Burnt Valves
Thread Starter
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Fleet Mechanic
Joined: Aug 2014
Posts: 1,723
Likes: 47
From: Charleston, SC
Lookin' good, Coastal.
You clearly have a lean burn condition. What caused it, we don't know. But here is what I would do: replace heads, torque all down, replace all rubber vacuum lines, retime to 6*, smooth out. Run it for 1500 miles, pull a plug, have a look.
Don't change anything more in that motor than you must. Confounding variables and all that.
The problem with rebuilt carbs is that you don't know what is inside. If they are supply chain items you can be assured that anything soft is garbage. As far as jets, you get what was on the last vehicle. Anything will start and run on any sized jet. Problems like yours take awhile to appear. It took me a year to burn a valve in my '34 with a SB because of a lean Carter AFB.
These 2100s are common and cheap. They tend to be garage clutter that we throw away on our periodic cleanings. My suggestion is to pick up a clunker with a tight throttle plate at a swap meet- or wherever- for a ten-dollar-bill.
Dealers still sell quality kits and there are some real smart guys in the carb and induction forum who can tell you exactly how to jet a 2100 for your climate. Rebuilding is a piece of cake.
But first, the heads, timing, rubber lines.
We will get you turning 11-second quarter miles
Semper Fi
You clearly have a lean burn condition. What caused it, we don't know. But here is what I would do: replace heads, torque all down, replace all rubber vacuum lines, retime to 6*, smooth out. Run it for 1500 miles, pull a plug, have a look.
Don't change anything more in that motor than you must. Confounding variables and all that.
The problem with rebuilt carbs is that you don't know what is inside. If they are supply chain items you can be assured that anything soft is garbage. As far as jets, you get what was on the last vehicle. Anything will start and run on any sized jet. Problems like yours take awhile to appear. It took me a year to burn a valve in my '34 with a SB because of a lean Carter AFB.
These 2100s are common and cheap. They tend to be garage clutter that we throw away on our periodic cleanings. My suggestion is to pick up a clunker with a tight throttle plate at a swap meet- or wherever- for a ten-dollar-bill.
Dealers still sell quality kits and there are some real smart guys in the carb and induction forum who can tell you exactly how to jet a 2100 for your climate. Rebuilding is a piece of cake.
But first, the heads, timing, rubber lines.
We will get you turning 11-second quarter miles
Semper Fi
Cargo Master
Joined: Sep 2012
Posts: 3,061
Likes: 39
From: Laramie, WY
The combustion hasn't gotten any hotter, the hardened seats are needed because gasoline no longer contains lead. The lead lubricated the old style valves and seats.
Having spent many years working professionally I recommend rebuilding what you have. At least do a very careful inspection if you are getting a set of remanufactured heads. I once got a short block in that had 13 welds going from the cylinders to the water jacket...no way I was going to install that even in someone else's car. Re-man heads might just have knurled guides and recut valves. Valves are cheap and I always install new bronze guides and new valves (and seats if needed) when doing a valve job. Knurled guides wear out much faster than new guides.
Good luck!
Having spent many years working professionally I recommend rebuilding what you have. At least do a very careful inspection if you are getting a set of remanufactured heads. I once got a short block in that had 13 welds going from the cylinders to the water jacket...no way I was going to install that even in someone else's car. Re-man heads might just have knurled guides and recut valves. Valves are cheap and I always install new bronze guides and new valves (and seats if needed) when doing a valve job. Knurled guides wear out much faster than new guides.
Good luck!
Thread Starter
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Fleet Mechanic
Joined: Aug 2014
Posts: 1,723
Likes: 47
From: Charleston, SC
The combustion hasn't gotten any hotter, the hardened seats are needed because gasoline no longer contains lead. The lead lubricated the old style valves and seats.
Having spent many years working professionally I recommend rebuilding what you have. At least do a very careful inspection if you are getting a set of remanufactured heads. I once got a short block in that had 13 welds going from the cylinders to the water jacket...no way I was going to install that even in someone else's car. Re-man heads might just have knurled guides and recut valves. Valves are cheap and I always install new bronze guides and new valves (and seats if needed) when doing a valve job. Knurled guides wear out much faster than new guides.
