Thread: 454 Missing and popping!

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So i have been restoring my car for 4 years and finally got it done. I put a 454 Chevy big block bored .030 over with a Holley 750cc carb. with a jet size of 74. I have driven the car for 2 days and it ran perfectly. Coming home last night it started popping really loud against the floor boards because im running straight headers and was missing. Today i changed the spark plugs because i used these plugs on breakin period and they were gas soaked. I started it up to drive it and it ran great again until i got about half a mile down the road again and it started missing again. It wasent popping like last night but i think if i would have kept driving it it would have because the further i went the worse the missing got. I checked the timing and it is set at what it was before so i know the distributor hasent moved. Do i need to go down on my jet sizing or what. I dont know what to do from here. HELP PLEASE!

well if the plugs were that wet then your oil on break in has fuel in it and could be you wipe the cam out .track in down to the plug that s missing .then pull valve cover off if rockers are not loose then you may be ok. could be a bent valve bent push rod .busted valve spring . or good plug wires and better/rebuild ... carb .get that oil out and put in new oil . you would be very lucky if the bbc did not eat flat lifter cams BBC love to eat cams . i only build BBC with roller cams

Originally Posted by pat mccarthy

well if the plugs were that wet then your oil on break in has fuel in it and could be you wipe the cam out .track in down to the plug that s missing .then pull valve cover off if rockers are not loose then you may be ok. could be a bent valve bent push rod .busted valve spring . or good plug wires and better/rebuild ... carb .get that oil out and put in new oil . you would be very lucky if the bbc did not eat flat lifter cams BBC love to eat cams . i only build BBC with roller cams

I have brand new 8.5mm MSD wires and new 750cc Holley Carb. Whats the best way to rule out what plug is missing. Ill pull the valve covers off tomm. and check the rockers and pushrods.

Originally Posted by 1987BBMonte

I have brand new 8.5mm MSD wires and new 750cc Holley Carb. Whats the best way to rule out what plug is missing. Ill pull the valve covers off tomm. and check the rockers and pushrods.

i use a heavy welding glove start it up pull one off wire at a time listen to it then put the wire back on. a timming light can be used to see if your getting spark on each plug make sure 5and 7 are not mix it may sound ok at ilde with no ex but will pop and miss at hirer rpms. with no ex i would pull the covers check for bent parts or a wipe out cam .check firing order

open exhaust will run super lean and also over scavage 5 and 7

750 holley running wet plugs at idle ? in a bbc . how big of cam ?? sounds like power valve are not dumping ??? at the right time so not working . that may make it abit lean ????????? hook a vacuum gauge to it at idle ?see were it drops to in gear with your foot on the brake

Originally Posted by pat mccarthy

750 holley running wet plugs at idle ? in a bbc . how big of cam ?? sounds like power valve are not dumping ??? at the right time so not working . that may make it abit lean ????????? hook a vacuum gauge to it at idle ?

I have a Lunati 292 cam with a 500 lift. Put a new power valve in it yesterday. Gonna take the valve covers off in a minute to check rockers and pushrods.

Originally Posted by 1987BBMonte

Put a new power valve in it yesterday.

How much vacuum is it pulling at idle and what # power valve did you install?

Originally Posted by 98 SNAKE EATER

How much vacuum is it pulling at idle and what # power valve did you install?

It is pulling 9.5 psi at idle, and not sure what size power valve, didn't know there were diff. sizes. How do i find out what size i need? So far i have taken every valve spring out and checked to make sure one wasn't broken, changed the oil and cut the oil filter open to make sure there wasn't any metal in it, it was spotless, did a compression check 120-125 psi on every cylinder, checked vacuum, ohm the wires out, changed the plugs #7 NGK plugs, octane booster and water remover, checked the pushrods for being bent or broken, put a new ignition module on, i don't know wtf is goin on. Tomm. i am gonna put another carb. my buddy has and if that don't work im gonna put another distributor he has also with another rotor button and cap. If that dosent work well i have no clue!

Originally Posted by 1987BBMonte

It is pulling 9.5 psi at idle, and not sure what size power valve, didn't know there were diff. sizes. How do i find out what size i need? So far i have taken every valve spring out and checked to make sure one wasn't broken, changed the oil and cut the oil filter open to make sure there wasn't any metal in it, it was spotless, did a compression check 120-125 psi on every cylinder, checked vacuum, ohm the wires out, changed the plugs #7 NGK plugs, octane booster and water remover, checked the pushrods for being bent or broken, put a new ignition module on, i don't know wtf is goin on. Tomm. i am gonna put another carb. my buddy has and if that don't work im gonna put another distributor he has also with another rotor button and cap. If that dosent work well i have no clue!

OK, assuming your power valve is still good, with 9.5psi at idle, you're in the ballpark with a #4.5 PV

First thing I'd do is check that you have enough fuel pressure and that the gauge is consistent and not erratic...

If erratic, start the engine, remove the air cleaner and make sure fuel isn't dribbling out of the boosters.

If you don't notice any dribbling at idle, slowly increase the throttle and keep an eye on them...

In most cases, this is the cause of popping and plug fouling.

If a pair of boosters dribble evenly, adjust the float level a little lower for that pair.

If one booster shows dribbling, the cause is usually internal (clogged passage in the metering block, clogged air bleed, etc.)

bracket master cam. 230/230@050 lift 544/544 ls109

here two things that worry me ...you need to get them wires off the headers even with heat socks on them you still want them up off the headers and how are you centering the fan with the alum top pulley with no pilot that fan can and will come off and out

Originally Posted by pat mccarthy

here two things that worry me ...you need to get them wires off the headers even with heat socks on them you still want them up off the headers and how are you centering the fan with the alum top pulley with no pilot that fan can and will come off and out

I would love to get the plugs off the headers, tell me how LOL! And as far as the fan what do you mean?

I took the valve covers off today and rocker arms are tight and pushrods look good! I went and got an ignition module today and replaced it and took it down the road and still missing. It has to be one of the plug wires it's just its to damn hot to pull them off while running even with a welders glove not only that they are very hard to get to!

with the gm G body car you need a boot end that you can bend most all boots you want better then 30 angle . what i am say is the water pump has a pilot that the stock steel pulley there was some left to center the fan humb with a ALUM thick pulley you do not have any thing to hold the fan and center on hub . bolts are not made to hold fan center.there is to much mass spining out there for just bolt the water pilot hub need to go in to the fan bass