Engine builder questions

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Badart

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Has anyone ever installed a 3.58" stroke crank in a 273? Here is the part link http://www.summitracing.com/parts/dcc-5007257

With a .030" 273 should put it at 3.67" bore and yeild 301 cubes correct? The reason I as is because I am bulding a 65 Barracuda to compete in SCCA Prepared C class. Anything under 5,100cc or 5.1litres gets a 300lb weight break, so the car can weigh 2,700 lbs and be more competitive against the 302 mustangs and camaros. Anything over the 5.1L will have to compete with the big boys.

I know that Ma mopar used a destroked 340 in Trans Am racing, but I don't have one of those cranks laying around and I doubt anyone does either. LOL

If anyone has done this then I have a few questions. What pistons can I run? How much meat is there on top of a set of 273 pistons, can they be machined down? What is the biggest intake valve that I can run in that tiny bore? 1.88"? 1.92"? I know there will be valve shrouding, but I also want the engine to perform.
 
Hmmm, never thought about putting that crank in a 273. Got me thinkin now of what to do with the 273 in the Valiant when I replace it with that 318.
Good luck with the build John!! Can't wait to see the results.
 
John..you are going to have to find a piston with a 1.66 compression height...plus or minus...

dont know much about 273s, using a stock piston is going to be pretty hard to do...not only will you have to cut the top of the piston...but the skirts will probably need to cut to clear the counter balances on the crankshaft.

a set of custom pistons might be the easiest way to go...certainly will get a piston that will properly fit and along with valve notches...and get a light weight piston ....

you might be able to cut the rods journals down to fit a sbc..and use a shorter rod...that might help with the piston dome cutting but the skirts are going to get closer to the crank.....
 
........I've done the 3.58 in a 318 b4..............i suspect u will have to get custom pistons made..........u will need to notch the bores for bigger valves........kim........
 
Thanks guys. I just am hoping to find someone who has been down this road before. I want to have a little info before I start collecting parts. I plan on running the 273 for now, but you know what they say about displacement.
 
IIRC, the 1.88 needs to have the bore notched for valve clearance.
Valve shrouding is something you should worry about. Other manufactures don't worry about it. While it is true you'll make more power with I shrouded valves, you have bigger fish to slay first.

The piston is one such item. If you plan on making use of the stock slug, you may have a problem. Reason being is lack of on the shelf slugs to start. Second, if you you have them custom made, it cod cost a grand to have them made since it'll be a one off slug.

Machining the stock slug down to make a zero deck height slug will also require that the valve reliefs be cut. That 318_349 stroker threads shows how it is done. Not to my liking. But ....... It gets done. The one bad point I did t get thrilled about was valve lift is limited due to shallow valve reliefs.
 
rumblefish360 said:
IIRC, the 1.88 needs to have the bore notched for valve clearance.
Valve shrouding is something you should worry about. Other manufactures don't worry about it. While it is true you'll make more power with I shrouded valves, you have bigger fish to slay first.

The piston is one such item. If you plan on making use of the stock slug, you may have a problem. Reason being is lack of on the shelf slugs to start. Second, if you you have them custom made, it cod cost a grand to have them made since it'll be a one off slug.

Machining the stock slug down to make a zero deck height slug will also require that the valve reliefs be cut. That 318_349 stroker threads shows how it is done. Not to my liking. But ....... It gets done. The one bad point I did t get thrilled about was valve lift is limited due to shallow valve reliefs.
Click to expand...

Rob there are a ton of variables here. LOL Why the heck couldn't ma mopar make a 302.
 
Now that you mention that, he can destroke the crank if need be.
OK, it's expensive. ...
 
Yea man. No doubt . The 318 has many different piston heights.
 
Interesting concept.

Custom pistons would be required. Also, the 360 crank would need it's main journal diameter reduced. Don't most current NASCAR efforts use the 3.0" stroke crank? So they may not be too hard to find "lightly used".

I think 1.88 valves will fit the 273 bore, but 2.02 require notching. I'm a big valve proponent, but once you get into bore notching shrouding puts gains from larger valves are in the realm of diminishing returns. As for the 1.92's, the swap to an aftermarket Magnum pattern head would have enough other benefits to be worth it even if notching was required.

This engine would probably have more low to mid range grunt than a 5.0 Ford, but probably lose when it comes to all out horsepower. In the right chassis, this may not be a big disadvantage in Solo competition.
 
the current nascar cranks used in a Dodge has a ford main bearing size...
 
Cheif, Ma MoPar sells cranks with the 3.58 stroke and 340 mains.

The nice thing a out the long stroke will be torque! He can come out of the corners real well a d gain ground/time. A lack of HP vs the short stroke engines will be a disadvantage on a long straight away. He'll have to dominate the twists since it is possible he can get stomp on in a long straight away. He'll need the advantage in the twisty parts.
 
