273 Supercharging?

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chrissock

chrissock

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I know, I know "just get a 360". I have a 273. I don't like doing what everyone else does. I am not going to say money is not an problem. But I like the cool factor. So now that all thats out of the way.
I plan to source a centrifugal super charger, No intercooler, and use a fast EFI throttle body that I have sitting here.

I have a stockish built 273. It has been rebuilt at some point and has a hydro cam and a set of solid lifters. I plan to take it all the way down and do bearings, degree cam, balance pistons and rods. Heads are at a buddies shop getting full race treatment only because he owed me money. So Good springs and guides, valves and such. I am not looking for a monster just a fun street toy for the family. Figured putting arp studs and a good set of gaskets. Figured 5-7 psi. Any other thoughts? Does anyone make forged pistons?

Anyone else done this? What is a good red line for these little suckers with what I have done. Can I get to 300 HP?

Any input would be appreciated.
 
Take a look a paxton superchargers, they make a complete bolt on kit for mopars.
 
I think fun would involve using two turbos from 2.2, 2.5 or 2.4 mopar 4 engines. Build a turned up log header for each side. Use a dual plane intake and partition the boost on the throttle body.
 
Just get a 360......hahaha....just kidding. I say yeah go for it. Might wanna get some better rods, and better pull out the ol' wallet if you want some 273 forged pistons. Chances are, your 273 crank is forged steel so that's good.

I was thinking of going the same route, except using a turbo. 273 engines are basically free, and that's always a nice starting point.
 
I know you are talking a centrifugal but you may want to look at a B+M roots style. Member jimjimjimmy has a complete setup for sale for a good price I believe. I picked it up for him and it appeared to be in very good shape. You would still be able to use you EFI and the wow factor is there as well. Just a thought.

Other than that I would say to keep your compression down and don't skimp on the cam. A cam for boost is a lot different than one for N/A engines.

Let the exhaust breath as well, that is where most bottlenecks occur in boosted engines. Go hang out in the Boosted forum and also visit YellowBullets boosted forum, it is a good one.

Jack
 
The other thing you might investigate is some of the belt drive factory optional stuff used on the mustangs and GM stuff
 
You can make NA 300 with a 273, blown 300-400 hp shouldn't be a problem
 
Just shooting from the hip here: I would be looking at CR's down in the 8.0:1 range for this, maybe less. Wild cams like for NA are certainly not the way to go, but I can't advise you on the right numbers.

Have you looked at flow versus RPM for the charger you are considering, with the drive/reduction combination? Too much of a flow mismatch will make problems either way: excessively rising boost with RPM or no boost with engine RPM.

No need to flow heads or go big valves; that is what the charger is for. Just make the valves seal well and the guides good, good valves, etc.

5-7 psi is mild so I suspect you can get by with cast pistons OK; I would certainly start there. I have raced rallies with hypereutectic cast pistons on a 2.6L Mitsu motor with 14 psi boost (turbo) with a true 7.3:1 CR; you can be on the boost for long periods at times and under all sorts of engines loads and RPM's in rallying so that is a good test, IMO. And I don't think the turbo'd Buick V6's in the 80's used anything but cast pistons. I later went to forged piston with a true 8.2:1 CR and 14 psi boost.

The stock pistons and the one model (L2221 for non-dome) available nowadays for the 273 have higher CR than you should use. So, maybe some work to open the combustion chambers might be in order and thicker head gaskets; you can always go to thinner ones to up the CR a couple of tenths.

Are you using the open chamber heads? With those, it may work out to not be too much work to lower the CR.
 
cudavert said:
Just get a 360......hahaha....just kidding. I say yeah go for it. Might wanna get some better rods, and better pull out the ol' wallet if you want some 273 forged pistons. Chances are, your 273 crank is forged steel so that's good.

I was thinking of going the same route, except using a turbo. 273 engines are basically free, and that's always a nice starting point.
Click to expand...

I would be fine spending a bit for rods and Pistons. I know pistons are a bit hard to find. Any thoughts on where to get them. Rods would be the same as a 318 correct?
 
Coyote Jack said:
I know you are talking a centrifugal but you may want to look at a B+M roots style. Member jimjimjimmy has a complete setup for sale for a good price I believe. I picked it up for him and it appeared to be in very good shape. You would still be able to use you EFI and the wow factor is there as well. Just a thought.

Other than that I would say to keep your compression down and don't skimp on the cam. A cam for boost is a lot different than one for N/A engines.

