Big Blocks: What breaks first?

RedVenom48

Let's go Brandon!
Established Member
Joined
Sep 29, 2014
Messages
7,973
Location
Arizona
BBF, BBC, 426 Hemi

Assume forged pistons, tool steel wrist pins, forged rods, forged crank, proper ring gaps, bearings, race valve springs etc.

Rev to 8000 rpm in the 1/4 or 1/8 with boost behind a PowerGlide.

Besides your wallet, what breaks first and when?
 

GTSpartan

Yield right!!!!
Established Member
Joined
Sep 15, 2004
Messages
9,343
Location
The Woods
Impossible to answer with any sort of objectively.

Will be a fun discussion nevertheless! The original Hemi based architecture was used for a long time and in large numbers outside of the factory in various pro-level applications. It is still today, the basis for Top fuel and Funny Car engines, so that says a lot about the design.
 

black4vcobra

Well-Known Member
Established Member
Premium Member
Party Liquor Posse
Joined
Feb 22, 2009
Messages
4,460
Location
Cottage Grove, WI
I have no personal knowledge of any of those big block engines but I always found it amusing that given a sufficiently strong rotating assembly, the Windsor small block splits in half somewhere between 6-700 hp.

I'm sure those blocks have their limits as well but idk what they are.
 

CobraSam

Well-Known Member
Established Member
Joined
Apr 26, 2020
Messages
418
Location
Mass
I have no personal knowledge of any of those big block engines but I always found it amusing that given a sufficiently strong rotating assembly, the Windsor small block splits in half somewhere between 6-700 hp.

I'm sure those blocks have their limits as well but idk what they are.

There’s nothing amusing about splitting your block...I never found it funny anyways.
 

Corbic

Well-Known Member
Established Member
Premium Member
Joined
Apr 14, 2015
Messages
10,930
Location
Desert Oasis
I have no personal knowledge of any of those big block engines but I always found it amusing that given a sufficiently strong rotating assembly, the Windsor small block splits in half somewhere between 6-700 hp.

I'm sure those blocks have their limits as well but idk what they are.
Yeah, block integrity of the old stuff is shockingly poor.

I've seen those 302's split at 350whp. Mainly an RPM issue as I recall.

Other issues the old blocks have is main caps, etc.
 

black4vcobra

Well-Known Member
Established Member
Premium Member
Party Liquor Posse
Joined
Feb 22, 2009
Messages
4,460
Location
Cottage Grove, WI
There’s nothing amusing about splitting your block...I never found it funny anyways.

Well ya, sucks for the guy that it happens to. I don't mean that it's funny, just interesting and surprising.

Yeah, block integrity of the old stuff is shockingly poor.

I've seen those 302's split at 350whp. Mainly an RPM issue as I recall.

Other issues the old blocks have is main caps, etc.

Wow, I knew it was a lower threshold but not that low!

Crazy how much better things got in the 90s then with aluminum blocks that are far stronger and lighter than the older iron blocks. I guess that's what you get when manufacturing capability improves as well as the computer modeling of components.
 

CobraSam

Well-Known Member
Established Member
Joined
Apr 26, 2020
Messages
418
Location
Mass
Haha ya, it sucks big time. At least it was for good reason. Too much boost.
Windsor SBF’s are always questionable as to what they can handle. I had 3 302 based engines that made over 500rwhp. Never had an issue as long as I kept the RPM’s low. Like 6,200 or below. I did break one, but that was making over 560rwhp.
My current 358 engine has about 750rwhp at about 22psi through a ProCharger F1C and c16. Bunch of track hits and street miles, so far so good. I keep rpms under 6,500
 

RedVenom48

Let's go Brandon!
Established Member
Joined
Sep 29, 2014
Messages
7,973
Location
Arizona
The original owner of my Fox apparently blew the original 302 to smithereens, quite literally blew apart the 5.0, with a 250 shot of nitrous. Lmao

Guy I bought my car from is friends with original owner and told me when I asked about the original engine.
 

RedVenom48

Let's go Brandon!
Established Member
Joined
Sep 29, 2014
Messages
7,973
Location
Arizona
My bet is you’ll send a rod through one of them eventually revving them to the moon like that
Probably, but the question is why? Is it rod failure due to stretch? Is the inertia of the the piston/rod combo too much for the oil film to keep the assembly from touching the bearing and spinning it causing bearing failure? Is the wrist pin boss on the piston too weak to control all that mass on the intake stroke? Lets assume no boost now, NA only.

Example: In the case of the Cheby 454, its got a 4.0" stroke. For comparison, the Boss 302 has a 3.65" stroke and can be revved out to 8k. A little over a 1/4" more stroke and the 454 shouldnt be revved past 6500 or so? Is it stroke at all thats the limiting factor?

Lets turn our attention to the size of the piston. There's obviously a significant difference between the 3.63" of the 302 versus the 4.25" of the 454. The .62" larger diameter of the 454 certainly adds more mass to each piston. Does this double or triple the forces on the rod/rod bearing/wrist pin compared to the 302? Or is is a harsher more exponential like increase in force?

In this theoretical exercise, the pistons are forged aluminum, the rods are forged steel, the crank is forged, the wrist pins are tool steel, all rod and head bolts are ARP2000 material, the ring gaps have been set for the appropriate level of gap, the valve springs are race quality capable of controlling the large mass of Big Block valves (Ford or Chevy or Hemi) and the fuel is correctly metered E85 or race fuel which eliminates pre-ignition or detonation.

