67 327/300hp Tune help
07-05-2013, 02:32 PM
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67 327/300hp Tune help
Hello guys I'm a new member to the forum but have rec'd a lot of information for our Vette from here, so thanks to all who help!
Background: My dad n I started the restoration on his '67 coupe 5-6 years ago. We got the engine rebuilt and it sat in the garage until a month ago. The 327/300hp was bored .030 over and a mild energy cam was installed. I know it's not a big cam just a little over stock. In the last three months we have purchased and installed all new ignition: points, coil, wires, cap, rotor, and plugs (original distributor).
Installed the engine and transmission (3 speed), installed new original style Holley 4160 585 cfm, new mechanical fuel pump, set the distributor (#1 TDC compression stroke), set the dwell to the points with dwell meter, double checked spark plug gap to 35. Originally she started and with the advance the timing was about 18* and she seamed to run pretty good on the blocks with no load. Was told to set timing to 10-12* with vac from carb plugged. Made the change and she did not want to idle good n would only stay running at that setting with an idle of 11-1200rpm or it would die out. It seemed to be a very rich air/fuel burn, closed the air fuel screws and backed out 1 1/2 turns, this seemed to help. Checked compression, compression is good on all cylinders 125-135psi. Checked plugs, a few had some carbon build up, 1 looked a lil wet but did not reek of fuel, the others had a tannish color. #1 plug was gapped at like 19, reset the gap, all others were good at 35. Passenger bank had a lil chatter, reset valve lash with a 1/2 turn cold. Was doing research and found a vacuum hose out of the manifold led to nowhere! Capped the vacuum. Performed vacuum test at 700-750 idle and it will only read about 6-8 hg at idle, as you give it throttle, the vacuum increases to normal about 22. The car still smells like it is burning rich will back fire through carb when trying to start from time to time. There is also a hesitation when you go from idle to WOT and then she will pick right up. Have check for leaks in the intake and at carb, no change when spraying with carb cleaner.
Currently have low vacuum at idle, burns rich, and has a hesitation when going to WOT. The more when run the engine the better it gets, but still having these symptoms. Dad and I are not professional mechanics but are good around a car. I think I need to back off the valve lash 1/4 turn due to the low vacuum, dad thinks we need more carb adjustments for the bowl level. Can anyone help out or have any suggestions on what needs to be done?!?!
Thanks in advance and I'm sorry so long but thought it would help diagnosis.
Regards,
Robert
Background: My dad n I started the restoration on his '67 coupe 5-6 years ago. We got the engine rebuilt and it sat in the garage until a month ago. The 327/300hp was bored .030 over and a mild energy cam was installed. I know it's not a big cam just a little over stock. In the last three months we have purchased and installed all new ignition: points, coil, wires, cap, rotor, and plugs (original distributor).
Installed the engine and transmission (3 speed), installed new original style Holley 4160 585 cfm, new mechanical fuel pump, set the distributor (#1 TDC compression stroke), set the dwell to the points with dwell meter, double checked spark plug gap to 35. Originally she started and with the advance the timing was about 18* and she seamed to run pretty good on the blocks with no load. Was told to set timing to 10-12* with vac from carb plugged. Made the change and she did not want to idle good n would only stay running at that setting with an idle of 11-1200rpm or it would die out. It seemed to be a very rich air/fuel burn, closed the air fuel screws and backed out 1 1/2 turns, this seemed to help. Checked compression, compression is good on all cylinders 125-135psi. Checked plugs, a few had some carbon build up, 1 looked a lil wet but did not reek of fuel, the others had a tannish color. #1 plug was gapped at like 19, reset the gap, all others were good at 35. Passenger bank had a lil chatter, reset valve lash with a 1/2 turn cold. Was doing research and found a vacuum hose out of the manifold led to nowhere! Capped the vacuum. Performed vacuum test at 700-750 idle and it will only read about 6-8 hg at idle, as you give it throttle, the vacuum increases to normal about 22. The car still smells like it is burning rich will back fire through carb when trying to start from time to time. There is also a hesitation when you go from idle to WOT and then she will pick right up. Have check for leaks in the intake and at carb, no change when spraying with carb cleaner.
