67 427/400 Fresh Rebuild Frustration Help

[Dereck S.]

Re: 67 427/400 Fresh Rebuild Frustration Help

I'll be interested in what you find. I love the term "trailer-hitching". That's exactly what the car is doing. Just to recap, idle quality is rather poor at 750 rpm. It's not lope. It feels like it is miss-firing occasionally. The engine has a shake. Trailer-hitching occurs at low speed and/or very light load (low throttle position). However, off-idle cruise at 2000 rpm (3.08 stock rear) is pretty good with the current timing and carb settings. If I advance timing the trailer-hitching worsens and occurs at cruise speeds. Low speed cruise through town is poor in terms of trailer-hitching. During acceleration it pulls like a freight train in all gears throughout the speed range. No detonation. Before I opened up the idle screws and increased the main jet sizes it was detonating under light load. This is why I remain focused on fuel delivery. I am noticing that the engine water temp climbs rather quick during idle relative to how it behaved prior to the rebuild. I know retarded timing and lean A/F ratio can contribute to that.

[Leif A.]

Re: 67 427/400 Fresh Rebuild Frustration Help

I'll be interested in what you find. I love the term "trailer-hitching". That's exactly what the car is doing. Just to recap, idle quality is rather poor at 750 rpm. It's not lope. It feels like it is miss-firing occasionally. The engine has a shake. Trailer-hitching occurs at low speed and/or very light load (low throttle position). However, off-idle cruise at 2000 rpm (3.08 stock rear) is pretty good with the current timing and carb settings. If I advance timing the trailer-hitching worsens and occurs at cruise speeds. Low speed cruise through town is poor in terms of trailer-hitching. During acceleration it pulls like a freight train in all gears throughout the speed range. No detonation. Before I opened up the idle screws and increased the main jet sizes it was detonating under light load. This is why I remain focused on fuel delivery. I am noticing that the engine water temp climbs rather quick during idle relative to how it behaved prior to the rebuild. I know retarded timing and lean A/F ratio can contribute to that.

A newly rebuilt, bored to .040 over will have higher temps than before rebuild, as well. As long as the temperature is staying within safe limits and not "puking" on shut-off, you should be OK.

[Timothy B.]

Re: 67 427/400 Fresh Rebuild Frustration Help

Dereck,

Are all the idle air bleeds in place, you didn't blow one out of it's hole.

As a test try raising the float four/five flats on the adjustment nut and go for a ride.

These are the same carbs that were on the engine before the overhaul, correct?

[Dereck S.]

Re: 67 427/400 Fresh Rebuild Frustration Help

Tim
Thanks for your thoughts on this. About two months ago I checked each idle air bleed. None were blocked. During the rebuild I focused on this ensuring they were open using a wire and carb cleaner. My carbs are the dated originals. This is why some of the parts were warped. I've addressed that as well. Regarding the float height. Last month I increased the height on each carb systematically to assess the effect. I ruled that out as not having any sensitivity to my issue. I appreciate your thoughts.
Dereck

[Eric T.]

Re: 67 427/400 Fresh Rebuild Frustration Help

Replying to subscribe to this thread.

[Danny P.]

Re: 67 427/400 Fresh Rebuild Frustration Help

All
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.

I would recheck the Leak down test remove plugs and loosing the rockers something not right, then check the center Carb. for metering plate gasket and check the complete Ignition system meaning if you have a New Delco coil made in China throw it away, CHECK THE COIL WIRE AND DIST. CAP AND WIRES ARCING UNDER CROME SHIELD.

[Timothy B.]

Re: 67 427/400 Fresh Rebuild Frustration Help

Another thought I had after reading your posts where you stated carburetor surfaces were warped and you sanded them flat. I have never had any luck short of a machine shop with a mill to get them all trued up flat. Sometimes it takes .030 +- to achieve this.

If you end up removing the carbs get a miti-vac and pull a vacuum on the small hole that goes to the power valve cavity to see if it will hold any vacuum. Usually this will loose the vacuum but slowly, if there is gasket or surface sealing issues the gauge will drop down fast or not even pump up.

If you encounter that, the problem could be the main body to metering block surfaces or throttle body to main body surfaces causing a vacuum leak and lean condition. I agree on the chinese coil, get a NAPA service coil, there are cheep to buy.

[William F.]

Re: 67 427/400 Fresh Rebuild Frustration Help

What's "trailer hitching'??

[Frank D.]

Re: 67 427/400 Fresh Rebuild Frustration Help

Anyone who has towed a car hauler, boat, camper, etc is pretty familiar with the sensation, usually occurs at cruise in a high gear, particularly with overdrive on a flat surface. A slight "bumping" as the towed object gently tries to move fore and aft, separately from the towing vehicle.

