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#1 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Help-carb back fireing
Hello:
I have a 350 V8. I just replaced the hi proformance intake with a stock intake. The hi profo n carb caught fire is the reason that I replaced the intake. Burnt n meltted the vac lines,dist n wires. I have replaced the intake carb Dist wires plugs n vac lines. When I try to start the engine it spits the fuel back thur the carb. With no responce. No timing advance when moving dist,no idle responce either. Have 110 to 120 comp per cyl. Pulled carb down ck the float n clean inside. Have ck the #1 to TDC n installed dis. FO 1-8-4-3-6-5-7-2 Have not had this problem ever before. It has me stumped ! ! ! All Help Appreciated T-P Auto Tim |
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#2 |
Registered User
Join Date: Apr 2014
Location: calgary alberta
Posts: 1,248
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Re: Help-carb back fireing
your 180 out if gas out the carb your not tdc on compression stroke your tdc on exhaust stroke
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#3 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Re: Help-carb back fireing
69chevytrucker;
I will ck that on Wed. I have a dr(eyes)appt tomorrow. I'm going to start over from the start. Ck the TDC first Then ck the dist pointer Reset dist so that #1 will point to #2 cyl . That give the vac adv room to set the advance. This eng come out of a corvette that caught fire. I don't know what caused the fire under the hood. So this as been a very big headache so far. Been on it for a couple of days. Going to take a brake tomorrow. Thanks T-P Auto Tim |
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#4 |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: Help-carb back fireing
Even if you pull #1 plug, turn it over till it blows your finger off which is compression stroke then pull cap and see where the rotor points, plus don't set timing to TDC, set #1 to approx 10atdc which is where the engine would approx fire and run, in other words set the rotor to match #1 plug on cap at factory rated timing, prob 10 or 12 degrees. if that doesn't solve the problem pull both valve covers and check all the pushrods, may have one bent or broken rocker arm which would cause a backfire also. Still sounds more like distrib is 180 or 1/2 turn out and trying to fire on #6 cyl instead of #1 as already mentioned. Good luck keep us posted.
__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#5 |
Registered User
Join Date: Apr 2014
Location: Bloomington Indiana
Posts: 1,041
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Re: Help-carb back fireing
This may help. On every Chevy V8, the crankshaft pulley key lines up with the #1 crank throw. That is, TDC is when the key is aligned with the #1 cylinder, 45* CW from straight up (as seen from the front). Ignition stroke is when no valves are open, so the cylinder will hold air; exhaust stroke both valves will be open a bit (exhaust is still closing, intake is already opening), so the cylinder won't hold air.
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Rich Weyand 1978 K10 RCSB DD. |
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#6 |
At the body shop.
Join Date: Aug 2009
Location: Land of fruits and nuts.
Posts: 5,211
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Re: Help-carb back fireing
The rotor should point almost straight ahead as it blows your finger off the plug hole.
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" That didnt make it any newer " " Dont antique the equipment " |
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#7 |
BAD BOW-Silverado XST
Join Date: May 2000
Location: Senior Member from Austin, TX
Posts: 6,431
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Re: Help-carb back fireing
If the distributor was dropped correctly as taken out, the problem was prior to intake installation. Is the timing chain stock? What year? If the nylon gears are breaking, it's only a matter of time before the chain strips the sprockets.
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#8 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Re: Help-carb back fireing
Mud,man,rick, koolit;
Thanks: I'll give it all atry later today.(6am) here. Have to drive 90 miles to the eye dr today(one way) I'm a vet so go to the VA dr's in Alb,NM Again thanks for the info,will try it later today or first thing tomorrow. T-P Auto Tim |
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#9 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,594
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Re: Help-carb back fireing
Here's a nice wiki on finding tdc #1.
Shows pics of what Rich Weyand is describing. http://www.crankshaftcoalition.com/w...op_dead_center |
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#10 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Re: Help-carb back fireing
Hello again;
Got back on ter 350v8 carb back firing. Reset the TDC Reset wires 1-8-4-3-6-5-7-2 First spin runs for about 30sec Then starts pushing fuel back thur carb. Pulled the front off the eng, cked the timming marks. Set cam dot to crank dot try to start now belching flame out of carb not just fuel spray. going to pull v/c off and ck the rocker arm n push rod tomorrow. going to back off the valve adjer nuts also. going to try to run with out the cover on the can n crank. still can not get any info from the person who burnt up the corvette engine. did find out that several people saw him rodding the vette on the back streets before it caught fire under the hood. that as one thing about a small town,someone will notice things. Till tomorrow; T-P Auto Tim |
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#11 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Re: Help-carb back fireing
Hi all;
Question? What is floating the valves? I have heard this term; Just do not know what it means? What are the reffect of this? I have never had this much trouble with a small block 350 v8. All Help Is Appreciated T-P Auto Tim |
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#12 |
Registered User
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 2,539
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Re: Help-carb back fireing
Any chance the distributor cap is cracked or carbon streaked?
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#13 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Re: Help-carb back fireing
Have changed out Dist cap n wires n plugs n intake.
took off the EGR intake,replaced w nonEGR intake. have try 2 different carbs. still same problem as stated in the first post. T-P Auto Tim |
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#14 | |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: Help-carb back fireing
Quote:
Mudman.
__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#15 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Re: Help-carb back fireing
mud man;
Thanks; Will try this out tomorrow n let you know what happens T-P Auto Tim |
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#16 |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: Help-carb back fireing
No problem, it will work for sure, it happens a lot, makes no sense the way Gm set the timing marks, a lot of engine guys laugh about it.
