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Author Topic:   intake runner size?
pbracer9
Dirt Roller

Total posts: 12
posted September 23, 2005 08:35 AM  
What cylinder head intake runner cc's work best for a 406 with no cam rule or intake rule, running flat tops and a 500 holley?

All help is appreciated

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted September 23, 2005 08:49 AM  
I'd go with 200's or no more than a 215 runner.

KP

Flanndad
Dirt Freak

Total posts: 255
posted September 23, 2005 09:11 AM  
Hey KP, I got a 406 also, but mine has a set 220 Pro Topline's.

I was wondering if with that size its a good idea to run a 4 hole spacer to help increase the throttle response.

Would the big runners along with a open 1" spacer cause it to be a little bottom end dead or sluggish.

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted September 23, 2005 09:25 AM  
Yes. I didn't mean to imply one should never run anything bigger than a 215, but it's about at that point where a 2bbl motor starts to feel that way. What happens is the heads, intake, etc are hitting their "prime" about the time the 2bbl carb is giving up.
Now, you mentioned a 4-hole spacer. That 215cc "limit" I'm talking about is only with a 2bbl carb, so if you're running a 4bbl, larger runners and better intake plenum flow is easily achieved, so a 220 Pro head is just fine for something like that.
But yes, an open spacer will sacrifice a little low end torque by moving the power band up in the rpm range some. 4-hole spacers create more laminar flow and less turbulence in the plenum area, boosting lower rpm torque.
The tapered/flared spacers are basically the closest one can come to the "best of both worlds", where they add some power on top without losing as much off the bottom as a purely wide open spacer does.

Hope that helps, everyone...

KP

pbracer9
Dirt Roller

Total posts: 12
posted September 23, 2005 11:35 AM  
Thanks for the help. That is the same thing I have heard form engine builders around here.

Thanks again

ss11
Dirt Maniac

Total posts: 153
posted September 26, 2005 12:04 PM  
KP, I am running a super victor on alcohol and I have a 1" super sucker spacer I was thinking about putting on but wandered if it would hurt the low end torque. It is on a healthy 383 chevy.
Thanks.

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted September 26, 2005 12:11 PM  
Only very slight reduction in low rpm torque, but mainly it'll help some in the mid-upper end. It mostly helps balance flow and reduce turbulence in the open plenum intakes, but if it's just the 1" spacer and not a 2", the differences won't be as pronounced or noticeable to the driver usually.
It CAN, however, be measured on a bench or dyno, or stopwatch.
If it's allowed, I see no reason not to. Take care in torque'ing the carb back down on it, as we've seen numberous carb baseplates broken using that spacer, especially if it's the composite one and not the aluminum one.

Hope that helps some,
KP

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