Thread: 6-71 supercharged 302 help needed

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Originally Posted by erik erikson

8-10 lbs. of boost I.M.O. would be to much for a stock 302 block plus I don't think at 10 psi. it will run on pump gas.

7.5:1 compression max 12psi and run 91 octane. it will run fine. if you run 87 octane it'll ping at higher rpms do to the boost pressure. its alot of work tuning it in to the way you want it with adjusting carbs and timing and your boost but can it be done.

Originally Posted by speedy55779

7.5:1 compression max 12psi and run 91 octane. it will run fine. if you run 87 octane it'll ping at higher rpms do to the boost pressure. its alot of work tuning it in to the way you want it with adjusting carbs and timing and your boost but can it be done.

12 psi on a stock 302/5.0 block???
Your kidding right??
I have built many a 5.0/302 block and we where breaking them at the 475 to 500 hp level.

No way I would consider that much boost on a stock Windsor block!!!! Investing a lot of money that a lot of which is going to get blown out the side when the block breaks!!!!!! Much as I love my Blue Ovals, I wouldn't consider even putting a blower on anything other then one of the SVT blocks....even then I'm not sure you could run enough boost without risking a major blow up to justify the expense.... The blocks are just way too week on the bottom end, if you go with the splayed caps and or main cap supports then it will split right down the valley......

Originally Posted by Dave Severson

No way I would consider that much boost on a stock Windsor block!!!! Investing a lot of money that a lot of which is going to get blown out the side when the block breaks!!!!!! Much as I love my Blue Ovals, I wouldn't consider even putting a blower on anything other then one of the SVT blocks....even then I'm not sure you could run enough boost without risking a major blow up to justify the expense.... The blocks are just way too week on the bottom end, if you go with the splayed caps and or main cap supports then it will split right down the valley......

What Dave says here times two.
Been there done that to many times.

Originally Posted by erik erikson

12 psi on a stock 302/5.0 block???
Your kidding right??
I have built many a 5.0/302 block and we where breaking them at the 475 to 500 hp level.

he'll be lucky if he even see's 400hp out of it if its a stock motor plus lowering the compression to 7.5:1, but i can see where your coming from if he builds it up for the strip she'll pop. plus i said a max of 12 psi.

Originally Posted by speedy55779

he'll be lucky if he even see's 400hp out of it if its a stock motor plus lowering the compression to 7.5:1, but i can see where your coming from if he builds it up for the strip she'll pop. plus i said a max of 12 psi.

Friend of mine split two 302 blocks right down the middle of the lifter valley running a 471 blower @ 9 psi..... After that debacle, he bought one of the SVT blocks, used the same internals and no more problems. Some say the Mexican built blocks are a bit stronger, don't know, never have tried one of them....

You "might " get away with 500 hp in a 351 block .....for awhile......maybe........
The 302 block will split ,there is no might to it.......
It is when you apply that power to the ground or hook up that its too much for the block to handle,a track run is extremely hard on them ,especially on the street where it may hook unhook very hard and irregularly.

Unfortunatly its a proven fact the 302 block will split at that power level.

They make a vally girdle and a main girdle to try and help the block along ,but by the time you purchase those parts ,machine the block,usually requires a line bore due to studs for the main girdle,you are getting real close to the price of a good block,but at the end of the day you only have a girdled up stock block for almost the same price as a good block.........
Plus its only a matter of time ,before you get tired of only 50 percent power from the blower ,knowing you have alot more under there ,but cant crank the boost up is frustrating and usually leads to another engine build or you blow it up ,leading to another engine build ,either way its cheaper to get the good block first ,it will hold its value for along time.

Originally Posted by shawnlee28

You "might " get away with 500 hp in a 351 block .....for awhile......maybe........
The 302 block will split ,there is no might to it.......
It is when you apply that power to the ground or hook up that its too much for the block to handle,a track run is extremely hard on them ,especially on the street where it may hook unhook very hard and irregularly.

