351w no start
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5th Wheeling
Joined: Jul 2017
Posts: 28
Likes: 1
351w no start
I bought a crate 351w from summit racing to replace the cracked one in my ski boat. It has a Mallory electronic ignition, and Holley 4160 carb. I can not get this thing to start. Best case, it'll fire for half a second then die. Mostly it's crank, crank, adjust, crank, crank, adjust. I'm using the firing order listed on summit. Cleaned and rebuilt the carb. Rotor is pointing at #1 TDC compression stroke. Good spark, everything is grounded to the block. I pulled the plugs and they are relatively clean. Not like I'd been cranking fuel mixture all over them for days. I get 0 vacuum, and the compression test shows most cylinders at 65ish, one at 35, and a couple at 100. Is that stupid low for rings that haven't seated yet? Any ideas on why this sucker won't fire?
Cargo Master
Joined: Mar 2007
Posts: 2,862
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Fuel. Is it any good? I don't like sprays to make engines start, but maybe you need to buy a can.
You mention that is starts for second, so that tells me you got the basics there, just not working in harmony.
Those compression numbers are low.
You mention that is starts for second, so that tells me you got the basics there, just not working in harmony.
Those compression numbers are low.
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5th Wheeling
Joined: Jul 2017
Posts: 28
Likes: 1
I put in new, ethanol free fuel to the tank and have 6psi from the pump to the carb. I adjusted the floats and idle screw to a solid baseline so I'm thinking it's getting fuel.
I did use some spray start with no luck. It feels like a timing issue, like one cylinder will fire then loose sequence. I may try the 302 timing and see if it changes but I'm more concerned about the compression.
when the rain let's up I'm going to try some oil in the cylinder and see if my compression goes up. I'm guessing those low numbers means the vacuum isnt enough to bring the fuel mixture into the cylinder? Anyone want to buy a boat?
I did use some spray start with no luck. It feels like a timing issue, like one cylinder will fire then loose sequence. I may try the 302 timing and see if it changes but I'm more concerned about the compression.
when the rain let's up I'm going to try some oil in the cylinder and see if my compression goes up. I'm guessing those low numbers means the vacuum isnt enough to bring the fuel mixture into the cylinder? Anyone want to buy a boat?
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5th Wheeling
Joined: Jul 2017
Posts: 28
Likes: 1
Of course it was off 180 initially, I thought that was protocol for putting together a new engine 
I lined the rotor to #1 tdc on the compression stroke with no luck, little changes clockwise and counterclockwise on the rotorcap didn't change anything.
No consistent output for any changes has been the frustrating part. It'll sputter stop occasionally but mainly just crank.
I'm way off somewhere just not the typical spots I look at.
I lined the rotor to #1 tdc on the compression stroke with no luck, little changes clockwise and counterclockwise on the rotorcap didn't change anything.
No consistent output for any changes has been the frustrating part. It'll sputter stop occasionally but mainly just crank.
I'm way off somewhere just not the typical spots I look at.
Cargo Master
Joined: Mar 2007
Posts: 2,862
Likes: 1,043
One thing for certain, if it was all good, it would run.
As a professional mechanic, I get blamed for everything, sometimes rightfully so. When things don't work right, I double check myself. I stop thinking it's right and start knowing it's right with facts.
If the compression is that low, have you done a CLT to confirm where it is all going? Maybe putting a bit of oil down the plug holes to see if the leak is past the rings. I've never done a compression test on a brand new/rebuilt engine because they always start. I don't know what to expect, but the numbers you have don't seem right.
Are the valves hanging up? Lifters? Push rods? Rockers? Coil weak?
As a professional mechanic, I get blamed for everything, sometimes rightfully so. When things don't work right, I double check myself. I stop thinking it's right and start knowing it's right with facts.
If the compression is that low, have you done a CLT to confirm where it is all going? Maybe putting a bit of oil down the plug holes to see if the leak is past the rings. I've never done a compression test on a brand new/rebuilt engine because they always start. I don't know what to expect, but the numbers you have don't seem right.
Are the valves hanging up? Lifters? Push rods? Rockers? Coil weak?
Thread Starter
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5th Wheeling
Joined: Jul 2017
Posts: 28
Likes: 1
Good advice! On double check the compression is still low, probably around a 20% increase with about 10ml of oil added to the cylinder. Will do a leak down next to see if a valve is hanging.
The spark seems to be another issue...I cleaned all the contacts inside the distributor but, I think the rotor and cap are worn beyond salvage. I unloaded a Christian dose of starting fluid and still could not get it to fire. Even with low compression I'm assuming it would try to fire with that much catalyst and a spark.
I do get a spark when I pull the plugs which confuses me.
The spark seems to be another issue...I cleaned all the contacts inside the distributor but, I think the rotor and cap are worn beyond salvage. I unloaded a Christian dose of starting fluid and still could not get it to fire. Even with low compression I'm assuming it would try to fire with that much catalyst and a spark.
I do get a spark when I pull the plugs which confuses me.
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5th Wheeling
Joined: Jul 2017
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Did a compression and leak down test
Cylinder ...compression... leak down
1................... 110 ..............32%
2 ...................120 ..............24%
3 ....................95 ...............20%
4 ....................75 ...............32%
5.................... 110..............32%
6 .....................40............... 20%
7..................... 80 ...............24%
8 .....................80 ...............44%
removed all the plugs and the numbers where better than my spot test on the compression. #6 still has me, how can the compression be garbage and the leakdown on par with the other cylinders?
Cylinder ...compression... leak down
1................... 110 ..............32%
2 ...................120 ..............24%
3 ....................95 ...............20%
4 ....................75 ...............32%
5.................... 110..............32%
6 .....................40............... 20%
7..................... 80 ...............24%
8 .....................80 ...............44%
removed all the plugs and the numbers where better than my spot test on the compression. #6 still has me, how can the compression be garbage and the leakdown on par with the other cylinders?
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Lead Driver
Joined: Nov 2000
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From: Albuquerque
Your compression and leakdown numbers are terrible.Probably something in the valve timing/train. It's not gonna work like that.
Might be miss aligned cam timing, missadjusted rockers or just a crap rebuild.
Might be miss aligned cam timing, missadjusted rockers or just a crap rebuild.
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5th Wheeling
Joined: Jul 2017
Posts: 28
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Leaking past the rings in all. Also the engine hasn't run since rebuild, rings haven't seated I'd say I expected the results besides the low comp on 6 I expected a humongous leak.
I spoke with a tech at the reman company, and sent him the test results. waiting to hear back. I don't know what I would expect them to do besides cover it under warranty and send me a new one. Pain in the dick either way
I spoke with a tech at the reman company, and sent him the test results. waiting to hear back. I don't know what I would expect them to do besides cover it under warranty and send me a new one. Pain in the dick either way
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5th Wheeling
Joined: Jul 2017
Posts: 28
Likes: 1
Took the valve covers off, no giant sign. Tried to upload a video of it cranking but not a forums super user so any guidance if it doesnt show up is much appreciated.
I fingered the hole (settle down) and cranked it, felt suction and blowing in #6 that didn't feel significantly weaker than the other cylinders. Re did comp test and still showing 40psi
I fingered the hole (settle down) and cranked it, felt suction and blowing in #6 that didn't feel significantly weaker than the other cylinders. Re did comp test and still showing 40psi