__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#17 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Re: Help-carb back fireing
mud man;
I pulled the ft of the 350v8 motor down to the timming chain. I brought #1 up on comp stroke with the vc off. When I did this the timing marks were at 12;00 on crank n also 12;00 on the cam.valves closed This was with #1 all the way up in cyl hole. With cam seting on the mark at 6;00 and crank at 12;00 , the intake was closed but the exhaust was just opening. NO nutral lash on valves as there should be,per all information on 350v8 sbc. So what I did was take the dist at TDC n turn it 180. With this set up it would fire n run for a short time with no foot feed. try to acc n it would pop /denonat. move the dist n would have a hard start.(kick back) Replaced the Q-jet with a 2bld n adptor plate,replaced dist with a known good dist. the carb n dist come out of my 79 chevy 350v8, been running for last 10 yr with out any trouble. would not let the 350v8 in the vette run. So going to go into the top end of motor the next few days. !st - check the lifters n push rods 2nd - pull the cam n ck the lobes 3rd - pull the heads if no problem found on cam n push rods. T-P Auto Tim |
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#18 | |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: Help-carb back fireing
Quote:
__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#19 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Re: Help-carb back fireing
mud man;
That is what I did several times yesterday. Once we change out the carb n dist, it try to run, we had to hold the gas open about a 1/4 to keep it running. Even with that going on it still had no responce to gass. Then when you went to start again ,you had to play with the dist. I think we run the batt down n cooked the starter try to get this eng running.. So today I think I'll remove the intake, ck out the push rods(take them out) pull the lifters out n ck them, might even pull the cam out n ck it. With useing known good parts(carb n Dist)that were in the old 78 chevy PU. This has both of us stumped. With today the 4th I not sure just how much I will get done. I just might take the day off from this problem, n just work on the rat rod truck that is in other shop. Need to plum in the fuel line n remove the fuel pump from the tank(45 psi pump). Then refresh the Q-jet that I have for the rat rod. Sometimes it is just better to walk away from a problem for a few days.(let the brain rest) ha ha. Thank for the info. Have a great 4th of July T-P Auto Tim |
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#20 |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: Help-carb back fireing
Well good luck Tim, hope you figure it out soon, me I would prob camp in my garage, but your right sometimes better to take a break, let us know how it turns out. Maybe the bottom crank gear is one of the type with advance and retard keys and not in the right one. Wish I was there to help you, got me scratching my head too.
__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#21 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Re: Help-carb back fireing
mud man;
Did not work on the 350v8 problem. I was going to try to work the rat rod. Instead I cleaned up the shop. I put up peg board n shelfs. Got the shelfs full. Hung a lot of tools up on peg board. Tomorrow I'll get on the rat rod. Plum in the fuel pump n lines, Drop in the Dist Refresh the Q-jet carb Plum in the heater hose n rad Trans lines Install oil press gauage (manuel) Temp gauge (manuel) Then try to get the valves adj Going to leave the trans un hooked till I get the engine running. Hope I can get most of the above done tomorrow. Still have to wire in the elect system to steering colume. Just going to use jumper n starter buttom to set the valves. T-P Auto Tim |
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#22 |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: Help-carb back fireing
So ..what do you have for a Ratrod Tim, car, truck, sounds interesting.
__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#23 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
|
Re: Help-carb back fireing
mud man;
I have a 52 chevy pu cab with a 51 bed setting on a 86 s-10 frame 305v8 just what I had laying around 86 pontiac 200r4 sets n steering wheel out of 1992 conversion van 15" smoothies on rear 14" cragers on front 92 olds 4x4 rear end 1.5" drop in rear end I have a post on this sitein the 47 to59 chevy I call it the "Frankenstine" due to all the different parts (All GM) Not working on the 350v8 till tuesday. Have another dr appt in Alb ( leg replaced) T-P Auto Tim |
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#24 |
Registered User
Join Date: Dec 2011
Location: Creighton Sask. Canada
Posts: 4,121
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Re: Help-carb back fireing
I kind of like frankenstine, cool project. Must be hard to find the time, especially if you have other stuff like Dr. appointments going on too. Still want to hear about the back fire engine.
__________________
1987 Green n Green machine. 5.0 4spd std. 7" lift w 35's. |
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#25 |
Registered User
Join Date: Jan 2014
Location: Grants New Mexico
Posts: 613
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Re: Help-carb back fireing
Mud man;
Got the heads pulled on the 350v8 Pulled the cam out n found 8 out of 16 lobes wore down. Also cked the exhaust valves, looks like new valves. cked the intake valves also looks like the exhaust valves were never setted in. could not find a wear ring on the valve thats looks like it was setted The intake valves show the wear ring Was told that the engine was a fresh rebuilt ! ! ! ! ! I just had to pull it down to see what was going on. I also think that who ever built the engine had the valves turned down to tight. Thats it for how. So did you ck out the build project I"m working on? I have a lower left artifical leg, a couple of month ago the leg fell apart. I was just lucky that I have an extra leg here. It has my tennies in it but it has gotten me thur. I had to have the VA order me a new set up with a liter spring setting. I get to see if it will be the right one on Monday. If it is then I will get them to order me another set up for the other leg. I have a work boot leg A dress boot leg n a tennie leg It was the work boot leg that broke. The dress boot spring is to hard to walk on, that is why I have not used it before. T-P Auto Tim |
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