Most HP out of a 273??????

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johnmucci

johnmucci

moparmucci
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I have a 66 273 engine that I want to rebuild.. the question is: what is the max hp I could get? the block is .30 over and I am going to buy new pistons, cam, etc.... any thoughts?? comments, etc? I want to stay w/the 273 .... need to piss off some chevy lovers..lol thanks!
 
I saw an article in M/M a while back where a guy had a B-body wagon running 12's with a 273. If you search their archives you could probably find the article.
 
I gess that depends on how much money you have..I seen a destroked 273 in I think a E modified production class car back in 81 at rockingham smoke the chevys the car left the lites at 12000 rpm and the shift setting was on 11000.the car had to have a 100lb.flywheel on it..I know this doset anser your question but I know they well run.$$$$$
 
At 1.5 hp per cube, that equals approx 410 hp. That's a serious build for a small displacement engine. A 360 would be 540 HP.

Making power costs money and if you have it in boat loads for seriously nutty builds, the 2.0 hp per cube is also doable. that equals 546 HP.

Exceeding a 2.0 hp per cube is getting really nuts. But it is possible, it just takes money and a damn good builder.
 
I was putting 275 at the tires at 7500rpm back in the late 70s, I have 6000 in the engine alone and that was back in 79. 273 was in my 64 Dart. Was a great 1/8 mile car, circle track car with tall gears and a fast as heck 0-60 street car with gearing too, but best ever was high 12s in the 1/4. Little motor had to little torque, but i should of modded the block with 340 heads and stepped up to at least 11.5 compression.
I ran a big solid cam, 360 valves in a modded 273 early style head and small block notches, stock 340 forged crank oil modded, drilled etc and 800 afs and a strip dominator port matched.

A lot of other stuff too and depending on what year and or track, ontario 500, 605 speedway, and 1/4 & 1/8 tracks many diff convertors and gear sets. I even ran a stick for 2 years and went through a crap load of clutches too.

A stong bottom end, decent heads, a roller modern cam and a turbo would be the way to go no a days, well astroker too, but then it is not a 273. The small stroke with the small pistons can pull 9k easy with the correct setup :)
 
Rumblefish:
I would be "tickled Pink" if I could get 350 hp.. I really won't "drag race" this car but I want it to "kick ***". Is is possible if you had the time, you might be able to lay out a "blueprint" to achieve this? I am planning on using TTI headers & exhaust w/904 w/shift kit. 8 3/4 rear end w/391 gears.

thanking you in advance, John
 
You could stroke it and get 450+ with a 10.5:1 motor and a 300 dur./550 lift
roller cam.
 
Ha Toolman!!! My Mopar Guru!!! the thing is, I need to be guided!! I need everything spelled out.............. like an outline, I am not Motor savy as I am sure you already knew that!!!! Thanks God of Mopars!
 
johnmucci said:
Rumblefish:
I would be "tickled Pink" if I could get 350 hp.. I really won't "drag race" this car but I want it to "kick ***". Is is possible if you had the time, you might be able to lay out a "blueprint" to achieve this? I am planning on using TTI headers & exhaust w/904 w/shift kit. 8 3/4 rear end w/391 gears.

thanking you in advance, John
Click to expand...

I could think about this and come up with something. What are your limits and peramters and budget? Theres a few been there and done that fellas right above. A detuned engine copy maybe?

In general, I'd start with a build able to spin 7,000 rpm and look for a 10-1 ratio.
Head flow of something like what Edelbrock says there S/B heads flow. Maybe look to Brain (OU812) for a look into the RHS heads for the "LA" ported.
A off the shelf cam is easiest to recomend at this point and I think I would look at (For example) the Comp Cams XE268 or a more agresive XE274HL. The 268 is a 1800 - 5800 and the 274hl is a 2000 - 6000 cam. The higher lift takes advatage of the ported heads with the higher lift.
Also a Huges cam or Lunati equal for this endevore.

If the engine is well built and look at carefully and thought about when being built up, then 350 HP will be shattered and passed with the abilty of still haveing good street manors.
 
I start with a desktop dyno program.
http://www.summitracing.com/parts/CCA-186011/ Although the dyno programs
are not totally accurate, they will give you a direction as to what works. Get on the Summit website and try different cams and intakes and carbs. Rumble knows what works. He also suggested contacting Brian (ou812) he may be able to help. You need someone like that that has built many small blocks. I know a few guys around my area that are all Mopar and have built small blocks but a 273 is a different breed compared to a 340/360. Even 318's are easier to build because of their larger bore. There has been posts about racers that have screaming 273's at the strip. Maybe you could contact them for some basics of their combo. I will post a link if I can find the post. As with any high perf. build
(1.5 hp/cu.in+) be prepared to spend some serious $$$'s. Here's alink to Matt Steens website. http://www.victoryengines.net/shop_services.html Mike

mattsteen.jpg
 
The name Mike Jeffrey of Lexington, Nebraska keeps surfacing on the net. He is a slant 6 racer now but used to build and race 273's and 318's. Find his number or address and contact him. He may have some suggestions for you.
 
