Pro's and Con's of trying this??

[pdq67]

The long "Cam Transparency" thread got me to thinking and you guys know how much I dream... He, He!!

What happens if you run a 268/218 cam with no overlap and as high a lift as possible, then blow hell out of the engine and intercool the blown air to ambient temp.

Oh, and use fast-burn modern combustion chamber design heads too... Long rods, flat-top pistons and .035" quench..

Can you run a low dizzy setting of something like 30 degrees total and run it on 92/93 octane gasoline without it detonating?

You know a modern, blown, junk301 engine....

Kick away...

pdq67

[groberts101]

dunno.. massive pumping losses to the point that you need to keep upping the boost levels?

Better have one hell of an intercooler with liquid nitrogen!

[ap72]

Why? Seems like a lot of effort/expense to build an engine that doesn't perform well at all. You'd be better off swapping in a stock BBC.

[jeff swisher]

Some new thinking towards turbo's I read somewhere is some modern turbos do not have the issues with more exhaust pressure than intake pressure.. they spool easier and internals are lighter and you can use tighter lobe separation cams on them.

Speaking of your 268H 218@.050 cam

I had my grinder build me one on a 106 lSA.. I installed it into my 350 with over 10.7 compression and 601 heads ported. I ran 1.84-1.50 valves. bla bla bla.
Now it turned R's really quick and had 225psi cranking pressure.. MPG was 12.. drove and tuned on it in my 47 dodge truck for 2 years.
Max TQ on a wheel dyno came in at 4700 rpm pretty flat though.. Max HP was at 5700 rpm for the little cam. Not max RPM but actual max HP reading do not confuse the 2.

Now I wanted more MPG and decided a cam change was in order.. But i like my early closing intake valve.. SO I had my grinder do me another cam .. same lobes but now grind it to 112 lSA but advance the intake lobe like the 106 cam and push the exhaust way back to the the 112 .

It worked great for a boost in MPG I now get 18 and the cranking pressure is the same 225 psi as the intake valve closes at the same time as the other cam.

HP and TQ curves were on top of each other until 5700 rpm.. the 112 LSA cam fell off rapidly.. and at 6500 rpm was down 40HP vs the 106.
112LSA needs shifted at 6000 or before as it noses over..The 106LSA would hit 7000 rpm before you knew it with 456's.


The first cars built ,, the Theory was you can't have overlap as you could not start the vehicle..Something like that anyway..I am not that old.

I found overlap can be your friend..

I know you have really wanted another junk 301.. maybe for the Revs. I have built 327" and 350" to the same specs and the 350" would spank it ..Usually a step larger cam and a bit more compression and the 327 will match the 350.
I done the same with a 388 stroker and the 388 would spank the 350.. Then a little more cam and compression and the 350 would match the 388.
You will need to really find a good way to make compression with the 301.. or big duration early closing intake valve trap the pressures and rev it to 8500rpm.

Or like you are thinking forced induction.. But You will need some overlap .

So think like this during the overlap the exhaust pulls on the intake tract to help fill the cylinder , You have a modern turbo with less back pressure than the old heavy rotating ones.. could overlap cool the turbine could the added scavenging of overlap increase exhaust flow and speed up the turbine?

I just recently began theorizing turbo's.. many questions.
If you get the answers pdq67 share them

[Ks Fats]

pdq,
This is not "kicking" but you are only looking at the induction side of the overlap equation. With forced induction the intake opening could be much closer to T.D.C. but that would be dictated by the efficiency of the blowdown and pump of the exhaust phase. It will take a better mathematician than me to calculate but with an increase in intake mass due to increasing pressures there would also have to be a commensurate increase in exhaust efficiency. If the exhaust phase is "weak" then an earlier intake opening (with the higher pressures you speak of) may be required to purge the exhaust on overlap. I believe UD Harold stated the shape of the overlap area becomes more important than the number of degrees between the I.O/E.C. points.

[ap72]

If you're running 218 duration at .050" then you're looking for a peak in the 5700ish range. So there's no reason. It to run a 3.75 or even 4" stroke, it can handle that rpm just fine.

If you're running a supercharger then I assume you're also wanting a strong torque curve, so there's no reason to run an insanely wide LSA.

so you're back at a supercharged 383+ with a 218/218 cam on a 108 or so LSA... Like has been done a million times before.

If you're actually trying to get performance then you need to stick with what performs.

The described engine would run like shit through the entire rpm band and be worth far less than the sum of its parts.

[F-BIRD'88]

In your lil blown Dream 302 use any of these 268 cams for supercharging.

Comp cams NX268H,,, CS268XFIH-13,,, CS268AH-14 or a Crane H278-2 (HMV278-2)
Isky 201271/281-12 is another.

A low cost generic Summit Racing SUM-1105 works great too.


If you want a lil solid lifter cam try Comps extreme energy solids. Pick one about 6 to 10deg bigger duration to account for the valve lash. The 110LSA XE solid lifter cams will run fine. If you want a wider LSA just call Comp and order it.

Use a roots blower like the 142 or 177 weiand . Or the Eaton based Edelbrock/Magnacharger MP122. Use Water methanol injection instead of a intercooler.

You would use a distributor with a boost retard function. A vacuum advance can be modified to do both vacuum advance and boost retard. Or a Electronic boost retard box can be run.
You'd love a lil blown 302.

With say a home ported 2.02" valve GM 062 vortec head or another equal head expect well over 480hp at 10-12psi boost on this 302.

Using a 70-72cc head instead of a 64cc head lowers the engine compression ratio allowing even more boost on pump gas.
(Either more boost/power with WI and low cr or less dependent on intercooling/water injection on pump gas.) 8:1cr

You don;t really need super high valve lift. .500"-.530" +/- is plenty. Duration and when (open close event timing) is more important.

302CID or works just as well on a simple 283 (287-292) or a 305 or a 307 SBC.

This dream can be a reality.

[groberts101]

What happens if you run a 268/218 cam with no overlap and as high a lift as possible, then blow hell out of the engine and intercool the blown air to ambient temp.

Lol.. either every one else read it wrong?.. or I must have read it wrong and assumed too much which is why I answered with my above reply.

I thought you meant.. 268 advertised intake duration.. and 218 advertised exhaust duration. As in heavily reversed split pattern cam design used in a Boosted application.

[pdq67]

What happens if you run a 268/218 cam with no overlap and as high a lift as possible, then blow hell out of the engine and intercool the blown air to ambient temp.

Lol.. either every one else read it wrong?.. or I must have read it wrong and assumed too much which is why I answered with my above reply.

I thought you meant.. 268 advertised intake duration.. and 218 advertised exhaust duration. As in heavily reversed split pattern cam design used in a Boosted application.

No, just like an old CC 268HE hy-cam with higher lift is all, but with no overlap. Then blow hell out of it.

My thinking is that with no overlap, timing could be set shorter to help hold off detonation. But the high pressure blow would still feed it even with no overlap regardless..

pdq67

[englertracing]

Are you talking about going Miller cycle like a Mazda mellinia?