Curious about displacement

While watching Mecum Auction on the Motor Trend Channel they often mention that the Chevy 383 stroker engine is obtained by putting a 400 small block crank (with a 3.75 inch stroke) into a 350 block (which has a 4.001 inch bore), which results a displacement of 383 CI. However, I did the math and an engine with a 4.001 in. bore and a 3.75 in. stroke has a displacement of 377.17 CI.

Is my math defective or are the commentators at the Mecum Auctions giving out bad information?

There’s also space in the combustion chamber, between the top of the piston and the cylinder head.

A 350 Chevy has a 4.000 inch bore but typically a 383 is a 4.030 inch bore with the 3.75 stroke crank. You are correct that a standard bore block with that crank is 377 ci.

Chevy’s own 383 crate motor has a 3.800 inch stroke with a 4.005 inch bore which gives 383 ci.

The combustion chamber doesn’t add to the displacement, it is only used to calculate compression ratio.


There’s a channel for everything. I’ve been to live auctions - can’t imagine watching it on TV.

Then actually try it sometime. It can be pretty addictive at times to watch.


People seem to be even crazier bidding when there’s live cameras on them, hard to forget the guy who jumped into the bidding on a Bugatti Veyron at Barret-Jackson Vegas years ago who thought he was helping the bid and had a deer in headlights look when he won. Total panic when they asked him how he intended to pay.

Thanks. I’ve never heard them say that the 400 crank went into a 350 block with a .030 overbore, but they may have. Anyway, glad to know my math skills haven’t totally deteriorated (at least so far).

Originally, I had done the math and figured out that with a 4.00 in. bore you’d need a 3.81 in. stroke to get a 383. Interestingly enough, with an 8 cylinder engine with a 4 in. bore, you can figure out the total displacement by adding .02 in. to the stroke and multiply by 100. With a 3 in. stroke you get a 302, 3.25 in. stroke is a 327, 3.48 in. stroke is a 350, etc.

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All of this does nothing to explain why a 396 Chevy actually displaced 402. :wink:

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It shouldn’t, the two are not related. The bore of the 396 was increased to 4.13 " for emissions reasons.

One reason the Chevy was listed as a 396 GM, at that time, limited their ‘muscle cars’ to 400 CI. Why Chevy called it a 396 instead of a 400 I don’t know, perhaps because Pontiac had a 400. Buick liked to put the torque rating on their air cleaner housing rather than HP rating, each devision had their own ideas.

There were lots of fudging of displacements from every manufacturer.

It’s very additive. This isn’t like your local auction where you can bid on 200 MiniVans. While there are some everyday vehicles there…most are classics and collectables. Many completely restored (most are retro-mod). Some are very exotic…some are complete one-offs. I like seeing many of the older vehicles that have been completely restored. Nice to see people saving these beautiful vehicles.

I do as well.

Many of which had far more money spent on the restoration than the car’s selling price. This is especially true of those less desirable cars - still great cars - but less desired by the collector car world, sell for $35,000 at auction when you know they spent over $100K on the restoration. The previous owner saved it because the car was special to them, not because they were trying to make money off of it.

And then there are the custom cars done to the owner’s taste…sometimes bad taste… that also go for peanuts.

And on top of that, before the auction you can go to the Mecum website and see all the cars that will be up for auction. Typically, the lower end cars will go on the block on the first day or two of the sale, with the more expensive cars saved for the weekend, especially the final day. What this means is you may actually find a kinda, sorta dream car you might be able to afford. For instance, there might be a 1969 Camaro Z28 in the auction which will typically go somewhere in the $50,000 to $150,000 range on Sunday, depending upon who is there that wants one, but there might also be a 1969 Camaro with a 307 or 350 that will for for $15,000 to $30,000 on Wednesday or Thursday. This could be a car you’ve always wanted, which you now could get for about the cost of a new compact car (or even less), and then could modify yourself as time and money allowed. Also, you don’t even have to be there to participate: you can bid online or by telephone - you just have to pre-qualify and put down a deposit, just as you’d have to do if you were there in person. I’m not saying this is for everyone, but it could be an option for some people.


It is. I particularly like it when one of the commentators makes a small mistake, but then the hordes of automotive super-nerds who watch these things get pretty vocal about something trivial and the commentators sheepishly correct themselves.

adjusts glasses

No Mike Joy, the font used on the AM radio’s bezel on the first generation Corvette did not change in 1959 as you erroneously claimed. it was a mid-year change for the 1960 model, on cars with the 283 fuelie only. I expect a full retraction at some point during the next segment.


Sports Car Market Magazine regularly covers auctions of all sorts and it’s not unusual to see someone buy the restoration at 50% or less of the cost and get the car for free. Or a Resto-Mod going for less than a perfect restored example. Really depends on the audience at the auction and how determined the bidders are.

The resto-Mod usually starts with a less-than-significant version of the car. A 230 6 cylinder 69 Camaro 3-speed manual that, if perfectly restored to show car condition, is worth $22K (per Hagerty). If it sells for $60K, that is far cheaper than the $120K a pristine Z28 RS/SS would sell for.


Normally yes, but some collectors prefer a 100 point example better than factory build, I wish It had been possible to get that 67 RS Camaro 327 convertible that I saw on the market years ago for about $25,000 that looked more like the sort of car you’d build into a clone or resto mod but looked like a good entry into the Camaro world.

It still IS a good entry. That car is worth about $29K today in #3 condition and sales prices have been flat since at least 2018. The market for those cars is shrinking as those that want them are dying off or selling out.

This was more than 10yrs ago before I had a garage to keep something like that, if I recall correctly it was a 327/Powerglide RS with rally wheels but looked like a basic white/black convertible otherwise. Really all i’d need to cruise around or drive to work sometimes.