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I was told to come her.......Had some questions about the engine wanted to know how much power it will hold I was looking to punch it out to a 408 and run a 76mm turbo .....
70s 351 cobra jet
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7-750hp is the limit on a street engine with a partiallly filled block. Fill the block all the way up and run methonal and you might get away with 800-850 in a race application (especially if you sleeve all 8 cylinders). The problem you get at higher power levels is the liklihood of breaking the mains out of the bottom. This all depends on how good the block is with the proper checks done regarding core shift, wall thickness, etc... These are very good blocks but these power levels were unexpected in the 1970's when these blocks were built. These ARE NOT race blocks and these blocks have the same limitations as any stock OEM small block.
Good luck and keep us posted with your build. I'm putting together a turbo street build myself to be done next winter. Shooting for 750HP on E-85.
Good luck and keep us posted with your build. I'm putting together a turbo street build myself to be done next winter. Shooting for 750HP on E-85.
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15 Posts
Sweet thanks for the information I was going to shoot for 850 I wanted to run boost see what I can get out of pump gas I will definitely be posting more
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1,029 Posts
sorry, trying to get 700+ hp from ANY factory stock C or W block is going to be a ticking time bomb, ive seen lots of Filled C blocks still split there cly's with 500/600hp . In a drag race they can get lucky/er because there only stressing the block for a few seconds at a time but these guys that say there making 700+ hp in a stock c/w block would BLOW there stock block shat up if they had to run it in any circle/road race.
first you need to do a sonic check with any C block for higher hp apps as most had thinner cly walls/shift and can be compromised with just a 30 over bore, if you have a good (thick enough) factory block and upgrade to steel 4 bolt main caps, fill it, it may be safe for 600+hp with other prep/mods.
some of the missconceptions about high hp with stock blocks came from some guys reading mags not understanding that the old c/w p/s racers that were pushing into the 700+ hp range where NOT using just any stock production C or W block to do this, they were using special selected castings/xe/aus stuff NOT just any regular production c block.
if you are looking for 700+ hp and having it last dont waist your money or time with a old antique block, get a aftermarket block.
stock production c blocks main webing and iron caps are definatly not up t o the task of holding 700+hp and if you try, make sure you find some "good" extra blocks for spares like the old p/s racers needed to do.
first you need to do a sonic check with any C block for higher hp apps as most had thinner cly walls/shift and can be compromised with just a 30 over bore, if you have a good (thick enough) factory block and upgrade to steel 4 bolt main caps, fill it, it may be safe for 600+hp with other prep/mods.
some of the missconceptions about high hp with stock blocks came from some guys reading mags not understanding that the old c/w p/s racers that were pushing into the 700+ hp range where NOT using just any stock production C or W block to do this, they were using special selected castings/xe/aus stuff NOT just any regular production c block.
if you are looking for 700+ hp and having it last dont waist your money or time with a old antique block, get a aftermarket block.
stock production c blocks main webing and iron caps are definatly not up t o the task of holding 700+hp and if you try, make sure you find some "good" extra blocks for spares like the old p/s racers needed to do.
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1,029 Posts
some more info about big hp p/s Clev's misunderstood/not known by some, the only production c block i understand old p/s racers looked for was the Early 69-70 4V eng which had crappy 2 bolt mains, this early c block, a J block (as was the early 69/70 c9 w block) was different from all later ones with some >different metallurgy/ductility<, less core shift issues and different oil drain backs in the casting than all later blocks. after sonic checking it for thickness they would pin/fill it, then convert the block to 4 bolt caps with main cap supports/girdles and do the necessary machining, oiling mods, restrictors & bushings, keeping the bore under 4.010" so it could live above 600+hp.
btw, another misunderstood thing with the high hp old p/s Clev's is the old edelbrock tunnel rams that some think were so good which they were not, the better p/s edel intakes were highly modifed inside with welded tops and undersides to work well as they had a bad pendulum design and carb placement, stock for stock the weiand tunnel ram would out perform it.
btw, another misunderstood thing with the high hp old p/s Clev's is the old edelbrock tunnel rams that some think were so good which they were not, the better p/s edel intakes were highly modifed inside with welded tops and undersides to work well as they had a bad pendulum design and carb placement, stock for stock the weiand tunnel ram would out perform it.