Currently have low vacuum at idle, burns rich, and has a hesitation when going to WOT. The more when run the engine the better it gets, but still having these symptoms. Dad and I are not professional mechanics but are good around a car. I think I need to back off the valve lash 1/4 turn due to the low vacuum, dad thinks we need more carb adjustments for the bowl level. Can anyone help out or have any suggestions on what needs to be done?!?!
Thanks in advance and I'm sorry so long but thought it would help diagnosis.
Regards,
Robert
07-05-2013, 03:08 PM
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Originally she started and with the advance the timing was about 18* and she seamed to run pretty good on the blocks with no load. Was told to set timing to 10-12* with vac from carb plugged. Made the change and she did not want to idle good n would only stay running at that setting with an idle of 11-1200rpm or it would die out. It seemed to be a very rich air/fuel burn, closed the air fuel screws and backed out 1 1/2 turns, this seemed to help. Checked compression, compression is good on all cylinders 125-135psi. Checked plugs, a few had some carbon build up, 1 looked a lil wet but did not reek of fuel, the others had a tannish color. #1 plug was gapped at like 19, reset the gap, all others were good at 35. Passenger bank had a lil chatter, reset valve lash with a 1/2 turn cold. Was doing research and found a vacuum hose out of the manifold led to nowhere! Capped the vacuum. Performed vacuum test at 700-750 idle and it will only read about 6-8 hg at idle, as you give it throttle, the vacuum increases to normal about 22. The car still smells like it is burning rich will back fire through carb when trying to start from time to time. There is also a hesitation when you go from idle to WOT and then she will pick right up. Have check for leaks in the intake and at carb, no change when spraying with carb cleaner.
Currently have low vacuum at idle, burns rich, and has a hesitation when going to WOT. The more when run the engine the better it gets, but still having these symptoms. Dad and I are not professional mechanics but are good around a car. I think I need to back off the valve lash 1/4 turn due to the low vacuum, dad thinks we need more carb adjustments for the bowl level. Can anyone help out or have any suggestions on what needs to be done?!?!
Thanks in advance and I'm sorry so long but thought it would help diagnosis.
Regards,
Robert
125-135 psi compression test is pretty low, especially for a fresh engine - should be 160-170 psi. Did you test it with all plugs out, warm engine, and throttle held at wide open as specified?
Idle mixture screws should be adjusted for highest steady vacuum, NOT "number of turns"; that's what the vacuum gauge is for.
Manifold vacuum is checked with the vacuum advance line connected and idle set at 650-700 rpm; checking it with the vac. advance line disconnected and plugged is meaningless. You should show 15"-18" Hg.
Leave the valve lash alone - once you set it, it isn't going to change; anywhere from 1/4-turn to 3/4-turn from zero lash will work fine. Did you break in the cam at initial start for 20 minutes, using break-in oil and/or break-in additive? Do you know you're getting full lift on every valve?
07-05-2013, 03:21 PM
#3
Race Director
And, do you have the correct timing cover for your balancer? Mismatch those, and your timing could be off about 10* either way. Did you replace the balancer or timing cover? And if so, did you get them from a Corvette supplier, or from teh local speed shop?
Low vac sounds like retarded timing.
You could rough set the timing with a vacuum gauge, using ported vacuum, ( and vacuum advance connected) hooked up to the vac gauge, advance the dizzy until you get max vac at idle, then back off 1-2" of vacuum. Now check your timing marks, vacuum advance DIS connected. A great difference could indicate a problem with your marks.
You really need to verify top dead center vs your timing marks with a dial indicator, but that is difficult with the heads on, unless you have a very special tool.
Doug
Low vac sounds like retarded timing.
