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After 30 years I decided to pull my original 67 427/400 engine over last winter to do a complete rebuild. When I was younger I pushed it a bit. Sent the block out for machine work as well as the original heads. Block bores are now 0.04" over with a calculated compression ratio of around 9.8-10.0. Had the distributor professionally rebuilt with verification to production specs done on a SUN machine. Cam is a new Elgin E-1589S which was recommended by several folks who run it in their hydraulic 427 engines. Sent the heads out to get professionally rebuilt. New guides, valves, seals, and exhaust seats were installed. Leak-down was checked. I sent the intake to McNeish for re-skin. I confirmed all plugs/ports are in place and not leaking. I also examined the casting in great detail for cracks. I re-assembled the engine myself. I broke in the cam as defined in posts listed on this forum. During break-in the engine ran hot. I put 1000 miles on the car as I broke in the new engine build and attempted to tune in run quality. My issue is a miss at steady state low speeds. Idle run quality is not very good. However, it does idle around 800. An off-idle miss is present. Starting is not as good as it used to be. Compression checked cold is between 165-170 psi on all cylinders. I measured engine vacuum at 800 rpm hot to be only 14 psi. I expected it to be in the 18-20 psi range. My vacuum gauge says 14 psi means late ignition timing. I advanced timing and vacuum increased to about 16 psi at max advanced timing. Engine miss is more evident. I retard timing and vacuum drops. I set initial and total timing to factory specs and the engine doesn't like it. I can positively affect the run quality by retarding spark. However, performance is affected and the miss is still present but the car is driveable. I observed extremely white plug electrodes suggesting lean operation. Thinking it was lack of fuel I opened up the idle screws to 2 1/2 turns which helped. I assumed engine operation at steady state below 2000 rpm runs off the idle circuit. Any screw change over that does nothing (no effect on vacuum). I also increased the main jets from 64 to 68 which seemed to help but only at higher speed operation. I've had this car for 34 years and know what good looks like. It's not there. I'm missing something. I believe the issues lies with fuel or spark but can't prove that. New cam has 66 degrees of overlap. It's not a radical cam but it may affect vacuum. Below is a list of what I've done all summer to identify the root of the issue. I started with the easy and logical changes first.
Elgin E1589S cam specs:
Intake lift 0.476" with 214 degree duration
Exhaust lift 0.496" with 218 degree duration
66 degree overlap
Valve train is stock with 1.7 ratio stamped arms
I need help. Everything I've done to fuel and spark only has a minor impact on the symptoms and doesn't go after the root cause. I'm going back to ground zero with a check list and systematically walking through everything. Unfortunately, here in Wisconsin the snow will be flying soon.
After 30 years I decided to pull my original 67 427/400 engine over last winter to do a complete rebuild. When I was younger I pushed it a bit. Sent the block out for machine work as well as the original heads. Block bores are now 0.04" over with a calculated compression ratio of around 9.8-10.0. Had the distributor professionally rebuilt with verification to production specs done on a SUN machine. Cam is a new Elgin E-1589S which was recommended by several folks who run it in their hydraulic 427 engines. Sent the heads out to get professionally rebuilt. New guides, valves, seals, and exhaust seats were installed. Leak-down was checked. I sent the intake to McNeish for re-skin. I confirmed all plugs/ports are in place and not leaking. I also examined the casting in great detail for cracks. I re-assembled the engine myself. I broke in the cam as defined in posts listed on this forum. During break-in the engine ran hot. I put 1000 miles on the car as I broke in the new engine build and attempted to tune in run quality. My issue is a miss at steady state low speeds. Idle run quality is not very good. However, it does idle around 800. An off-idle miss is present. Starting is not as good as it used to be. Compression checked cold is between 165-170 psi on all cylinders. I measured engine vacuum at 800 rpm hot to be only 14 psi. I expected it to be in the 18-20 psi range. My vacuum gauge says 14 psi means late ignition timing. I advanced timing and vacuum increased to about 16 psi at max advanced timing. Engine miss is more evident. I retard timing and vacuum drops. I set initial and total timing to factory specs and the engine doesn't like it. I can positively affect the run quality by retarding spark. However, performance is affected and the miss is still present but the car is driveable. I observed extremely white plug electrodes suggesting lean operation. Thinking it was lack of fuel I opened up the idle screws to 2 1/2 turns which helped. I assumed engine operation at steady state below 2000 rpm runs off the idle circuit. Any screw change over that does nothing (no effect on vacuum). I also increased the main jets from 64 to 68 which seemed to help but only at higher speed operation. I've had this car for 34 years and know what good looks like. It's not there. I'm missing something. I believe the issues lies with fuel or spark but can't prove that. New cam has 66 degrees of overlap. It's not a radical cam but it may affect vacuum. Below is a list of what I've done all summer to identify the root of the issue. I started with the easy and logical changes first.
- I've replaced the distributor rotor, cap, plugs, coil, plug wires all twice with no impact.
- I replaced the Lectric Limited breakerless system that I've run for 30 years with a new one. I also ran the car briefly with points. Neither change had any impact.
- I've not evaluated nor replaced the original ignition switch. I didn't think that had any effect. But it remains an open item.
- I replaced the entire distributor with a friends known good one. No impact.
- I installed a NOS AC fuel pump I've had for years during the rebuild. I replaced it again after having the issue with a cheap repro with no impact. I'm convinced I have correct fuel pressure and float height.
- I've rebuilt the 3 carbs twice thinking I made a mistake during the rebuild. The metering plates on both end carbs were warped. I replaced them with correct -3 new plates from Allstate Carb. I replaced the center carb with a friends carb that was known good with no impact. I confirmed float setting via sight plugs. I also replaced the fuel filters twice. No impact.
- I've run the car at high advanced timing and high retarded timing. Only retarding had a positive impact on the issue. However, retarding the timing increased engine temperature at idle. Advancing timing caused a bad misfire.
- I went on a hunt for a vacuum leak using propane with no findings. I pulled the intake thinking I had an intake gasket leak since I used a 40 year old NOS gasket set. No impact.
- While the intake was off I confirmed the cam didn't have any lobe wear issues following break-in. I also confirmed the cam timing chain was not off a tooth.
Elgin E1589S cam specs:
Intake lift 0.476" with 214 degree duration
Exhaust lift 0.496" with 218 degree duration
66 degree overlap
Valve train is stock with 1.7 ratio stamped arms
I need help. Everything I've done to fuel and spark only has a minor impact on the symptoms and doesn't go after the root cause. I'm going back to ground zero with a check list and systematically walking through everything. Unfortunately, here in Wisconsin the snow will be flying soon.
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