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Pontiac - Boost Turbo, supercharged, Nitrous, EFI & other Power Adders discussed here. |
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#1
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Cast Iron Block Boosted engine - Rotating Assembly Weight Specs?
I know some will say go to an aftermarket block... if that's your response, please move along to another post. This is about data collection.
I'm trying to put some information together that may be helpful for those who are about to build up their Cast Iron Pontiac blocks. The idea is to identify the limitations with more of a mathematical approach than a generalization approach. Most of the information I have found has placed a HP number on the limitations however this is a very loose limitation as there is little consensus as I have heard as low as 600 and as high as 1300... I have to assume there where inconsistencies in those builds that led some to fail low and others to live high... I have been unable to find any real information about block limits when it comes to what the specs of the failed blocks where enduring when it comes to rotational mass, inertia forces, stroke, Piston speeds @ Rpm. I personally believe these all play a part in the blocks ability to hold things together. Case in point, you can have two engines making the same 700HP yet both have completely different parts with completely different rotational mass. One built with heavy components will likely add more stress to the block than one built with lighter parts. So instead of giving a generic HP number... Id like to see a list of parts used and their weights. From there we can figure out the Inertia forces and piston speeds... And if your block is still together, do mention that fact. If you have specs on blocks that have given up the farm, by all means those are the numbers we really need to see. My hope is that this information would help give a better understanding of the actual limits of our cast iron blocks. I'm working on a build, and so far the specs I have are on the heavy side... So I will have to chose my cam to work within the limitations of those weights and inertia forces... 1974 455 block Stroke = 4.5 Bore = 4.19 Pistons = 501 grams .040 dish Wrist pins .990 x 2.50 (Titanium) = 102 grams Locks = 4 grams Rings = 36.70 grams Rods 6.7" ARP2000 Rod big end = 560 grams Rod small End = 254 grams Splayed mains Mega Brace x3 80lb oil pump EDL 72cc RP Heads = 340cfm (2.19/2.77) ARP everything (Topped off with 15psi) Inertia force @ 6500: 5,682.36lbs Piston Speed @ 6500: 4,875.00 fpm I will likely chose a cam that will be in and out by 6000RPMs if the above proves to be excessive for the block. Inertia Force @ 6000:4842.77lbs Piston Speed @ 6000: 4500 fpm I want to thank everyone ahead of time for your help in collecting this data.
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"The grass is not greener on the other side, its just fertilized with different $h!t" Last edited by AIR RAM; 06-08-2019 at 11:15 AM. |
#2
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I am no expert but Do not go with a 4.5" stroke and lightweight pins are also a big no no. U need thick wall pins. I went with a 4.25" stroke and was pretty happy with the power it made. I feel that the block will survive with the splayed caps and 3.25" main will make the crank strong vs 3" at the cost of rpm capability which does not apply with your 6000 rpm red line. Good luck.
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#3
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Try a short stroke and aluminum rods!
