thoughts about 273er combo

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lilredridinghoo

lilredridinghoo

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hi there Fabo Bros and Sis...

just wanna here your opinions about this combo for my 65 bcuda

- 273 block from 1965 (we will see if i have to overbore, at the moment it still stored in my friends hotrod shop, it´s the original block the car came with as i bought it)
- a pair of 920 casting heads (plans are gasket match the intake runners, bowl blending, little port job on intake and exhaust, polish combustion chamber)
- also planned to use 360 head sized valves on these heads
- long tube headers and 2,5 dual exhaust
- cam will be an ssi 11309 (lob 112, duration 050 lift 204-214, ad dur int.270 exh.280 Valve lift .420 .443)
- valve springs compcams 901-16 (353lbs seat load 101 closed load 242)
- intake LD340
- stock crank and rods (maybe i will polish them)
- pistons not sure about which way to go, as i have a set of low comp standards and also a set of sealed power aftermarket 0,30 laying around
- carb will be a TQ 750 or 850cfm (got 4 carbs laying on my workbench 1x750 3x850, we will see which one will be worth rebuilding)
- trans will be standard 904 (pushbutton) with standard converter (may be i will use a /6 converter)
- gears are 3,23 at the moment but thinking about getting 3,73 or maybe 4,10 (depends on what i can get for the 741 case)
- 26 inch tires

goal is to build a streetable car with nice acceleration (just to make the chebby guys wandering about this tiny engine) using pump gas is also a must as fuel is getting more and more expensive and more worse in quality here in Germany (the worse quality of sheel v-power-fuel has killed my 11,8:1 CR 318 teenie-screamer)
 
I think you'll need to relief cut the 273 cylinder bores to run the large valve heads.
You'll need headers to get as much cfm out as you are putting in too.
 
I'm not familier with those heads. I'm a fan of aluminum but i'm sure they'll work. Only thing is check with your machinest on the oversize valves and how that works with the small bores. Just make sure it wil work.

Cam sounds a bit small to me.

I beam polished my rods and had them re-sized. I used ARP waveloc bolts and also had them shot peened.

I'd recomend studding the engine top and bottom.

What compression ratio are you looking for?

750 or 850cfm sounds big to me especially considering how mild the combo is. While the vacum sec may mask the problem, I think you'd see more all around driveability and performce with a smaller carb.


I'm not sure what a /6 convertor will yied you. I would get a quality convertor for it and get a stall speed in the 2500 range.

3,73 or maybe 4,10 (depends on what i can get for the 741 case)
- 26 inch tires YES

goal is to build a streetable car with nice acceleration (just to make the chebby guys wandering about this tiny engine) using pump gas is also a must as fuel is getting more and more expensive and more worse in quality here in Germany (the worse quality of sheel v-power-fuel has killed my 11,8:1 CR 318 teenie-screamer)[/QUOTE]

I don't know about making the chevy guys wonder but I think you'll have a nice peppy driver. You have to remember a 385 HP sportsman engine is in the 3k range and runs on pump swill.
 
A guy I met in Pittsburgh a few years ago was running a 68 Dart with a 273, street car, that was running in the mid 12's.Don't know his combo but nothing to sneeze at.
 
I drive a 273 in my Valiant 62 with this combo:
65 273 Commando.
318 heads full flow ported with 2.02/1.60 Stainless steel valves.
340S cam shaft
stock exhaust with 2.5" dual pipes and an home made X-pipe. 2 small mufflers.
Open Air dual plane intake. made in China from ebay.
Edelbrock 1406 600cfm.
Hei distrubutor.

Run it on a chassie dyno and after 5 runs and alot of tuning
Here is the numbers at the top at 4500rpm:

Torque = 544.8 (ft.lb)
Torque = 738.9 (Nm)
Power = 466.8 (B.H.P)
Power = 348.1 (Kw)

I´m sure that there´s a lot of people out there that scream " oh no, not with a 273."
Well we will see in the spring, when I´m going to do anóther test in Another dyno :)
the Engine runs like a Dream anyway, so really I don´t give a **** :B
 
@valle, that sound´s great, these are very stout numbers !!

how much compression ratio ?

what pistons ?

i also do have a set of ported and polished 318 heads coming from my former 318combo maybe i should go on with them...