You could rough set the timing with a vacuum gauge, using ported vacuum, ( and vacuum advance connected) hooked up to the vac gauge, advance the dizzy until you get max vac at idle, then back off 1-2" of vacuum. Now check your timing marks, vacuum advance DIS connected. A great difference could indicate a problem with your marks.
You really need to verify top dead center vs your timing marks with a dial indicator, but that is difficult with the heads on, unless you have a very special tool.
Doug
Last edited by AZDoug; 07-05-2013 at 03:23 PM.
07-05-2013, 04:38 PM
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JohnZ,
- The vacuum can is the original can, we put e pump test to it, no leaks/held the pressure, started reading at 3 and topped out at 10. I believe it is the correct can, could be wrong!
- No, apparently compression test was done incorrectly, all plugs were out, but did not have WOT or have engine warmed up. Will try this and see what she says.
- Will retest manifold vacuum as suggested, I think at 1 time it was tested with advance plugged, so will retest to verify.
- As far as break in, we used regular 5w30, did not know about any special fluid. I understand to leave the valve lash as is, and I'm not sure if we are getting lifted, that's why I was thinking to back off the lash.
Something I did leave out of the original post: after cranking motor the first time it was not running good at all and only seemed to be running on #1 & #7, took valve cover off of driver side and confirmed all valves were articulating, them left for the night. The next day performed cold compression test, had compression on all drivers bank cylinders and no compression on the passenger side (Not good). Removed valve cover to see the intake rods were broken, 2 bent to he{{ & 2 were broken. After the motor sat on the garge floor for 5 years we filled the cylinders with diesel to lube and break down any sticky old lube before turning it over. It was very hard to turn by hand but worked the crank back and forth until being able to turn it over by hand. Did not think to lube the valves, I think I may have bent the rods when turning it by hand. So valve cover off rocker arms all off of the intake valves. Intake valves were all stuck. Took out the damaged rods and put in the rods that came out of the motor before being rebuilt. To loosen the valves we used PB Blast and used a P&C of oak and hammer, tapped them down and pried up until the valves seemed to move freely. The valves were not quite as springy as the exhaust but were springing back up. Reinstalled the rocker arms and adjusted lash to where there was no slack. Cranked up and let it run a lil while. The next day, cold compression test again this time only taking out the plug in the cylinder I was checking. This is when we set the dwell and played with the timing to get it were it is now. We ran the original oil/ PB Blast for about 2 nights while playing with the timing and just letting her run a lil, then changed the oil to a 30 SAE we happened to have in the garage as all the stores were closed by this time.
Could the valve springs be shot from sitting so long, and could the cam possibly be hurt by running the oil w/o additive? THX JohnZ
AZDoug,
We did have a new timing cover put on and a brand new 8" balancer put in. These 2 pcs came from Carquest not a quote speed shop. If I am able to get better vacuum at idle I will test the marks to see what happens! Thx AZ
I will do some tooling and return with the results. Thx again!
- The vacuum can is the original can, we put e pump test to it, no leaks/held the pressure, started reading at 3 and topped out at 10. I believe it is the correct can, could be wrong!
- No, apparently compression test was done incorrectly, all plugs were out, but did not have WOT or have engine warmed up. Will try this and see what she says.
- Will retest manifold vacuum as suggested, I think at 1 time it was tested with advance plugged, so will retest to verify.
- As far as break in, we used regular 5w30, did not know about any special fluid. I understand to leave the valve lash as is, and I'm not sure if we are getting lifted, that's why I was thinking to back off the lash.
