Help! Engine Rebuild Issue
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,677
Likes: 1
From: Potomac Falls VA
Help! Engine Rebuild Issue
So I started my top-end re-build tonight (see details here: http://forums.corvetteforum.com/c3-t...tion-long.html)
I have my new camshaft in and my timing chain / gears on, timing marks aligned, etc but I am getting a "binding" or some sort of interference when I try and rotate the entire crank and cam. Specifically, if I try and spin the lower timing gear clockwise from TDC, I get some binding / interference after about 15-20 degrees. If I turn the lower gear counter-clockwise, I get some binding at about 200 degrees from TDC. I have spun the block upside down on the stand and tried to examine from underneath but I can not figure out what the issue is.
I am not forcing it past these points and I also have not put in any lifters or anything else so I am really at a standstill. And before I put the cam in, the crank rotated smooth and completely.
The only thing else I can think of is I should degree the cam to ensure I have everything perfect. When I checked with comp cams this week, though, they said degreeing a cam was not necessary for street engine. Is it possible the cam is off enough to cause some interference with the crank/pistons/connecting rods somehow?
Any help would be greatly appreciated.
Thanks
Shane
I have my new camshaft in and my timing chain / gears on, timing marks aligned, etc but I am getting a "binding" or some sort of interference when I try and rotate the entire crank and cam. Specifically, if I try and spin the lower timing gear clockwise from TDC, I get some binding / interference after about 15-20 degrees. If I turn the lower gear counter-clockwise, I get some binding at about 200 degrees from TDC. I have spun the block upside down on the stand and tried to examine from underneath but I can not figure out what the issue is.
I am not forcing it past these points and I also have not put in any lifters or anything else so I am really at a standstill. And before I put the cam in, the crank rotated smooth and completely.
The only thing else I can think of is I should degree the cam to ensure I have everything perfect. When I checked with comp cams this week, though, they said degreeing a cam was not necessary for street engine. Is it possible the cam is off enough to cause some interference with the crank/pistons/connecting rods somehow?
Any help would be greatly appreciated.
Thanks
Shane
Burning Brakes
Joined: Jul 2009
Posts: 1,132
Likes: 14
From: A town SC
So I started my top-end re-build tonight (see details here: http://forums.corvetteforum.com/c3-t...tion-long.html)
I have my new camshaft in and my timing chain / gears on, timing marks aligned, etc but I am getting a "binding" or some sort of interference when I try and rotate the entire crank and cam. Specifically, if I try and spin the lower timing gear clockwise from TDC, I get some binding / interference after about 15-20 degrees. If I turn the lower gear counter-clockwise, I get some binding at about 200 degrees from TDC. I have spun the block upside down on the stand and tried to examine from underneath but I can not figure out what the issue is.
I am not forcing it past these points and I also have not put in any lifters or anything else so I am really at a standstill. And before I put the cam in, the crank rotated smooth and completely.
The only thing else I can think of is I should degree the cam to ensure I have everything perfect. When I checked with comp cams this week, though, they said degreeing a cam was not necessary for street engine. Is it possible the cam is off enough to cause some interference with the crank/pistons/connecting rods somehow?
Any help would be greatly appreciated.
Thanks
Shane
I have my new camshaft in and my timing chain / gears on, timing marks aligned, etc but I am getting a "binding" or some sort of interference when I try and rotate the entire crank and cam. Specifically, if I try and spin the lower timing gear clockwise from TDC, I get some binding / interference after about 15-20 degrees. If I turn the lower gear counter-clockwise, I get some binding at about 200 degrees from TDC. I have spun the block upside down on the stand and tried to examine from underneath but I can not figure out what the issue is.
I am not forcing it past these points and I also have not put in any lifters or anything else so I am really at a standstill. And before I put the cam in, the crank rotated smooth and completely.
The only thing else I can think of is I should degree the cam to ensure I have everything perfect. When I checked with comp cams this week, though, they said degreeing a cam was not necessary for street engine. Is it possible the cam is off enough to cause some interference with the crank/pistons/connecting rods somehow?
Any help would be greatly appreciated.
Thanks
Shane
Racer
Joined: Nov 2006
Posts: 264
Likes: 0
From: McLouth Kansas
See if the cam will rotate by itself freely as well as the crank does by itself.
when I put a engine together I check to see if each component rotates freely as I install it. As each rod and piston is installed the rotation gets progressively difficult, and that is normal.
But if one component is installed and I detect a significant "binding" I then know what specific component is the trouble maker.
I degree every cam,,,just to make sure the manufacture did not make a mistake on the grind and have the center line off or duration and lift is correct. I have found them to be off a few deg's sometimes and when I do I just adjust it to where I want it.
Let us know what you find
when I put a engine together I check to see if each component rotates freely as I install it. As each rod and piston is installed the rotation gets progressively difficult, and that is normal.
But if one component is installed and I detect a significant "binding" I then know what specific component is the trouble maker.
I degree every cam,,,just to make sure the manufacture did not make a mistake on the grind and have the center line off or duration and lift is correct. I have found them to be off a few deg's sometimes and when I do I just adjust it to where I want it.
Let us know what you find
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,677
Likes: 1
From: Potomac Falls VA
Thanks for all of the responses. I have to take my son to soccer this morning but I will be back on the project mid-day. I will check the fuel pump pushrod as I have rotated the engine upside a few times.