@roccodart, conc. the carb; i wanna give the Thermoquad a try because of the small primaries, which should work well with the small cui engine. But the TQ also offers a lot of benefit on higher RPMs due to the large secondarie buttflie air-door - so maybe the best of 2 worlds

about the cam, i know it´s not so fancy at all, on my former 318 i was running the compcams xe274. a nice cam and the teenie was climbing up to 6.500 pretty fast. but i also noticed a huge lack of low bottom power and tourqe.

one of the main problems is to deal with the needed stall for a more redical cam.
first prob. - normal city traffic will drive you made with a stall of 2500 or more
sec. prob. - to find a converter with higher stall for the pushbutton trans. here in Germany. (thats why i play with /6 converters, on my 318 i realized a brake stall about 1950 to 2050 with the /6 conv)

@redfish - thanks for your suggestion about the big valve probs conc. shrouding the cylinder.
the headers will provide enough flow i think (special set up hand made by a good friend of mine)

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I've run a 750 cfm TQ off a 71 340 on a 273 for years. Loved it, Power and gas milage. You can also adjust the air valve on the secondaries for the 273 and auto trans. The first thing I'd decide is what octane gas you are going to run. That will decide compression ratio. But I'm a bit cheap. Since you have ported heads, 2 barrel pistons, that should get you down to 87 octane. If you can get higher octane, then I'd use the 273 closed chamber heads you also have. 1.88 intake valves will fit but you have to check. Mock up your engine and measure the clearance at the bore on both heads. 1.60 exhaust valves should not be a problem. I like a 340 cam in a 273, but somewhere around that should do. If you are running solid lifters The Isky E-4 grind has pretty good torque and will pull past 6,000 rpm. I'm running a 4 speed so the only trans issue I have is getting a clutch to last. There have been some nice threads on 273's lately so I'd check them out.
 
hi folks,

as she is allready out or order, due to a broken driveshaft yoke, and it will take some time to get the spare parts, i decided to let the trans checked and revised by Mr.Shift aka as KickDown here on FABO.

Meanwhile i just want to up-date the family, and furthermore wanna ask for your suggestions conc. camshaft (maybe also a suggestion on numbers to order a custom made one)

current state:

- 273 .040 over
- CR 8.8:1
- Heads #920 with opened up runners to 340heads size, bowl blended, valve bosses grinded down, exhaust runners and combustion chamber polished
- Rockers stock hydro
- Valve springs compcams 901-16 (353lbs seat load 101 closed load 242)
- Headers (long tube custom made)
- intake LD340
- Intake OEM spread-bore 4bbl cast from an 1971 340engine
- Carb 850cfm Thermoquad
- stock 273 bottom end (crank, rods)
- Windage tray
- 9 quart deep oil pan
- Trans TF904 pushbutton with stock /6 converter
- Rear end 3,91 clutch-type
- Tires 26.1 hight

at the moment i run this mild cam (as mentioned in my first posting) ssi 11309 (lob 112, duration 050 lift 204-214, ad dur int.270 exh.280 Valve lift .420 .443)
some kind of nice cam, similar to a 340 cam as far as i know

now it´s up to the FABO members to give me some new suggestions/ideas
wanna get her into mid 14sec times
 
66fs said:
You should be there with the stock 71 340 intake and TQ, as is.
Click to expand...

:) thanks, due to the current circumstances (new job, moving from South to North Germany) i really did not have the chance to try and test it .

i only had the opportunity to make 2 runs on a track (prepared and sticky and i was there with street tires and the timing crew forced my to roll through the water and do a short burnout) result was 16.6 sec. whole set up not tuned in, carb and ignition not dialed in and set properly

last month i purchased a set of Mickey Thompson SportsmanPro- So i will be more prepared for the next time on a sticky track.:burnout:

guess i have to take some time to tweak the TQ ( for the moment i have no expierence with them)


any thoughts about the cam ?
 
My advice is to go as high compression as you are comfortable with on street gas. At least 9.5:1. The 4bbl Commando was nominally 10.5:1. A small displacement motor won't do anything on low compression, unless you're using a power adder (NOS, turbo, etc.).
 
My experience with cams in 273's are stock solid Commando, pretty sweet. 284 duration solid, pretty strong. Used 340 stock cam, 1.88 intake J heads and 71 340 intake and TQ, Wow! All got 20's for mpg cruising highway. " 69 Cuda 440" did a 273 cam comparison in a 67 4 speed Barracuda, If I remember correctly. Very informative. I'd say if you tune your engine correctly and your cylinders sealed up, good valve job, good bores and rings, you should be there.

http://www.forabodiesonly.com/mopar/showthread.php?t=225211
 
Just want to bump up this thread, as i have a Chinese Knock off Air-Gap-style intake lsying around. (Think mist of you know this crosswind called intake )

Engine etc are pretty much the same like when starting this thread. In the meantime i dropped the TQ as i still had problems when hitting the go-pedal hard and fast, replaced it with a 650 spreadbore 4011 Holley which responses right when i'm going to hit the pedal.

Question wil be now? Any benefit or loss when changing frfrfrom the iron 4bbl stock intake to the Air-Gap intake?
 
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