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454 Carburetor question?
- Thread starter Siddhi
- Start date
- Status
vinny p.
Active member
This has been hashed out here before. Crate motors are designed specifically for cars not boats. If the question is asked...Will a Gm crate engine run in a boat? The answer is yes. Will it work well, the answer is no. There are several differences between the 2 usages af engines. There is no formula that works for both.
happy
Active member
i think we need to get back on track here.. the man is looking for advice on how to repair and upgrade his engine..
and for the record... take a twin 502 engine boat.. pull out the marine version of the engine on one side.. and slap in a crate motor.. see which one lags behind..
and for the record... take a twin 502 engine boat.. pull out the marine version of the engine on one side.. and slap in a crate motor.. see which one lags behind..
happy
Active member
now to the discussion at hand we have an ill chevy big block, with a zit for a carburator on top. lets take another look at the leak down numbers..
1, 28% 2, 72% 3, 38%, 4, 30% 5, 16%, 6, 56%, 7, 38%, and 8, 30%
These #s arnt very attractive, seing only 1 cyl is even close to optimum..
now lets approach these figures in relation to the rotational assembly..
#1, #6, are respectivly 28 / 56
#3, #2, are 39 / 72
#5, #8 are 16 / 30
#7, #4 are 38 / 20
What we were told earlier, was that the exhaust valves were suspect, due to noise heard during the leak down test, now if this were true guys and gals, what may have caused this type of failure??
is it a lean condition??
is a lean condition due to the carburator?
bad gas perhaps?
or leaky manifolds?
how do these numbers interact with the intake?
how is it that we can conclude a definitive cause to the failure that has occured.. ?
once we find the cause, then we can offer repair alternatives.
this is to get some new inspiration running in this thread.. and vinny is probably typing as we speak.. (he's a slow typer).. think about your answers, and lets get some real theorys going here.
1, 28% 2, 72% 3, 38%, 4, 30% 5, 16%, 6, 56%, 7, 38%, and 8, 30%
These #s arnt very attractive, seing only 1 cyl is even close to optimum..
now lets approach these figures in relation to the rotational assembly..
#1, #6, are respectivly 28 / 56
#3, #2, are 39 / 72
#5, #8 are 16 / 30
#7, #4 are 38 / 20
What we were told earlier, was that the exhaust valves were suspect, due to noise heard during the leak down test, now if this were true guys and gals, what may have caused this type of failure??
is it a lean condition??
is a lean condition due to the carburator?
bad gas perhaps?
or leaky manifolds?
how do these numbers interact with the intake?
how is it that we can conclude a definitive cause to the failure that has occured.. ?
once we find the cause, then we can offer repair alternatives.
this is to get some new inspiration running in this thread.. and vinny is probably typing as we speak.. (he's a slow typer).. think about your answers, and lets get some real theorys going here.
vinny p.
Active member
Hey there Happy,
Yeah, you're right I type slow. I am not a typist, but I am a mechanic. The subject of crate engines has been hashed out here and also OSO. It has been beaten to death. Everyone is entitled to their opinion. You and I usually agree, I know on this subject our opinions would be no different. Lets just leave it at that.
If this engine has that kind of leakage from only the exhaust valves, we know it sucked back water. Truth is, there are too many other variables that are not answered here. If it were my decision, I woudlnt give it a second thought. Pull the engine and tear it down. See whats in there, then determine what caused this, see what can be saved or trashed. Anything other than that is guessing.
BTW, I am still looking for a -2 Imco SC lower case. I dont care about internals, blown up or not. Keep me in mind.. I am trying a set of cryogenic and micronite treated lower gears this season. I hope to get good results. Stock Merc gears were wearing out in a season. Maybe this will help them last longer.
Yeah, you're right I type slow. I am not a typist, but I am a mechanic. The subject of crate engines has been hashed out here and also OSO. It has been beaten to death. Everyone is entitled to their opinion. You and I usually agree, I know on this subject our opinions would be no different. Lets just leave it at that.
If this engine has that kind of leakage from only the exhaust valves, we know it sucked back water. Truth is, there are too many other variables that are not answered here. If it were my decision, I woudlnt give it a second thought. Pull the engine and tear it down. See whats in there, then determine what caused this, see what can be saved or trashed. Anything other than that is guessing.
