Reverse intake engine [Archive] - Chevelle Tech

: Reverse intake engine

Apr 8th, 06, 9:13 AM
This is about the most bizzare thing i have ever seen.

Reverse intake engine (

Apr 8th, 06, 10:24 AM
That builder got some "engine-newity" That is some crazy stuff.

Apr 8th, 06, 11:24 AM

1971 Chevelle
Apr 8th, 06, 12:17 PM
He should have used a big block.

Apr 8th, 06, 3:19 PM
Thats friggin awesome. It probably runs like a disaster....I mean you gotta figure....the exhaust side of any engine(like head ports for example) isnt exactly intended to work the opposite way and draw in an intake charge. So, I dont know how he worked that out. Obviously with time and effort you can make the thing run....but Id have to think that it dont run all that well(cause that would be hard to work out). Either way, even if he was only able to wring 175 horses out of it at best(and probably not even that much).......he is practicly driving a go cart so Im sure it could have some getup if it does indeed run! Either way, if it runs and drives at all the guy gets an A for effort just cause it sure is neat and definitely not something you see everyday. Plus, it had to take some smarts to make it work too. Neat thread. Thanks for the link!

Apr 8th, 06, 3:41 PM
I saw that car in Minneapolis back in February. I think the show was "World of Wheels" sponsored by O'Reileys. Good luck buying a camshaft with the intake and exhaust lobes reversed. Has anyone actually seen this thing RUN??? I have a dollar that says it's a static display--non-functional.

[edit: Y' think those carbs will catch a lot of dust coming off the front wheels? I did find a BB where the owner made it clear that he DOES intend to make the thing run, though.]

Not, mind you that it COULDN'T be done. They used to reverse the ports like that on the Buick Nailhead engines. The intake valve was small enough to be an exhaust valve, and then they supercharged the thing so that the REALLY TERRIBLE exhaust port could supply the intake charge.

Cut down on overheating, I'm sure. Have you seen how a nailhead exhaust port winds around the head casting?

Apr 8th, 06, 3:50 PM
Another one like this is Bruce Crowers indy engine that had the intake ports right next to the exhaust ports!! TALK about REWORKED STOCK HEADS!!!

It was single turbo'ed too..

The old HPBooks, book, "How to Hotrod Small-Block Chevys" has a picture of it on page 148..

This actually started with the old Fathead motors b/c guys use to switch ports to try to hold the engine heat-sink down b/c the intake port made a shorter exhaust port when switched!!

AT least, I figure it was b/c of heat-sink??????? Maybe I'm all wet here, I donno??


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Apr 8th, 06, 4:09 PM
The power must be awesome with the "2 racks of Honda 750 carbs" . Wow, take a 5000cc engine and put on carbs that worked for a 1500 cc engine.

Apr 8th, 06, 4:51 PM
carb cfm = rpm x displacement / 3456 x VE

For a Honda 750 cc (45 cid--11.25 cid per cylinder) engine turning 10,000 RPM and assuming 100% volumetric efficiency (100% probably generous)

X = 10,000 X (45/4) / 3456 X 1
X = 10,000 X 11.25 / 3456
X = 32.55 CFM per cylinder

For a Chevy 350 (44 cid per cylinder) engine turning 4,000 RPM and assuming 70 % volumetric efficiency (70% is probably generous)
X = 4000 X (350/8) / 3456 X .7
X = 4000 X 44 / 3456 X .7
X = 35.65 CFM per cylinder

Leaving out ram tuning, valve sizes, cam timing, etc, it would appear that this engine is CFM limited to "about" 4K. Add a plenum so those carbs could talk to each other, though, and you'd maybe be onto something. Remember that in their natural state, they're an independent runner design--something on the order of a 25% duty cycle. They're only active during the intake stroke. Add a plenum and that could go to nearly 100% duty cycle.

Oh, and a photo from the 1958 NHRA Nationals, of the supercharged "backwards airflow" Buick--note that the supercharger is ahead of the engine:

Apr 8th, 06, 6:02 PM
I read an article a while back about an engine builder (possibly smokey yunick **spelling**) that was reworking sb head for that purpose, he would raise the exhaust ports for a straight shot into the cylinder, he had also made a single equal length header that looked like a octopus tied in knots. if I rember correctly it made good horespower and torque up to 8 or 9000 rpm.. I'll see if I can find the article

Apr 8th, 06, 6:13 PM
That's an old "nail-head" Buick!!

They had terrible exhaust ports and well, "nail" sized valves!!

I think I read somewhere that GM only half made their heads b/c they were supposed to have been a cross-flow "hemi-head", but turned out a "pent-roof" with dinky side-by-side valves!

But it cost too much so they did what they did to it! That, and GM said a Buick V-8 with hemi-heads was too wide to fit into the frame of the cars back then....

They used a lot longer timimg on the exhaust side to make up for their terrible exhaust ports and that's why they kinda "cacked" just a tad, being Old-Man's car motors. AND the suckers do make some GOOD torque too, just check out a 401 and 425 engine's torque outputs!


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Apr 9th, 06, 7:54 AM
I believe the reasoning behind the I/E switch was that the shortest intake will provide the broadest torque curve. There is nothing the human mind cannot rationalize.

I'd like to see a BB with 8 exhaust mounted Mikunis with reed valves running on hydrogen peroxide. With a Potvin blower, of course. And a Wyco V mag mounted to the front of the blower. That would be cool!!! With the cam driven from the center of the crankshaft. Now, that's the ticket. And idler sprockets on the cam chain that could be used to advance or retard timing by switching slack from one side to the other. I'm on a roll!

Apr 9th, 06, 10:54 AM
I just wish Coates would get the bugs worked outta his rotary OHC set-up!!

AND I would buy onna Pete Ardema's OHC SB conversions!!


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Bomber '67
Apr 9th, 06, 1:38 PM
Special for PDQ

Note that there are two "A"'s in Aardema

You can thank me later for the drain on your wallet - I'm just doing my best to to help PDQ do one of his "gonna" do someday projects. LOL


Apr 9th, 06, 2:13 PM
Any way you look at it it is cool to be different.