Ideal Drag Race Bore and Stroke

[RustyRatRod]

Shut up. You will have all the LS spies switching to a good engine.

Yeah and drivin slant prices up.

 

[fishmens67]

I'm still waiting for my wife's honest answer, she knows how to make HP.

 

[MOPARMAGA]

This is why I’m now suggesting to ALL bracket racers to swap to the slant 6.

Time Between Overhauls is exceptional, between race maintenance is drastically reduced and therefore the fun factor is through the roof.

It’s not about the ET or MPH, it’s about fender racing, playing the game, hiding a tenth in your dial in and turning on win lights all while never opening the hood between two season oil change intervals.

All that savings means you can now buy an enclosed trailer, a new motor home to pull it with, and all the extra special fixings for those trailer side BBQ’s.

Oh yeah, and the best part is you can buy MORE beer of the expensive brands so the bench racing after a long day of shoe polish racing is done is all cooled off and washed down with style.

The slant 6 bracket engine program is a win, win, win, win win on every level.

Hell, you don’t even need a throttle stop. You caint beat that.

Comedic relief

 

[PROSTOCKTOM]

I find interesting that a NHRA Pro Stock engine stroke is only 3.600, it seems like most people are about the 4 inch crank for a small block and a 4.15 or 4.25 for big block.

In a normally aspirated racing engines the bigger the bore the bigger the intake valve you can get in the heads and clear the cylinder walls. Bigger valve, bigger potential flow.

I can tell you that most tracks are not prepped enough to run lots of stroke and hope to keep the tires hooked up.

For this reason a more successful bracket car should run the biggest tire you can and limit the stroke to 4.00" or less.

You can't win if you break loose at the start, or can't keep it hooked up all the way down the track at a subpar facility.

Tom

 

[Charrlie_S]

For this reason a more successful bracket car should run the biggest tire you can and limit the stroke to 4.00" or less.



Tom

I would counter that statement. I am a firm beliver of "run the smallest tire that works on your car/suspension". Any time I tried running a "big" tire (at least on a car no quicker than 10.50) I lost speed (mph and et) and was less consistent. It will have less rolling resistance, and less inertia.

 

[Dartswinger70]

In a normally aspirated racing engines the bigger the bore the bigger the intake valve you can get in the heads and clear the cylinder walls. Bigger valve, bigger potential flow.

I can tell you that most tracks are not prepped enough to run lots of stroke and hope to keep the tires hooked up.

For this reason a more successful bracket car should run the biggest tire you can and limit the stroke to 4.00" or less.

You can't win if you break loose at the start, or can't keep it hooked up all the way down the track at a subpar facility.

Tom

Thank you. I had tried explaining this to a 318 guy who replied "the bore doesn't matter" I then replied "look back at all the classic era small bock performance engines, they were all 4 inch bore to accommodate the big valves. Theses folks dot get it and you cant tell them.

 

[LO23M8B]

12 inch x 8 inch x 8.

 

[33IMP]

Fact is, most situations your stuck with the bore that's possible in the block family you've chosen.
And since making it bigger tends to make more power (assuming enough cylinder head!), more stroke is almost always my choice.
Then do whatever it takes suspension-wise, to make it hook. Little tires are all the rage nowadays, but I'll still take more tire than I need, thankyou.

 

[33IMP]

Thank you. I had tried explaining this to a 318 guy who replied "the bore doesn't matter" I then replied "look back at all the classic era small bock performance engines, they were all 4 inch bore to accommodate the big valves. Theses folks dot get it and you cant tell them.

4 inch, or more! (Remember the 400 chevy? 4, 125)

 

[273]

This guy is too much, makes wild *** assumptions then has strawman arguments.

No one is saying a smaller bore is better, just for 200-400 or so hp you don't need a huge bore a 318 bore is more than adequate, even a 273 bore could handle those power levels without too much work, I bet the block strength is more of a limiting factor than a 318 bore size.

Available bores 3.625, 3.91, 4.00, 4.04, 4.125, 4.185, 4.25, 4.32, 4.34 why is 4" the magic choice ?

A 3.98 bore is half way between a 273 and a 400 bore, 318/360/340 are all not too far from being a mid size bore from our available options, better than a 273 worst than every big block.

 

[fishmens67]

I like the idea of a stock stroked 400 with a 440 rod and custom piston.

 

[MOPARMAGA]

I like the idea of a stock stroked 400 with a 440 rod and custom piston.

In a 4.402 bore

 

[273]

I like the idea of a 496/440 gives a good bore, rod to stroke ratios, decent piston height etc..

 

[MOPARMAGA]

Id just build my engine.
If I had a low deck aftermarket block it would be same stroke 3.915 with a 4.500 bore and predator cylinder heads. Right
@fishermen67

 

[gregsdart]

So much depends on personal restrictions. Say you have ported 440-1 heads, but must limit rpm to 7800 or less to give your valvetrain some life. Max Cubes (572?) provides a good way to keep rpm at a reasonable level, and provide a wide enough power band. You can make decent power this way, north of 900 if built right . Each motor combo will have different parameters for what you want, but i strongly believe in BIG shortblocks.