A light cruise "miss" in an engine feels quite similar. A subtle sensation, but easily distinguishable from a bog or stumble or "dead miss"...often a symptom of too much timing advance. This description is NOT the vulgar definition as found in "The Urban Dictionary". View that at your own peril.

I won't even bring up "eight stroking"...
Both monikers "old school" expressions....

[Mark M.]

Re: 67 427/400 Fresh Rebuild Frustration Help

Dereck, one quick check of plug wire firing order can't hurt. Of the countless times I've installed wires, I for the second time that I remember crossed 2 wires. It was on port engine of searay boat this summer and it had similar symptoms. Switched wires back and the engine woke right up.

[Hector G.]

Re: 67 427/400 Fresh Rebuild Frustration Help

This is Duke on Hector Guzman's computer. We pulled the distributor from his '66 L-36 and found some issues. The cam assembly is stamped 522 CCW, which could not be OE. In fact I have not run into one of these. Most I've seen end in 24 or 30, which I take to be the maximum centrifugal, and that's 30 at 5000 for this engine. I only measured no more than 20 @ 2000 before pulling the distributor. We're going over to David Sokolowski's place to hopefully find a proper one later today,

The limit pin had a brass bushing, which is definitely not OE. I believe those OE distributors that have bushings are plastic or hard rubber. These bushings that are not on all distributor's can limit the total centrifugal advance.

Also the dimple on the gear was opposite the rotor tip. I'm not sure it this is an issue with big blocks as it is on small blocks due to the latter's limited angular freedom, but I just talked to Lars and he said align the dimple with the rotor tip.

Hector has to other L-36 distributors, both TI rather than single point. One, rebuilt from Long Island Corvette and the other used from David Sokolowski with the correct band. These both also have the dimple opposite the rotor tip and rubber bushings.

I also want to confirm that the #1 wire is indexed that same as on a small block - next to the passenger side edge cap window. It's not shown in the '66 CSM that I could find.

Duke

[Tim S.]

Re: 67 427/400 Fresh Rebuild Frustration Help

There are contributors to this thread who are much smarter than I. Having said that, I'll ask this question. Was the cam degreed in when installed? I cannot see where that question has been addressed. If the cam is not in the correct spot, most every other item is secondary.

I've heard enough stories about cams not being ground where they should be or timing sets that are off.

Just a thought,
Tim

[Dereck S.]

Re: 67 427/400 Fresh Rebuild Frustration Help

Well, I just spent the last 4 months timing an engine with a damaged Craftsman dial back timing light. I completely ignored my common sense on what the engine was telling me it needed based solely on the early results from timing the engine with this light. I even went so far as to pull the distributor and rotate it a tooth despite where the rotor contact was pointing. I remembered the timing light had fallen off the top shelf onto the floor at the end of last year. When this occurred the plastic dial knob flew off and the light housing separated slightly. I did my best to put it back together and thought nothing more about it. On a whim as part of my investigation into the Vette issue I attached the timing light to my 70 Challenger 440 which runs fantastic and found it reported the timing off about 15 degrees. I then attached an old non-dial back light I've had from the 70's and it indicated my Challenger timing was spot on. Using my old timing light I repositioned the Vette distributor and set the initial timing to 7 degrees with the vacuum pod hose plugged and the ignition miss cleared up. Regarding the lean spark plugs I once again pulled the carbs and found that the front carb had a blockage in one of the idle feeds below the throttle plate. I previously cleaned every passage with a wire and carb cleaner. I was surprised to find a piece of debris blocking that feed. I was also surprised to find it had an effect on idle and off-idle run quality. I suspect the timing also had a lot to do with it as well. The engine runs strong. Going down the road the temp gauge reads around 185 degrees. When I idle over three minutes the water temp rises to around 210 degrees. I'm not sure the cause of this. I'll put some mileage on the car to further break-in the engine and determine if it improves. The radiator was re-cored five years ago and I never had any idle temp issues. Needless to say it's been a very humbling experience. Since I retired several years ago I feel my brain has begun to dry up. Not being mentally challenged as I previous was has taken it's toll. It's a bit frightening. Thanks for all the replies and help on this issue. I guess the lesson here is to question everything if it doesn't pass a common sense test.

[Owen L.]

Re: 67 427/400 Fresh Rebuild Frustration Help

WHEW! It's always the last place you look! I realize it was extremely frustrating to solve, but in the end the fix is pretty simple and doesn't require engine surgery -- that's a good thing.

[Mike M.]

Re: 67 427/400 Fresh Rebuild Frustration Help

regarding the BBC temp elevation at idle: i had a 400/427 that had a fresh rebuild and it took 5000 miles on the engine before the elevated temp problem returned to normal. mike