What you got SVTP? What fails and why.

Hmmm... @James Snover what say you good sir?
 
Last edited:

598

Well-Known Member
Established Member
Joined
Apr 13, 2008
Messages
1,494
Location
Frankfort IL
If you are putting all aftermarket stuff into a stock block, you dont need James to tell you that the stock part remaing, the block, will fail first. I ran my 600 ci BBF to 8k pretty much every pass and was never concerned about failure, but I had very expensive lightweight valves and valvetrain and a balance that the factory copuld only dream of. Not to mention a wonderful aftermarket block. In stock form, 427 will out rev a 428 to the moon and back, because of bore stroke ratio. If im looking for low rpm torque in a galaxie, pick the 428. For the strip, 427 all day.
 

coposrv

Well-Known Member
Established Member
Joined
Sep 4, 2007
Messages
5,030
Location
boston
Probably, but the question is why? Is it rod failure due to stretch? Is the inertia of the the piston/rod combo too much for the oil film to keep the assembly from touching the bearing and spinning it causing bearing failure? Is the wrist pin boss on the piston too weak to control all that mass on the intake stroke? Lets assume no boost now, NA only.

Example: In the case of the Cheby 454, its got a 4.0" stroke. For comparison, the Boss 302 has a 3.65" stroke and can be revved out to 8k. A little over a 1/4" more stroke and the 454 shouldnt be revved past 6500 or so? Is it stroke at all thats the limiting factor?

Lets turn our attention to the size of the piston. There's obviously a significant difference between the 3.63" of the 302 versus the 4.25" of the 454. The .62" larger diameter of the 454 certainly adds more mass to each piston. Does this double or triple the forces on the rod/rod bearing/wrist pin compared to the 302? Or is is a harsher more exponential like increase in force?

In this theoretical exercise, the pistons are forged aluminum, the rods are forged steel, the crank is forged, the wrist pins are tool steel, all rod and head bolts are ARP2000 material, the ring gaps have been set for the appropriate level of gap, the valve springs are race quality capable of controlling the large mass of Big Block valves (Ford or Chevy or Hemi) and the fuel is correctly metered E85 or race fuel which eliminates pre-ignition or detonation.

What you got SVTP? What fails and why.

Hmmm... @James Snover what say you good sir?

A boss piston weighs a lot less than a big block Chevys. Run a piston speed formula and add the mass. A lot of force being slung around. Faster pistons speed longer rods AND the additional mass.


Sent from my iPhone using the svtperformance.com mobile app
 

coposrv

Well-Known Member
Established Member
Joined
Sep 4, 2007
Messages
5,030
Location
boston
I’m going to check back in tomorrow. I need to get to sleep and if I start getting to far down the rabbit hole I’ll be up all night. I’ve done a ton of calculating shortblock dimensions very recently with a stroker 5.4 I have underway.


Sent from my iPhone using svtperformance.com
 

01yellercobra

AKA slo984now
Established Member
Joined
Oct 5, 2005
Messages
21,126
Location
Cali
I've only dealt with a couple big blocks. My personal engine was a 460 with worked over heads, decent cam, but stock intake. Never got the chance to swap that out. The torque was fun. I left a lot of rubber on the road.

Next was a Chevy 454 taken out to a 496. Bored and stroked with aluminum rods, forged crank and pistons, stock block, and everything done to the heads. That thing spent a lot of time at 7k in a flat bottom boat with a Powerglide. Never had an issue. Eventually it ended up in a C3 Corvette. That was a fun ride too. What ended up killing it was he decided to reassembled it one night after a few beers. He didn't torque one of the rods. So when he fired it up on the engine stand it flung a nut around and broke the cam.
 

biminiLX

never stock
Established Member
Premium Member
Joined
Jan 17, 2003
Messages
13,253
Location
Toledo, OH
Depends on budget but aftermarket block, good rods and quality valve train and probably the top 3 places to spend the money.
I know all 3 have great aftermarket support with BBC and Hemi winning there, but hard to beat a stroked 460 in a light Foxbody. TFS A460 heads, tunnel ram and good block will make awesome power. Or Kasse Boss 9 top end on a standard 460 block would both make power and look killer.
For the same price as the Bear block Holbrook Coyote I’m building I could have a Kasse Boss 9.
Good luck
-J
 

apex svt

MEAN STREAK
Established Member
Joined
Jun 29, 2012
Messages
2,162
Location
USA
Setup usually determines the failure. But I’d say the first thing to go will be top end lifters/rocker arms, cam.

I know on my buddies drag week cars they throw new lifters in before they leave and bring an extra set as well as they are the first to go. They will also put a new cam in depending on mileage, unfortunately a broken cam ruined his drag week last year.

Cheap bottom end parts will go first. Eagle crank - Chinese garbage didn’t like 1000hp.
55E36C05-457F-475D-AD14-B122FBD111BC.jpg


Big cam, a lot of RPM. Shit will eventually give.
AFE6CF59-2028-4405-A4E3-6BAB6285FF56.png
 

Junior00

Hurter Of Delicate Vaginas
Established Member
Premium Member
Joined
May 20, 2005
Messages
2,574
Location
Ga
Don’t forget to add rod length and piston ch to the mix. Those factors play an important role in longevity. It also changes things, as the average piston speed may stay the same, the dwell is increased or decreased at tdc or bdc depending on the rod.
 

Users who are viewing this thread



Top