Am I on the Right Track; Budget Lightweight 289 SBF Short Block Build…

[crazy_caseys_customs]

I’m trying to plan out my short-block build for what will be a 7,500rpm limited 289 Ford road racing engine. And I’m on a mid-range budget (i.e. no custom crazy billet stuff). The last caveat is that I still want to be able to run 91 octane pump gas, so I am limiting compression to 11:1 (w/ aluminum heads for now). The street mileage will be extremely limited, but I’m trying to have my cake and eat it too…but I won’t actually be eating any cake, because I’m on a diet…

I overheard a discussion that some of the vintage racer Ford crowd use a 5.700” Chevy rod and a 1.065” compression height piston to keep things light, so that got my wheels turning. I want to keep the weight of the rotating assembly as light as possible because the strength of the stock block will be the weakest point of this build.

Here’s what I’m looking at:

RPM International 4340 Forged Crankshaft; I have no idea the weight on this piece, but it’s the only forged 289 crank in my budget. Even though it is listed as a 28oz imbalance crankshaft, I know a couple of vintage racers who run it, and they said there was more than enough material there to internal balance without adding mallory…which means it’s heavy, but…it’s strong.

K1 Lightweight 5.700” 4340 Forged H-beam Rod; (492 GRAMS - 80 gram savings over stock) I’ll have to cut these down to the Ford big end width of 0.830”; but they are the lightest rods I can find in my budget, and plenty strong.

Racetech Custom domed 11:1 Forged Pistons in 1.065” compression height; (~380 GRAMS - 234 gram savings over stock) I can get these made to fit my cylinder heads, and in the custom compression height for about 2/3 the price of a JE custom piston. They also use a metric ring pack which will save even more weight. The only bummer is that they are only offered with standard weight wrist pins…

Tool Steel Wrist Pins; (~75 GRAMS - 66 gram savings over stock) Can I get away with running tool steel wrist pins? Should I just stick with the 129 gram heavy wall pins spec’d by Racetech?

Metric Ring Pack: (~29 GRAMS - 25 gram savings over stock) Just guessing at the weight here. But including it so that I can list a total weight of…

972 GRAMS, which is a savings of about 400 grams per hole from the stock 289 stuff with only about a $2,500 outlay for the entire rotating assembly. That’s a reduction of over 7 lbs in rotating/reciprocating weight. Add to this a lightweight ATI balancer and a McLeod aluminum flywheel, and internal balancing the engine, and it should be a potent, strong short block.

Am I on the right track? Are there any pitfalls to this combination of parts that I may have potentially overlooked?

[mag2555]

You can reduce a good amount of stress by getting the balance job done by a shop set up to balance at what’s termed + or - 1/4 once at 1” instead of the all too common + or - 1/4 once at 3”.

Also for the 200 to 300 buck cost I would very much look into running a girdle on the main caps.

[PackardV8]

I want to keep the weight of the rotating assembly as light as possible because the strength of the stock block will be the weakest point of this build.

Let's examine this rationale of going for the lightest rotating assembly. Why do you think a heavier but balanced rotating assembly is trying to pound its way out of your thinwall block?

[crazy_caseys_customs]

You can reduce a good amount of stress by getting the balance job done by a shop set up to balance at what’s termed + or - 1/4 once at 1” instead of the all too common + or - 1/4 once at 3”.

Also for the 200 to 300 buck cost I would very much look into running a girdle on the main caps.

I’ve always been a fan of girdles as extra insurance, but there are a whole lot of folks on this very board who say not to bother. I suppose I should read up a bit more on this idea…

[crazy_caseys_customs]

I want to keep the weight of the rotating assembly as light as possible because the strength of the stock block will be the weakest point of this build.

Let's examine this rationale of going for the lightest rotating assembly. Why do you think a heavier but balanced rotating assembly is trying to pound its way out of your thinwall block?

I’m probably not smart enough to really speak to it, but I know that reciprocating weight imparts a load on a crankshaft that attempts to flex it, as well as spin it, and that those flexing forces are absorbed by the block’s mains. I’m sure that combustive forces are doing the same thing, regardless of the weight of the components, so maybe it is a moot point, to some degree.

What are you saying? All things being equal, wouldn’t a block have any easier time absorbing the forces of lightweight reciprocating parts than heavy ones?

I’m not speaking about the weight of the crankshaft itself, so much as I am about the connecting rod beams and everything attached to them. My understanding of desiring “lightweight” in relation to the crankshaft itself, is that if everything else is light, so to can the crankshaft be.

Many on these forums with much more knowledge than myself have written that the best we to make a stock Ford block live at high rpm is with lightweight parts. I’ve never really questioned the validity of those statements…

[SupStk]

I may of missed the power level you are shooting for, but you might be underestimating the stock crank. I have built several 289-302s with OEM cranks and to date had no failures. Some of these are in the 550hp range, spinning 8000 and going on 10 years of racing.

