Another 273 cam question.

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KevenP

KevenP

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Hey all,
I just picked up a '68 Dart with a rebuilt 273/904/8 3/4 rear end combination.
I'm wanting to add some power. The motor is a '68 2bbl with 9.2 to 1 compression.
It has headers, MSD ignition, Edlebrock intake and a Summit 600 cfm 4bbl carb installed.
I'm going to add some '302' casting heads.
The tranny has a 2300 stall converter and the 8 3/4 has a 489 case with 3:91's
and a clutch style Sure Grip.

I'm looking at the Lunati Voodoo cam below:
Voodoo Hydraulic Flat Tappet Cam & Lifter Kit - Chrysler 273-360 268/276 - Lunati Power

Any words of wisdom for me? :)
 
So the previous owner threw all his coins at not enough cubes ?
 
Seems like a lot of cam for a 273 and only 2300 stall. Ill bet real compression is closer to 8.5 to 1 if that. I would go two steps down from that cam in the voodoo series. If the original heads are open chamber the 302s will give you a compression increase if not it a wash. Make sure you use Mr. gasket .028 thick gaskets from summit racing. Stock replacement felpros are around .050 . Just my opinion. There are a lot smarter people on here than me.
 
aaronk785 said:
Seems like a lot of cam for a 273 and only 2300 stall. Ill bet real compression is closer to 8.5 to 1 if that. I would go two steps down from that cam in the voodoo series. If the original heads are open chamber the 302s will give you a compression increase if not it a wash. Make sure you use Mr. gasket .028 thick gaskets from summit racing. Stock replacement felpros are around .050 . Just my opinion. There are a lot smarter people on here than me.
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Aaron....you're already pretty smart as everything you wrote is totally correct!!
 
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Thanks for the input. According to the info I've managed to find. The 2bbl's were 9.2:1 and the 4bbls were over 10:1.
 
aaronk785 said:
Seems like a lot of cam for a 273 and only 2300 stall. Ill bet real compression is closer to 8.5 to 1 if that. I would go two steps down from that cam in the voodoo series. If the original heads are open chamber the 302s will give you a compression increase if not it a wash. Make sure you use Mr. gasket .028 thick gaskets from summit racing. Stock replacement felpros are around .050 . Just my opinion. There are a lot smarter people on here than me.
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All 273 heads have the same heart shaped chamber hump as the 302s have. 302s do offer swirled ports and hardened seats. A 273 aint never gonna be a heck of a lot more than a 273.
 
Why not go solid lifter? The rockers should already be the adjustable type. Some nice springs and a little head porting........
 
RedFish said:
All 273 heads have the same heart shaped chamber hump as the 302s have. 302s do offer swirled ports and hardened seats. A 273 aint never gonna be a heck of a lot more than a 273.
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Not quite....

'920 heads...
20160122_185012_zps1zz7zlkp.jpg


'302 heads...
302head.jpg
 
We put a comp cams 270-s in dads 67 273. Stock 2bl style pistons. Backyard port job. Ld4b Eddy 1406. Sounds awesome, great choppy idle but I want more power.
 
I'd PM trebor75 and I can't remember his name right now but he's running a tunnel ram 273, talk it out with them. Their running big ish cams and seem happy with them.
 
273 said:
I'd PM trebor75 and I can't remember his name right now but he's running a tunnel ram 273, talk it out with them. Their running big ish cams and seem happy with them.
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Yes on the cam,282 xs solid Comp,no tunnel,though..Air Gap,I do believe ...
 
I agree that cam is too large for the converter. One step down though would work well.

What these guys are trying to tell you is, your engine was RATED at 9.2 compression, but it IS NOT actually 9.2. It is more like 8.5 at best.

Chrysler's deck heights were very tall compared to the "nominal" spec. Nominal is a fancy word for "about". In other words, there's a RANGE around what the spec is, and Chrysler's deck heights were always very tall......and usually crooked and that cut way down on the actual compression ratio.

Also the actual combustion chamber volume was usually always larger than spec, leading to even more compression loss compared to the rated spec.

This is why when a professional builder builds an engine it gets"blueprinted" to a certain spec. Blueprinting means adjusting everything to a certain spec, such as those used by the factory, or a set of predetermined specs the builder and or customer agree on to achieve an actual compression ratio.

Can you imagine the added cost to cars had Chrysler blueprinted each and every engine they built? It is always best to "assume" the compression to be lower than the factory spec if the engine is still in stock condition regarding piston style and cylinder head configuration. This way, it will be less easy to over cam the engine.
 
Abodybomber said:
Yes on the cam,282 xs solid Comp,no tunnel,though..Air Gap,I do believe ...
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I meant besides trebor75 there's a guy running a tunnel ram 273, there like 3 or 4 guys running pretty hot 273 everyone else are pretty mild but I'd search them up since they have 1st hand info, or stick to a more mild cam.
 
273 said:
I meant besides trebor75 there's a guy running a tunnel ram 273, there like 3 or 4 guys running pretty hot 273 everyone else are pretty mild but I'd search them up since they have 1st hand info, or stick to a more mild cam.
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Your tunnel ram guy,"Prostock273",IIRC,273...I like a mild cam ,here....Close to what you chose,for yours....
 
I used a Isky E4. Mild but it works well. Screams? No but it works. Check out my 273 building thread below.
 
toolmanmike. Thanks. I have been reading your build thread for a few months. Even got it book marked. :D

To everyone else that has taken time to post useful information........Thank you!

I know the 273 is the least loved of the LA motors, just tryin' to get some more power out it. :steering:
 
I don't think its the least loved if you look at views 273/318 always get more than 340/360/408. It's just an upward battle to compete with 360 and the like. A 360 is 32% larger so a 273 needs 32% more gear, stall and rpms to be on a level playfeild.

But like any engine more CR head flow and cam will bring more power I'd go with something like 260-265 and .450 lift.
 
I had a 2 bbl 273 with a solid 262 4.73/4.73 and 273 heads ported by a member here to flow 204cfm int & @.450 lift. I would have loved to use it with the gears and exhaust you have. Even so, It was a lot of fun and I can't wait to put it back to use.
 
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