I think the biggest two issues are the pistons, and the heads to use. IMO, I'd go full custom pistons and for heads I'd be looking at a set of EQ Magnums. I don't think using the 340/360 port or a valve over 1.92 is goign to help. A lot has been learned between the 70s and now especially in regard to port size and air speed.
 
I dont understand.. You dont want to drag race but you do want to kick azz... karate lessons ? LOL
You can sink a small fortune in a 273 for a dyno print out that shows you could kick azz if you wanted to. You'll also throw away streetable performance, fuel economy, and long term dependability for that piece of paper.
A little bit of cam and tuned exhaust will make the 273 interesting and you wont need to spend all your spare time under the hood. Just my .02
 
If all you want is 350 hp that shouldnt be to hard. The D dart had 275 from factory. I ran a 273 from 66 to 69 I dont remember having any problem beating bowties then. I dont know but it was rummered way back then you could turn the pistons around and gain a bunch of hp. I think it was the compression that went up when you turned them around. This was of course old school talk, never knew anyone that did it.
 
Unless your pockets are VERY deep, do yourself a favor and get a 318 or better yet, a 360. You'll be so much happier with the bigger engine and it won't break the bank. Believe me, been there, done that.
 
If you are only looking for a hot street car, and not for a specific class drag car, big inches are the way to go.a 360 with headers, intake, cam, carb,
will outperform a big$$$ 273 all day long,and will be streatable.
my $.02
Roscoe
 
I agree with Moper here. Custom pistons will be needed since there not a shelf item. Be forewarned that custom fordged slugs will run about a $1,000. While fordged units are not needed, cast pistons will be cheaper. Try Egge for cast slugs. They'll cut them for you to your spec easy and quick. Someone from Egge even popped up here once.
http://www.egge.com/

Valve size is an issiue and bore notching may be required for bigger valves. Bigger heads like the 340/360 heads are needed.

Redfish is concerned about a few things, but, I beileve a cam of approx. 230* of duration at .050 will deliver the goods with the proper parts working togther. This cam duration isn't to big at all and long life shouldn't be an issue.

Wedgie makes good sense, but, if a 273 is what the heart is set on, so be it.

Jack makes a good history note. The D-dart was a 275 HP engine with , as delivered *IIRC* Dougs headers on the engine, A Holley carb and the discountinued MoPar 284/.484 cam. It has since been reground and the advertised numbers stayed the same.
The new 284/.484 cam is bigger than the OE cam.

Lets not forget about ToolmanMike. First I'd like to say thanks to him for kind words.

Second, he makes a mention of a dyno program. While he did link you with a basic program, you need to take it with a grain of salt and also understand that some of the programs accurate issues are with parts selection and real world engine dyno's. Also, it will assume that every thing is not just well built, but expertly built and run on optinum days and conditions.

Real world engine dyno's can be happy ones or even stingy ones. Bottom line, there a tool just like the dyno sim is. When you use a computer dyno sim, stay with a dual plane intake on that menu's choice. The single plane gives away to much HP.

Also enter accurate head flow figures and when ever possible, along with cam valve timing as per the cam company spec card as it reads. Keep exhaust selection with mufflers, not with open exhaust. The truth is somewhere in the middle.

Lastly, take note and look closely to the cams size & timing. This over talked about item is a critical part in it operation. The smallest amount of timing movement adjusted in any direction will effect power and it could be in a big way. I suggest looking at several cams from several sellers/companies and jot down the timing events to enter in the sim.

For a 273 build, I would focus in on low to mid range torque, the HP will come without worry. Use the sim mostly as a learning tool and not so much as concreate fact. You'll be much happier this way.
Also, over build the dyno sim engine - so to speak - because it assumes alot. This way, when you hit the pavement with the "Theoretical build", you'll be happy with the results rather than saying and quoting old TV Wendy slots with,
"Wheres the Beef!"

When in doubt, select the smaller cam.

These basic guide lines will keep the results a bit closer to real honest world results.
 
From the outside, most people would not know the difference between a 273 and a 360, or better yet, a stroked 360! You could even use the 273 valve covers, timing cover and balance the engine internally to get away from the external counterweight on a 360 balancer/damper. Just mark the balancer accordingly - I think 273 timing marks are on the passenger side? You could also grind off any identifying casting logos off of a good aftermarket dual plane intake and paint it the engine color also to add to the "illusion".
Even better if you could figure out a way to put OEM appearing firing info and casting numbers on the aluminum intake before painting!