Let the exhaust breath as well, that is where most bottlenecks occur in boosted engines. Go hang out in the Boosted forum and also visit YellowBullets boosted forum, it is a good one.

Jack
Click to expand...

I considered the roots type. I want to keep this car able to be drivin in the rain if needed. I have a 1971 VW Ghia that is turbo charged. This is supposed to be my "family hotrod"
 
273 said:
You can make NA 300 with a 273, blown 300-400 hp shouldn't be a problem
Click to expand...

Cool. Any thoughts on what is pushing the envelope for the crank and say a set of decent rods and forged Pistons. HP wise? Or how many psi is the don't go any further point?
 
nm9stheham said:
Just shooting from the hip here: I would be looking at CR's down in the 8.0:1 range for this, maybe less. Wild cams like for NA are certainly not the way to go, but I can't advise you on the right numbers.

Have you looked at flow versus RPM for the charger you are considering, with the drive/reduction combination? Too much of a flow mismatch will make problems either way: excessively rising boost with RPM or no boost with engine RPM.

No need to flow heads or go big valves; that is what the charger is for. Just make the valves seal well and the guides good, good valves, etc.

5-7 psi is mild so I suspect you can get by with cast pistons OK; I would certainly start there. I have raced rallies with hypereutectic cast pistons on a 2.6L Mitsu motor with 14 psi boost (turbo) with a true 7.3:1 CR; you can be on the boost for long periods at times and under all sorts of engines loads and RPM's in rallying so that is a good test, IMO. And I don't think the turbo'd Buick V6's in the 80's used anything but cast pistons. I later went to forged piston with a true 8.2:1 CR and 14 psi boost.

The stock pistons and the one model (L2221 for non-dome) available nowadays for the 273 have higher CR than you should use. So, maybe some work to open the combustion chambers might be in order and thicker head gaskets; you can always go to thinner ones to up the CR a couple of tenths.

Are you using the open chamber heads? With those, it may work out to not be too much work to lower the CR.
Click to expand...

From working with the Air cooled VW stuff I am fully aware of the CR and Piston selection. I honestly have not got the engine or heads back yet. I definatly will cc the heads and shoot for 7.5-8/1 compression. As far as the blower selection.....I figured I would call Paxton or someone like that and see what they recommend.
 
So my buddy and I have been doing some bench building lol. He is trying to push me to a nitrous set up instead of the supercharger. I have 0 experience with nitrous. Not that that is a deterrent but I'm curious your thoughts? Nitrous express makes a pretty easy kit and they claim its super easy set up. What do you guys think?
 
some times doing what the rest of folks are doing is not a bad thing.

with a 360 you get more cubes and better heads, if you want to go fast than 360 is the way to go.

if you just want to tinker to say that you supercharged a 273, then go for it, but its a dubious achievement a) because its probably already been done before b) because of the platform you are working with it won't really put out impressive numbers.

not trying to crap on your idea, but if your goal is 300HP there are better alternatives. Plus with the 273 your going to have to do a lot of updating to the whole package to make it work, i.e. fuel system, intake, water pump/radiator, trans/converter. so it not just lets play slap a supercharger on it and see if it works.


if you really want to keep the 273, i think you can get 300HP NA, but with some over bore, new pistons, cam, intake and head work. its already got a steel crank and ductile iron rockers so its a good base to start with something. check out the D-darts and get some specs on their 273s.


PS i tossed the 273 from my 66 dart because 318s are cheap and drop right in. so for me it was money thing.
 
Like has been said, Paxton makes a complete kit. Also, you could run low boost on the 273 and then while you enjoy it you could be building up a different engine (over time, no rush because you would already have a fun supercharged small block) that could take more boost and make more power. Then when it's built and ready to go, just pull out the 273 and drop in a different, larger small block, put the supercharger on it and crank up the boost.
 
Exactly /\ /\ /\

The whole thing will work on any small block he uses in the future.
 
BlueDream said:
Like has been said, Paxton makes a complete kit. Also, you could run low boost on the 273 and then while you enjoy it you could be building up a different engine (over time, no rush because you would already have a fun supercharged small block) that could take more boost and make more power. Then when it's built and ready to go, just pull out the 273 and drop in a different, larger small block, put the supercharger on it and crank up the boost.
Click to expand...

This is exactly what I was thinking.
 
My heads should be back next week from the machine shop. As soon as I have a long block I will go through and figure out what cam and Pistons are in it and go from there. Thanks for the help!
 
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