Unfortunatly its a proven fact the 302 block will split at that power level.

They make a vally girdle and a main girdle to try and help the block along ,but by the time you purchase those parts ,machine the block,usually requires a line bore due to studs for the main girdle,you are getting real close to the price of a good block,but at the end of the day you only have a girdled up stock block for almost the same price as a good block.........
Plus its only a matter of time ,before you get tired of only 50 percent power from the blower ,knowing you have alot more under there ,but cant crank the boost up is frustrating and usually leads to another engine build or you blow it up ,leading to another engine build ,either way its cheaper to get the good block first ,it will hold its value for along time.

Read what Shawnlee say's here.
He is 100% right.
We have done 575+ hp out of a 420 Windsor in a 1/8 mile bracket car but after about 60 pass's the car slowed way done and we had anti-freeze in the oil.
This block was prepped just like Shawn talks about above.
It put a crack about 3 inches long right down the drivers side of the lifter valley.

If you have your mind set on running a 671 blower on a 302 . Then you will need a HD Block like the Worlds Man o' War or the DART block . Then you may even want to go up to a 347 stroker build . Some of these blocks are built up with twin Turbos ( Blowers ) Or large NOS systems with up to 1500 HP COOL Engine builds like these put FORD back on the map

well you guys can stick with your blue ovals. i'll stick with my bow ties. a buddy of mine built a mustang II cobra 4 banger car into a 302 car by changing a bunch of parts and alot of $$$ where gm just drop in a V8 with a th350 and go, even the 7.5 rearends hold up to V8 abuse.

Originally Posted by speedy55779

well you guys can stick with your blue ovals. i'll stick with my bow ties. a buddy of mine built a mustang II cobra 4 banger car into a 302 car by changing a bunch of parts and alot of $$$ where gm just drop in a V8 with a th350 and go, even the 7.5 rearends hold up to V8 abuse.

The 7.5 rear ends might hold up a little while, but as soon as you make that car "hook" you may just shove the spider gears through the rear cover.
We us to break these 7.5 ring gears with about 375 lbs. of torque and a 9 inch wide slick.

Originally Posted by erik erikson

The 7.5 rear ends might hold up a little while, but as soon as you make that car "hook" you may just shove the spider gears through the rear cover.
We us to break these 7.5 ring gears with about 375 lbs. of torque and a 9 inch wide slick.

seen many break not that hot of a rear end not chevy best the old 10 bolt is much better

Originally Posted by pat mccarthy

seen many break not that hot of a rear end not chevy best the old 10 bolt is much better

I think I broke one I had in a 86 Camaro now that I think about it.

My only experience with a supercharger was on a tiny 1300 cc VW with a positive displacement vane-type Judson compressor. So far nobody has said anything about heat. For a 10-12 second run in the quarter mile this may be the least of worries but reading the original beginning of this thread he says only occasional drag use with probably a street cruiser use most of the time. Adding 30% more fuel-air mixture means 30% more heat. In my case it meant a melted piston while on a trip from Virginia to Florida and two trips to emergency garage service to get home. The first stop was to replace the melted piston but the VW mechanic did us a favor by washing down the engine with Varsol. The second stop was about 90 miles up the road when the combination of engine heat and Varsol melted the wiring loom. Amazingly the second stop at another VW agency only cost us $12 for the complete engine wiring loom (plus meals and another night's lodging!) For regular running of a supercharged engine probably lower psi is adviseable for longer engine life and forged pistons would seem to be a good idea but don't forget provision for extra cooling too!

Don Shillady
Retired Scientist/teen rodder

Originally Posted by erik erikson

I think I broke one I had in a 86 Camaro now that I think about it.

Erik you would know when you break one ! The Tow bill is a good reminder There is a guy at the track with a FORD 8.8 rear end . But the COOL thing it's in a 1984 G body Monte Carlo with a SB Chevy 383 .