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Discussion Starter #1
hey i just put my new 383 in my monte ss and im having a huge problem. first off the motor is a 383, 272 comp cam, world sportsman two heads, 10.5 comp, all new msd ignition, demon 650 and other basic stuff. well i went to break in the cam, and the motor fires out the carb. now i top dead centered the motor about 6 times, and even moved them 180 each time for a total of 12 attempts. firing order is good, balancer line is right on the timing tab each time. this has been going on for three days. i have tdced motors numerous times and i never had a problem. my only other idea is that it has to do with the valves. let me expain, i had a hard time finding the right lengh pushrods, so i bought the manley measuring tool and a feeler gauge and came out with 7.9"
rods. when i was adjusting the valves, i had to really tighten the rocker(roller tip) nut to get the lash out of the rods, i have done valve timing before and never had a problem so i am familar with the method of doing it right. it is possible that the rods were a bit too short and in order to set the lash i had to tighten the rockers enough that it actually opened the valves a bit, causing the carb backfires? the car cranks good, and will hit about 500 rpm and when i give it gas it fires out the carb, so either its:

i did something wrong with the timing proving i am an idiot
the valves are slightly open
one of the valves is bent
or one of the rockers is just way too tight

the car feels like it wants to start but as soon as it catches out comes the fire, any help is greatly appricated, thanks guys im only 19, i need all the advice i can get

ps i lined the cam up right too with the timing chain, so it shouldnt be that. . . i hope
 

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Are you sure the timing chain is correct? It is somewhat easy to mistake the markings on some of the gears.
 

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Assuming that this is a hydraulic cam, are you absolutely sure that you did not pass the zero lash point and go to the bottom of the lifter plunger. I dont know why you would have any trouble finding push rods since there is nothing special about what you have built. Off the self should have worked fine. The fact that you had to tighten them down so far makes me think that you bottomed the lifter. It is easy to do if you are just spinning the push rod and you dont have a good "feel" for it.

Other than that, I would say dist. is 180 out. Remember that the engine is at TDC on exhaust and compression stroke and the valves appear to be in the same position as well. It is not hard to get it confused and alot of people do.

Chris
 

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The Smell of Nitro in the morn
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If those are raised runner heads you need at least .100 long hardened push rods with guide-plates.
Hope you did not round off the cam if the lifters are to tight.
Is the firing order correct ?
Could be off one or two teeth on the dist can cause this.
 

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I dun learned sumthin
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Had the same trouble with my engine on break in. Crank it over and once it fired it would just shoot out the carb. Turned out that the valves were way to tight. Loosened them up and the thing fired right off. With out a lot of experience finding zero lash is a little hard. I found going a little loose on the lash is good then running the engine without the valve cover at idle then tightening the lifters until the clatter stops.
 

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7.9 sounds too long for the pushrods. I used dart heads with harland sharp rockers and only need a .100 longer pushrod for the dart heads, which are definately raised runner heads. I think your pushrods may be way too long on this one buddy. If I were you, I'd put a stock set in it and see how it adjusts and fires with those.

Do this: line up your distributor to about 8 degrees before TDC (just a hair more than a 1/4 inch almost 3/8). Inspect the distributor to make sure the weights are free. I would disconnect the vacuum advance as its unnecessary and just one more thing that could fail and cause problems (btw, I mean just for the start-up). When you're satisfied that your distributor is doing its job correctly, give the motor a try. If you're getting pops pack through the carb it means things are going off while the intake valve is open. There are too options, A: the charge is firing too soon or in a volitile nature, or B: the valve is simply staying open too long.

Call up world, find out if these are stock type heads ( I think they are, I'm pretty sure they are NOT raisted runner heads). If so I think you need to look into the pushrod issue. Illustrate exactly how you came to the conclusion that you needed such long pushrods. My guess is as you were checking the geometry you had the pushrod compressing the lifter more and more, and got an inaccurate reading. Now as your pushrods get oil in them they're becomming firmer, and a few of your intake valves are letting compression seep out.

pushrods. 10-1 man.

K

NovaSS350 said:
Had the same trouble with my engine on break in. Crank it over and once it fired it would just shoot out the carb. Turned out that the valves were way to tight. Loosened them up and the thing fired right off. With out a lot of experience finding zero lash is a little hard. I found going a little loose on the lash is good then running the engine without the valve cover at idle then tightening the lifters until the clatter stops.
do NOT adjust your valves at idle if you haven't broken your cam in yet!!!
 

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Discussion Starter #8
i have loosened all the pushrods, checked the timing chain and it
has perfect alignment (6 and 12 at tdc) and done the timing tdc deal about 15 times in 3 days(with trying 180 out each time) and still fires out the carb. the only two things i can think of are this:

1- when 1 is at tdc, so is 6, so is it possible that the cam is 180 out even, like saying that the cam was at 6oclock and the crank was at 12oclock when number six was at compression? the manual said that line the cam up 6 and 12 when number one is at compression, so i how could i have known when i putting the motor together that is was really one or six at compression.

2-the dist was rebuild by a reputable shop, car has no vacuum advance and the dist is set up 14 initial 36 total. a new pick up was installed too, and a mechanic i know said that the pick up could have been installed wrong, causing this problem.

any thoughts?
 

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It is not possible to have the cam 180 out. If it is 180 out then the engine is just retiming so that number 6 would be at tdc compression instead of number 1. Distriutor can be 180 out, and I would still suspect that. What method are you using for lining up the distributor and number 1 tdc before starting the engine....exactly all the steps?

When you say you loosed the pushrods, how much? Did you loosen all of them 1/2 turn so that they were back at 0 lash? Either I dont understand what you are doing with this or you dont understand valve lash setting. Give some more detail. For example: If you go one more 1/2 turn on the rockers are all the pushrods now loose and able to rattle between the rocker and lifter?

Chris
 

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The Smell of Nitro in the morn
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If the push-rods were to long the locknut's would NOT have to be down so low. The distributor plays no part in the problem.
If you had the adjusting nuts down so far, I think its time for a upper end tear-down to look at all the parts, Esp the lifter and cam for ware.
You could collapse a few lifters cranking down that far.
Time to go thru the valve train to be safe before starting up anymore and ruin something else.
You may have the wrong set of lifters in it
 

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my money is still on the pushrods. I just don't see why you would need a pushrod thats almost a full quarter inch longer than stock. I have raised runner heads on my motor AND roller rockers (which sometimes require the use of a longer pushrod) and they're nowhere close to that. You've got ignition coming through your carb, you'd adusted the timing a million times, THIS IS NOT A TIMING ISSUE. Its in your valves.

K
 

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as far as timing the cam and crank all you should do is line up the dots. have you tried un hooking your msd stuff? i know my box didnt work worth a crap and i had to bring it back. it kept shutting off after some driving time and tech never got back to me. it ran worse with it than with out. id look at push rods too, something is off in the valvetrain.
 
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