HP gain of 10.5-1 pistons vs 8.8-1 in a 273.

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txas2step

txas2step

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How much difference in HP would be gained by replacing the 8.8 to 10.5 pistons? 8-10%??Been working on a 1965 2 barrel 273. It was a low miles (35K) original motor from a Dart. Rebuilt with original 8.8 pistons,rods. Honed cylinders not bored, crank polished.Heads redone.
Added the E4 isky cam and lifters. Factory 4 barrel intake and 575 cfm AFB. Electronic ignition .Have the finned valve covers and chrome air cleaner. It is dressed out top to bottom although I have not secured the intake,timing cover or pan gaskets or primed the oil pump. Just sitting on the stand contemplating what to do with it. I never intended for it to be a hot rod...just a bit more pep. than the 2 barrel version. Plan was to find a early dart/valiant /6 car and change it out with a 4 speed. Plans changed when I bought my Dart Gt this past Feb. The hp 273 in my 1965 dart Gt has plenty of power for me even though it has the 904 auto. I guess if I sell it in the present state, buyer could change to the Egge 10.5 -1 pistons with a bit of effort.

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Not much. And did you blueprint and measure everything to come up with your compression ratio, or is it a guess?
 
txas2step said:
the Egge 10.5 -1 pistons with a bit of effort.
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According to my reading/study/knowledge the Egge piston is not a true duplicate of the factory 10.5 piston. Don't know if it is due to a lower compression height or what. If that is the case, not much reason to swap the pistons. On the other hand, the old school TRW forged pistons are(were) the real deal (I ran the TRW's in my bracket car).
 
txas2step said:
How much difference in HP would be gained by replacing the 8.8 to 10.5 pistons? 8-10%??Been working on a 1965 2 barrel 273. It was a low miles (35K) original motor from a Dart. Rebuilt with original 8.8 pistons,rods. Honed cylinders not bored, crank polished.Heads redone.
Added the E4 isky cam and lifters. Factory 4 barrel intake and 575 cfm AFB. Electronic ignition .Have the finned valve covers and chrome air cleaner. It is dressed out top to bottom although I have not secured the intake,timing cover or pan gaskets or primed the oil pump. Just sitting on the stand contemplating what to do with it. I never intended for it to be a hot rod...just a bit more pep. than the 2 barrel version. Plan was to find a early dart/valiant /6 car and change it out with a 4 speed. Plans changed when I bought my Dart Gt this past Feb. The hp 273 in my 1965 dart Gt has plenty of power for me even though it has the 904 auto. I guess if I sell it in the present state, buyer could change to the Egge 10.5 -1 pistons with a bit of effort.

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Looking good. If your short block is together I wouldn't mess with it. The Egge pistons will get you about 9.6/1 with milled heads. Run what you have and it will perform well. If you want a tire smoker build yourself a 400 horse 318, a 340 or a 360 but with those combinations you may need upgrades to the drivetrain.
 
toolmanmike said:
Looking good. If your short block is together I wouldn't mess with it. The Egge pistons will get you about 9.6/1 with milled heads. Run what you have and it will perform well. If you want a tire smoker build yourself a 400 horse 318, a 340 or a 360 but with those combinations you may need upgrades to the drivetrain.
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I'd like to add he could also bolt on an Edelbrock D4B. If possible maybe switch the heads to 920s. With stainless valves the flow excellent. Of course he'll need some gear to make that little 273 scream.
 
toolmanmike said:
Looking good. If your short block is together I wouldn't mess with it. The Egge pistons will get you about 9.6/1 with milled heads. Run what you have and it will perform well. If you want a tire smoker build yourself a 400 horse 318, a 340 or a 360 but with those combinations you may need upgrades to the drivetrain.
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Thanks Mike, I'll go with it as is.
 
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The bigger difference from higher CR is not in the HP as much as it is in the low RPM torque. As stated, the factory 'CR' was not what you really got.
 
A friend of mine just dyno'd a .030 273 with factory intake, Isky E-4, 2 barrel pistons, 920 heads, .039 large bore Fel-Pro gaskets, Edelbrock carb and headers. 266 HP
 
66fs said:
A friend of mine just dyno'd a .030 273 with factory intake, Isky E-4, 2 barrel pistons, 920 heads, .039 large bore Fel-Pro gaskets, Edelbrock carb and headers. 266 HP
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That's what we like to hear.If I ever pull mine out I will dyno it just for fun. Then my first Desktop dyno run would be pretty close. I set it up with manifolds and it made 255 hp. Headers should add 10 hp or so. The Desktop Dyno is very close again.
 
This was an option I was thinking about. By the time I bought new Egge/Kanter pistons and had them shipped i would be close to $1K in price. So the price as well as "downtime" with me having to pull perfectly good running 273 had me looking at different small block options. I now have 3 small blocks in the shop...dammit.
The way I looked at it was the Chrysler tech' spent a bucketload of time/research and $$$ to get what maybe 300-325 HP?? I wanted a bit more, and eventually I was offered up a fresh machined sb shortblock.
I like that all my Commando pieces will swap over to the new build.
Yours looks awfully nice!
 
If I don't sell the motor it may wind up in a 1961 D100 /6 shorty I sold to a friend several yrs ago and I may be getting it back. Had the hairbrained idea of a Dart Charger D100. '61 was the first year of the Sweptline series '61-'71. It was marketed as a " Dart Truck" ( '61 only). I would add the '65 dart buckets and maybe some 273 fender badges. This is the '61 shorty. Dare to be different. LOL.
( I also have headers and 2.5 exhaust and flow masters to fit the d100 shorty).
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txas2step said:
If I don't sell the motor it may wind up in a 1961 D100 /6 shorty I sold to a friend several yrs ago and I may be getting it back. Had the hairbrained idea of a Dart Charger D100. '61 was the first year of the Sweptline series '61-'71. It was marketed as a " Dart Truck" ( '61 only). I would add the '65 dart buckets and maybe some 273 fender badges. This is the '61 shorty. Dare to be different. LOL.
( I also have headers and 2.5 exhaust and flow masters to fit the d100 shorty).
View attachment 1715117242

View attachment 1715117243
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Now that's cool!
 
Much better served either getting headers, or doing some basic head port cleanup (not massive porting - just cleaning a few things up). Compression alone won't do much.
 
txas2step said:
If I don't sell the motor it may wind up in a 1961 D100 /6 shorty I sold to a friend several yrs ago and I may be getting it back. Had the hairbrained idea of a Dart Charger D100. '61 was the first year of the Sweptline series '61-'71. It was marketed as a " Dart Truck" ( '61 only). I would add the '65 dart buckets and maybe some 273 fender badges. This is the '61 shorty. Dare to be different. LOL.
( I also have headers and 2.5 exhaust and flow masters to fit the d100 shorty).
View attachment 1715117242

View attachment 1715117243
Click to expand...


Son of a mother bear that's a freaking nice truck.
 
That is a nice looking truck.
I had a 69 and a 71, hate the old straight axle steering.
 
You got a answer to my question or you just want a feel good answer?
 
toolmanmike said:
That's what we like to hear.If I ever pull mine out I will dyno it just for fun. Then my first Desktop dyno run would be pretty close. I set it up with manifolds and it made 255 hp. Headers should add 10 hp or so. The Desktop Dyno is very close again.
Click to expand...
Care to do a 68 318 on that desktop dyno? I hear 180HP thrown around quite often, I think it has more beans than that.
 
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