the stuff money gone that you don't need to spend-in my opinion:)
 
I've long thought that Magnum heads would be perfect on a 273.
 
jos51700 said:
I've long thought that Magnum heads would be perfect on a 273.
Click to expand...
They would work well but oo bad the valve train needs replaced to make them work as well as a different intake.
 
dont know if you all got me right (maybe my German-English leads to the wrong conclussions)

- the head job was allready done some years ago ... and these 318 heads are the heads i will use just because it´s the only set that i have laying around (and i´m not willing to purchase another set
- the deep pan is allready here in my hands
- the windage tray is allready here
- the 340 cam is allready here
- the 340 intake is allready here
- the offenhauser 360° intake is also allready laying in my Basement

- the deep pan would not an issue because the headers reach lower than the deep pan.
- no i wouldn´t change gears, just because it´s f*ing expensive in Germany to get parts like proper gear sets for an 8 3/4
(we could not walk into a summit store or what ever .. everything has to be shipped and imported to Germany, which means we have to add approx 20% taxes which have to be payed for the part+shipping costs, and we do not have junkyards with old american cars. so it´s not so easy to get parts. most of the time we try to trade with other mopar guys)

my questions will be:
- would you go with a deep pan or with the stock pan with or without windage tray - it´s just to hear what you would prefer and why ?
- which intake would you prefer the stock 340 iron one, or the offenhauser 360° single plane and why ?
- would you advance the cam-timing or not ?

what will be your choices if you have to deal with the given parts ??

thanks
 
Would you have to notch the block for the larger 318 Valves?
I build my 273 with a stock oil pan and MP windage tray-I like it.
I would choose the aluminum intake for the weight issue.
To put hydraulic lifters in a 273 requires different pushrods than 273 stock.
The 340 grind is significantly different from 273 stock and may require some problem solving.
The stock install for my aftermarket Lunati cam is 4 degrees advanced-I degreed it in to that.
 
DesertRat said:
Would you have to notch the block for the larger 318 Valves?
I build my 273 with a stock oil pan and MP windage tray-I like it.
I would choose the aluminum intake for the weight issue.
To put hydraulic lifters in a 273 requires different pushrods than 273 stock.
The 340 grind is significantly different from 273 stock and may require some problem solving.
The stock install for my aftermarket Lunati cam is 4 degrees advanced-I degreed it in to that.
Click to expand...

Thanks DesertRat
no the 318 valves fit without any Problems - i´ve also tested a pair of Magnum-Heads, no way, the larger Magnum-Valves will deffo hit the bore
the 273 valve train was changed to hydraulic lifter some years ago before i bought the car.. so i´m fine with pushrods and hydro-flat-tapped cams

okay, good to know that the lunati stick will have 4 degrees advance on stock install
 
lilredridinghoo said:
dont know if you all got me right (maybe my German-English leads to the wrong conclussions)

- the head job was allready done some years ago ... and these 318 heads are the heads i will use just because it´s the only set that i have laying around (and i´m not willing to purchase another set
- the deep pan is allready here in my hands
- the windage tray is allready here
- the 340 cam is allready here
- the 340 intake is allready here
- the offenhauser 360° intake is also allready laying in my Basement

- the deep pan would not an issue because the headers reach lower than the deep pan.
- no i wouldn´t change gears, just because it´s f*ing expensive in Germany to get parts like proper gear sets for an 8 3/4
(we could not walk into a summit store or what ever .. everything has to be shipped and imported to Germany, which means we have to add approx 20% taxes which have to be payed for the part+shipping costs, and we do not have junkyards with old american cars. so it´s not so easy to get parts. most of the time we try to trade with other mopar guys)

my questions will be:
- would you go with a deep pan or with the stock pan with or without windage tray - it´s just to hear what you would prefer and why ?
- which intake would you prefer the stock 340 iron one, or the offenhauser 360° single plane and why ?
- would you advance the cam-timing or not ?

what will be your choices if you have to deal with the given parts ?




What casting number 318 heads do you have. Except for #302 casting heads which came on mid-80s 318 s, all other 318 heads are open chambered and you will lose compression by using them. The high performance 273 had closed chamber heads and Dome Pistons to get the compression up to 10 and 1/2 to 1 the four-barrel the dual-point distributor in the very slightly larger camshaft is what made 235 horsepower out of a 180 horsepower 2 Barrel engine with low compression. I personally wouldn't want to put open chamber 318 heads on a 273 I think you're going backwards.
thanks
Click to expand...
 
