What would you build if limited to 372ci - with boost as an option

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71GSSDemon said:
With boost and a late firing event, combustion pushing merely straight down, I would bet these engines would handle way more than most think. High combustion/compression pressures take heavy tolls.
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Because the air is much more dense when on boost, the flame travels much faster through it. The retarded timing (compared to NA timing) ends up just being the right amount of timing. Try not to think of it as a late firing event. It just takes less time to make complete combustion so you don’t need to start it as soon.
 
TT5.9mag said:
Because the air is much more dense when on boost, the flame travels much faster through it. The retarded timing (compared to NA timing) ends up just being the right amount of timing. Try not to think of it as a late firing event. It just takes less time to make complete combustion so you don’t need to start it as soon.
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Ok thanks for the clarification. I was picturing less advance timing so combustion would be after TDC and direct push down. Less cylinder pressure than a high compression NA engine. Maybe I was wrong, or just using the wrong words. Likely both.
 
71GSSDemon said:
Ok thanks for the clarification. I was picturing less advance timing so combustion would be after TDC and direct push down. Less cylinder pressure than a high compression NA engine. Maybe I was wrong, or just using the wrong words. Likely both.
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It’s just normal for people to phrase it the way you did. The “push down” ends up happening at the same time. If that makes sense now.
 
71GSSDemon said:
So, do I remember correctly that Max Wedge sized heads don't work well with the smaller bore of a 383?
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Part of the problem would be finding an intake for max heads on a 383.
Indy is the only one I know of.
The 413 and 426 maxwedges both had bore notches for the 1.88 exhaust valve. (4.187 and 4.25 bores. ).
The aftermarket heads, even with maxwedge ports, have a smaller exhaust valve, so a 383, .060 over probably doesn't need em a 383 +.030 might, but I don't think so.
But why the question? 383 is too big, and I don't know of any destroker cranks. Gonna have a crankshop offset grind a steel 383 and use bbc rods and pins?
Come to think of it.... didn't original B1's use a 440 width intake on a low block, and spacers for an RB?
Hmmmmm.....
 
33IMP said:
Part of the problem would be finding an intake for max heads on a 383.
Indy is the only one I know of.
The 413 and 426 maxwedges both had bore notches for the 1.88 exhaust valve. (4.187 and 4.25 bores. ).
The aftermarket heads, even with maxwedge ports, have a smaller exhaust valve, so a 383, .060 over probably doesn't need em a 383 +.030 might, but I don't think so.
But why the question? 383 is too big, and I don't know of any destroker cranks. Gonna have a crankshop offset grind a steel 383 and use bbc rods and pins?
Come to think of it.... didn't original B1's use a 440 width intake on a low block, and spacers for an RB?
Hmmmmm.....
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I only mention it as it is what I have. Not sure the best way to lower the displacement, pull a plug wire off or what. Offset grinding a crank to use BBC rods is intriguing. Or just run 373-439ci and up the game. It is a lower record that, in theory, should be easier to obtain. I ask about max heads because I would assume head flow is critical and curiosity.
 
If you think about it, max heads, even trick flows, are still smaller than the big port chevy head used on the 375 hp 396.
I would think a maxwedge port head would work fine on a 371 on the salt.
N/A or boosted.
 
71GSSDemon said:
I only mention it as it is what I have. Not sure the best way to lower the displacement, pull a plug wire off or what. Offset grinding a crank to use BBC rods is intriguing. Or just run 373-439ci and up the game. It is a lower record that, in theory, should be easier to obtain. I ask about max heads because I would assume head flow is critical and curiosity.
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I guess a good thing about pulling plugs easier to move up a class.
 
33IMP said:
If you think about it, max heads, even trick flows, are still smaller than the big port chevy head used on the 375 hp 396.
I would think a maxwedge port head would work fine on a 371 on the salt.
N/A or boosted.
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Especially since bottom power ain't much of a concern.
 
A 383 +.030 block would need a 3.23 stroke crank to get to 371.7.
I'm not sure you could offset grind .150 stroke off of a 3.38 crank, and still use bbc rods.
IF it's possible, the crank shop had better be really good at what they do.
 
71GSSDemon said:
So, in this scenario, what displacement class did you want to drive?