BTW, I am still looking for a -2 Imco SC lower case. I dont care about internals, blown up or not. Keep me in mind.. I am trying a set of cryogenic and micronite treated lower gears this season. I hope to get good results. Stock Merc gears were wearing out in a season. Maybe this will help them last longer.
happy
Active member
i'm thinking two possible causes,
leaking manifolds, or some type of water reversion..
or
detonation due to bad fuel..
either way i say the engine needs to come out.. and pull the heads.. more than likely the lower end will need some help too.
now lets get some info from the owner as far as the expectations of the new engine
what is the boats main use?? family outings? skiing, or flat out how fast can you go?
what is the budgett as far as the engine build.. do you have a realisic figure in your head as to how much the entire job may be?
what shape is the transom/drive in? what drive are you running? are there any other items that need to be addressed for repair while the engine is out?
should your goal be reaching into the 70mph range, what type of steering do you have, have you calculated in appropriate steering figures into such an upgrade?
i know vinny knows the engine #s in his head, i have them on paper.. we just need a bit of info to get you rolling..
ps vin.. i'll put the word out on the sc's..
leaking manifolds, or some type of water reversion..
or
detonation due to bad fuel..
either way i say the engine needs to come out.. and pull the heads.. more than likely the lower end will need some help too.
now lets get some info from the owner as far as the expectations of the new engine
what is the boats main use?? family outings? skiing, or flat out how fast can you go?
what is the budgett as far as the engine build.. do you have a realisic figure in your head as to how much the entire job may be?
what shape is the transom/drive in? what drive are you running? are there any other items that need to be addressed for repair while the engine is out?
should your goal be reaching into the 70mph range, what type of steering do you have, have you calculated in appropriate steering figures into such an upgrade?
i know vinny knows the engine #s in his head, i have them on paper.. we just need a bit of info to get you rolling..
ps vin.. i'll put the word out on the sc's..
Hey guys,
Thanks for all the advice so far! Well to start with I have a TRS drive with Borg Warner Trans. I have hydraulic steering, Insta-Trim Boat Leveler trim tabs, and 4" stock exhaust. The exhaust is above the water line and comes straight out the back of the boat. The boat is a 1982 Convincor 242. I said crate motor but I am not sure if it is an auto motor or marine. I would guess marine and maybe saying crate was incorrect. I know it was a new motor and a Mercruiser shop installed it. I did not know that only crate motors are auto. I was saying that to say it was a complete motor replacement. Sorry for all of the confusion.
As far as my budget. Obviously everyone wants to do the job as cheap as they can. I would say I have up to about $2,000.00 to spend on it. I have a friend who will help build the motor with me. He has a dyno and builds race motors for mud boggers, circle track and inboard marine. He is a big time offshore racing fan so he knows the ends and outs of a motor. He can also bore the cylinders if that is needed. This is what he does for a living. Actually, he said he puts marine cams in his mud bog trucks because they perform better. So getting the work done right should not be a problem. However, he is crazy busy all the time and I plan to only use him if I get into a bind and need some help somewhere down the line. Basically, I want to do all the research and plus it gives me a chance to chat with the guys on this board. Plus, you guys know checkmate boats better and I am sure anything I can think to do with my convincor you guys have already done before. That way I do not make many mistakes.
I use my boat mostly offshore and skiing. I spend at least one day a week on the river skiing and the other time my boat hits the water is to go about 30 to 40 miles offshore and fish. So I am looking to keep as much bottom end as I can. But I do want to increase my top end. But it sounds like if I get my motor healthy again I should get all the top end I am looking for. Basically I would be very happy if I could see around 70mph gps. Honestly I do not care to go much faster than that.
I was wondering if I should try to run a decarb through the motor to see if I can bring down the leakage. I know the guy that had it before me mostly let it sit in the yard and he would go out and crank it and let it idle about once every week or so. I was wondering if a year and a half of this would build up carbon and not let the valves seat all the way. I was thinking about doing that and then redoing the test. Also I do see leakage around I guess it is called the risers. It is where the exhaust comes out and makes a turn up then there is another piece that turns 90* back and my 4" hose attaches and goes out the back. The place it leaks is between the top piece that my 4" hose attaches and the manifold for the exhaust. So I know I need to fix that. but everything else looks pretty good.
Well thanks again for the info thus far and I hope I have answered your questions enough to get me started.
Thanks for all the advice so far! Well to start with I have a TRS drive with Borg Warner Trans. I have hydraulic steering, Insta-Trim Boat Leveler trim tabs, and 4" stock exhaust. The exhaust is above the water line and comes straight out the back of the boat. The boat is a 1982 Convincor 242. I said crate motor but I am not sure if it is an auto motor or marine. I would guess marine and maybe saying crate was incorrect. I know it was a new motor and a Mercruiser shop installed it. I did not know that only crate motors are auto. I was saying that to say it was a complete motor replacement. Sorry for all of the confusion.