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2,508 Posts
A good 4 bolt main block using studs and a girdle might be reliable at the 850 horsepower level using a turbo. What kills any block more than anything else is detonation, higher rpms above 6500, or a combination of the two. The old 70s pro stock 351Cs probably made around 850 horsepower, but they had to spin the motor to 10,000 rpm to get it. Thus, they didn't last long.
Since a turbo is in the equation, this means the peak horsepower will be at a much lower rpm. At 850 horsepower, the stock block better not see much over 6000 rpm if any degree of longevity is expected.
If it were mine, I would go ahead and spend the extra money and get a Boss block since you using a stroker kit. You don't want to risk breaking the block and destroying the custom crank/rods/pistons.
However, if you were planning on getting around 850 horsepower using the stock crank, rods, and a lot of boost, that's a less costly experiment to trash the stock rods, stock type pistons, and stock crank.
Since a turbo is in the equation, this means the peak horsepower will be at a much lower rpm. At 850 horsepower, the stock block better not see much over 6000 rpm if any degree of longevity is expected.
If it were mine, I would go ahead and spend the extra money and get a Boss block since you using a stroker kit. You don't want to risk breaking the block and destroying the custom crank/rods/pistons.
However, if you were planning on getting around 850 horsepower using the stock crank, rods, and a lot of boost, that's a less costly experiment to trash the stock rods, stock type pistons, and stock crank.
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1,029 Posts
lol, these old antique cleveland blocks seem to be holding more horse power every year that goes by 
...just some common sence for those thinking of trying to put alot of hp through a 40+yr old antique factory block...
the superior/thicker aftermarket Dart shp block is rated safe to 600HP by Dart them selfs, the block itself can handle more hp but the reason Dart them selfs only rate the shp block good for 600hp is because of its 2 bolt front/rear iron caps, with a 4 bolt iron cap upgrade on front/rear the block is good for 700hp and if you are looking to make more hp than this it is recomended by block manufacturers themselfs to upgrade to billet STEEL main caps which can hold much much more hp.
("Designed for high-performance and heavy-duty applications producing up to 600 horsepower")
Dart SHP (Special High Performance) Blocks - Free Shipping on All Orders @ JEGS
...just some common sence for those thinking of trying to put alot of hp through a 40+yr old antique factory block...
the superior/thicker aftermarket Dart shp block is rated safe to 600HP by Dart them selfs, the block itself can handle more hp but the reason Dart them selfs only rate the shp block good for 600hp is because of its 2 bolt front/rear iron caps, with a 4 bolt iron cap upgrade on front/rear the block is good for 700hp and if you are looking to make more hp than this it is recomended by block manufacturers themselfs to upgrade to billet STEEL main caps which can hold much much more hp.
("Designed for high-performance and heavy-duty applications producing up to 600 horsepower")
Dart SHP (Special High Performance) Blocks - Free Shipping on All Orders @ JEGS
Follow the recommendations and you will be fine.
Check wall thickness. Check core shift.
Partial fill. Sleeves preferred. Oiling mods.
4bolt stud bottom end. Girdle optional. Balance is critical. Consider slight overbalance.
Keep rpm limit 6500-6700. This depends on stroke. Remember, you're trying to keep the bottom end from "buzzing" too much.
Run E-85 or methanol injection with gas.
Turbo 7-750hp. You'll be fine for street/strip. Not Nascar, road racing or the 24 hours of Daytona.
If in doubt, buy a Ford Racing block and build a Clevor. Your money.
Check wall thickness. Check core shift.
Partial fill. Sleeves preferred. Oiling mods.
4bolt stud bottom end. Girdle optional. Balance is critical. Consider slight overbalance.
Keep rpm limit 6500-6700. This depends on stroke. Remember, you're trying to keep the bottom end from "buzzing" too much.
Run E-85 or methanol injection with gas.
Turbo 7-750hp. You'll be fine for street/strip. Not Nascar, road racing or the 24 hours of Daytona.
If in doubt, buy a Ford Racing block and build a Clevor. Your money.