AA/BFALT?
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How bout we focus on achieving your goal, then we’ll work on mine. I get the feeling after you get to 200mph you’ll want to get to 201mph. If you know what I mean.
 
33IMP said:
A 383 +.030 block would need a 3.23 stroke crank to get to 371.7.
I'm not sure you could offset grind .150 stroke off of a 3.38 crank, and still use bbc rods.
IF it's possible, the crank shop had better be really good at what they do.
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I pretty sure one of the engine shops on here said he stroked a B crank to 3.54 so + 0.17, I imagine you probably could go - 0.17 3.21.
 
361 plus .0625 overbore would be 372, and get you the same bore as a 413. You'd have to notch the bores like a 413 max did.
I'd bet the 383 destroker combo would run faster.
 
273 said:
I pretty sure one of the engine shops on here said he stroked a B crank to 3.54 so + 0.17, I imagine you probably could go - 0.17 3.21.
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Theoretically, from 2.375 to 2.17 (.030 under stock 2.2 bbc) is a possibility, so.minus .205. Id offset as little as possible to get to 371". Then you need to find a bbc rod you like, and custom pistons to fit.
(I'd use B1's, have pistons made for them, use the B1 intake, single four, blow thru 4150, and a big single turbo. )
 
33IMP said:
Theoretically, from 2.375 to 2.17 (.030 under stock 2.2 bbc) is a possibility, so.minus .205. Id offset as little as possible to get to 371". Then you need to find a bbc rod you like, and custom pistons to fit.
(I'd use B1's, have pistons made for them, use the B1 intake, single four, blow thru 4150, and a big single turbo. )
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I like it, not sure i can get all of that, but i like how you think.

We are discussing twin 72mm turbos
 
71GSSDemon said:
So, would there be an advantage to destroking a big block, like 400 to take advantage of the bore size, or just use a 360 or 360mag. The 400 could use Max Wedge ports. Does the same opinion hold true when considering boost?

This is for my Bonneville effort. The class I would rather be in would have a limit of 372ci
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Scanning thru this thread but not reading every post, I'll say that engineering anything to live for a duration at bonneville will be more difficult than making power. I'd use any NASCAR platform as a basis and make tweaks from there. I do have a good r3w8 I took it apart to inspect and make changes. I was going to use it for my class but decided to stay big block.
 
ValiantS said:
Scanning thru this thread but not reading every post, I'll say that engineering anything to live for a duration at bonneville will be more difficult than making power. I'd use any NASCAR platform as a basis and make tweaks from there. I do have a good r3w8 I took it apart to inspect and make changes. I was going to use it for my class but decided to stay big block.
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We are talking 5 miles of fighting for traction. Maybe a mile of true sustained WOT.
 
ValiantS said:
Scanning thru this thread but not reading every post, I'll say that engineering anything to live for a duration at bonneville will be more difficult than making power. I'd use any NASCAR platform as a basis and make tweaks from there. I do have a good r3w8 I took it apart to inspect and make changes. I was going to use it for my class but decided to stay big block.
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Likely out of my budget, but what would you want for the R motor? Shoot me a PM
 
In the mean time, I spoke with a local race engine machine shop that is highly recommended. They can offset grind the crank if that becomes the plan. $350-400.

Now talk to be about rehardening the crank or nitriding. When does this come into effect, or is it any grinding beyond clean up??
 
So, a 383 has bore of 4.25 and stroke of 3.375 and 6.358 rod.

Reduce stroke by 0.275

So destroke to 3.1 and use BBC rods measuring 6.635. (Eagle H beam shelf stock) This is a 0.002" difference from stock current piston pin height, yes? So a 383 piston with a 0.990 pin should work for 351ci?

Or the 400 bore of 4.342 and get 367"

Please let me know if I am wrong.
 
71GSSDemon said:
In the mean time, I spoke with a local race engine machine shop that is highly recommended. They can offset grind the crank if that becomes the plan. $350-400.

Now talk to be about rehardening the crank or nitriding. When does this come into effect, or is it any grinding beyond clean up??
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For a street car, or drag car, I probably wouldn't bother.
For a salt car, I would assume you would have to do anything possible for durability sake.
 
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