Good luck!
Having spent many years working professionally I recommend rebuilding what you have. At least do a very careful inspection if you are getting a set of remanufactured heads. I once got a short block in that had 13 welds going from the cylinders to the water jacket...no way I was going to install that even in someone else's car. Re-man heads might just have knurled guides and recut valves. Valves are cheap and I always install new bronze guides and new valves (and seats if needed) when doing a valve job. Knurled guides wear out much faster than new guides.
Good luck!
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
A fast an quickie way, I found to check for a lean or rich condition is while engine is idling slowly cup your hand over the choke horn. Carb opening
As you slowly close off the air supply going into the carb the engine will do one of two things.
If it's to lean the engine will increase rpm. If just right with in an okay range the engine will slowly drop in rpm as it's loading up the gas with getting less air supply.
For lean go 3 sizes richer and recheck if ok check plus color after a few hundred miles for correct burn. This the way, I do things ..
Orich
As you slowly close off the air supply going into the carb the engine will do one of two things.
If it's to lean the engine will increase rpm. If just right with in an okay range the engine will slowly drop in rpm as it's loading up the gas with getting less air supply.
For lean go 3 sizes richer and recheck if ok check plus color after a few hundred miles for correct burn. This the way, I do things ..
Orich
Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
Orich, I don't see how that trick works. If its idling with the choke open, the main jets are out of the picture. If you put your hand over the air horn creating choke, you move vacuum up into the throat and the main jets flow.
But how does that give you any information on how the jets feed at high rpms?
But how does that give you any information on how the jets feed at high rpms?
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
Orich, I don't see how that trick works. If its idling with the choke open, the main jets are out of the picture. If you put your hand over the air horn creating choke, you move vacuum up into the throat and the main jets flow.
But how does that give you any information on how the jets feed at high rpms?
But how does that give you any information on how the jets feed at high rpms?
As we all know a lean condition the vehicle falls on it face when getting on it,
a three sizes larger jets normally correct that problem.
When adding headers & dual pipes an boring the cylinders can cause a need for a jets change
.................................................. ..
By Working my hand as a choke cutting air down gets more vacuum pulling through the carb pulling more fuel into carb. Same as having the choke pulled when the engine is just idling it will sucks a bunch of gas. Or choke the engine to is stalls by putting your hand over the carb air horn you'll get raw gas all over hand. May be will help you understand what , I was dong.
Orich
John
Cargo Master
Joined: Sep 2012
Posts: 3,061
Likes: 39
From: Laramie, WY
With the engine idling as directed, the main jets are above the throttle plates. The pressure drop will still be across the throttle plates; above the plates will be very close to atmospheric pressure and below them will be the vacuum. Fuel will not begin to flow out of the main jets if the throttle is left closed. Cupping your hand over the opening will only cause a very slight decrease in the air flow. Even if some gas does come out of the mains it will still be figured into the rich/lean equation.
I prefer to add a small amount of propane to see if the engine speed rises. It is normal for it to raise about 50 rpm when tuned properly, more than that means the engine is lean, and no speed increase means it is rich.
I prefer to add a small amount of propane to see if the engine speed rises. It is normal for it to raise about 50 rpm when tuned properly, more than that means the engine is lean, and no speed increase means it is rich.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
We have all learned are own ways of doing little trick on doing thing that others say won't work an is impossible or they disbelieve that is possible.
And what would ya said if, I said I just saw a flying saucer BS right!!
Orich
And what would ya said if, I said I just saw a flying saucer BS right!!
Orich
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Posting Guru
Joined: Aug 2012
Posts: 1,241
Likes: 2
From: Rockville, Ct.
Looks to me like modern fuels combined with improper timing killed your FE.
Colder plug too.? AC makes them.
When you get the valve job done make SURE they install HARDENED EXHAUST valves and seats with special inserts and guides. This is to counter the increased combustion temperatures.
That way you can SAFELY run the unleaded fuels.
ALSO...
Look elsewhere on this awesome site for info on PROPERLY setting the timing on these FE motors using today's fuels.