Scat ,was doing the cast cranks,for M.P./ D.C. a few years back.Nice product.Would be a fun project,like vintage Trans Am racing.
 
yes...MP dumped some of those 3.58 stroke 340 main cranks a few years ago...great price for them back then....
 
rumblefish360 said:
Cheif, Ma MoPar sells cranks with the 3.58 stroke and 340 mains.

The nice thing a out the long stroke will be torque! He can come out of the corners real well a d gain ground/time. A lack of HP vs the short stroke engines will be a disadvantage on a long straight away. He'll have to dominate the twists since it is possible he can get stomp on in a long straight away. He'll need the advantage in the twisty parts.
Click to expand...

SCCA Solo racing rarely gives you a chance to get out of second. They really like to limit speed. It's more tight and technical racing. Cars like this Mustang would be the competition. Most courses are actually tighter than this.
[ame="http://www.youtube.com/watch?v=fPde0SNEQ_c"]Fox Mustang Autocross SCCA C Prepared CP - YouTube[/ame]
 
Check out my thread on 400+hp 273 in my signature below I haven't built it yet, but there's some good info. I was thinking of going 3.58" stroke but I don't like the bore to stroke ratio I know there's a hyper piston for an Holden engine that will fit a 273 with a 3.58" crank but it got Chevy pin size, could use Chevy 6.125" rods by turning the crank down or bushing dodge rods for Chevy pins. But I think custom piston are the only way to go. I wouldn't worry about stroking a equally built 301 make the same power as a 273 only 600rpms lower and will make a little more torque like 20-30lb-ft but step up the rear gear one size over what the 301 would need and all would be equalled out.

I don't think you really need to run bigger valves look at 1wild&crazyguys sticky on porting 318 heads with stock 1.78-1.50 valves they flow enough for 450hp, people have run 2.02 but I think that's to much but I'm temped to be able to run eddy heads for weight savings, but EQ would probably the best bet if you don't want to port the stockers and just bolt on aftermarket heads, RHS are too heavy.

What's the power level you looking for?
Is this race only?
 
273 said:
Check out my thread on 400+hp 273 in my signature below I haven't built it but there's some good info. I was thinking of going 3.58" stroke but I don't like the bore to stroke ratio I know there's a hyper piston for an Holden engine that will fit a 273 with a 3.58" crank but it got Chevy pin size, could use Chevy 6.125" rods by turning the crank down or bushing dodge rods for Chevy pins. But I think custom piston are the only way to go. I wouldn't worry about stroking a equally built 301 make the same power as a 273 only 600rpms lower and will make a little more torque like 20-30lb-ft but step up the rear gear one size over what the 301 would need and all would be equalled out.

I don't think you really need to run bigger valves look at 1wild&crazyguys sticky on porting 318 heads with stock 1.78-1.50 valves they flow enough for 450hp, people have run 2.02 but I think that's to much but I'm temped to be able to run eddy heads for weight savings, but EQ would probably the best bet if you don't want to port the stockers and just bolt on aftermarket heads, RHS are too heavy.

What's the power level you looking for?
Is this race only?
Click to expand...

Good info there 273. Sounds like the idea may not even be worth it and may try to get as much as I can out of 273 cubes. I wonder how much one can be punched out and just keep the same 3.31" stroke? I have checked out wild&crazy's tread in the past and have actually cleaned up the bowls and runners on the 318 heads on this motor.

I plan to keep the car street legal, but not real sure on a hp goal yet.
 
Here's something I put together for ya 278 0.030" over, 9.5:1CR, 650 and Airgap, Headers, Heads ported out to 1wild&crazyguys flow numbers with 1.78-1.50 valves, Comp Cams Hydraulic roller 20-746-9 with 1.6 roller rockers. Probably could get away with cast domes with some milling and most your money would be spent on valve train. 350hp@5500 380@4000
 

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Badart said:
SCCA Solo racing rarely gives you a chance to get out of second. They really like to limit speed. It's more tight and technical racing. Cars like this Mustang would be the competition. Most courses are actually tighter than this.
Fox Mustang Autocross SCCA C Prepared CP - YouTube
Click to expand...

That's awesome, thats what I'm building my 65 Cuda for SCCA C Prepared and Time Attack GT class. I still want to keep full interior though.
 
273 said:
That's awesome, thats what I'm building my 65 Cuda for SCCA C Prepared and Time Attack GT class. I still want to keep full interior though.
Click to expand...

Dang those are some impressive numbers. I never would have thought it would be possible with that small of a bore and intake that small.
Years ago I raced Autocross with a couple of VW GTI's then I got into Rallycross and never looked back. I spent a ton of money building a Group 2 car. Now I am ready to hit the pavement again. :burnout:
 
I do think my dyno simulator program is a little torque happy but I try to keep things on the conservative when I input them. The Horsepower & Torque curves are more important than the numbers. I was surprise how low and much the peak power was for a fairly mild 273 I think the secret is the roller valvetrain gets the most out of the head flow without going crazy with duration to keep bottom end, that's how I like designing an engine extending the powerband far as possible without sacrificing too much bottom end.
 
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