GTO George |
#4
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Quote:
► 501 + 102 + 4 + 36.7 = 643.7 Bore_=_4.19___Stroke_=_4.5___Rod_Length_=_6.7___RP M_=_6000 Wrist_Pin_Offset_=_0.0 Piston_Weight_=_643.7___Rod_Weight_=_814.0 Small_End_Rod_Weight_=_254.0___Big_End_Rod_Weight_ =_560.0 Rod_CG_/_Distance_from_Small_End_=_4.609337______GAS_PRESS URE_=_0 Crankpin_/_Rod_Big_End_Acceleration_=_74022.03 Crankpin_/_Rod_Big_End_Rotational_Force_=_2840.387 ____________Reciprocating____Total_____Piston_Side ___Piston______Crank_Pin__Instantaneous Crank_Angle____Force_________Force________Force__I nertia_Force__Tangent_Force__Torque __Degree_______Pounds________Pounds_______Pounds__ ____Pounds_______Pounds___FT-Pounds ___.000______6082.316______8922.703_________.000__ __4361.353_________.000________.000 ------------ Bore_=_4.19___Stroke_=_4.5___Rod_Length_=_6.7___RP M_=_6500 Wrist_Pin_Offset_=_0.0 Piston_Weight_=_643.7___Rod_Weight_=_814.0 Small_End_Rod_Weight_=_254.0___Big_End_Rod_Weight_ =_560.0 Rod_CG_/_Distance_from_Small_End_=_4.609337______GAS_PRESS URE_=_0 Crankpin_/_Rod_Big_End_Acceleration_=_86873.08 Crankpin_/_Rod_Big_End_Rotational_Force_=_3333.509 ____________Reciprocating____Total_____Piston_Side ___Piston______Crank_Pin__Instantaneous Crank_Angle____Force_________Force________Force__I nertia_Force__Tangent_Force__Torque __Degree_______Pounds________Pounds_______Pounds__ ____Pounds_______Pounds___FT-Pounds ___.000______7138.274_____10471.784_________.000__ __5118.533_________.000________.000 Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#5
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Quote:
I already posses my my components... so that approach although great advice would not be in line with the goal of the build. Do you have any build specs of your build? Specifically with weights of components? It would be interesting to see what type of forces your block is containing vs others. Thank you both for your input.
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"The grass is not greener on the other side, its just fertilized with different $h!t" Last edited by AIR RAM; 06-08-2019 at 12:48 PM. |
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GTO George Last edited by GTOGEORGE; 06-08-2019 at 12:46 PM. |
#7
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897.7grams = 1.98lbs total... It does look like your calculator is a bit more precise though... Just curious, whats all that tell us? And do you have any examples like the one above that you have used with success and others that failed?
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"The grass is not greener on the other side, its just fertilized with different $h!t" Last edited by AIR RAM; 06-08-2019 at 01:13 PM. |
#8
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Quote:
Whats your current build look like on paper?
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"The grass is not greener on the other side, its just fertilized with different $h!t" |
#9
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JMO. I think if you keep the rpm's down say 5600 it will live. If you have a good tune it will live a long time.
Your goals are set high for a mainly street car. I have a 462 and my boost setting with self ported 6x heads is 12psi. If I run 15 traction is not very good borderline dangerous on the street. 500cid @15 psi. good luck. |
#10
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One of the other factors that need to be considered is the type of power-adder used. Turbos put much less strain on the block and rotating assembly by virtue of the fact that they are not driven by the crankshaft.
Back in the 1960s, Arnie Beswick was using long-stroke cranks, heavily-overdriven blowers, super-high rpms and doses of nitro. This made for an immense amount of stress on the shortblock. Even the blower itself put huge twisting strain on the crank. Marty Palbykin used a 1967 400 block, forged bottom end, mildly-ported D-port heads, turbos and methanol to get 1,600 horsepower back in 1996. If you are building a street or road racing engine, there is no need whatsoever for a stroke over 3.75 inches, the torque production will be just too much for any untubbed chassis. Even a boosted 350 will get you deep in the tens for a lot less money, the block will be plenty beefy for that application and any valve shrouding issues will be more than compensated for by the boost.
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Don Keefe, Founding Editor-in-Chief, Poncho Perfection Magazine (October 1, 2015- present) www.ponchoperfection.com Contributing Editor: Collectible Automobile (1999- present) Author: "Grand Prix: Pontiac's Luxury Performance Car" (Released April 27, 2007) "How to Restore Your Pontiac GTO" (Released July 15, 2012) "Pontiac Concept and Show Cars, 1939-1980" (Release Date April, 2016) "Leave the gun, take the cannoli." |
#11
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Is anybody actually reading the OP's post? He wants DATA about your combo -not an explanation of why his combo is or is not going to work!
We all know short stroke,long rod, lightweight rotating assembly is best for factory block longevity -especially with a turbo (over a blower or high rpm n/a), so if you have the data and want to disclose it then do so. No point clogging up the thread with more of the same info. I'll post mine when I get time to dig out my paper work. |
#12
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Quote:
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"The grass is not greener on the other side, its just fertilized with different $h!t" Last edited by AIR RAM; 06-11-2019 at 02:11 PM. |
#13
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Sorry to have "clogged up" the discussion but I was pointing out that one factor had not been previously mentioned or considered in the discussion. Trust me, it won't happen again...