For rods I'd consider Scat 5.400 I beams.

Watch the dome height and shape, it's easy to go backward on a SBF trying to chase compression.

[racear2865]

Im going to look at this as a engineer. If you take a engine with heavy rotating assembly and hold at 4000RPM and measure torque, it will be the same as one with light rotating assemble, BUT if you measure acceleration TQ and deceleration torque, there will be a discernible difference. Also, there will be a noticeable difference as both make the turn at top and bottom. Ill give you a guess at which one has the least amount of FORCE on all the parts. Gues which one will try to spit out the bottom? Just put a little thought in it. Oh by the way, you can calculate those forces if u know the weights.
reed

[dannobee]

A couple of things. Save your money on the crank and buy the lightest clutch and flywheel that you can afford. Dual disc Tilton comes to mind. Because of the MOI, lightening up the crankshaft won't make anywhere near as big a difference as lightening up the flywheel and clutch. And if you're spinning it up that high, don't forget the valvetrain. Lighter valves and retainers will help.

Since you're road racing it, every time you come out of a corner, the lighter weight parts will make it accelerate that much quicker. Tiny increments add up when you count up all of the corners.

[crazy_caseys_customs]

I may of missed the power level you are shooting for, but you might be underestimating the stock crank. I have built several 289-302s with OEM cranks and to date had no failures. Some of these are in the 550hp range, spinning 8000 and going on 10 years of racing.

For rods I'd consider Scat 5.400 I beams.

Watch the dome height and shape, it's easy to go backward on a SBF trying to chase compression.

I didn’t post the hp target because it will be whatever it will be. I would think that I’d be in the mid 400’s flywheel range. AFR 165’s and Weber’s complete the package.

My original plan was to run the stock crank with the 5.400” Scat Pro Stock I-beams, but Scat doesn’t advise them past 6,500 rpm, and a couple of the vintage racers I’ve spoken with have experienced crankshaft failures at 7,000 rpm.

Was the 550@8k combo you’re talking about a drag race motor? Because I’m hoping to be able to hold this thing at 7k down the back straight at Miller.

The stock crank/Scat rod combo would certainly be easier and cheaper, but it would still give up 100 grams per cylinder (mostly reciprocating) over the weight of those K1 Chevy rods and 1” CH pistons. I had considered running the Scat ultralight Chevy rod on the stock crank, but they’re strangely heavy for what they are. And running the K1’s on the stock crank seems kinda like wearing a tuxedo jacket with sweat pants to a party…but if enough people tell me that that’s the dress code, I’ll go with it.

Oh, and as to the dome height, yes sir, I copy. I’m thinking I’m only going to be about 6.5-7ccs, which I think equates to about a quarter inch tall dome based on reading catalogs. Shouldn’t affect things too adversely, I wouldn’t think.

Thank you for the reply.

[racear2865]

Take a look at Molnar Technology. Tom Molnar is one sharp Dude and Ive used his stuff at 1500 HP and up.
reed

[piston guy]

Light weight pins are a POOR choice especially in a road race application . Thin wall induces pin flex which costs power and continued flex will cause the pin to fail costing you LOTS of money. Been there , done that.

[nhrastocker]

I’m trying to plan out my short-block build for what will be a 7,500rpm limited 289 Ford road racing engine. And I’m on a mid-range budget (i.e. no custom crazy billet stuff). The last caveat is that I still want to be able to run 91 octane pump gas, so I am limiting compression to 11:1 (w/ aluminum heads for now). The street mileage will be extremely limited, but I’m trying to have my cake and eat it too…but I won’t actually be eating any cake, because I’m on a diet…

I overheard a discussion that some of the vintage racer Ford crowd use a 5.700” Chevy rod and a 1.065” compression height piston to keep things light, so that got my wheels turning. I want to keep the weight of the rotating assembly as light as possible because the strength of the stock block will be the weakest point of this build.

Here’s what I’m looking at:

RPM International 4340 Forged Crankshaft; I have no idea the weight on this piece, but it’s the only forged 289 crank in my budget. Even though it is listed as a 28oz imbalance crankshaft, I know a couple of vintage racers who run it, and they said there was more than enough material there to internal balance without adding mallory…which means it’s heavy, but…it’s strong.

K1 Lightweight 5.700” 4340 Forged H-beam Rod; (492 GRAMS - 80 gram savings over stock) I’ll have to cut these down to the Ford big end width of 0.830”; but they are the lightest rods I can find in my budget, and plenty strong.

Racetech Custom domed 11:1 Forged Pistons in 1.065” compression height; (~380 GRAMS - 234 gram savings over stock) I can get these made to fit my cylinder heads, and in the custom compression height for about 2/3 the price of a JE custom piston. They also use a metric ring pack which will save even more weight. The only bummer is that they are only offered with standard weight wrist pins…

Tool Steel Wrist Pins; (~75 GRAMS - 66 gram savings over stock) Can I get away with running tool steel wrist pins? Should I just stick with the 129 gram heavy wall pins spec’d by Racetech?

