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Old 05-18-2018, 03:58 AM   #1
LHD D21
 
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Default 1986 D21 2.4L engine problems

Short story is I bought this 1986 Hardbody fourbanger a few weeks ago and, the motor has issues.

Come to find out: my truck was supposed to be TBI but, someone slapped a (probable) 720 carb on it.

My big Q being is since the center two cylinders have 90 PSI whereas the front and back holes have 180; I'm thinking I have a head gasket problem; which brings me to the next point. Motor had eight spark plugs and, since the head has to come off; is there any realistic way to swap out an older four (1342 firing order) vacuum advance distributor firing on one set of spark plugs only and, the other four plugs as dummies? Or would I be better off in finding a four plug head instead?

Note I'm an alignment/suspension tech by trade so, my knowledge of especially OHC and/or import engines is sketchy at best.
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Old 05-18-2018, 03:03 PM   #2
cadillacdude1975
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Pour a small amount of oil in the weak cylinders. Retest the compression. See if it changes. I would suspect the piston rings are allowing a great deal of cylinder leakage.
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Old 05-18-2018, 03:34 PM   #3
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Seems like I read years ago that there are not many things you can do with the 8-plug Z24i.
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Old 05-18-2018, 11:57 PM   #4
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Quote:
Originally Posted by cadillacdude1975 View Post
Pour a small amount of oil in the weak cylinders. Retest the compression. See if it changes. I would suspect the piston rings are allowing a great deal of cylinder leakage.
Good point there re rings. The weird thing is this motor doesn't seem to use oil.
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Old 05-25-2018, 11:42 PM   #5
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Originally Posted by cadillacdude1975 View Post
Pour a small amount of oil in the weak cylinders. Retest the compression. See if it changes. I would suspect the piston rings are allowing a great deal of cylinder leakage.
Pulled the head: there's a dead 'short' between cylinders 2 and 3; head's at machine shop to be milled and, possibly welded to get rid of the erosion at the blown head gasket. I looked a bit deeper and, noticed the block is slightly eroded at the same place, between 2 and 3. Short of yanking the engine and, doing a full overhaul; is there anything that I could place between the gasket and the block deck, along the lines of a sealer to bring the rough spot flush with every else? The cylinder walls look perfect and, there are no ridges in the walls
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