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Old 04-23-2007, 10:44 PM
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406 sbc questions

Hey guys i got a couple quick questions,, Im looking to make a different motor combo!!!!! i have a 400 .30 over (406) in my 55 chev now that has pop up dome pistons i think around .200 dome.. hyd 500 lift cam and a set of 76cc 882 heads on it 2.02 valves...750 Holley, victor jr intake, and a good msd...350t trans 3500 stall and a 389 gear,,, shifts at 5500 rpm... the car only has been running 12,98 on slicks w/o exhaust and it only runs 99 mph at the track???? i think it should be doing alot better then that really,,,, I WANT IT TO BE BETTER THEN THAT like more mph and maybe somewhere around 12,30s to 12,50s or lower,,,,,,, but still drive it on the street........

long story short i think it might be the cam being mismatched making it only run 99 mph but not sure?? BUT i do have a set of new dart heads 215 runners, 64cc and i was thinking about sticking them on there to see if that helps or not but im scared it will bump my compression to the roof with them dome pistons where i wont be able to run pump gas,,,,

but if i did go ahead and switch to the dart heads what would be a good cam choose for the 406 that will have good hp and most of all i got to have it pounding the ground lol (gotta love a mean cam sound)

ALSO another thing i have been thinking about,, i have a fresh 400 sbc with new flat tops!! i could just stick a good hyd cam and the dart heads on it and hope it to run better then whats in my car now!!! i know a lot of people like the solid cams but i would like to stick to a great sounding hyd cam.... What would you guys do if you had my trouble and had to motors and some parts laying around?? (i will buy i different cam if a few of you think you might have a good combo for me!!!

so what do you guys think? 406 pop ups with a bigger cam and dart heads or run the flat top motor with the darts??? Thanks for any and all info guys.......

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Old 04-23-2007, 11:45 PM
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406 sbc questions

Just get the Dart's with a 72cc chamber and then port the chamber around the intake valve to gain a few more cc's of volume would do the trick.
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Old 04-23-2007, 11:54 PM
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Quote:
Originally Posted by ericnova72
Just get the Dart's with a 72cc chamber and then port the chamber around the intake valve to gain a few more cc's of volume would do the trick.

Im a poor boy,, i already got the 64cc darts, i cant afford another set of good heads,, 72cc would be nice though...
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Old 04-24-2007, 06:50 AM
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You will have very high compression with the dart heads but the 882's are what is holding you back at the strip esp with the Vic Jr. Its a mismatched set up. 64cc chambers would work with race gas or you might be able to compensate somewhat with a big cam, say in the 250@.050 range. In any case, you will wind up with an engine that will have very limited streetability. Even flattops on your other block with 64 cc combustion chambers will have high compression. I have 18cc dished pistons in my 406 with 64 cc Sportsman ll heads and I'm just under 10:1. If the heads are aluminum you might be alright compression wise and with the Vic Jr you will have a pretty decent set up, better than with the domed pistons. Use a cam in the 240-245@.050 range and that should give you some decent streetability and excellence performance.
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Old 04-24-2007, 11:20 AM
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Quote:
Originally Posted by Steve karch
You will have very high compression with the dart heads but the 882's are what is holding you back at the strip esp with the Vic Jr. Its a mismatched set up. 64cc chambers would work with race gas or you might be able to compensate somewhat with a big cam, say in the 250@.050 range. In any case, you will wind up with an engine that will have very limited streetability. Even flattops on your other block with 64 cc combustion chambers will have high compression. I have 18cc dished pistons in my 406 with 64 cc Sportsman ll heads and I'm just under 10:1. If the heads are aluminum you might be alright compression wise and with the Vic Jr you will have a pretty decent set up, better than with the domed pistons. Use a cam in the 240-245@.050 range and that should give you some decent streetability and excellence performance.
That's what I was going to say. I have the dished pistons in mine, too, gives me I think 9.9:1. Wish I had flat tops!!! IF only I could do it over (cheaply).

Hey - you better rebalance your motor again if you change pistons! Ouch.

Flat tops (in theory anyway) always work better than pop-ups if you can get the compression you want, due to less in the way of the flame front. I've heard it said many times.