As for clearancing on the bottom end, that should have done before as this 383 was put together and has been running for 3 years now. Unless there is something else I am missing? Something specific to themore aggressive profile of this cam.
As for clearancing on the bottom end, that should have done before as this 383 was put together and has been running for 3 years now. Unless there is something else I am missing? Something specific to themore aggressive profile of this cam.
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
Thanks for all of the responses. I have to take my son to soccer this morning but I will be back on the project mid-day. I will check the fuel pump pushrod as I have rotated the engine upside a few times.
As for clearancing on the bottom end, that should have done before as this 383 was put together and has been running for 3 years now. Unless there is something else I am missing? Something specific to themore aggressive profile of this cam.
As for clearancing on the bottom end, that should have done before as this 383 was put together and has been running for 3 years now. Unless there is something else I am missing? Something specific to themore aggressive profile of this cam.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
You say you had a new cam installed. If it has more lift the lobes may be contactiing the rods at some point. Just because it worked before does not mean it is clear now. You now have different components in there, the clearances will need to be checked again.
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,677
Likes: 1
From: Potomac Falls VA
If this is the issue, what are the likely contact points I should look for? Some point on the connecting rod toward the top? Also, what is the remedy? Removing material from the rods? Is that structurally ok?
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Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Usually the fix is to grind some off the rod bolt. I have never had to do this and would be afraid it might throw off the balance some. It really depends on how much has to be removed. I set mine up with using .060 as a minimum clearance for everything. My rods were stroker rods so no clearance issues were there from the cam to rods.
Race Director
Joined: Jul 2004
Posts: 12,705
Likes: 329
From: Scottsdale Arizona
I didn't read your original post, but if you didn't use a small base circle camshaft, you may have binding on one of the lobes. Easy enough to see from the bottom while rotating the engine to the point of binding.
Also, if you used a long bolt in the front of the block to hold the fuel pump pushrod in place during instalation, make sure that you've removed it.
Also, if you used a long bolt in the front of the block to hold the fuel pump pushrod in place during instalation, make sure that you've removed it.
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,677
Likes: 1
From: Potomac Falls VA
I didn't read your original post, but if you didn't use a small base circle camshaft, you may have binding on one of the lobes. Easy enough to see from the bottom while rotating the engine to the point of binding.
Also, if you used a long bolt in the front of the block to hold the fuel pump pushrod in place during instalation, make sure that you've removed it.
Also, if you used a long bolt in the front of the block to hold the fuel pump pushrod in place during instalation, make sure that you've removed it.
So is the rememdy to call comp pams and recommend a similar cam with "small base circles" or to grind of the edges of the connecting rod to crank bolts?
If the latter, do I simply go one piston at a time.....Remove, grind, replace, test, repeat until the binding is gone on that one and then go to the next??
Or does this cause enough out of balance to affect a street engine? And I really need to re-think this rebuild?
Thanks
Shane
Last edited by ShaneLU97; Mar 13, 2010 at 11:47 AM.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
if you are grinding anything on the recipocating assembly it may be best to balance all the rods again.....also you problay need to figure out how much extra to grind the rods for clearance when hot.
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,677
Likes: 1
From: Potomac Falls VA
Hey guys....Quick update.
One of the guys from the club came over and helped me out for a few hours. We used a light/medium hand file and took off just a couple hundredths of an inch on the connnecting rod bolts on 3 pistons (only necessary on one side of each connecting rod) which were interfering with the cam lobes. We were able to get a nice clean, binding free rotation.
So, as Bob, suggests, should I try and re-balance the rods for a street engine? If so, is there a DIY process for that?
Also, is there a minimum clearance I should verify I have for the parts that were interfering?
Thanks
Shane
One of the guys from the club came over and helped me out for a few hours. We used a light/medium hand file and took off just a couple hundredths of an inch on the connnecting rod bolts on 3 pistons (only necessary on one side of each connecting rod) which were interfering with the cam lobes. We were able to get a nice clean, binding free rotation.
So, as Bob, suggests, should I try and re-balance the rods for a street engine? If so, is there a DIY process for that?
Also, is there a minimum clearance I should verify I have for the parts that were interfering?
Thanks
Shane
Thread Starter
Drifting
Joined: Aug 2004
Posts: 1,677
Likes: 1
From: Potomac Falls VA
Hey guys....Quick update.
One of the guys from the club came over and helped me out for a few hours. We used a light/medium hand file and took off just a couple hundredths of an inch on the connnecting rod bolts on 3 pistons (only necessary on one side of each connecting rod) which were interfering with the cam lobes. We were able to get a nice clean, binding free rotation.
So, as Bob, suggests, should I try and re-balance the rods for a street engine? If so, is there a DIY process for that?
Also, is there a minimum clearance I should verify I have for the parts that were interfering?
Thanks
Shane
One of the guys from the club came over and helped me out for a few hours. We used a light/medium hand file and took off just a couple hundredths of an inch on the connnecting rod bolts on 3 pistons (only necessary on one side of each connecting rod) which were interfering with the cam lobes. We were able to get a nice clean, binding free rotation.
So, as Bob, suggests, should I try and re-balance the rods for a street engine? If so, is there a DIY process for that?
Also, is there a minimum clearance I should verify I have for the parts that were interfering?
Thanks
Shane
http://www.carcraft.com/techarticles...y_stroker.html
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
I set mine up for a minimum of .060 clearance. This was cam and rod to block clearance. I had no issue with my cam due to the stroker rods I used. The block did require work to clear everything. I did not touch the rods.