As far as my budget. Obviously everyone wants to do the job as cheap as they can. I would say I have up to about $2,000.00 to spend on it. I have a friend who will help build the motor with me. He has a dyno and builds race motors for mud boggers, circle track and inboard marine. He is a big time offshore racing fan so he knows the ends and outs of a motor. He can also bore the cylinders if that is needed. This is what he does for a living. Actually, he said he puts marine cams in his mud bog trucks because they perform better. So getting the work done right should not be a problem. However, he is crazy busy all the time and I plan to only use him if I get into a bind and need some help somewhere down the line. Basically, I want to do all the research and plus it gives me a chance to chat with the guys on this board. Plus, you guys know checkmate boats better and I am sure anything I can think to do with my convincor you guys have already done before. That way I do not make many mistakes.
I use my boat mostly offshore and skiing. I spend at least one day a week on the river skiing and the other time my boat hits the water is to go about 30 to 40 miles offshore and fish. So I am looking to keep as much bottom end as I can. But I do want to increase my top end. But it sounds like if I get my motor healthy again I should get all the top end I am looking for. Basically I would be very happy if I could see around 70mph gps. Honestly I do not care to go much faster than that.
I was wondering if I should try to run a decarb through the motor to see if I can bring down the leakage. I know the guy that had it before me mostly let it sit in the yard and he would go out and crank it and let it idle about once every week or so. I was wondering if a year and a half of this would build up carbon and not let the valves seat all the way. I was thinking about doing that and then redoing the test. Also I do see leakage around I guess it is called the risers. It is where the exhaust comes out and makes a turn up then there is another piece that turns 90* back and my 4" hose attaches and goes out the back. The place it leaks is between the top piece that my 4" hose attaches and the manifold for the exhaust. So I know I need to fix that. but everything else looks pretty good.
Well thanks again for the info thus far and I hope I have answered your questions enough to get me started.
The steering is hydraulic with a ram. I am not sure the name brand but it looks pretty stout. Then transome and stringers all seem very solid. I checked all this out be for I bought the boat. And now the boat is in my garage where before me it was out in the weather. I hope I have given enough info. Let me know if you need anything else.
-B
-B
vinny p.
Active member
happy
Active member
ok.. since your a mechanic, and you have a machinist mechanic.. and you have 2k to spend..
now we need to know how to spend the 2k.. we know you need a carb.. and i have several that need rebuilding. i can hook you up with that.. or i can send you a fresh rebuild.
now we need to concentrate on the cause of the problem.. whats the fuel look like?? how does the exhaust look ?? or did i miss a pic in this thread? how do the spark plugs look? rust corrosion??
i'm sure there is a way to keep life support on this engine, but it will take some work, and the dependability will be low.. i wouldn't suggest offshore trips,
your leak down #s suggest water intrusion, or detonation. your heads should be gone thru, and your exaust addressed.. and fuel system diagnosed..
most of this you can do yourself, save some labor time.. let us know what you find
now we need to know how to spend the 2k.. we know you need a carb.. and i have several that need rebuilding. i can hook you up with that.. or i can send you a fresh rebuild.
now we need to concentrate on the cause of the problem.. whats the fuel look like?? how does the exhaust look ?? or did i miss a pic in this thread? how do the spark plugs look? rust corrosion??
i'm sure there is a way to keep life support on this engine, but it will take some work, and the dependability will be low.. i wouldn't suggest offshore trips,
your leak down #s suggest water intrusion, or detonation. your heads should be gone thru, and your exaust addressed.. and fuel system diagnosed..
most of this you can do yourself, save some labor time.. let us know what you find
Big Dave
Member
If you are not going to pull the motor, fix the riser leaks before you run it. I know the merc units are not great, but your machinist friend should be able to plane all of the mating surfaces if there is not too much rust on the inside. use merc gaskets not aftermarket.
I love my holley carb!!!
I love my holley carb!!!
Thanks everyone,
I do not plan to run the boat anymore until I do get these problems fixed. I did go ahead and run some valvetech thru the motor and let it sit. I then ran another leak down test ( after I ran out the valvetech) and here are the new results:
Cylinder 1) 9%
Cylinder 2) 52%
Cylinder 3) 22%
Cylinder 4) 22%
Cylinder 5) 12%
Cylinder 6) 72%
Cylinder 7) 22%
Cylinder 8) 22%
All of the numbers are better accept for cylinder number 6 it acually got worse. It sounds like it is going to cost me alot more money then I can really spend right now. I would like to upgrade what I can but I will settle with bringing it back to stock and seeing what I get from there. I guess my next step would be to pull the heads and see what I have or should I just go ahead and pull the motor and figure what is wrong then.
Happy,
What would be a better carb (Holley or Quadrajet) and how much will you sell me one for. I can rebuild it or if you have one already rebuilt that I can purchase from you I might go that route.
Well I guess given the situation what will be my best point of attack? Should I just change the carb and manifolds and run it like it is or should I replace what parts I can? I am not sure what will be best for me.
Thanks!