As others have suggested, the extra cubic inches will do wonders for HP, torque, reliability and streetablity. A 360+ would work well with 3.91 gears because it will have a lot more torque to get it going. Even NHRA/IHRA Stock-classed 273's run as much as 5.38 (possibly 5.57) gears, depending on the weight of the vehicle, for optimum accelleration, not to mention VERY loose torque converters.

400 HP with OEM heads would be a piece of cake with a 360 while adding to the OEM appearance.
Just find a machine shop that has Mopar experience. One having a torque/honing plate available would be a good sign.

If at all possible, tie the frames together. It will reduce body flex and help weight transfer, even without a roll bar.
 
I should add like Loco said.. I'm using a 360 in my '65, using all stock parts but the intake and carb. I am using the manifolds which would choke ANYTHING because they are horrid. But my goal is dead stock reliability, about 300hp and as much torque as I can get, running with 3.55s and updating the trans to modern guts and rear slip yoke but retaining the factory consolette and cable shift.
 
The trick is figuring out what you really want before you start. Streetability, power, torque, reliability, handling, 1/4 mile times and what mix of the above. Then things get easier and advice more helpful.
 
Thanks to all for your comments, suggestions! Now I Really Have a Headache!!! just kidding.. I really do appreciate all your remarks.. I guess I want my "cake and eat it too". $$=HP.. i guess that equation will determine the outcome of the 273! thanks again guys!
 
Good luck John and we'll be here for ya'. It's a complicated scenario. Like Rumble said, and I always disclaim, the desktop dyno is a place to start but not the gospel as far as the numbers. I put together a combo that the dyno program estimated at 322 hp. If I get to 300 I would be happy. The stock motor is only supposed to put out 235 so anything would be an improvement. The E-4 cam is a bit bigger, the heads have been ported and port matched a bit as well as the intake and the exhaust manifolds, and I am planning on a
better exhaust system. I should notice a performance improvement with those
modifications. Will I get to 322 hp? I don't know. I may never dyno it. If you want to build a screemin' 273 take it slow and do your homework. I have been planning mine for a year now and I'm only going for 300 hp. You will need a well thought out plan to get to your objective.
The basic 273 is a sound piece to start with. You could use the stock forged crank or jump up to a lightweight aftermarket crank depending on the pistons and rods you use. Don't forget to get everything balanced. I wouldn't use much more than a 10.5:1 piston unless you want to use high octane gas. The cam you use depends on where you want the power to come in at. I would think a modern hydraulic roller would be a good choice and the cam companies are great about helping you find what you need. I would also use shaft roller rockers for the valve train. I would use the stock heads or a set of the #302 castings (they have hardened seats) and have them port matched, bowl blended, and the runners ported a bit. How far you go depends on the cam you use and the rpm you need to turn. I would use stainless valves or have the stock valves back cut. (the stainless valves flow better) If my memory serves me correctly the stock valve size is 1.50/1.78. I would go with a 1.60/1.80. That should improve high rpm flow without causing clearance or shrouding problems. Have the seats done on a Serdi type machine for better flow and smooth transition into the port. Intakes and carbs work with your cam/compression combo. If you need power at 6000 rpm you need a intake that will flow a bit past that rpm. The 273/318 intake ports are smaller than the 340/360 ports so an intake for the bigger engines won't work as well as an old Ld4 Edelbrock which is made for the small port heads. Have your head guy port match the intake also. I would think a 650-750 cfm carb would do the trick. Vacuum secondaries seem to work better on automatics. A good ignition system is a plus. The Mopar electronic system works good but not as hot as a Msd or the like. Headers and a free flowing dual exhaust with an x pipe is good stuff. You will also need a strong automatic or a good clutch (minimum of 10.5") and a 833 4 speed. You will need a 8 3/4 Sure Grip rear with which ever gears match your engine build.
The stock springs may not get you the traction you need but you will be trying to hook up on the street so what works best there I don't know fore sure. Super Stock springs are good an Cal Traks are superior but they are strip pieces. I'm sure I left out a bunch of stuff but I've rambled on for long enough. Good luck and keep us posted as you build. Mike
 
Locomotion said:
Sorry for the headache! lol

I did find a company that makes 273 pistons, cast I believe. One is suppose to be around 9-1 and the other 10-1 or so. Numbers are at the bottom of the page. But I know nothing else about them. You'll need to contact them if you decide to stick with the 273.

http://www.egge.com/site/?d=48&dt=1&SubCategoryId=2&make=DODGE&rpp=10&pageCursor=2
Click to expand...

There are a few of us (me included) that have ordered Egge pistons lately and are very satisfied with the quality and the service. I am putting my short block together and hope to have it driveable by Memorial day. I used the 10.5:1 pistons. Mike

09_24_0.jpg


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