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2,508 Posts
Of course Dart only claims their blocks will only handle 600 horsepower. That way, when someone scatters a 1000hp motor they can always claim it was only capable of handling 600.lol, these old antique cleveland blocks seem to be holding more horse power every year that goes by
...just some common sence for those thinking of trying to put alot of hp through a 40+yr old antique factory block...
the superior/thicker aftermarket Dart shp block is rated safe to 600HP by Dart them selfs, the block itself can handle more hp but the reason Dart them selfs only rate the shp block good for 600hp is because of its 2 bolt front/rear iron caps, with a 4 bolt cap upgrade on front/rear the block is good for 700-750hp and if you are looking to make more hp than this it is recomended by block manufacturers themselfs to upgrade to billet STEEL main caps which can hold much much more hp.
("Designed for high-performance and heavy-duty applications producing up to 600 horsepower")
Dart SHP (Special High Performance) Blocks - Free Shipping on All Orders @ JEGS
A stock 4 bolt 351C block with no modifications other than maybe a girdle will easily handle 600 horsepower. I have built them, and spun them to 8000 many times with no problems. Even a 2 bolt 351W block will handle 600 if the rpms are kept below 6000 and the tune is correct.
Keep in mind a 4 bolt 351C is 4 bolt caps on all 5 mains, not just 2,3 & 4.
If he wants to try to make 850 horsepower with a turbo using a stock 351C 4 bolt block, he should do it without the stroker kit. With a turbo, the goal can be easily accomplished with the stock cubic inch as it has already been done using the regular 351W 2 bolt blocks which are not near as strong. It's a very worthwhile experiment, and would open the eyes of many who claim it is impossible to make more than 400 horsepower with a stock ford block. Which is absurd thinking unless the person is clueless about what they are doing.
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1,029 Posts
this is the superior thicker vintage ford nascar/xe C block tipically used by the old p/s racers of there time (notice solid pan rail) that was fully race prepped & filled and it still let go because of fretting main caps, billet steel main caps on after market block is best for big HP.
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...Billet Steel caps would of helped this old C block hold the power it was making...
...Billet Steel caps would of helped this old C block hold the power it was making...
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Boss, what are the details on the build? Compression, fuel type, timing, cam specs, rpm limit, etc...
Rod and stroke combination? What type of racing?
Boosted or no? Nitrous? How much?
Have to get a complete picture of what's going on.
Nasty break. Looks like considerable cap walk. Buzzin' the hell out of it?
Rod and stroke combination? What type of racing?
Boosted or no? Nitrous? How much?
Have to get a complete picture of what's going on.
Nasty break. Looks like considerable cap walk. Buzzin' the hell out of it?
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2,508 Posts
He said pro stock racing, which explains why the block failed.
Compression as high as possible, pistons probably less than .010 from hitting the heads. Cam specs? Who knows? Top secret pro stock stuff. Rpm limit? Shift point probably a tad over 10,000.
Apples to oranges comparison. RPM will destroy a block far quicker than much lower rpms making the same power with boost. No telling what kind of harmonic vibrations that motor saw at 9000 rpm+.
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1,029 Posts
the blocks not mine, pic from YB, the guy was running a boosted roots app without using steel caps, the point is some have had problems with the stronger old nascar c blocks so a factory production block is not going to be any better for high hp apps.
if a guy really wants to stay with a c block i would suggest to go with the new Arrow c block, it comes with billet steel caps, much better for high hp builds.
info on new Arrow Cleveland block - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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if a guy really wants to stay with a c block i would suggest to go with the new Arrow c block, it comes with billet steel caps, much better for high hp builds.
info on new Arrow Cleveland block - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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2,508 Posts
There is also a thread on YB where a guy mentions cracking a Dart block.
Dart block cracking - Yellow Bullet Forums
Also, the XE cleveland blocks were rare, even in the 70s. Many racers were using the standard US 4 bolt blocks.
The point is any block can be broken. Simply posting pictures of broken blocks without knowing the real reason exactly why it broke in the first place is not good enough reason to run out and buy an $1800 block.
Is the Dart or Boss block stronger? Sure they are. Whether or not they are necessary for a given application is the real question.
stock shortblock 351W goes [email protected]! - Yellow Bullet Forums
If this can be accomplished with one of those junk 2 bolt 351W blocks, a 4 bolt 351C block will damn sure hold together.
