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454 engine wont start

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454 engine wont start

Charlie10 Charlie10
New User | Posts: 5 | Joined: 01/13
Posted: 01/26/13
04:15 PM

I changed the oil and wiped out two lobes on my 454 chevy. When the cam went there was a loud banging on passenger side as the cylinder was building up pressure and couldn’t get out as the valves were not opening. I installed a new Comp Cams Thumper flat hyd Cam. The car ran great till I over revved it and bent 3 pushrods and 2 lifters came apart. This time I changed the valve springs to match the cam. The engine fired right up but a week later started to run rough. When I ran a wire from the battery to the HEI dist. the car ran ok again. After a month or so it started to run real rough again. I changed the ignition wires and was up and running again. After 2 weeks it wouldn’t run at all so this time I installed a new distributer. I drove about 50 miles and it happened again. It seemed like water in the fuel could be the problem so I added some fuel treatment. By the time I got home the engine was banging again like it did when I wiped out the cam. No matter what I try the engine will not start. I checked the cam and all the lobes were fine so I changed the plugs, wires and carb and it still won’t start. I pulled the heads off and #6 and #8 were black with carbon. I took the heads to a engine shop to check if I had a bent or stuck valve but the only problem found was my spring pressure was to high (430lbs)  #6 and #8 cylinders. Before I took the heads off the compression in all cylinders was 160lbs. Any thoughts on whats happening? Thanks  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 01/26/13
08:09 PM

wow... thats a 12 course meal...

changing the oil usually does NOT wipe out the cam... its usually been going bad for a while...

first... HOW MUCH FUEL TREATMENT did you pour in.. to HOW much gasoline... fuel treatments are not that combustible... if you get too much in.. it won't burn off and the spark plugs will foul...  or it will create a SMOKE screen like a navy destroyer can put out..

is it back together now.. or still apart???

can you post the part numbers you used... thumper cam.. lifters.. matching springs..

well... lets look at diagnosing the ignition system

hopefully since its been hours since your first post.. you have it fixed but if not..

do you have a TIMING LIGHT...   and a CIRCUIT TESTER/TEST LIGHT...

with a timing light.. clip it around each spark plug wire one at a time while you have a friend crank the engine.. or while you crank the engine if you have tape or rubber bands holding the trigger on.. so it flashes without you holding it.. this would indicate that you have some kind of spark..

if you GET NO indication from the timing light..

you might want to use your test light hooked to ground.. and PROBE the BAT Connector/wire on the HEI cap...   you should get power as soon as the helper turns the key to the ON position.. and still while you are cranking the engine and still when he releases from the cranking position to the ON position... this proves the power is getting thru the ignition switch and wires to the HEI...

this is an important test above..  i had to drive from LA to palmdale to rescue a friend who's only problem was the HEI power wire fell out of the cap...   it was only 140 mile round trip..  and i had warned him that the terminal body needed replacing as it was broken...

if you don't get spark at the wires...  but DO have power at the BAT terminal on the cap...

pull the cap.. then the rotor...   turn the rotor over...  examine the bottom for signs of burn through...  my automotive tool man.. truck full of tools.. had his truck die.. he replaced the module.. the pick up coil.. the ignition coil .. the cap...  it still would not run...  he never bothered changing the ignition rotor.. the chevy dealer did..   5 bucks parts and a 300 buck tow and it was running..

say.. pull the cap... but look at which way the rotor is pointing .. reach in and crank the engine for a split second.. did the rotor change directions..   try not to wind up the wiring or spark plug wires in the spinning rotor...  this verifies that the timing chain and distributer gear are probably OK..   if you bring the TIMING MARK on the harmonic damper to TDC..  the rotor should be pointing at either the #1 or the #6 spark plug wire position on the cap... you will have to determine where those are as distributers can be installed in a bunch of directions..   only one is technecly correct so the spark plug wires fit perfectly..

now.. the module....  its probably a 4 pin GM module..   many parts stores have testing machines for them...

you can check the PICK UP coil with an ohm meter...  set to 2K ohms...  500 to 1500 OHMs is expected...  usually around 980 is where you find it..  before you disconnect the meter.. flip it over to 2 volts AC... or 20 Volts AC and either spin the shaft or have somebody crank the engine.. you should get just over 1.0 volts AC or something very close to it..  if the pick up coil has failed.. or the microscopic wires have failed.. it may fail the resistance test.. and also fail the AC voltage output test..

you might also want to pull the cover off the top of the distributer cap.. if yours has the coil in the cap...    verify the sides of the coil show no signs of high voltage leaks...


