Internal vs external engine balancing

[rustbucket79]

What's the real pros & cons of converting an externally balanced engine to totaly internal balance?

SKeown

The cons? How about 4 slugs of mallory in a factory 400 small block crank, only to make it 1 season before it starts cracking on the underside of the rod pins. Oh, and mallory nicely welded in so it wasn't worth the effort to reclaim. I suppose it was good experience for someone early in his balancing career.

[SKeown]

What's the real pros & cons of converting an externally balanced engine to totaly internal balance?

SKeown

The cons? How about 4 slugs of mallory in a factory 400 small block crank, only to make it 1 season before it starts cracking on the underside of the rod pins. Oh, and mallory nicely welded in so it wasn't worth the effort to reclaim. I suppose it was good experience for someone early in his balancing career.

Just be thankful you caught it before it broke. Yes, that's the kind of learning experience I'm used to.

SKeown

[289nate]

Cheap and internal balance with a 302 Ford don't really go together, and REALLY don't go together with the later 50 in oz cranks. With the relatively compact crankshaft/rod/block assembly so long as you stick with the earlier heavy casting (2MAE) crank with the early 28 in oz harmonic/flywheel I wouldn't sweat the internal/external debate, they don't seem to mind 7500. If you're heart's set on an internal setup, you might be better off starting with a standard weight Scat 3" stroke forged crank since it should need less mallory and shouldn't have any factory balance holes to intersect with said mallory.

I understand and agree. The new combo I'm working on will include a cored 255 crank that I've ground some material off the rod throw side, a light Probe Molecultie piston, light weight tool steel wrist pin, and an RPM ultralite I beam rod. All that will help. My point is that if it's close, I see no reason not to spend a little money on Mallory to go zero. I'll go 28oz external if it ends up still costing a small fortune in Mallory metal to go internal.

I simply see no reason not to go internal if it's an affordable option. How could moving the imbalance weight closer to the center of the crank be a bad thing???

[avengerengines]

What's the real pros & cons of converting an externally balanced engine to totaly internal balance?

SKeown

The cons? How about 4 slugs of mallory in a factory 400 small block crank, only to make it 1 season before it starts cracking on the underside of the rod pins. Oh, and mallory nicely welded in so it wasn't worth the effort to reclaim. I suppose it was good experience for someone early in his balancing career.

In a 40 yr. old cast crank with an unknown history used in a race engine I think it would be common to see cracks, or an exploded motor.

[rustbucket79]

What's the real pros & cons of converting an externally balanced engine to totaly internal balance?

SKeown

The cons? How about 4 slugs of mallory in a factory 400 small block crank, only to make it 1 season before it starts cracking on the underside of the rod pins. Oh, and mallory nicely welded in so it wasn't worth the effort to reclaim. I suppose it was good experience for someone early in his balancing career.

In a 40 yr. old cast crank with an unknown history used in a race engine I think it would be common to see cracks, or an exploded motor.

The crank would have polished std/std when I started so it hadn't suffered any major trauma up until I used it.

[rustbucket79]

Cheap and internal balance with a 302 Ford don't really go together, and REALLY don't go together with the later 50 in oz cranks. With the relatively compact crankshaft/rod/block assembly so long as you stick with the earlier heavy casting (2MAE) crank with the early 28 in oz harmonic/flywheel I wouldn't sweat the internal/external debate, they don't seem to mind 7500. If you're heart's set on an internal setup, you might be better off starting with a standard weight Scat 3" stroke forged crank since it should need less mallory and shouldn't have any factory balance holes to intersect with said mallory.

I understand and agree. The new combo I'm working on will include a cored 255 crank that I've ground some material off the rod throw side, a light Probe Molecultie piston, light weight tool steel wrist pin, and an RPM ultralite I beam rod. All that will help. My point is that if it's close, I see no reason not to spend a little money on Mallory to go zero. I'll go 28oz external if it ends up still costing a small fortune in Mallory metal to go internal.

I simply see no reason not to go internal if it's an affordable option. How could moving the imbalance weight closer to the center of the crank be a bad thing???

Stay the heck away from that crank, if it's as factory lightened as I think it is, it will not stand up to any amout of abuse. Even the later 50 oz 302 cranks were the only ones we've seen broken in a stock application. You are MUCH better off starting with an early 28 in oz 302 crank. We have converted SEVERAL newer 302's with the early, much more durable crank.

[289nate]

Rustbucket79, PM sent.

[rustbucket79]

Got it, read it, still think you're bonkers for using that crank. If you're planning to put a clutch behind that crank, don't even think of it. I would be starting with an early 28 in oz 302 2 pc seal crank, but that's me.

All that's left to do is wish you luck.

[289nate]

Got it, read it, still think you're bonkers for using that crank. If you're planning to put a clutch behind that crank, don't even think of it. I would be starting with an early 28 in oz 302 2 pc seal crank, but that's me.

All that's left to do is wish you luck.

Soft hitting light weight fully adjustable pressure plate, sintered iron disc, hollowed out super light weight flywheel. I bet it hits softer than some C4 combos do off the brake. Small slick and lots of street driving. Hope I get lucky. A 28 oz 302 crank would just be too easy.

[Baprace]

There is an old saying, you can lead the horse to water...........

[289nate]

There is an old saying, you can lead the horse to water...........

I shouldn't run solid roller lifters on the street either. There are people out there that have pushed this crank 1,000 rpm past where I want to go while leaving it 28 oz and not had a problem in a drag racing application. One of them used to post here. I sure wouldn't use it where sustained rpm is necessary.

[avengerengines]

There is an old saying, you can lead the horse to water...........

I shouldn't run solid roller lifters on the street either. There are people out there that have pushed this crank 1,000 rpm past where I want to go while leaving it 28 oz and not had a problem in a drag racing application. One of them used to post here. I sure wouldn't use it where sustained rpm is necessary.

That's all we had years ago. Nobody internally balanced anything. I met a drag boat boat guy in the early 70s that ran in the 150 c.i. class. He started with a 221 Fairlane motor and offset ground the crank to get his 150 inches. His redline was 11,500 rpm. The young guys have it good now. They have no idea what we could do with what was available at the time. Bill Jenkins was using Chevy 327 blocks to set Pro Stock records. Today, no one would use that block even in a bracket car. We had to use our heads and not our check books. Ah.....the good old days.

[rocks409]

Avengerengines makes me smile. Ah, the good old days. when the 409 stroker becames popular in the early 90s, the common build was 454 crank, 400 sbc damper, 454 flexplate, external balance. I have many great memories from those old motors. bracket racing every Fri. night, sometimes 2 different classes per night. 8 month season. We punished those old engines and never lost one ( probably just lucky) rpms under 7,000 so I;m sure that was the reason the engines lasted. Things evolved over the last few years and now its Eagle/Scat cranks, internal balance, 6.385 rod and pistons around 660-680 grams compared to the old stuff of 6.135 rods and 750-780 gram pistons. Yes, internal balance is a better engine but we did have success with the external balance engines. Shoot!, I still have one in my street car. Ah, the good old days.

[bmcdaniel]

Ah, the good old days....the early 90s,

That's not very old....
Showing my age now, LOL.