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Don Keefe, Founding Editor-in-Chief, Poncho Perfection Magazine (October 1, 2015- present) www.ponchoperfection.com Contributing Editor: Collectible Automobile (1999- present) Author: "Grand Prix: Pontiac's Luxury Performance Car" (Released April 27, 2007) "How to Restore Your Pontiac GTO" (Released July 15, 2012) "Pontiac Concept and Show Cars, 1939-1980" (Release Date April, 2016) "Leave the gun, take the cannoli." |
#14
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Quote:
I try to work hard giving advice so that their engines will not fail. The key on that comes to mind for me on a boosted engine is the distance the piston is down in the hole (When the crank is at TDC) or in simple terms surface of the piston top to the surface of the head deck. If you have a .060 head gasket and you have a piston that is down in the hole .032" then I would say you are rolling the dice on how well the engine runs, boost or no boost. If you do not have stable combustion (the 8 valve relief pistons do not help in that area either) then trying to make the engine run right is not the engine's fault, it is the builder's fault. So posting info on engines that actually did run well with boost can be educational. I do not go over 8.75 to 1 with boost. I do not exceed 27 degrees of total timing under boost. I do not use slotted oil groove pistons (only drilled oil hole pistons) under boost. I run lots of exhaust duration on centrifugal supercharged engines. Like a 280-300 cfm intake and a 250 cfm exhaust port. With boost you can make lots of power with those airflow specs. Marty P went 6.95 with a 260 cfm intake iron head. So there are a few of MY RULES for success. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. Last edited by Tom Vaught; 06-11-2019 at 04:58 PM. |
#15
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There was nothing wrong with your advice... it was good advice.
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"The grass is not greener on the other side, its just fertilized with different $h!t" |
#16
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The only iron block Pontiac I've built that could possibly have been a "block breaker" was the blown alky 400 I used in mini-rod pulling for most of two seasons (my guesstimate is 750 HP). Sorry though, no failure data for you- the short block is still together and healthy after many 8,300 RPM runs. Not a bunch of lightweight parts- I'd have to look up some of the numbers (heavy JE blower pistons and pins, old M/T rods, 84 pound crank, etc.) I feel that the full counterweighting of the crank was a big help. Plus not making much torque down low (mild lift, long duration cams) helps avoid block stresses.
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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) |
#17
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Sorry Don my post was out of line, every bit of advice is helpful to somebody.
What year was that block Jack? 2 or 4 bolt mains? Maybe I should have followed your advice on fully counter weighted cranks-it seems to be the hot ticket at the moment and obviously worked for you. |
#18
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Whats the length of a "Mini-Rod"? Do you remember if the engine was bored at all or was it the Std bore? Was it de-stroked as well? That must have sounded like music to the ears at full 8500RPMs!!! My next build may be something similar. High RPM engines are just fun to drive, the sound of 8000+ is intoxicating.
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"The grass is not greener on the other side, its just fertilized with different $h!t" |
#19
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My build is really a "Just because" build. I started with zero HP goal... It all began 15 years ago when I decided one day I wanted to build a 500ci Pontiac... Then as time rolled on, I added Fuel Injection to the goal... then soon after that I decided I wanted to build that same combo with 15psi as well... I was never concerned about what HP would be... SO this means I have room to adjust accordingly which I likely will do. Many of those replying are straight up drag racers and can only ask "WHY"... because it does not fit into their category of reasoning. Which is completely understandable. To them my thoughts are flawed because we all know I could make a lot more with a lot less. The questions I'm asking are simple to answer if the build specs are known or jotted down someplace... what I do with that information should be of little concern to anyone as there is no negative outcome to sharing such information. Its almost like i'm being protected from such a crusade for the math. If it leads to nothing useful... Awesome! If it leads to something useful Awesomer!
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"The grass is not greener on the other side, its just fertilized with different $h!t" |
#20
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Quote:
GTO George |
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