Your factory cam choices are
1) The 273 2bbl cam; 240/248/112 ,this is same as the 318cam
2) the 360 2bbl cam; 252/260/112
3) the 340........cam; 268/276/114
Read about VP here; V/P Index Calculation
For the following exercises,all cams are in at split overlap,

1) Just for kicks,here is the 273 with the oem cam,ICA of 50*
Static compression ratio of 8.0:1.
Your dynamic compression ratio is 7.04:1 .
Your dynamic cranking pressure is 135.24 PSI.
V/P (Volume to Pressure Index) is 96 ...........................factory... 96 ..

1B) same 273,A/A, with more compression
Static compression ratio of 9.2:1.
Your dynamic compression ratio is 8.07:1 .
Your dynamic cranking pressure is 161.70 PSI.
V/P (Volume to Pressure Index) is 115 ..................................... 115 ..
This is about as good as a 273 2bbl cam gets
This level of VP should be your target, This should be reasonably peppy........
even tho..........,Oh well;Put a 4bbl on this and a free-flowing exhaust, headers optional, and it will be super-fun with 3.91s.
______________________________________________________
2) Here is the 2bbl 360 cam, in at ICA of 56*
Static compression ratio of 8.0:1.
Your dynamic compression ratio is 6.79:1 .
Your dynamic cranking pressure is 128.93 PSI.
V/P (Volume to Pressure Index) is 88.......................................... 88 ..
This is pretty doughy

2B) That 360 cam wants more Scr.
Static compression ratio of 9.5:1.
Your dynamic compression ratio is 8.03:1 .
Your dynamic cranking pressure is 160.66 PSI.
V/P (Volume to Pressure Index) is 109 ...................................... 109
This is as good as this combo gets
_________________________________________________
3) At same Scr of 8.0 the 340cam,in at ICA of 66* looks like
Static compression ratio of 8.0:1.
Your dynamic compression ratio is 6.32:1 .
Your dynamic cranking pressure is 117.18 PSI.
V/P (Volume to Pressure Index) is 73............................................ 73 ..
What can be said about 73 except that this is as weak,or weaker,than a factory slanty

3B) that 340 cam wants more compression
Static compression ratio of 9.5:1.
Your dynamic compression ratio is 7.46:1 .
Your dynamic cranking pressure is 145.95 PSI.
V/P (Volume to Pressure Index) is 91 ...still super doughey city........91 ..
So, as you can see, the 340 cam would want a new TC, cuz 91 is like slanty territory. Or it would need more compression to bring up the low-rpm torque.

3C) the 340 cam with most compression
Static compression ratio of 10.25:1.
Your dynamic compression ratio is 8.03:1 .
Your dynamic cranking pressure is 160.66 PSI.
V/P (Volume to Pressure Index) is 101........................................ 101 ..
This is as good as this combo gets,and will now feel about like a stock 273 from stall to maybe 3000 rpm,or about 23 mph.
_______________________________________________________
I wouldn't put that 340stick in there; but if you do, and with,long-tubes,I would put it in at 112. This is split overlap, and it gets you 2 extra degrees of extraction, to help with fuel economy, cuz that cam sucks gas pretty bad, as I imagine do most 114* cams of that size or bigger.

One problem I see in that 273 is that trying to build compression for any other than the stock cam, is gonna suck, so the bottom end will likely be doughy. Personally, I think the 340 cam is not right for Mrs.Red. You already have the 3.91s, so you don't need a lot of engine to motorvate the fish after that. So I'm kindof liking 2B cuz with 3.91s you can afford to give some VP up, and the 2bbl 360 cam does pretty good at the top, so long as you control the valve gear, and don't get into lifter pump-up.

So I think I would put the high compression pistons in there, and work the formula backwards after I see the actual Scr available. Yeah, that's probably the way I'd do it, except I might use a solid lifter cam.

But I also think the best idea I heard was the one about just detuning the engine you have in there already. And that was memike in post #3
 
Last edited:
lilredridinghoo said:
@toolmanmike , my heads are open chambered #675

And yes i know about loosing compression with these heads.
But maybe you remember the test runs 69 cuda 440 made
The comptession advantage isn't that big in a small motor

#920 vs. #675 Heads "Compression vs. Cylinder Flow"
Click to expand...
Make sure you cc it before you final assemble. Depending what pistons you use with those open chambered heads, your static compression will probably be in the 8.5:1 area and with a big cam your dynamic compression might be in the 7:1 range (or worse) @AJ/FormS can chime in.
 
