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  #16 (permalink)  
Old 07-21-2012, 11:20 PM
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Quote:
Originally Posted by vinniekq2 View Post
just looked up your cam.107 intake angle/117 exhaust, extra 10 degrees exhaust. That 400 can use all of that cam.If its not damaged and the carb is the problem I wouldnt rush out to buy a new one yet.dial in what you have before pulling the grille on your truck.You could advance it 2 degrees if bottom end is low out put.I cant see it though
When he corrects the distributor advance curve he will have no lack of low end torque or throttle response.
As long as he did not fubar the cam install its fine as is.
Correcting the engine compression ratio is not that hard on this motor
with the dished pistons. Its not an issue to "driveability" or idleing etc

But will add power by correct ing the true compression ratio.

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Old 07-21-2012, 11:20 PM
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400 sbc

@ vinnikq2 yes I am far away. I'm here in California, central valley. Yes I do have a carb for testing.
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Old 07-21-2012, 11:32 PM
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400 sbc

@fbird88 I will use the hei set and use your formula for the correct setup. The heads I will check and see what I have from the casting.number and foe.from there after I get the carb to function properly. Yeah I thought I could use a rpm air gap myself.
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  #19 (permalink)  
Old 07-21-2012, 11:37 PM
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test your car with the borrowed and hopefully known carb.You can power time your car for testing,by plugging vacuum advance,set max timing around 34- 36 total timing.This usually happens by 3k rpm.make sure the weights are free in the distributor of course. I built a low compression 400 for a friend before,it ran 14.1s and got over 20 to the gallon. with 2.7 gears and stock stall,stock 400 heads,,,78 monte carlo
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Old 07-22-2012, 01:34 AM
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feuling gone arye

Quote:
Originally Posted by hotboy454 View Post
I started to drive it to iron out all the bugs one day it backfired through the carb. then started sputtering upon acceleration idling it does fine but runs rich. I cant seem to get idel dialed in without it shutting off. 1100 rpm its where its comfortable at in gear 400rpm something weird there. It run like a champ driving it in traffic seem to want to die out with out keeping my foot on the gas. 600 summitt carb
Is the 600 a holley? you may have blowen the power valves when she back fired, now shes loading up on you and thats not tunable, replace the power valves.
Keeping your foot on the gas to feed it more air is another indecation shes loading up.
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Old 07-22-2012, 09:57 AM
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400 sbc

@ cridder the 600 carb is a summit brand. I believe its a clone of holley 4150 or 4160 old style carbs. It's real easy to change the jets and power.valves.
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Old 07-22-2012, 10:25 AM
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400 sbc

Now is the power valves causing it to run rich and making the spark plugs black. Also you can smell the gas coming through. Is the a indication of it running rich and needing to be netted to or just power valves and adjusting the idel mixture screws. Also the description for the cam said Cai idile with lope can't hardly tell. Elgin1015p cam. Or crane 274 h06.
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Old 07-22-2012, 11:49 AM
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When you fix the distributor and replace the power valve and the spark plugs the rich smell at idle will be gone.
lack of idle timing. Cams like that need a lot more idle timing. You do not need to rejet. Its not the jets.
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Old 07-22-2012, 12:14 PM
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400sbc

Ok, I thought it was the jets. Because right after breakin that's when I noticedit running rich. Assuming that summit carb. Bought a edelbrock and it was doing the samething. I all by the recieve kit and in a few week look into the heads, vortex or something. But first I need to know what I have. I pretty sure raising the compression to a ponit or even a half a.point.with better flowing heads will wake it up. I'm almost considering having a dunk tune and let them calibrated everything.
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Old 07-23-2012, 02:45 AM
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Power valves and back fires

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Originally Posted by hotboy454 View Post
How is the power valves causing it to run rich and making the spark plugs black? Also you can smell the gas coming through. Is the a indication of it running rich and needing to be netted to or just power valves and adjusting the idel mixture screws. Also the description for the cam said Cai idile with lope can't hardly tell. Elgin1015p cam. Or crane 274 h06.
When the the power valve is acted upon by manifold vacum it stays shut and no additional feul inrichment complemnts the jetted curcit.
A backfire if severe enough effectively blows the small diaphrame in the power valve, now fuel is drawen through the holed diaphram into the engine.
you can see the raw feul in the power valve cavety when you take the carb apart, this area is normally dry.
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Old 07-23-2012, 08:02 AM
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Quote:
Originally Posted by hotboy454 View Post
hello, I have a sbc 400 that i had rebuild 2 years ago it sat in a project now that I'm building a 468bbc for. I took the motor out and put it in my 73 c-10. This motor had 0 miles on it. far as i took it was around the block Since it been in my truck. I started to drive it to iron out all the bugs one day it backfired through the carb. then started sputtering upon acceleration idling it does fine but runs rich. I cant seem to get idel dialed in without it shutting off. 1100 rpm its where its comfortable at in gear 400rpm something weird there.
Hopefully it IS the timing.

