I saw this in an old HOTROD and was wondering what you guys thought about this. I think they basically said that with longer runner length less duration was needed bcuz of the decrease in the ability of the intake to flow well relative to the heads? Is there a direct corrilation between the two?

Thanks
Jeremy

 

There is no set rule really.

One thing that is interesting is to look at the 2 F-body motors.

LT1 3" runner
LS1 8" tappered runner

Now the best HR cams for the best average power up to 6500 are completely different for these two engines, and alot of it has to do with the intakes. The LS1 does have better heads, but don't worry about that here.

A LT1 can use a much smaller cam because the runners don't help to make any TQ for the motor. Where a LS1 can run a ton of cam and it still makes midrange TQ that's on par with a 383 LT1 due to the intake manifold.

So I would say that a LT1 with it's shorter runners needs less cam than a LS1 with it's longer runners.

But this is all a oversimplification of the complex system of a engine.

Bret

 

What about something like the TPI vs Stealth Ram? Would the same apply there since they are both avaliable for the sbc?

 

The big diff between the TPI and the Stealth Ram is that the the TPI is too long and the Stealth Ram is just about right.

A TPI is alot like a 5.0L EFI intake where the intake runners are too long to make any decent power over 5500 without a ton of cam.

The Stealth Ram has nice length runners, more like a single plane intake so it will use more cam than a LT1 intake and still make great midrange.


Bret

 

Can you put a big cam in a TPI and make hp without lossing lowend? I just dont see guys running much larger then a LPE 219 cam in even a 383 TPI.

 

The cam still does dictate what's going on, and with the long runners on a TPI you are really fighting them to try and make HP with a big cam, so the LPE cam is probably as big as what will work in the low RPM range those motors work in.

Bret

 

I was doing some more reading on the old Adv look at Hotcam. I got to wondering how intake runner lenght effects how well a small cam would work with a good heads and intake? Mostly I am working on building a 351w right now(yea I know I'm asking for Ford advice on a Chevy mb) with TFS TW heads and TFS 351(13.4" runners) intake. I was looking for a cheap cam to make good power, and was wondering how well a zz3 sized cam would work on the longer runner intakes? I can get a Crower cam that specs out at 202/211 112LSA .506/.528 w/ 1.6s, for dirt cheap. Bigger and better things will come, but I am just trying to get it together as cheap as possible and still go as quickly as I can. I hope to be running some 12s.

 

That Crower is WAY to small to make any HP with the TFS intake and heads on a brand X-- been there.Now Crower makes some B****** cam's for a 351 or bigger so call them ask for Dave he's the MAN to fix you up.

You didn't give flow # but have them ready if you call Crower.


Total system air flow and RPM's will tell you what cam to run.Port length helps to shape the air to get it into the cyl.
Correct length intake ports along with cross section area (to a point you cain't go overboard) , help an LT-1 over a stock intake.

 

Well, it was either that of the FMS X cam(224/224 112 .542/.542). I am just looking to get the motor together as cheap as possible. A new cam is not in the budget right now. Just looking for a cam that will send me down the track in respecable time.

 

The 224 cam would be better.Not my choice ----but its a budget thing.

 

One of the biggest mistakes you see people making is in not properly matching components.

Take the example of the TPI intake and a large cam. One is designed to make low end torque and the other, to make high-end hp/tq. Kinda like putting chocolate and pickles together.... although I'm sure some people like that kinda thing.

-Mindgame

 

Boy thats a REAL bad Combo ugh--poooe
Yea some people think if it's got a nasty chop--it's GOT to be fast.

 

 

I've learned that New Yorkers have rather peculiar tastes in things. Thought it was just them NYC folks but I guess it spreads northwards.

I bet Bret likes chocolate covered pickles too doesn't he?



-Mindgame

 

He's an omnivore when it come to eating/drinking and thinking. Truth be told, he's a dry red Aussie wine kind of guy. He's come up with some great, economical wine finds. (He probably won't appreciate this post.)

He's never developed a taste for Scotch like his old man, however. We all can't be perfect.


Back to topic:

As far as the 351 with the long runners, some decent simulations could of course come up with a custom cam, but then plugging in the currently available stuff that's close could be useful.

Are you married to the long runners? If another intake/fuel delivery system is a possibility in your plan, there's power to be made. Think out of the box. Some $10 Aussie Shiraz beats some $20 CA reds for some of us.

"So many (cams, wines, women),...so little time."

Choose one or more...