I have found that the Distributor, timing and curve are set RADICALLY different than what they were the 1970's.
I'm running 12 degrees advance (Compared to 6) because I modified the distributor to provide only 20 degrees mechanical advance.
I added a Crane Adjustable vacuum Advance unit too.
Doing this WOKE THE MOTOR UP!
It runs cooler now, no ping, more lower end power and it provides more vacuum at idle.
What more is there to like?
PM me if I can help.
Bill
Colder plug too.? AC makes them.
When you get the valve job done make SURE they install HARDENED EXHAUST valves and seats with special inserts and guides. This is to counter the increased combustion temperatures.
That way you can SAFELY run the unleaded fuels.
ALSO...
Look elsewhere on this awesome site for info on PROPERLY setting the timing on these FE motors using today's fuels.
I have found that the Distributor, timing and curve are set RADICALLY different than what they were the 1970's.
I'm running 12 degrees advance (Compared to 6) because I modified the distributor to provide only 20 degrees mechanical advance.
I added a Crane Adjustable vacuum Advance unit too.
Doing this WOKE THE MOTOR UP!
It runs cooler now, no ping, more lower end power and it provides more vacuum at idle.
What more is there to like?
PM me if I can help.
Bill
BTW, love your quote at the bottom.
Thread Starter
|
Fleet Mechanic
Joined: Aug 2014
Posts: 1,723
Likes: 47
From: Charleston, SC
Waiting on parts, so I tore the carb down. #53 jets in there now. I'll order a pair of 55s and see how that goes. Any advice?
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
I've got many sizes if you need any more. Those sound about right. for a F100.
Most likely it was the the vacuum hose at the tranny module cheap gas.
Back in the day even tho these were built to run regular gas it was 91 octane.
Most guys don't want pay for the higher grade octane gas or can afford the top grade gas.
Then still want to run there timing up 12* BTDC cause others can do it and wonder why their having problem with it pinging or not shutting off with pre-ignition..
While engine is down a good time to replace all the old rubber bake , gas, & vacuum line check brake power booster if Equip.
Orich
Most likely it was the the vacuum hose at the tranny module cheap gas.
Back in the day even tho these were built to run regular gas it was 91 octane.
Most guys don't want pay for the higher grade octane gas or can afford the top grade gas.
Then still want to run there timing up 12* BTDC cause others can do it and wonder why their having problem with it pinging or not shutting off with pre-ignition..
While engine is down a good time to replace all the old rubber bake , gas, & vacuum line check brake power booster if Equip.
Orich
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Can get away with 12 on a stock Y block because the compression is so low. 7.9 to 1, higher compression motors need higher octane fuel no way around it. Ys can tolerate substandard fuels pretty well.
*******s had #43 jets installed in my "professionally" rebuilt carb, 48 was stock, 46 and 44 for high altitude. My fault for not double checking, but. The carburetor had installed before that was recommended 20 years ago. It's a frickin' fire hose and not really suitable. Carbs need adjustment but the most important adjustment of all is choose the right carburetor to begin with.
Both deals illustrate or tells me overall a bunch of so called "experts" too often don't know their head from their *** and it always pays to do your own research and learn this stuff for yourself. Probably had $400+ just wasted in carburetors and none of it was necessary. Doing your homework is a real money and aggravation saver.
Too rich will wash out rings and dilute crankcase oil, too lean will burn holes in pistons or roast valves.
*******s had #43 jets installed in my "professionally" rebuilt carb, 48 was stock, 46 and 44 for high altitude. My fault for not double checking, but. The carburetor had installed before that was recommended 20 years ago. It's a frickin' fire hose and not really suitable. Carbs need adjustment but the most important adjustment of all is choose the right carburetor to begin with.
Both deals illustrate or tells me overall a bunch of so called "experts" too often don't know their head from their *** and it always pays to do your own research and learn this stuff for yourself. Probably had $400+ just wasted in carburetors and none of it was necessary. Doing your homework is a real money and aggravation saver.
Too rich will wash out rings and dilute crankcase oil, too lean will burn holes in pistons or roast valves.
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