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Sounds crazy but who knows?

Doc, The rotor turns to the right and when #1 cylinder is at TDC on the compression stroke, the rotor is pointing at #1 on the dist. cap. All wires are on the dist. cap in correct firing order and go to the correct plugs. All plugs have spark. NOTE- When we had two wires on the wrong plugs (#4 and #6) it tried to start, back firing through the carb, but when we noticed and fixed that problem, now the engine will not even try to start.
As for the valves, we'll adjust them as you say but thats been done 4 times already. Maybe we'll notice something that we missed before.
The problem still exists with no gas reaching the cylinders. That has me puzzeled. The carb was rebuilt twice so far so it should be suitable to at least get a "pop" or two from the engine. The intake was cleaned fine and a new gasket was used (no leaks) yet no gas to the cylinders!
All I can do is keep trying. Thank you all, Bob
 
heres a way to tell, rt or left

on the vibration damper are the timing marks. TDC comes last to the timing pointer as you rotate the eng. The advance markes come first. So which way is it turning with the starter????
 
pilot481 said:
heres a way to tell, rt or left

on the vibration damper are the timing marks. TDC comes last to the timing pointer as you rotate the eng. The advance markes come first. So which way is it turning with the starter????
Click to expand...

If you look down the throat of the carb when you pump the throttle youll see fuel entering the manifold from the accelerator pump nozzels. If not there's your problem. If so, not enough fuel wouldnt be the problem.
 
Pilot, When I work the acelerator pump on the carb, yes, it sprays gas. However, I can move the pump 3 or 4 times in quick session watching it spray gas and then immediately pull all 8 plugs and only two plugs will have a gas odor. They are not even damp and the other 6 plugs are bone dry. One would think carb, right, well we rebuilt the thing twice now and no difference! In addition we have spark and compression but it will not try to start.
I'll tell you men, I could stand in a field and pour a gallon of gas at my feet and throw lighted matches in the gas and with my luck it would not burn!!
Thanks again for everyones' help, Bob
 
I'm a semi retired R+D engineer and tend to take things very literally. That said..

Does,

"However, I can move the pump 3 or 4 times in quick session watching it spray gas and then immediately pull all 8 plugs and only two plugs will have a gas odor."

mean that you did not crank the engine between the time you pumped the throttle and pulled the plugs?

If that is so, then 2 plugs with gas odor is just about right.
 
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Any chance the cam was replaced ,if so ,with what.
when you installed the cam chain and sprockets did you line up the 2 dots. crank gear and cam gear
Only thing starter fluid does is "pop" holes in the piston tops
Only other thing to do is make an adaptor from a spark plug to connect to a air supply and screw into the cylinder while on a compression stroke and listen. Thru the carb :intake valve
Thru exaust: exaust valve,Thru dipstick : rings
 
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Also put a timing light on the engine on number one sp plug wire and crank engine over and watch were the light flashes to see if the timing mark is anywhere near the timing tab on the timing chain cover...

I see 2 things, timing / timing chain issue, valves not seating.

remember 3 things needed to fire,
1. compression, Measure it and post for all 8 cylinders, should be ~ 150 psi
2. fuel, you have fuel or so you say
3. ignition, you say you have spark BUT you have no idea when it is actually "sparking". The fact that it popped with 2 wires crossed clearly shows this as the most likely issue.........and it "could" be due to cam/timing chain or you are just way off with the distributor set up
 
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I like all of your responses. We did a compression check and all 8 cylinders were between 60 and 62 psi. My associate then said the valves were too tight and backed the nut on the rockers off to where we had zero lash and then he went 1/8th of a turn down (tightening them). He said if we tighten them any more that will reduce our compression because it would hold a valve open. We then rechecked the compression and got between 75 and 78 psi on the dry type test. We poured a small amount of gas down the carb and cranked the engine. We had nothing so I pulled the plugs again and all but two were bone dry. My associate left the area so I am in charge now. When all else fails, read the shop manuel. It says to align the marks on the pulley and timing tab. I should hold the rockers for #1 and if I feel any movement it is on #6 cylinder so I go 1 full turn to #1. Then I tighten certain intake and exhaust valves and go a complete turn to #6 and tighten 1 complete turn on the remaining intake and exhaust valves. (you all said 3/4 turn so which do I do?). As for the distributer being off 180 deg. how do I check that? When we put the engine on #1 by aligning the pulley and timing tab at TDC (0 deg.) I pulled the dist. cap off and the rotor was right on the money pointing at #1. It's a new cap, rotor, wires, new plugs and we have spark at the plugs but yet nothing happens! I'm thinking if I get the valve lash corrected that should give me a true reading on the compression and get the intake valves to open so I get gas to the cylinders. If it does not try to start then it has to be the distributer off 180 deg. Which should I check or do first. The valve covers are off right now so I guess I should adjust the valves and then if some one can tell me how to determine the status of the distributer (off 180 or not) I will do that and then it should start up. Thank you to everyone for your help thus far, I know I'm basically a pain in the a$$, but please help me out with this, Thanks again, Bob
 
Doubtful if it can run with low numbers like that .normally it`s 130-170 psi
Even I cant follow those directions for doing the valves. Do 1 cylinder at a time like I described.then set #1 on compresion.drop dist in with rotor facing #1 on the cap.
 
