Thread: 406 sbc combo-need help!
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11-24-2007 11:32 AM #1
406 sbc combo-need help!
I have a 400 sbc bored .030 with flattop pistons (2 valve relief) and I am using 5.7 rods with a stock crank. My cam is a comp cams solid lifter 288/292 duration .550/.560 lift 106 lobe centers with 1.5 full roller rockers. The heads are #461 casting 2.05 intake 1.6 exhaust valves. My intake is a weiand team G single plane with a 800 holley DP carb. HEI dist with MSD coil. The trans. is a turbo 350 with a 3200 stall and the rearend is a 8.5 ten bolt 4.56 gears. The car is a 1971 nova that weighs 3100lbs with me in it. I recently took this car to the strip and with slicks went 12.80 at 101mph at Heartland Park in Topeka Kansas. What am I doing wrong?
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11-24-2007 11:42 AM #2
Seems head limited. The combo looks strong except for small converter and heads. Other than that, it's very close to my 383cid combo in my Luv that runs 10.80's on pump gas.
Does it feel like it's laying down on you above 5K rpms? Seems like it should run better than that even with the humps.RAY
'69 Chevelle--385
'68 Camaro--Twin Turbo
'78 Luv--383
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11-24-2007 11:44 AM #3
Try a better intake and a bigger stall speed . Also what tube size are your headers ? And are those fuelly heads ported ? I like fuelly heads but on a SB 406 you need some heads like world sportsman II 200cc intake runners . But I do really like your build .
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11-24-2007 01:04 PM #4
What rpm are you shifting at? And what rpm does it start to drop off power? Camel Hump heads if they aren't ported will only let a 406 make power to about 5000rpm or less. Your cam is designed to make power up to 6500rpm. It takes a VERY expensive/good portjob to make camel humps support that RPM. Like the others I would suggest getting an aftermarket set of heads around 200cc intake runner.
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11-24-2007 01:09 PM #5
Another question is who ever did the heads... Did they deshroud the valves when they installed the 2.05's? The combustion chamber is real small on the 461's and will not flow well unless that is done. They will actually flow less than 1.94 1.5's if it is not done.
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11-24-2007 01:30 PM #6
Originally Posted by 69elko
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11-24-2007 01:35 PM #7
It appears the mph is very low for the et which is telling me your gear isn't matched to your revs.
You must be nosing over on top? What rpm do you shift and what rpm at the traps?
Two ways to skin the cat:
-get the motor to rev higher (per suggestions above, i.e. better flowing heads, intake, etc)
-use a taller gear (numerically lower) to make better use of the torque down low...
Sounds like the cam is a high winder so either use a shorter cam and shorter gears or better heads
Two cents...
-Chris
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11-24-2007 06:33 PM #8
Originally Posted by ghostchaser6t9
I would also like to see a min. of 12.5 to 1 for a comp. ratio.
If this is a true drag car then I would run a 4,500 to 5,000 stall speed.
What are your 60 ft times?
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11-24-2007 06:52 PM #9
.................... some people just dont get it
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11-25-2007 03:17 AM #10
..............Get what????
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11-27-2007 07:01 PM #11
My 60ft time was a 1.81 and I was shifting at 6500 rpm. I went thru the traps at 6500 rpm. The heads have not been ported and the valves have not been unshrouded. First and second gear felt like the car was pulling hard but when I shifted into high gear, the car nosed over past 5000 rpm.
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11-27-2007 08:02 PM #12
With those heads I'm surprised you got it to wind up in 2nd. The nosing over is the heads. Terry Rosebush on Ebay is selling the old style Dart heads for 399.00 a pair bare. They are a good buy. I got a set for a friend, put a good valve job in them and swapped all his stuff over. That along with an intake swap picked him up a second in the quarter. A 200cc head will be good on there and if you think you might ever want to go faster, 215cc would be better.RAY
'69 Chevelle--385
'68 Camaro--Twin Turbo
'78 Luv--383
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11-27-2007 08:40 PM #13
If it pulled hard in 1st and 2nd all the way to 6500 and then nosed over in 3rd I wonder if you may have a fuel delivery problem. What sort of fuel pump do you have? And what size fuel line are you running from the tank? Also if you are turning 6500 at only 101 mph you are either running a very short tire, or the converter is slipping. With a similar set up in a 63 Nova, with 5.13 gears and a 28 inch tire I was running through the traps at 110-111 mph turning 6500.
PatOf course, that's just my opinion, I could be wrong!
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11-28-2007 12:44 AM #14
Originally Posted by ghostchaser6t9
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11-28-2007 06:40 AM #15
Your's very similar to my old 406. The biggest differance being the heads, I had Canfield 197's and a small solid cam, and 373 gears. I ran 12.20's in a 72 Monte Carlo 3800lbs. My recommendation would be to maximize the torque, there is only so many 6500rpm run's in a stock bottom end.
'76 2 bolt block .30 over studded main's
stock crank turned 10-10
5.7 rod's resized
cast flat top's (less weight)
Lunati 501-508 lift solid cam
Canfield Aluminum heads 2.05 valves
1.6 intake 1.5 exhaust both crane gold
Performer RPM intake w/ 750 vac. sec out of the box
MSD dist, 6al box
t-350 w/TCI street fighter converter foot braked to 2500rpm
12 bolt with 3:73's
BFG drag radials
Best 60' 1.69
Ron
Welcome to CHR. I think that you need to hook up your vacuum advance. At part throttle when cruising you have less air and fuel in each cylinder, and the air-fuel mixture is not as densely packed...
MSD 8360 distributor vacuum advance