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1,029 Posts
That Cracked Dart block link is a good example of what im saying. The Billet Steel caps were the ONLY! thing holding all those piles and piles of broken/brittle Dart blocks together after they all cracked up through the mains... Cracked Dart Blocks ...
Thats why I also posted about upgrading the iron caps on my Boss block with Billet Steel main caps because iron main caps are inferior to the steel caps in every way for eng builds over 750hp... >https://forums.corral.net/forums/5-0-5-8-engine-tech/1743185-boss-9-2-9-5-blocks-2.html< im pissed off about Ford cheaping out with using cast iron main caps on the 351 boss block unlike there billet steel doweled cap Z351 block.
and that stock 351w short block is going, tick tick tick tick tick lol, must be all the China parts on it thats holding it together lol. got to say though, seeing the hundreds of cracked dart block threads made me happy about not over spending on brittle dart blocks and buying the better bang for the buck... >fps-rpm 351 Maxx block< instead lol.
I have thought about that but I would be too worryed about the Dart ie block Cracking/Busting in half as guys have been complaining about Dart ie blocks Cracking/Busting/Splitting in half since 2006 with NO answers from any of the online/internet bigot/racist/islamist YB dart dealers/peddlers that sell Dart blocks out of there barns/sheds online as to why cracks keep happening on ALL these (brittle imo) Dart blocks...
again, ("here's just one example (post #81) ... of dozens of Cracking Dart blocks in the same spot...
http://www.yellowbullet.com/forum/showthread.php?p=20529242#post20529242
("I also have at least 12 racers that have broke their dart blocks as I have and the problem is the block. Burning a plug and blowers blowing up I'm sure don't help but from all that has come forward to say their blocks have broke in the same spot leads me to believe the block is failing.")...
Lyle671's Cracked Dart block ...http://www.yellowbullet.com/forum/showthread.php?t=770506
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nos stroker's Cracked Dart block...http://www.yellowbullet.com/forum/showthread.php?t=465317
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and just a few more YellowBullShat CRACKED DART BLOCK links...
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cracked dart
http://www.yellowbullet.com/forum/showpost.php?p=27836506&postcount=123
cracked dart...
http://www.yellowbullet.com/forum/showthread.php?t=1096170
cracked dart
http://www.yellowbullet.com/forum/showpost.php?p=20441242&postcount=14
cracked dart
http://www.yellowbullet.com/forum/showthread.php?t=1370489
cracked dart
http://www.yellowbullet.com/forum/showpost.php?p=44178754&postcount=21
cracked dart
http://www.yellowbullet.com/forum/showthread.php?t=1469234
cracked dart
http://www.yellowbullet.com/forum/showpost.php?p=3730325&postcount=10
cracked dart
http://www.yellowbullet.com/forum/showthread.php?t=770506
cracked dart
http://www.yellowbullet.com/forum/showpost.php?p=26057850&postcount=3
cracked dart
http://www.yellowbullet.com/forum/showthread.php?t=356696
cracked dart
http://www.yellowbullet.com/forum/showpost.php?p=26054754&postcount=122
cracked dart
http://www.yellowbullet.com/forum/showthread.php?t=465317
cracked dart
http://www.yellowbullet.com/forum/showpost.php?p=20571458&postcount=84
cracked dart
http://www.yellowbullet.com/forum/showthread.php?t=455927
cracked dart
http://www.yellowbullet.com/forum/showpost.php?p=39247522&postcount=12
cracked dart
http://www.yellowbullet.com/forum/showthread.php?t=257285
cracked dart
http://www.yellowbullet.com/forum/showpost.php?p=20575866&postcount=85
cracked dart
http://www.yellowbullet.com/forum/showthread.php?t=424438
cracked dart
http://www.yellowbullet.com/forum/showpost.php?p=20618090&postcount=100
main break/cracking issues even with the Aluminum Dart Blocks...
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BBC DART ALUMINUM BLOCK CRACKED - Yellow Bullet Forums
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Cracked Dart Block...http://www.yellowbullet.com/forum/showthread.php?t=623577
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... > CRACKED DART BLOCKS < ...