Something I did leave out of the original post: after cranking motor the first time it was not running good at all and only seemed to be running on #1 & #7, took valve cover off of driver side and confirmed all valves were articulating, them left for the night. The next day performed cold compression test, had compression on all drivers bank cylinders and no compression on the passenger side (Not good). Removed valve cover to see the intake rods were broken, 2 bent to he{{ & 2 were broken. After the motor sat on the garge floor for 5 years we filled the cylinders with diesel to lube and break down any sticky old lube before turning it over. It was very hard to turn by hand but worked the crank back and forth until being able to turn it over by hand. Did not think to lube the valves, I think I may have bent the rods when turning it by hand. So valve cover off rocker arms all off of the intake valves. Intake valves were all stuck. Took out the damaged rods and put in the rods that came out of the motor before being rebuilt. To loosen the valves we used PB Blast and used a P&C of oak and hammer, tapped them down and pried up until the valves seemed to move freely. The valves were not quite as springy as the exhaust but were springing back up. Reinstalled the rocker arms and adjusted lash to where there was no slack. Cranked up and let it run a lil while. The next day, cold compression test again this time only taking out the plug in the cylinder I was checking. This is when we set the dwell and played with the timing to get it were it is now. We ran the original oil/ PB Blast for about 2 nights while playing with the timing and just letting her run a lil, then changed the oil to a 30 SAE we happened to have in the garage as all the stores were closed by this time.
Could the valve springs be shot from sitting so long, and could the cam possibly be hurt by running the oil w/o additive? THX JohnZ
AZDoug,
We did have a new timing cover put on and a brand new 8" balancer put in. These 2 pcs came from Carquest not a quote speed shop. If I am able to get better vacuum at idle I will test the marks to see what happens! Thx AZ
I will do some tooling and return with the results. Thx again!
07-05-2013, 08:34 PM
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Ok so we have advanced the dizzy to the manifold, and opened the air/fuel on the carb and she seems to be burning leaner, but still a lil rich. With idle of 675 -725 we have the dizzy advanced all the way to the intake and the intake vacuum seems to hang around 6-7". There is still a hesitation, but is improving when going to WOT. we are thinking about going one more tooth to see if this will help the vacuum and increase the timing to bring up the vacuum in the event the timing is retarded. Does this sound correct?
07-05-2013, 08:35 PM
#6
Race Director
Ok so we have advanced the dizzy to the manifold, and opened the air/fuel on the carb and she seems to be burning leaner, but still a lil rich. With idle of 675 -725 we have the dizzy advanced all the way to the intake and the intake vacuum seems to hang around 6-7". There is still a hesitation, but is improving when going to WOT. we are thinking about going one more tooth to see if this will help the vacuum and increase the timing to bring up the vacuum in the event the timing is retarded. Does this sound correct?
Hitch
07-05-2013, 08:55 PM
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Ok will advance one tooth, just put the light on it and the indicator mark on the balancer is almost pointing straight up/Due North. We are going to try to verify TDC using an old spark plug wire. Lets say the timing mark on the balancer is off, we mark the accurate TDC before adjusting the dizzy. IMO if the balancer and our TDC was off then I will need to readjust the valve lash and this together might be causing the low vacuum?!?!
07-05-2013, 09:35 PM
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Ok will advance one tooth, just put the light on it and the indicator mark on the balancer is almost pointing straight up/Due North. We are going to try to verify TDC using an old spark plug wire. Lets say the timing mark on the balancer is off, we mark the accurate TDC before adjusting the dizzy. IMO if the balancer and our TDC was off then I will need to readjust the valve lash and this together might be causing the low vacuum?!?!
07-05-2013, 10:04 PM
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Hitch
07-06-2013, 05:13 PM
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Ok we verified the marks on the balancer and timing tab are accurate. We aren't sure that the rings are bad as there is no smoke from the exhaust when it is running. My question is, is it possible the low compression and low vacuum at idle could be caused by having weak/bad valve springs? I was told by a local competition head shop that springs can go bad from sitting up. Also the vacuum gauge tells us that we have late valve timing. If we did not use a break in oil/additive what might have happened to the cam w/o these products? The higher compression readings are from the passenger bank where the intake pushrods were bent and broken??? Any ideas?? Thx in advance!
07-07-2013, 03:19 AM
#13
Le Mans Master
I think John Z already mentioned it but his note on proper cam break in is very important if this was a new engine start up. If the engine ran before it was parked not a problem.