You would have to at least do the flat tops with the heads, and yeah, the heads you have on it now (iron) are definetely holding you back!

Get a hyd. roller cam, though, if you can sport the money. They are awesome. I have the Crane HR306 part 119651. 240/248 @ .050 and it sounds great and really rips. My camaro runs 95 or so in the 1/8th. The cam still has excellent bottom end on a 400, but it's not happy cruising below about 2000 RPM.

If you do flat tops (which will be about 11.5:1), I would up the cam one more step to like a 245/250 or 248/252 or something. You could call Chet Herbert and get a recommendation also - they can grind whatever and their prices are good. Remember to keep your quench distance to .040" to mimimize any issues with detonation, use a little more relaxed timing curve and I think you'll be okay on pump gas.
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Old 04-24-2007, 01:03 PM
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882 heads are both obsolete in terms of combustion chamber shape and port flow. Even ported they don't provide enough flow, they just need to go. You really need to pick a combustion chamber size that gives the desired compression with a flat top or D dish piston rather than a dome. Leave the domes to 14+ to 1 compression and racing gas in strip only motors. Go here and pick out the head of your dreams, you need from 190 to 220 cc intake port volume. http://racingfeed.com/downloads/Chevy_flow_data.pdf The most flow for the least volume is what works best.

Your rear gears are no where stiff enough, 4.11s or more would be better. These need to match the cam, more cam equals stiffer gear ratios.

The converter probably has too much stall for the cam and rear gears. Remember high stall converters convert more power to heat than rotation. The laws of physics being what they are the higher the stall speed the more power is lost in the converter, I'll bet your 60 foot times suck and you don't have enough top end to make up for it. I'd prefer less stall and stiffer gears with or without a cam change.

The cam, what can I say, knowing it lifts the valve a half inch isn't very much info. Needed is duration and lift for intake and exhaust the duration also needs to have the point from where it's measured from .050 inch lift is very useful, the SAE standard from .006 inch is OK, the manufacturers measurement at the stat of the ramp makes the duration look real long and is I guess better info than nothing but not by much. Also needed is the Lobe Separation Angle (LSA) very important, and or the Lobe Center Angle (LCA) in that case for the intake and exhaust so I can compute LSA. Whether the cam is timed straight up or with some advance or retard is important too. In your case with lots of converter slip and weak rear gears some advance would make the car a bit faster but maybe not enough difference to escape the effects of weather and traction. This stuff looks better on a dyno than in ETs. Oh yeah, the rocker ratio and whether their roller or not is good info.

Bogie
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Old 04-24-2007, 10:19 PM
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THANKS for all the great info guys!!!!!!

Here are the spec for The cam i already got and was wanting to stick in the 406 with the pop ups pistons, using 1.6 roller rockers..

Lunati Bracket Master II Cam and Lifter Kits 515/515
Hydraulic flat tappet
Basic Operating RPM Range: 2,500-6,500 RPM
Intake Duration at 050 inch Lift: 246
Exhaust Duration at 050 inch Lift: 246
Duration at 050 inch Lift: 246 int./246 exh.
Advertised Intake Duration: 300
Advertised Exhaust Duration: 300
Advertised Duration: 300 int./300 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.515 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.515 in.
Valve Lift with Factory Rocker Arm Ratio: 0.515 int./0.515 exh. lift
Lobe Separation (degrees): 108
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.


Do you guys think this thing is going to run ok in my 406 using my dart heads with the 3500 stall and 389 gear or is it going to be a ticking time bomb and hard as heck to start?? like we all know the compression is going to be really high but is there a chance i can get away with pump gas and octane booster?? and racing fuel at the track,, i want to drive this car ever other weekend or so...... also what is the Major ups and downs for have a high compression motor??
you guys have gave me a lot of great info on this subject already and i thank you all for that!!!!!!!!
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Old 04-24-2007, 11:00 PM
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406 sbc questions