AJ/FormS said:
Your facrory cam choices are
1) The 273 2bbl cam; 240/248/112 ,this is same as the 318cam
2) the 360 2bbl cam; 252/260/112
3) the 340........cam; 268/276/114
Read about VP here; V/P Index Calculation
For the following exercises,all cams are in at split overlap,

1) Just for kicks, here is the 273 with the factory cam, ICA of 50*
Static compression ratio of 8.0:1.
Your dynamic compression ratio is 7.04:1 .
Your dynamic cranking pressure is 135.24 PSI.
V/P (Volume to Pressure Index) is 96 .....................................factory... 96 ..

1B) same 273,A/A, with more compression
Static compression ratio of 9.2:1.
Your dynamic compression ratio is 8.07:1 .
Your dynamic cranking pressure is 161.70 PSI.
V/P (Volume to Pressure Index) is 115 ............................................... 115 ..
This is about as good as a 273 2bbl cam gets
This level of VP should be your target, This should be reasonably peppy........
even tho..........,Oh well;Put a 4bbl on this and a free-flowing exhaust, headers optional, and it will be super-fun with 3.91s.
______________________________________________________________
2) Here is the 2bbl 360 cam, in at ICA of 56*
Static compression ratio of 8.0:1.
Your dynamic compression ratio is 6.79:1 .
Your dynamic cranking pressure is 128.93 PSI.
V/P (Volume to Pressure Index) is 88.................................................... 88 ..
This is pretty doughy

2B) That 360 cam wants more Scr.
Static compression ratio of 9.5:1.
Your dynamic compression ratio is 8.03:1 .
Your dynamic cranking pressure is 160.66 PSI.
V/P (Volume to Pressure Index) is 109 ................................................ 109
This is as good as this combo gets
__________________________________________________________
3) At same Scr of 8.0 the 340cam,in at ICA of 66* looks like
Static compression ratio of 8.0:1.
Your dynamic compression ratio is 6.32:1 .
Your dynamic cranking pressure is 117.18 PSI.
V/P (Volume to Pressure Index) is 73..................................................... 73 ..
What can be said about 73 except that this is as weak,or weaker,than a factory slanty

3B) that 340 cam wants more compression
Static compression ratio of 9.5:1.
Your dynamic compression ratio is 7.46:1 .
Your dynamic cranking pressure is 145.95 PSI.
V/P (Volume to Pressure Index) is 91 ........still super doughey city.............91 ..
So, as you can see, the 340 cam would want a new TC, cuz 91 is like slanty territory. Or it would need more compression to bring up the low-rpm torque.

3C) the 340 cam with most compression
Static compression ratio of 10.25:1.
Your dynamic compression ratio is 8.03:1 .
Your dynamic cranking pressure is 160.66 PSI.
V/P (Volume to Pressure Index) is 101.................................................. 101 ..
This is as good as this combo gets,and will now feel about like a stock 273 from stall to maybe 3000 rpm,or about 23 mph.
________________________________________________________________
I wouldn't put that 340stick in there; but if you do, and with,long-tubes,I would put it in at 112. This is split overlap, and it gets you 2 extra degrees of extraction, to help with fuel economy, cuz that cam sucks gas pretty bad, as I imagine do most 114* cams of that size or bigger.

One problem I see in that 273 is that trying to build compression for any other than the stock cam, is gonna suck, so the bottom end will likely be doughy. Personally, I think the 340 cam is not right for Mrs.Red. You already have the 3.91s, so you don't need a lot of engine to motorvate the fish after that. So I'm kindof liking 2B cuz with 3.91s you can afford to give some VP up, and the 2bbl 360 cam does pretty good at the top, so long as you control the valve gear, and don't get into lifter pump-up.

So I think I would put the high compression pistons in there, and work the formula backwards after I see the actual Scr available. Yeah, that's probably the way I'd do it, except I might use a solid lifter cam.

But I also think the best idea I heard was the one about just detuning the engine you have in there already. And that was memike in post #3
Click to expand...

FWIW: I ran the 360 2bbl OEM cam in a bone stock '85 318 2bbl with headers and a quicker-curved OEM distributor in my '85 D-150 A-833 O/D truck (3.55 gears) and it sounded boss (almost lopey, especially cold) and had great driveability-even with the steep O/D gears lugged down around town, no need to downshift. Got 20mpg highway and was a blast to drive!!
 
That's a great explanation AJ/FormS. Thanks.

I do also have 2 other stick stored, if I remember right one was pulled out of a 318 and the other was an older aftermarket cam which was sold by PAW, must be SuperStockIndustries-11309
ssi 11309 (lob 112, duration @050 lift 204-214, adv dur int.270 exh.280 Valve lift int.420 exh.443)

Maybe i can check the other one if it's really a 318 stick
 
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