Metric Ring Pack: (~29 GRAMS - 25 gram savings over stock) Just guessing at the weight here. But including it so that I can list a total weight of…

972 GRAMS, which is a savings of about 400 grams per hole from the stock 289 stuff with only about a $2,500 outlay for the entire rotating assembly. That’s a reduction of over 7 lbs in rotating/reciprocating weight. Add to this a lightweight ATI balancer and a McLeod aluminum flywheel, and internal balancing the engine, and it should be a potent, strong short block.

Am I on the right track? Are there any pitfalls to this combination of parts that I may have potentially overlooked?

The RPM International 289 crankshaft will take the punishment and have used team in drag racing engines turning 10200 rpm's.
Go with the Molnar connecting rod and do not look back.
Do not go light on the piston pins and for longevity, get DLC coated pins.
Go with a Total Seal metric ring package.
Internally balance the rotating assembly, use an ATI lightweight harmonic balancer and a SFI approved lightweight flywheel assembly.

[rustbucket79]

Displacement rule class?

I ask because I would much rather build a 331 internally balanced than a 289, where the torque coming out of the turns will far outweigh what a light 289 could do.

I have a Scat superlight crank, good stuff but where it is light doesn’t have much influence since it’s relatively close to the centre of the crank. The light weight flywheel and clutch make much more sense.

[crazy_caseys_customs]

Light weight pins are a POOR choice especially in a road race application . Thin wall induces pin flex which costs power and continued flex will cause the pin to fail costing you LOTS of money. Been there , done that.

Ok. Thank you. That’s why I was asking.

[crazy_caseys_customs]

I’m trying to plan out my short-block build for what will be a 7,500rpm limited 289 Ford road racing engine. And I’m on a mid-range budget (i.e. no custom crazy billet stuff). The last caveat is that I still want to be able to run 91 octane pump gas, so I am limiting compression to 11:1 (w/ aluminum heads for now). The street mileage will be extremely limited, but I’m trying to have my cake and eat it too…but I won’t actually be eating any cake, because I’m on a diet…

I overheard a discussion that some of the vintage racer Ford crowd use a 5.700” Chevy rod and a 1.065” compression height piston to keep things light, so that got my wheels turning. I want to keep the weight of the rotating assembly as light as possible because the strength of the stock block will be the weakest point of this build.

Here’s what I’m looking at:

RPM International 4340 Forged Crankshaft; I have no idea the weight on this piece, but it’s the only forged 289 crank in my budget. Even though it is listed as a 28oz imbalance crankshaft, I know a couple of vintage racers who run it, and they said there was more than enough material there to internal balance without adding mallory…which means it’s heavy, but…it’s strong.

K1 Lightweight 5.700” 4340 Forged H-beam Rod; (492 GRAMS - 80 gram savings over stock) I’ll have to cut these down to the Ford big end width of 0.830”; but they are the lightest rods I can find in my budget, and plenty strong.

Racetech Custom domed 11:1 Forged Pistons in 1.065” compression height; (~380 GRAMS - 234 gram savings over stock) I can get these made to fit my cylinder heads, and in the custom compression height for about 2/3 the price of a JE custom piston. They also use a metric ring pack which will save even more weight. The only bummer is that they are only offered with standard weight wrist pins…

Tool Steel Wrist Pins; (~75 GRAMS - 66 gram savings over stock) Can I get away with running tool steel wrist pins? Should I just stick with the 129 gram heavy wall pins spec’d by Racetech?

Metric Ring Pack: (~29 GRAMS - 25 gram savings over stock) Just guessing at the weight here. But including it so that I can list a total weight of…

972 GRAMS, which is a savings of about 400 grams per hole from the stock 289 stuff with only about a $2,500 outlay for the entire rotating assembly. That’s a reduction of over 7 lbs in rotating/reciprocating weight. Add to this a lightweight ATI balancer and a McLeod aluminum flywheel, and internal balancing the engine, and it should be a potent, strong short block.

Am I on the right track? Are there any pitfalls to this combination of parts that I may have potentially overlooked?

The RPM International 289 crankshaft will take the punishment and have used team in drag racing engines turning 10200 rpm's.
Go with the Molnar connecting rod and do not look back.
Do not go light on the piston pins and for longevity, get DLC coated pins.
Go with a Total Seal metric ring package.
Internally balance the rotating assembly, use an ATI lightweight harmonic balancer and a SFI approved lightweight flywheel assembly.

AWESOME! Talked to Tom today, and I think that he is going to dial me in with a lightweight 5.700” rod setup for the Ford crank and block. Already had my eye on ATI for their lightweight internal balance dampener. Already have a 13 lb McLeod flywheel, and a 13 lb Ram clutch in the works.

What is the DLC costing for the pins?