I do not plan to run the boat anymore until I do get these problems fixed. I did go ahead and run some valvetech thru the motor and let it sit. I then ran another leak down test ( after I ran out the valvetech) and here are the new results:
Cylinder 1) 9%
Cylinder 2) 52%
Cylinder 3) 22%
Cylinder 4) 22%
Cylinder 5) 12%
Cylinder 6) 72%
Cylinder 7) 22%
Cylinder 8) 22%
All of the numbers are better accept for cylinder number 6 it acually got worse. It sounds like it is going to cost me alot more money then I can really spend right now. I would like to upgrade what I can but I will settle with bringing it back to stock and seeing what I get from there. I guess my next step would be to pull the heads and see what I have or should I just go ahead and pull the motor and figure what is wrong then.
Happy,
What would be a better carb (Holley or Quadrajet) and how much will you sell me one for. I can rebuild it or if you have one already rebuilt that I can purchase from you I might go that route.
Well I guess given the situation what will be my best point of attack? Should I just change the carb and manifolds and run it like it is or should I replace what parts I can? I am not sure what will be best for me.
Thanks!
Big Dave
Member
sounds like a valve job may help in the short term, I would like to see a wet/dry compression test though.
has the valve lash been adjusted lately?
What kind of oil pressure are you running? at idle? at 3000rpm?
cold, hot?
do you have any blowby coming out the breather holes while running?
has the valve lash been adjusted lately?
What kind of oil pressure are you running? at idle? at 3000rpm?
cold, hot?
do you have any blowby coming out the breather holes while running?
happy
Active member
the debate on which carb is better is a path i chose not to go down.. both carbs are reliable, as long as they are clean, and assembled correctly. today i'll go thru my carb bin.. and pic out the best one i have.. , then i'll go thru my stashed carb parts.. and then i'll come up with a figure for you.. i'll have that this evening
Hey Happy,
That sounds great. I am not sure which one I should try. I understand not wanting to get into a big debate about it, but if it was you which one would you put on your boat? Given my engine and boat.
I have started taking the motor out of the boat. I found a good used set of gil manifolds and stainless risers. My buddy took them off of his boat (38' Cigarette Top Gun). He wants $500 for the pair. I plan to get a valve job done ($100) and while I am there I am buying a new roller cam, Hydraulic lifter, push rods, and roller rockers. My friend said he would sell me everything for $1,300 including the manifolds and risers. Let me know if that is reasonable or not. I also plan to at least change the rings. I will know more when I get inside it. My buddy told me I might have to bore the cylinders if they are in to bad of shape due to the water ingestion. Which means I am sure new pistons.
My old risers and manifolds are not in very good shape and I am sure I have leakage into the motor from them. They were very rusted and I had a terrible time getting them off with all the rust. That is why I am looking at some new/used ones. Let me know if that price is good or not.
Well I am on my way to the rebuild and I will just bite the bullet and spend what I have to in order to make it right.
Also about the cam I am getting, let me know if this is an ok one. It is a Crane marine cam. The lift is 590/610. My buddy said it would give me more top-end but I might lose some low-end. Please advise me if this is the wrong cam. I am changing it over to a roller cam. The rpm limit with the new cam is 5600rpm with a cruise at 3,000 to 3,600 rpm. Well I know you guys know more about this than me and I want to make sure I put the right stuff in it so I do not have to do this agian anytime soon.
Thanks,
-Barry
That sounds great. I am not sure which one I should try. I understand not wanting to get into a big debate about it, but if it was you which one would you put on your boat? Given my engine and boat.
I have started taking the motor out of the boat. I found a good used set of gil manifolds and stainless risers. My buddy took them off of his boat (38' Cigarette Top Gun). He wants $500 for the pair. I plan to get a valve job done ($100) and while I am there I am buying a new roller cam, Hydraulic lifter, push rods, and roller rockers. My friend said he would sell me everything for $1,300 including the manifolds and risers. Let me know if that is reasonable or not. I also plan to at least change the rings. I will know more when I get inside it. My buddy told me I might have to bore the cylinders if they are in to bad of shape due to the water ingestion. Which means I am sure new pistons.
My old risers and manifolds are not in very good shape and I am sure I have leakage into the motor from them. They were very rusted and I had a terrible time getting them off with all the rust. That is why I am looking at some new/used ones. Let me know if that price is good or not.
Well I am on my way to the rebuild and I will just bite the bullet and spend what I have to in order to make it right.
Also about the cam I am getting, let me know if this is an ok one. It is a Crane marine cam. The lift is 590/610. My buddy said it would give me more top-end but I might lose some low-end. Please advise me if this is the wrong cam. I am changing it over to a roller cam. The rpm limit with the new cam is 5600rpm with a cruise at 3,000 to 3,600 rpm. Well I know you guys know more about this than me and I want to make sure I put the right stuff in it so I do not have to do this agian anytime soon.
Thanks,
-Barry
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