Author Topic: Bottom End Capabilities  (Read 1217 times)

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fe468stroker

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Bottom End Capabilities
« on: April 22, 2022, 09:52:10 AM »
Watching the Robert Pond interview he stated that he normally shifted at 9000+.  That is the stratosphere for the most of us.  It would be nice to know what the bottom end of our FE's might handle - just the rotating assembly.  There are too many valvetrain possibilities out there so let's just figure crank, rods and pistons.  Say stock 390, 427 and 428.  Then add in some common stroker combinations.  Mine is a 427 side oiler block 4.250 bore and 4.125 stroke with 6.700 H beam rods.
If we can get a ballpark figure for the bottom end then there would be no need to spend extra money on the valvetrain to go beyond the limitations of the rest of the engine.

blykins

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Re: Bottom End Capabilities
« Reply #1 on: April 22, 2022, 12:02:59 PM »
Pretty vague question I think.   Ton of variables there.

The factory crankshafts (at least the 352 and 390) will take more than what the average home builder can make for horsepower.   I've taken both 390 and 352's to almost 8000 rpm. 

Rods are a different story.  I don't trust 50-60 year old factory rods for more than a grocery getter.

Most aftermarket cranks and rods will also take more than what the average home builder can make. 

Also other variables like balancing, setting up bearing clearances, which bearings, which oil pump, which oil pan, etc. 

Ton of variables. 

Buy the valvetrain for the cam and rpm you're going to be turning.
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MRadke

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Re: Bottom End Capabilities
« Reply #2 on: April 22, 2022, 12:27:11 PM »
You also have to remember that he is not running a stock block, but one of his own design.

frnkeore

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Re: Bottom End Capabilities
« Reply #3 on: April 22, 2022, 01:10:26 PM »
I think the most important thing to consider, if your looking for rpm, is the weight of the rod and piston, that is where all the stress comes from and that will leave out stock components. Smaller crank journals with 1/8" radii and H bearings will help and metric rings with short WP's.

The real stress on the bottom end, at high rpm, comes from the piston reversing direction, so anything you can do, to reduce weight, will help.
Frank

Falcon67

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Re: Bottom End Capabilities
« Reply #4 on: April 22, 2022, 01:40:55 PM »
I have had a stock 351C cast crank with neutral balance to north of 7500 without issue.  Using lighter than stock H-beam rods and pistons so light you'd think they would float off the bench unless you covered them with a shop rag.  Without issue to the crank that is.  Other stock components, not so much.  Cylinder blocks wiggle, cylinder walls split, stocker type 4 bolt caps walk, etc. The stock crank experiment was just that, and in retrospect a total waste of time and $$$.   The last stock block/crank/rod 351C combo here is limited at 6200.  Anything over that - no more stockers. 

>Buy the valvetrain for the cam and rpm you're going to be turning.
This, and work your way down from there.  Piston velocity and direction change are ruff enough.  Freewheeling with a floating valvetrain is known to be just as much a stressor. 

jayb

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Re: Bottom End Capabilities
« Reply #5 on: April 23, 2022, 08:12:30 PM »
Just thinking about the crank, Robert's car uses a factory 3.78" 427 stroke.  If you calculate average piston speed with his combination, at 9000 RPM that is 5670 feet per minute.  If you are running a 4.25" stroker kit, that piston speed equates to just about 8000 RPM.  The 585" SOHC that I've run multiple times at Drag Week uses a 4.6" stroke, where that piston speed would equate to about 7400.  I shift with that engine at 7500, and go through the lights at 7800.  I think that the moral of the story is that really good aftermarket components will let you run successfully at very high piston speeds, and as mentioned previously, the crank is probably not going to be the weak link.  Really good rods, and lightweight pistons, will extend the RPM range.
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

Tommy-T

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Re: Bottom End Capabilities
« Reply #6 on: April 23, 2022, 08:51:10 PM »
I think these discussions about RPM and "capabilities" are really fun. Trouble is finding out what will/won't live at 7000+ doesn't leave much to salvage once you've found out.

Two things come to mind. Comparing my reality to someone on the cutting edge of Super Stock or Stock eliminator with an Fe motor is difficult. They are really on a different level than that of street/strip or bracket racer guys.

Second thing is, it's not really difficult to run in the 10 second zone with an FE of 428+ cid shifting at 6500rpm or even slightly less in a 3200lb. car.

If you need to run faster than that I will kindly shut up because I have no experience of how to do so. 7000rpm is exponentially more hazardous to a motor than 6500. Aftermarket blocks seem to be the breakthrough that makes higher rpm's less hazardous along with light pistons and good rods. 

XR7

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Re: Bottom End Capabilities
« Reply #7 on: April 23, 2022, 09:32:38 PM »
I watched the interview and didn't catch where he said he shifted at 9000+. That seems a little high in Stock, but maybe.... or in high gear only? Or maybe you are you thinking of the recent Ray Paquet interview possibly? He runs in super stock, completely different combo even though they are both 427 high risers, I think he mentioned he turns it 9300 ish in his interview video posted while back.

For most guys, as bracket racers or hot rodders, ultra high RPM is not warranted, longevity and repeatability is. For class racers with strict rules, more RPM equals more power, so they go as high as they can stand, and at a severe cost I might add. Both in expensive parts and short duty cycle, with possible carnage along the way.