The cam has to be broken in correctly or it can fail. If a lobe has worn off (along w/the bottom of the lifter in most cases), it can act how you are describing.

So, did you use cam break in lube on the lifters and lobes as well as break in oil or oil additive like ZDDPlus? At least 2000 rpm w/NO IDLING for the first 15-20 minutes? Details here.

If you suspect this may be the problem you can measure the lift at the retainer. Sometimes it can be seen by just removing the valve cover and checking for excessive looseness of the rockers. This is often (but not always) accompanied by a loud or ticking valve train, and it tends to not hold the lifter adjustment- it will keep loosening up on you.
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Old 07-23-2012, 10:50 AM
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400 sbc

Break-in went smoothly. I used Joe Hubbard break-in oil no problem. The carb just ran a little rich even with the eldelbrock carb switched to a sumitt brand still the same. The carb was running rich after break-in. I just started to drive it under load since removing the motor del my project car to my truck. Three days under load is when the backfire through the carb happened. Started back up then the sputtering started. Looked at my plugs all of them are black and these are new plugs.
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Old 07-23-2012, 11:04 AM
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Originally Posted by hotboy454 View Post
Break-in went smoothly. I used Joe Hubbard break-in oil no problem. The carb just ran a little rich even with the eldelbrock carb switched to a sumitt brand still the same. The carb was running rich after break-in. I just started to drive it under load since removing the motor del my project car to my truck. Three days under load is when the backfire through the carb happened. Started back up then the sputtering started. Looked at my plugs all of them are black and these are new plugs.
Could be nothing more than the engine needs some run time to finish breaking in and a new set of plugs will likely clear up the miss- although the root cause of the carb being too rich obviously still has to be dealt with. Did I understand correctly that both carbs ran rich, or was the engine running rough w/both but not necessarily too rich?

But, if you're getting an eye watering exhaust smell, that's unburned fuel from not enough initial timing, not a rich a/f mixture. So if that's the case, the odor will go away when the base timing is high enough. Now, that's not to say adding timing will suddenly make the carb spot-on. You still may need to fine tune it. And the idle mixture will need to be checked/reset after changing the timing, too. Set it to fastest clean idle or the most vacuum at idle if you have a gauge.
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Old 07-23-2012, 11:16 AM
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400 sbc

Yes both carbs were running.rich. it ran smooth.but not as.smooth as.it should.be. I change to carb to summit brand still the same thing. Exhaust black and gas through exhaust. My wife hates when I start that thing up it get all in the house and the smell on my clothes. We tried idel mixture screws.didn't change. Thing. I almost thought that it qW the carb spaced drawing to much fuel. Tried 3 sets of plugs all are dark within days. The motor was broke in many months ago. It just sat untill I took the motor out and put it in my truck. Now its being driven under a full load. Oh by the way that's Joe gibbs break-in oil not Hubbard. My phone tries to think ahead of me.
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Old 07-23-2012, 11:44 AM
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Quote:
Originally Posted by hotboy454 View Post
Yes both carbs were running.rich. it ran smooth.but not as.smooth as.it should.be. I change to carb to summit brand still the same thing. Exhaust black and gas through exhaust. My wife hates when I start that thing up it get all in the house and the smell on my clothes. We tried idel mixture screws.didn't change. Thing. I almost thought that it qW the carb spaced drawing to much fuel. Tried 3 sets of plugs all are dark within days. The motor was broke in many months ago. It just sat untill I took the motor out and put it in my truck. Now its being driven under a full load. Oh by the way that's Joe gibbs break-in oil not Hubbard. My phone tries to think ahead of me.
OK, I see. In any event, I usually try to sort the timing out first, THEN set about fine tuning the carb. But in this case it sounds like something is amiss, like the fuel pressure way too high, that sort of thing. I say that because you've had two different carbs perform basically the same way. Odds are against that happening, but just the same, unless they are known by you to be jetted stock or at least within reason, I would want to baseline them (or it) back to stock to eliminate that from being the problem.

Someone mentioned power valves earlier. If it's blown or the wrong number it could be adding fuel when it's not needed. If there's any doubt replace it w/a PV more to the middle ground like a 65.

Getting back to timing, you saying the idle screws do nothing tells me the throttle blades are probably open too far in order to get it to idle w/the initial timing set where it is. Having the primaries open too far is enough to cause it to run partially on the transition circuit. Fixing the timing by adding to the initial (which will increase the idle speed) while keeping the mechanical from adding TOO much will allow the throttle blades to be closed back down enough that it will be idling primarily on the idle circuit- and then the idle screws will become responsive again.

For testing purposes you can basically ignore the mechanical advance just for now. Add the initial timing, lower the curb idle screw setting, and see if that lets you get control w/the idle mixture screws and see if that improves the idle situation. You can even drive it that way as long as you are gentle on the throttle and don't romp on it. Keep the revs down and keep it from pinging by being gentle on it.

You can make a temporary timing tape if you don't already have a timing tape on the damper or a dial back timing light. That'll let you see the advance beyond what the timing tab can show you.
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