 

[273]

So much depends on personal restrictions. Say you have ported 440-1 heads, but must limit rpm to 7800 or less to give your valvetrain some life. Max Cubes (572?) provides a good way to keep rpm at a reasonable level, and provide a wide enough power band. You can make decent power this way, north of 900 if built right . Each motor combo will have different parameters for what you want, but i strongly believe in BIG shortblocks.

I basically see it as the Top end is the power you want and displacement is where you want it (rpm).

 

[33IMP]

I like the idea of a 496/440 gives a good bore, rod to stroke ratios, decent piston height etc..

I like the idea of a 383/496.
Some don't care to make a 383 that big... but the end result is the identical bore/stroke as a 454/496 that the chevy guys love so much....... and if you use a 440 rod, better r/s ratio.
Just have to put enough head on it (easier to do than it used to be).
Edit: if I did have a 383, I'd actually try to make a 489 out of it, just bore it .030 if possible.

 

[Oldiron440]

Best bore and stroke for drag racing is the biggest and bigger yet….

 

[PROSTOCKTOM]

I like the idea of a 383/496.
Some don't care to make a 383 that big... but the end result is the identical bore/stroke as a 454/496 that the chevy guys love so much....... and if you use a 440 rod, better r/s ratio.
Just have to put enough head on it (easier to do than it used to be).
Edit: if I did have a 383, I'd actually try to make a 489 out of it, just bore it .030 if possible.

I just sold a guy in Germany a 491"/ 383" balanced rotating assembly. 4.29" bore x 4.25" stroke.

I am sure I'll get some feedback later in the summer.

Tom

 

[tvt59]

The answer above hasn’t been the current answer for decades.

The answer is:

P
L
A
N

That is the only answer and thats what the answer is.

Back in the 80's I talked with Bob Glidden and Robert Yates about these things. When Brett Miller and I were planning this 441" W5 engine that he built for me. I told him the things that Yates and Glidden told me. He told me that pretty much everything that we believed back then has been proven wrong. And when we dyno'ed the engine all the things that Brett wanted to try on my engine worked.

 

[Newbomb Turk]

Back in the 80's I talked with Bob Glidden and Robert Yates about these things. When Brett Miller and I were planning this 441" W5 engine that he built for me. I told him the things that Yates and Glidden told me. He told me that pretty much everything that we believed back then has been proven wrong. And when we dyno'ed the engine all the things that Brett wanted to try on my engine worked.

It wasn’t wrong.

Physics didn’t change.

The rule book changed.

 

[tvt59]

It wasn’t wrong.

Physics didn’t change.

The rule book changed.

The things that we talked about. Really don't matter as mush as I thought. And for my racing, which is braket racing their really isn't and rules. When I made the statement to Brett that I didn't like a short rod engine. He said don't worry about it they just connect the pistons to the rods. He said you'll never know the difference. So we used the 6.125 rods I had and the engine revs fine. I wanted longer rods. But he said to save that money and buy a really nice set of pistons. And he was right.

 

[9secRR]

The things that we talked about. Really don't matter as mush as I thought. And for my racing, which is braket racing their really isn't and rules. When I made the statement to Brett that I didn't like a short rod engine. He said don't worry about it they just connect the pistons to the rods. He said you'll never know the difference. So we used the 6.125 rods I had and the engine revs fine. I wanted longer rods. But he said to save that money and buy a really nice set of pistons. And he was right.

6.125 aluminum rods in my 355” and it rpm’s very quick

 

[Newbomb Turk]

The things that we talked about. Really don't matter as mush as I thought. And for my racing, which is braket racing their really isn't and rules. When I made the statement to Brett that I didn't like a short rod engine. He said don't worry about it they just connect the pistons to the rods. He said you'll never know the difference. So we used the 6.125 rods I had and the engine revs fine. I wanted longer rods. But he said to save that money and buy a really nice set of pistons. And he was right.

You totally missed my point.

I’ll add this because it matters. This is just one point.

If rod length doesn’t matter, why not use a 6 inch rod? It’s cheaper. Bearings are easier to find. And it doesn’t matter right?

Or why not a 5.7 rod? Again, it’s a Chevy length so they are easy to find and bearings are everywhere.

The reason it’s not done is because rod length does matter.

The shorter the rod, the heavier the piston. The shorter the rod, the lower the pin height and the piston has more rock around TDC and it hurts ring seal.

Rod length changes cam timing as well.

So when you boil it all down you find in the end that what Smokey Yunick said 50 years ago was and is right as rain.

Use the longest rod you can fit. And EVERYONE does it, but they slam the guy and say he didn’t know what he was talking about blah blah blah.

Of course, with Chrysler junk you can get the rod too long because the deck heights are too high for the stoke length they use. But that’s the exception and not the rule.

Not one single engine builder I know uses a rod shorter the longest they can fit. To the point they run the oil ring around the wrist pin.

That should prove to you that rod length matters otherwise you’d never see a piston that has the oil ring around the wrist pin.

Physics didn’t change. Smokey wasn’t wrong. Rules changed. And shoe polish won the day.

 

[33IMP]

If I remember right.....
EM did a dyno test of two otherwise identical short blocks, a long rod engine vs a short rod engine..... and didn't find any substantial difference. (bbc).