Alls the book is saying about the valve adjustment is to follow the fireing order, saves time and labor when rotating the engine to the next one in line in the fireing order.
Im beginnig to think most of your troubles are comming from bad or wrong advice from your local help. Ive been in automotive repair over 40 yurs, built many many enginges most of chev and ford. I could build an engine damn near with my eyes closed. So far all the advice you have recieved from the folks here has been right on the money. =
From your last post regarding your compression, sounds like all your cylinders are dry, washed cleaned from all the fuel. The new rings, I hope they are new, neeed oil to help seal them in the new surface of the cylinder, I hope, newly honed cylinders. Hopefully again, I hope you dipped the pistons in fresh engine oil before installing them. Cast rings need the oil more then chrome. Get your self an oil squert can pull all the pulgs again, shoot several shots of oil into each cylinder as you go and recheck your compression. Record them so you have dry reading and wet readings. I bet a dime to a dollar youll see a big increase. By the way, did you use chrome rings or cast iron???? Chrome will take forever to seat, in a boat motor, they WILL last longer. Cass iron will seat faster but not last as long. But we're talkin 75,ooo mile verses maybe 125,000 miles, are you keeping your boat that long????
One last word here, From what Ive read most all the regulars on here are very experianced to experts on these subjects, please head our help and advice. The term mechanic is used very loosely, our expert advice is free and well thought out. Listen to what we say and head our advice, you'll be on the water in no time.
 
Here we go again, sorry to say. Yesterday I adjusted the valves to the tightness you said without any problems. (They all had a good bit of valve lash so I took the lash out and then went 3/4 turn tighter. Engine cranks fine but didn't start. I then said it has to be the distributer sending the spark at the wrong time (as in being off 180 deg.). We checked and it is on the money. The marine mechanic then gave me a hand for about 2 hours (free of charge). We rechecked everything and saw nothing wrong. He did however think our spark is a little light. So we jumped a wire from the coil to the positive terminal on a back up battery but there was no difference in spark so the coil is OK. We switched the ignition advance module on the exhaust manifold but there was no difference there either. The mechanic then turned to me and said " ok, I give up, what did you do to it?" I replied "nothing". He then asked "it's a joke right? Everyone is watching to see if I can find out what is wrong but there is no reason this is not starting".

So there you have it, what do I try next? Thank you, Bob
 
Bring the boat and motor to BT. I live 15 minutes away from him, i'm free of charge, BT charges cause he's a pro. and is a paid mech. Ask him what he gets paid, it's too little cause there is no peer.
 
Conestoga is in southeastern Pa. (southern Lancaster county) but the boat is located in Baltimore, Md in Edgemere near Sparrows Point.
 
I was thinking, should I try one of car coils that makes double the amps that the engine calls for? Like the drag racers install. That should help build up the weak spark. Thank you, Bob
 
Looked it up. DC is 3 1/2 hrs. from me and your before that.Went to Richmond once .for a waterpump and shift cable.Gas, tolls and 3 cartons of smokes.. The coil is not going to matter if something else is wrong.What was the compression reading after you readjusted the valves.
PM`d my cell.
 
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ive done this on a cple of 350s keep rotateing your wires by 1 and try starting your engine after each rotation if you do this and go through all plug wires and it never hits you have another prob
 
It has the Thunderbolt IV type system. No points. I going to try to get the coil checked at the local Auto Zone today. That could be bad but yet we tried with 3 coils already, so I don't know. See what happens. Thank you all again, Bob
 
Woa this motor has the computer doesn't it ?

Jeez went thru this exact chit with my friend Michaels boat.

He went online and bought a hei dist, one wire in one out, 3 years latter it still runs like a top.

All of 89 bucks, it's the one piece unit coil and dist all in one piece.

It bypasses all the bull chit computer crap.

Let me see if i can find the one on ebay i'll come back and post it.
 
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THUNDERBOLT IV WIRING
TYPICAL MOST V8
TBOLT-IV-WIRING.gif
 
Chiefalen, above is the diagram of my motor. It doesn't have a computer. It is much like the old 1958 and 1959 Corvettes. The distributer and coil are not together at the distributer and there are no pionts. I am wondering if the coil is partly broken down if that could account for a weak spark? But yet when we sprayed eyther down the carb it still wouldn't try to start. I hope this helps. Thank you, Bob
 
Tests for Thunderbolt Ignition:


W/ignition key on AND BILGE WELL VENTILATED OF GAS FUMES!!!


Check the kill switch first!


#1 - Connect your voltmeter neg. lead to the engine ground and pos. lead to the white/red wire terminal at the dist. It should read 12 volts.

#2 - If 12 volts are present, remove the coil spark wire from the distributor and connect it to a spark gap tester to ground. Remove the white/green lead from the dist. terminal. Turn the ign. key to on and strike the white/green lead to ground. If there is spark, replace the ignition sensor in the dist.

#3 - If there is no spark, substitute a new coil and repeat test #2. Now if you get spark, install a new coil. NO SPARK, replace ign. amp.

#4 - In #2, if there is No voltage present, disconnect the white/red wire and check it again for 12 volts. If 12 volts is present, replace the ignition sensor inside the dist. cap. If no 12 volts present w/it disconnected--ignition amplifier is shot and must be replaced.
 
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