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#1
05-12-2005, 07:40 PM
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What do you think is the same RPM limit for my stock 400 short block?
I am using the original untouched 1973 shortblock that has about 60K miles on it. With the current mods, it generates approximately 350 gross HP. Right now it runs out of breath around 4900 RPM, using some stock/rebuilt 1971 #96 heads and a custom ground cam (202/208 114 sep). I may upgrade to some milled & ported 6x heads from a 350 motor. My performance Engine Analyzer progams projects that the motor will then be making 396 HP at 5400 RPM, with 387 HP at 5700 RPM and 346 HP at 6000 RPM. What is a safe RPM limit for my stock short block? |
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#2
05-12-2005, 07:40 PM
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What do you think is the same RPM limit for my stock 400 short block?
I am using the original untouched 1973 shortblock that has about 60K miles on it. With the current mods, it generates approximately 350 gross HP. Right now it runs out of breath around 4900 RPM, using some stock/rebuilt 1971 #96 heads and a custom ground cam (202/208 114 sep). I may upgrade to some milled & ported 6x heads from a 350 motor. My performance Engine Analyzer progams projects that the motor will then be making 396 HP at 5400 RPM, with 387 HP at 5700 RPM and 346 HP at 6000 RPM. What is a safe RPM limit for my stock short block? |
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#3
05-12-2005, 07:58 PM
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I wouldn't run it past 5700.
Shift it at 5500.
__________________
1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/3.08 2002 WS6 Convertible LS1/4L60E/3.23 1966 VW Type 2 Single Cab Pickup 140hp 2276 1956 VW Type 2 Panel Van 36hp 1200 1957 VW Type 1 Beetle 180hp 2276 |
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#4
05-12-2005, 09:21 PM
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Iv`e been runnin my 455 stock rod to 5600 for about 15 yrs. Missed a few gears before the MSD6AL also. Bearings look fine when i check em. Don`t see why a 400 can`t go to 6000.
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#5
05-13-2005, 05:32 AM
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I agree with 5.5-5.6k and KEEP THE OIL CHANGED AND DON'T DIVE IT HARD IF IT'S GETTING ON THE HOT SIDE!
__________________
Uneasyrider “To find yourself, think for yourself.” ― Socrates “The unexamined life is not worth living.” ― Socrates “Wise men speak because they have something to say; fools because they have to say something.” ― Plato |
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#6
05-13-2005, 04:03 PM
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High RPM dont mean squat if you dont have the right springs.... Just my .02
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#7
05-13-2005, 06:20 PM
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ryche:
High RPM dont mean squat if you dont have the right springs.... Just my .02 </div></BLOCKQUOTE> Well yes. If it all doesn't make it to 5,500rpm (valves, springs, cam, etc., etc.) then of course one of the other weak links will break. Poncho's tend to have bottom end bearing oiling problems.
__________________
Uneasyrider “To find yourself, think for yourself.” ― Socrates “The unexamined life is not worth living.” ― Socrates “Wise men speak because they have something to say; fools because they have to say something.” ― Plato |
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#8
05-13-2005, 08:34 PM
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Thanks for the input, right now my heads have new H.O. Racing VS-11 springs. If I put on ported heads, I am sure I will use adaquate valvetrain parts. I am more worried how the bottom end will hold up.
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#9
05-13-2005, 08:40 PM
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ive spun a rod bearing hi revving for too long...
__________________
'74 formula 400, w/shaker (3 scoops) black deluxe interior, '70 406 balanced assembly, .30 trw slugs, moly rings, 4x heads 2.11/1.77 stainless valves, ra 4 cam, e-rpm intake, holley 750 vac. sec, msd hei, hooker headers w/ dual 3'' flowmaster 50 series ending at axle, t400 w/ GM6 convertor, transgo shift kit, b&m starshifter, 3.08 gears, centerlines, 265/50-15 bfg's rear and 235/60-15 front...yes im over cammed but it is still very fun... |
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#10
05-13-2005, 10:38 PM
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I'd have to agree with the above answers. If you do go with better flowing heads, I would personally do a couple minor things to the bottom end- not serious modifications, for oiling of rod bearings. I'd check oil pump condition, bump the pressure relief to about 65-70 PSI, chamfer the rod journal oil holes a little, and use grooved-top-half main bearings (see prior posts about grooving the ends of the bottom halves). And of course pay attention to all the usual bottom end measurements- bearing clearances, roundness of journals, trueness of rods, rod side clearances, etc., and you should be good to about 6200-6300 RPM.
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Anybody else on this planet campaign a M/T hemi Pontiac for eleven seasons? ... or has built a record breaking DOHC hemi four cylinder Pontiac? ... or has driven a couple laps of Nuerburgring with Tri-Power Pontiac power?(back in 1967) ... or has a Pontiac born the same year as Jim Wangers? (1926} 
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