Hi Guys, After the glee that comes with putting a newly built motor into your hot rod I'm begining to have some serious issues which is taking the shine off. I come to my fellow HAMBers for advice. ***Updated 27.09.2010 at the bottom of this post*** ***Updated 28.09.2010 at the bottom of this post*** ***Updated 30.09.2010 at the bottom of this post*** Background: A couple of great guys on the hamp Flazoz and Lowsuire helped rebuild an old race motor I had the chance to grab off another HAMBer. 1942 Merc block, 4" Merc crank, 286 CID in total. Had forged pistons, an Isky 1007LD cam and some other goodies. Basically replaced what needed replacing (kept crank, cam, resurfaced the original Johnsons) and machined everything back ready to go. The ignition is stock 2 bolt crab with a new coil, rotor and cap. Lowsquire said the points and timing checked out ok prior to handing it over. We did have a bit of an issle getting the motor to advance enough at idle. The bolt controling the vaccum break is wound out but the mechanism is still there. Click below for a video of the start up Install: The motor sounded nasty on break in. The 3 x 97's a I grabbed from Dickster went on to a Harrel 3x2 manifold. All 3 carbs are operated with a straight linkage. Fuel delivered via a electric fuel pump and low pressure regulator. Break in seemed to go fine. We noticed that a couple of lifters were loose and would back off causing it to sound like a sewing machine. Issues: At this point the car was running like a raped ape with the motor running to 5k easily and powerfully. The sewing machine noise came back due to the lifter backinig off and it seemed to me that the issue with the way the motor ran started at this point. As the noise got worse so did the way the motor ran - it would snap and pop out the exhaust, it would stumble and generally run rough. We took the manifold off and tightened the lifters, even Loctiting in an effort to save the expense of replacing. After doing this the first time the motor returned to its former glory and both Lowsquire and I were kinda amazed two lifters backing off slightly would have that much of an affect. Driving the motor for about an hour saw the lifter rattle come back and the motor degrade in performance to the point it would struggle up hills in any gear, misfire and generally carry on. Lifter Replacement I brought a set of lifters (know good ones) and Lowsquire installed them. When I picked the car up I noticed that it was not running as good as it had and it got worse the more I drove it. There is no lifter noise although it runs like it did when there lifters had backed off. The Symptoms The car starts and idles fine. The idle is a bit lumpy at 900RPM but the cam is a big cam. It sounds like it may be missing slightly at idle but its hard to tell accuratly. The car will rev fine and relatively smothly in neutral. When accelerating on the road the car will do a few different things: Accelerate for a about 10 seconds then slightly bog and backfire Going up a hill it will bog really badly in any gear when trying to accelerate It will hold an RPM relatively smoothly btrying to accelerate off that will cause issues You can sort of drive through the worst of the bog sometimes into the upper RPM ranges but it is rough even then The bog (especially up hill) will force me to shift down even into first in order to get some sort of acceleration. Hills that would normally be fine in 3rd now need babying in 1st. In order to get through the bogging I will need to almost let speed build up with about an inch or so of throttle - previously I could boot it almost to the floor in 1st and 2nd with the thing taking off. My Efforts So Far This is what I have done in an effort to resolve the issue: Check accelerator pump works on carbs (it does) Check that carbs are synchronised using a flow guage (they are) Check that linkage operates without binding and returns to idle ok (it does) Replace condensor with a new one (slight improvement in running) Correctly gap current spark plugs (some improvement again in performance) Gap new spark plugs to '25 and replace (a more noticable improvement but still having issues) So that is where I'm at - I know the potential of the motor because it ran exceptionally well at one stage. However, returning it to that state is proving difficult! Danny Progress Update 27.09.2010 Replaced coil - no improvement Check fuel pressure again - getting a constant 2.5 psi Replaced entire distributer with a known good one - marginal improvement Checked continuity between dizzy cap and spark plug. Found one suspect lead fixed and retested. No difference. Verified timing - is 5 degrees BTDC. Verified advance - advances to + 20 degrees at RPM