COIL Highvoltageleakage

please go thru this step by step...

post what you find...  

Charlie10 Charlie10
New User | Posts: 5 | Joined: 01/13
Posted: 01/27/13
10:42 AM

Thanks for your help. I took the engine to the machine shop to freshen it up as all the metal from the cam lobes ended up in the oil. Just a hone, new rings and bearings. I went through all the trouble shooting steps and even bought a new MSD HEI distributor, new plugs and Taylor wire which didn't help. I checked the timing many times but it still wouldn't fire. I put just a bit of treatment in the fuel but it made no difference either. The shop where I took the engine has a dyno so we'll fire it up before I put it back in the car. I have a Lunati Voodoo roller cam going in (.600 ) and retro roller lifters, a new pro billet MSD distributor. 6aL box. I've been trouble shooting this engine on and off all summer so I'm going to start over with a fresh build. Any ideas on the banging? it's not like a back fire but sounds just like it did when the cam went and the pressure would biuld up in the cylinders. Your right about the cam taking a while to wear out. I adjusted loose lifter more then once. Thanks again  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 01/27/13
01:30 PM

a few things...
and some are really basic.

is the distributer in the proper way. the rotor turns once to 2 turns of the crank.. its really easy to get it in 180 out...

are the spark plug wires inserted in the cap in the proper direction... clockwise..

the last two spark plugs on the drivers side... #5 and #7.. need to be separated by more than an inch..  or they will cross fire..

big block chevys share camshafts between the 454/7.4 motors and a visually almost identical 8.1 cam..

except the 8.1 cam has the 4/7 swap already ground into it..  and that cam will fit a 454/7.4 motor..  or the other way... a miss fire will result..  and it will drive people crazy as everything looks PERFECT...    sometimes you have to use your fingers or multiple compression testers in several holes to see which one comes up on compression first to tell the difference.. yep...

is the distributer cap cracked...  yes.. i know its new... ever seen the video of the delivery driver tossing the flat screen tv over the 6 foot fence to deliver it..

please... do another thing.. before the pan goes on.... pick up some super magnets and stick them inside the engine oil pan.. in a corner away from the oil pump pick up screen... they will attract all the steel and iron bits to them... keeping it out of the oil pump..  yea i know.. it will be really hard to clean them.. but just knowing they are there should be a huge help...  

Charlie10 Charlie10
New User | Posts: 5 | Joined: 01/13
Posted: 01/27/13
03:52 PM

Thanks for the reply, The timing was OK. Some days I would drive 100 miles and be fine. Then the next time out it would start to run like crap. I would check things out, changed the plugs (looked ok, dry and good colour) and it would run again for a week or two. Then it would start to run like crap again, almost where I needed to tow the car home. Then I changed the ignition wires and it would run again but only for a few days this time. Put in new distributer and got 3 more days of driving and then that was it for the season. If it was a auto I would have had to tow it. It was banging real loud. I thought it could be a bent or stuck valve because of the intermitent problem and the banging noise like when the cam was wiped out but the machine shop said they were ok. Thanks for the tip with the magnets and the 8.1 cam. I heard of a 4/7 cam for small blocks but didn't know of the Big Block ones.  

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 01/27/13
06:48 PM


Do you live where its hot. I'm thinking about Vapor Lock....

Are you sure the fuel pump isn't dieing. Or is your fuel filter doing funny things.

I've seen fuel pumps run fine have good pressure test it to days later it comes in a flat bed. Now what do you do?

1.Fuel pumps can have a pin hole in the diaphram and work fine. Until they crap out completly.
2.Fuel filters can be very dirty. When the car sits beit 8 hours, 2 hours whatever. The dirt will fall to a spot where it won't get pickup. Then you hit a bump in the road it diturbs the dirt and plugs the fuel filter...
My 2 cents.


Charlie10 Charlie10
New User | Posts: 5 | Joined: 01/13
Posted: 01/28/13
06:01 AM

I live up in Toronto Canada but now that you mention it the weekends when I had the trouble it was really hot and humid. Twice when I stopped for fuel the car ran like crap as I was leaving the gas station. The one time I put fuel conditioner in thinking I might have some water in the fuel. It has a year old Holley mechanical fuel pump and Russel filter. Its off the road for the winter so I'll check the fuel system front to back. Thanks for the help