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(":rofl:also find it more than moronic for some with there China cast scat,eagle,callies,rpm,lunati,molnar,ohiocrank cranks&rods
typing on there China made computers&ipods lying/crying about about Kevins/Troys >fps/rpm maxx 351w block<
when the factory Chevy LS blocks that are so popular with the 7sec $200 junkyard LS crowd were Cast in...
India Mexico and Canada :rofl:.
and lets not even mention all the other offshore Asian parts from...
weiand,msd,mrgasket,bbm,fordracing,holley,compcams,arrow,afd and many others :rofl:")
Thats why I also posted about upgrading the iron caps on my Boss block with Billet Steel main caps because iron main caps are inferior to the steel caps in every way for eng builds over 750hp... >https://forums.corral.net/forums/5-0-5-8-engine-tech/1743185-boss-9-2-9-5-blocks-2.html< im pissed off about Ford cheaping out with using cast iron main caps on the 351 boss block unlike there billet steel doweled cap Z351 block.
and that stock 351w short block is going, tick tick tick tick tick lol, must be all the China parts on it thats holding it together lol. got to say though, seeing the hundreds of cracked dart block threads made me happy about not over spending on brittle dart blocks and buying the better bang for the buck... >fps-rpm 351 Maxx block< instead lol.
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1,029 Posts
another tidbit not well known, some old C & W block p/s racers were concerned about cly sealing with the more ductile/softer/malleable early 69/70 Cleveland J block casting (which the early 69/70 Windsor C9 block casting also was) so some didint like using reg eng stands as they said it could affect ring seal on the 2 back cly's so some did not use them...
btw, notice Gliddens highly modded edel T ram...
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btw, notice Gliddens highly modded edel T ram...
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2,198 Posts
Tonys car (stock bottom end 351 in the 8s) has been together for like 2 years, has been in the 8s, and has made over 1000rwhp. All with a stock 2 bolt 351w block, and STOCK bottom end. He just recently upon tear down noticed that his rods were bent a little. Now it's going back together with some other cheap rods.
I love guys that get on here that have never had a turbo car claiming that stock 351w blocks only hold 60prwhp. Maybe back in the 90s with ####ty tunes and fuel. Tuning has come a long way, and that's why you see guys pushing these blocks further and further all the time.
I love guys that get on here that have never had a turbo car claiming that stock 351w blocks only hold 60prwhp. Maybe back in the 90s with ####ty tunes and fuel. Tuning has come a long way, and that's why you see guys pushing these blocks further and further all the time.
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1,029 Posts
so how many perfect tune 8 sec runs has that 1000+hp stock w block made? , guess those of us with aftermarket blocks, cranks, rods and pistons should throw our shat away and go buy a bunch of $100 junkyard c&w stock cast piston short blocks as they must be just as good :rofl:.
tick tick tick tick tick
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, guess those of us with aftermarket blocks, cranks, rods and pistons should throw our shat away and go buy a bunch of $100 junkyard c&w stock cast piston short blocks as they must be just as good :rofl:.tick tick tick tick tick
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2,198 Posts
Its been running for 2 years in the 9s, and 8s now. Countless passes. There's plenty of proof bud.so how many perfect tune 8 sec runs has that 1000hp stock w block made?
tick tick tick tick tick
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The tune is everything, and you have posted absolutely no proof of anything you own breaking to back your "claims".
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2,508 Posts
You don't understand the difference between a low compression, low rpm, non stroked motor vs. a higher compression, higher rpm stroked motor.so how many perfect tune 8 sec runs has that 1000hp stock w block made?
tick tick tick tick tick
An old 2 bolt 351W block half filled with stud/girdle with a high compression 408 stroker kit shifting on 6500 rpm is about at it limits. I had one in my last race car and could see signs of slight cap walk upon inspection. The more awkward rod ratio of the longer stroke, added with the high compression and rpm stresses the stock blocks to almost their limit, especially if the car isn't really light.
A 2 bolt 351C block can handle more because of the slightly thicker main webbing, but is still not that great of a choice for an expensive stroker application unless the rpm is kept below 7000. Forget power adders with either of the two in a stroker application unless you like oiling the track down.
However, take a non stroked motor with lower compression, and the stock block can handle a good bit more. That is how these guys are getting these boosted, specifically turbo motors to last much longer.
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