With 64cc heads and domed pistons you will be somewhere in the 13.8-14.5 to 1 compression ratio-- race gas only because octane boosters are a big scam(if it says it raises octane 5 points it only raises an actual 5/10ths of a point, i.e. 93 super unleaded only becomes 93.5! This is true of ALL octane boosters) To run on pump gas you would have to retard your timing something like 15-20 degrees killing an easy 100-150 HP. Not worth even driving it like that. About the cam- too small, need more like 256 to 265 dur. @ .050, .530"-.570" lift hydro roller or better yet for power(if you don't mind a little maintenance) a flat tappet solid. Again, domes and 64cc is a no go on pump gas, 400 flat tops and 64cc is 11.25 to 1 will go on pump gas but you have to be spot-on with the tune up or destruction will result. Rear gear and converter will be fine, jump the rear gear hurdle only if track testing shows you need more gear.

Last edited by ericnova72; 04-25-2007 at 12:46 AM. Reason: forgot about rear gear and converter
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Old 04-25-2007, 01:10 AM
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Ok guys another question for ya,,,,, what is it going to cost me to change a hyd to a roller cam and what all would i need??
I did some thinking and i might stick a roller cam in the flat top 400 i got and use the darts on it instead of using the pop up motor... ( still cant make my mind up) lol

well I know i will have to get the roller cam and lifters of course, do i have to get a brass gear for the disturber? cam button/lock plate? What all does it take to change a hyd cam to a good lift roller that pounds the ground..... thanks again
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Old 04-25-2007, 06:46 AM
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I'm using a Crane 296HR roller cam (way too mild for your engine). It is a 2 piece cam with a billet cam and pressed on cast distributor gear. If you go with that type of cam (2 piece) you don't have to worry about distributor gears. It cost me, I believe, about $700.00 cdn for a roller cam upgrade but my lifters were the most expensive part of the deal. Cams are generally in the $300.00 range and lifters are in the $300-$500 range (US$). These are approximate #'s so don't quote me please. One the the main reasons I went with the roller cam is that todays oils, even synthetics to some degree are not compatible with flat tappet cams especially high lift with aggressive lobe profiles. Even using Mobile 1, 20W50 I had excessive lobe wear on my old flat tappet cam in 10,000 miles. I now use Rottella oil...but thats a hole nudder discussion.
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Old 04-25-2007, 04:42 PM
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406 sbc questions

Karch is right about the flat tappet unless you spend a little more and get them with the tiny oil hole drilled thru the face' and good with the cam info. Thru Doug Herbert Perf. here in the states the cam (hydro or solid roller) , lifters, dist. gear, button and lock plate, roller-strength pushrods and springs will set you back about $650(solid roll) or 580(hydro roll)(only cheaper on the chance that the springs on your Dart's will handle a hydro roller). I've had no trouble with their stuff.
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Old 04-26-2007, 05:36 AM
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All good advice above....

Sell the Dart Irons and get a set of Elderbrock Allum. with a .70cc chamber and run the flat top motor.

What torqe converter is in it? Stall?

I think your gear ratio is ok.

Change one thing at a time. But change the motor first

I ran a 406 in my camaro with a flat tappet hyd. (Nitrous HP cam) with Performer RPM heads and flat tops. Made 10.7-1 and ran on pump gas just fine. With a 2800-3200 stall and a 3:89 gear it went 11.61@115mph
(On motor) and mid 10's on the bottle at 133mph.
Daily driver through the mufflers on DOT's.
That was over 10yrs ago when gas was cheap... Lol.

Flat top motor with allum. heads is the key. Keep the gear and put that kinda stall in it you'r good to go.
~Scott
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Old 04-26-2007, 05:46 AM
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Im running a new 3500 rpm stall in the 55 right now......

I think i got a little bit of work/fun in head of me for this week lol Im gonna to start working on it asap... im thinking the flat top motor is the one ill go with,, still hate to see the pop up motor go on the shelf though thanks for all the info guys,,,,,,
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Old 04-26-2007, 10:50 AM
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The other thing you might consider is what you are running for rear gears. You might want to see what some of the experts here think about the gear combo. Its not always the motor but other factors in the setup. Someone could have 600 hp but if you have it geared wrong for your setup(too steep or the opposite) you could have crap quarter mile times.
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