Checked to see if fuel was leaking into the carb throat at idle (butterflys looked ok and we couldnt see anything dripping or hosing in). Checked to see if fuel was in the bowls - fuel level check ok (even immediatly after we experienced bogging). Battery - charging circuit works, battery has good charge (spins the motor over like crazy). Put timing light on every ignition lead and all have regular flashes Checked for vac leaks and tightened all carb and manifold scews, bolts and stud nuts. More clarification on symptoms AdamF came over and helped with some trouble shooting. There just seems to be a massive flatspot between 2,500RMP-5,000RPM. Even off idle its sluggish but from 2,500 its worse. If you keep your foot flat to the floor in first it will eventually wind up to 5k. Feathering the throttle doest make any difference. Acceleration is best just off idle (so if you hold 3k in first with the accelerator pedal as close to idle as possible and just give a slight push it will have a quick burst of acceleration but will quickly hit the sluggishness again). Doing some more trouble shooting last night the car at idle is even worse. Without changing anything since the last test run, the idle has droppped from 950RPM to 600RPM and is rougher. We have replaced just about all of the ignition componants which I guess leads to fuel? With such a large plenum on the manifold it could be possible that if one of the carbs was not functioning properly (ie blocked jets etc) that it would still allow the motor to run but would be leaning right out? I guess from here I need to swap out the carbs one by one onto a stock manifold and see what happens. Or I could block of two of the carbs on the current manifold and swap each into the centre position. Progress Update 28.09.2010 Cleaned up lead placement (not for trouble shooting but to get it tidied regardless). Started engine and let idle for 8 or so minutes to come up to 180 degrees. Gave timing another check 0 at 8* BTDC. Took car for a drive around the block a couple of times - the motor runs better then it has since we replaced the lifters but the dead spot is still there. Compression check - read 80-85 PSI on all cylinders HOWEVER aparently the guage reads low or so I was told by its owner. All cylinders are consistant. I wouldnt trust the absolute PSI reading through. At least I know none of the cylinders are down compared to the others. More clarification on symptoms With the car at least semi-drivable last night I noticed a couple of things. The car is better at idle and off idle but with any more then say 1/4 or 1/3 of accelerator it begins to bog. If I hold a specific rev range (say 3k) with minimal accelerator and then press it again it will accelerate before bogging higher up the rev range. Holding it at 3k or 4k with minimal accelerator the car runs relativly smoothly with some slight popping out of the exhaust and a very slight misfire. Its not juddery or surging but again I'm gussing at this point its either running on idle circuit or off idle circuit not main jets? Plan of attack for tonight. Drain oil and look for chunks of cam lobe (oil needs replacing regardless). Remove main jets on each carb and examin for blockage, debris, issues etc. Check fuel draining out for anything suspect.See below for results Block of end carbs with block of plates and run each carb in turn in the centre. See if any one carb plays up. Run outside carbs only to see if over carbed (however it really ran well with all three originally). Well discovered alot of this sort of thing when I drained the fuel from one of the carbs: So, where to from here? The jets looked ok from what I could see there was no debris in the jets themselves but I'm guessing this stuff is throughout the carb. Complete disassemble, clean and reassemble? Partial rebuild? Blow through carb cleaner and hope for the best? Progress Update 30.09.2010 Went over to Lowsquire's pad with the carbs in tow to blow apart and rebuild. The carbs all had some black crap in the bottom of the bowls. One of the carbs had a stuck powervalve. All emulsion tubes were removed, carbs thouroughly cleaned and reassembled. Big thanks to Lowsquire for the help. None of the jets were plugged, none of the emulsion tubes were bent, blocked etc. So not exactly a smoking gun in terms of finding the cause of this issue. Maybe the one blocked PV was enough but I suspect not. I noticed that the linkage was a little out of alignment and felt like it was binding. Certainly the differing arm and linkage lengths/alignment was meaning carbs were opening at differing rates. I've made sure all the arms are parralelle and equal lenght and all of the linkages are equal length. Will see what that does tonight.