Too many variables as others have said, build to the best you can afford, put a number on it and don't turn it above that RPM, or at least not very often. I turned my old 428 only 6500 and did it for years and years, no problems, hundreds of passes if not 1000. I turn my old center oiler with a forged 4.25 crank 7000 on the shifts and on a good run 7300 through the traps. Pistons aren't real lightweight and neither are the rods. I plan on building another high riser with much lighter pistons and rods, and a shorter stroke 4.125 that has been lightened as well, in an aftermarket block, will turn it higher, how much higher I don't yet...
68 Cougar XR7 GT street legal, 9.47@144.53, 3603# at the line, 487 HR center oiler, single carb, Jerico 4 speed, 10.5 tires, stock(er) suspension, all steel full interior

cammerfe

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Re: Bottom End Capabilities
« Reply #8 on: April 23, 2022, 09:48:56 PM »
The mention of lightweight parts makes me think of such things as billet pistons, aluminum or titanium rods (and wristpins), and even---how about using a flat crank. I don't know how much the harmonics of the flat crank increase when you go from 300 cubic inches to 500, but 300 or thereabouts are being offered commercially. Might be edifying to give it a go in order to find out. ;D

KS

GerryP

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Re: Bottom End Capabilities
« Reply #9 on: April 24, 2022, 10:55:30 AM »
Dyno Don ran a 427 cammer Maverick in Pro Stock.  He even won an NHRA Pro Stock title at the 1971 Summernationals.  Stock block.  Lots of RPM.  Pro Stock back then was pretty unsophisticated compared to today.  A long time back, there was a theory a lot of engine failures -to include cracked blocks- were attributable to valvetrain harmonics.  I don't necessarily think you can attribute every cracked crank or piston to a valve spring issue but it is easy to mismatch and incorrectly assemble valvetrain components and have cascading consequences.  This is where the pro builder distinguishes themselves from guys like me who just slap stuff together and cross our fingers.

67xr7cat

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Re: Bottom End Capabilities
« Reply #10 on: April 24, 2022, 04:05:46 PM »
 :)
« Last Edit: April 26, 2022, 11:05:31 AM by 67xr7cat »

FERoadster

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Re: Bottom End Capabilities
« Reply #11 on: April 24, 2022, 09:48:34 PM »
Maybe Henrysnephew will reply here but I do know they ran a 68 Mustang and an early Pinto with either a 427 HR and a 427 TP in the Mid to low 9's
RPM's had to be up there.
Randy and his brother Mark I've known for 40+ years
Richard >>> FERoadster

mike7570

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Re: Bottom End Capabilities
« Reply #12 on: April 24, 2022, 11:12:55 PM »
Maybe Henrysnephew will reply here but I do know they ran a 68 Mustang and an early Pinto with either a 427 HR and a 427 TP in the Mid to low 9's
RPM's had to be up there.
Randy and his brother Mark I've known for 40+ years
Richard >>> FERoadster

I ran my tunnel port for 16yr and had no problems with the block turning 7000 - 7300 every pass. It did spin a rod bearing one time when it had the heavy Nascar rods and stock 12.5-1 pistons with factory adjustable rockers. On the rebuild I ground the stock steel crank to 3.99 stroke used BBC 6.8 eagle rods Arias pistons and new POP roller rockers and shaft. It ran mid 9’s at the same rpm but if you didn’t catch it on a burn out it would easily head north to 8K. Everything was still in great shape when I sold it after 16yrs.

bobb428

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Re: Bottom End Capabilities
« Reply #13 on: April 25, 2022, 05:15:08 PM »
I can guarantee you, Pond does not turn that HR in that range.

machoneman

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Re: Bottom End Capabilities
« Reply #14 on: April 25, 2022, 06:33:58 PM »
Dyno Don ran a 427 cammer Maverick in Pro Stock.  He even won an NHRA Pro Stock title at the 1971 Summernationals.  Stock block.  Lots of RPM.  Pro Stock back then was pretty unsophisticated compared to today.  A long time back, there was a theory a lot of engine failures -to include cracked blocks- were attributable to valvetrain harmonics.  I don't necessarily think you can attribute every cracked crank or piston to a valve spring issue but it is easy to mismatch and incorrectly assemble valvetrain components and have cascading consequences.  This is where the pro builder distinguishes themselves from guys like me who just slap stuff together and cross our fingers.

Yes, in 1966-1967, the fabled injected nitro cammer Mercury Comets on nitro were generating 900 hp or so with OEM iron 427 blocks. When these factory backed teams (Schartman, Nicholson, et al) added blowers they and the dragster crowd (Kaliita, Robinson, Prudhomme, etc.) were at or over 1,500 hp. Admittedly, famed nitro SOHC builder Ed Pink did note that the block's webs were the weak point and main cracks did appear after not so many runs. Still, when running injected, I read that few engines failed and many lived a long season of racing before replacement was needed. The blower engines? No so much! 
Bob Maag

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Re: Bottom End Capabilities
« Reply #15 on: April 26, 2022, 07:57:23 AM »
I can guarantee you, Pond does not turn that HR in that range.

Agree.