The Lifters and Camshaft must break in together, this gets the lifters spinning in the bores as they should and if properly done the lifters and cam will last long enough that your engine will wear out from high mileage before the cam or lifters fail.. If they are not broken in properly one or more lifter will fail to rotate, when this happens the cam will hit on the same spot with every rotation and quickly wear away the lifter foot and the face of that cam lobe.
The most obvious thing with this type failure is noisy lifters. You can adjust them quiet but within a half hour run time they are ticking again. I did not see any wording indicating your lifters are ticking so you may be good.
Proper break in involves starting your new engine and as soon as you confirm you have good oil pressure and the cooling system is flowing coolant you bring up the RPM to a minimum of 1500 to a high of 2,500 and keep it at that RPM for 20 minutes. This is necessary for all Flat Tappet engines on initial start up. A flat lobe on the cam can be caused by poor break in or a hard initial start up, one where you needed to crank the starter many times while you figured out why it had not yet started.
As far as checking the lifter adjustment at this point to confirm you are not leaking past the valves a running adjustment would allow you to quickly set your valves properly and quickly. The only negative is containing the mess while you adjust the valves. Oil will be squirting out the push rods with every rotation of the engine. While running with one valve cover off back off a rocker arm until you hear the valve start tapping, wait 10 seconds and see if your lifter adjusts it quiet again, once you are able to back off a 1/4 turn and hear the valve tap without the lifter adjusting the noise away you are ready to tension the lifter. Tighen the Rocker Arm nut down slowly until the tapping noise just stops. Now add 1/2 turn more, your engine should miss on this cylinder for less than 10 seconds then smooth out and stay quiet. This Rocker arm is now done, move on down the line and do them all. Only remove the valve cover you are working on to reduce the amount of oil spillage. There are many tools available to do a hot adjustment with minimal oil mess. A hot running adjustment allows you to correct an engine that has been guessed at.
Could your bent / broken push rods be a result of hydro lock in the cylinders that had diesel fuel in them?
The Lifters and Camshaft must break in together, this gets the lifters spinning in the bores as they should and if properly done the lifters and cam will last long enough that your engine will wear out from high mileage before the cam or lifters fail.. If they are not broken in properly one or more lifter will fail to rotate, when this happens the cam will hit on the same spot with every rotation and quickly wear away the lifter foot and the face of that cam lobe.
The most obvious thing with this type failure is noisy lifters. You can adjust them quiet but within a half hour run time they are ticking again. I did not see any wording indicating your lifters are ticking so you may be good.
Proper break in involves starting your new engine and as soon as you confirm you have good oil pressure and the cooling system is flowing coolant you bring up the RPM to a minimum of 1500 to a high of 2,500 and keep it at that RPM for 20 minutes. This is necessary for all Flat Tappet engines on initial start up. A flat lobe on the cam can be caused by poor break in or a hard initial start up, one where you needed to crank the starter many times while you figured out why it had not yet started.
As far as checking the lifter adjustment at this point to confirm you are not leaking past the valves a running adjustment would allow you to quickly set your valves properly and quickly. The only negative is containing the mess while you adjust the valves. Oil will be squirting out the push rods with every rotation of the engine. While running with one valve cover off back off a rocker arm until you hear the valve start tapping, wait 10 seconds and see if your lifter adjusts it quiet again, once you are able to back off a 1/4 turn and hear the valve tap without the lifter adjusting the noise away you are ready to tension the lifter. Tighen the Rocker Arm nut down slowly until the tapping noise just stops. Now add 1/2 turn more, your engine should miss on this cylinder for less than 10 seconds then smooth out and stay quiet. This Rocker arm is now done, move on down the line and do them all. Only remove the valve cover you are working on to reduce the amount of oil spillage. There are many tools available to do a hot adjustment with minimal oil mess. A hot running adjustment allows you to correct an engine that has been guessed at.
Could your bent / broken push rods be a result of hydro lock in the cylinders that had diesel fuel in them?