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Old 10-28-2012, 01:28 PM
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350 chev, confusion

I got a "rebuilt" 85 sbc 350, sat taped off and covered for years. Was the spare motor that came with an 81 s/c s/b resto we inherited from my wifes grandfather. I gave the spare 350 a home, in my 2wd s series blazer, headers, dual 3" flowmaster super 40's, 90* dumps at the axel, 3l80 hd trans.

Ive never known what this motor has for bottom end work, so I swapped the stock intake for an edelbrock performer, and an edelbrock 600cfm carb. Its running stock HEI ignition, 8.5m wires, ngks. When I swapped the intake I noticed some crazy loose rockers, so I reset the lash to spec and fired it up. Runs good, sounds awesome, but when your driving the power doesnt seem like its there at all, sounded like a dead cylinder. Put it in the shop and realized I forgot 2 Delco plugs behind the d/s header, swapped them out and seemed to run better, took it out and still wasnt feeling it. Tested each wire with a node light for consistant sparking. I popped the valve covers off, adjusted the lash warm @ idle, twice. And I think I had them too tight, but still no changes.

So....... I was thinking dead cylinder, round cam, possible worn timing chain (but this thing came taped off assembled with a new gasket kit and some chome shiny stuff?)

Compression test in order of how I checked, plugs out one at a time 1,3,5,7,2,4,6,8

160, 150, 145, 155, 155, 150, 145, 150

Anything wrong with these numbers?
One thing about the carb im running is that it was from my buddies 92 350 corvette EX-tpi motor, tons of machine work, lots of power. its only a 600cfm, but could it be way over jetted and tuned for alot more motor? and it could be possibly overfueling this thing? When I pull the plugs cold they're fuel soaked and unburned fuel/ black, but when I pull them hot, they are nice and golden brown. I also dont hear 4 barrel when I mash it it just seems to cough and not do much under load.

Im going to play with timing, advance a bit, and another set of wires, but im confused. Been told to check the coil, as its not "new" but not sure if they commonly fail and cause this?

Ryan350 :thumbup:

Last edited by boneyard Buick; 10-28-2012 at 01:37 PM.
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Old 10-28-2012, 02:16 PM
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Well comp numbers are not great but good enough to react the mixture
So next I would do a blowdown(cyl leakdown test) I suspect maybe valve problems
if thats ok check the cam for a round lobe with dial indicator method
So if these 2 things are acceptable then go to your ignition and carb tuning
There is a lot of things left out of your post like wheres the total timing at,jetting and PV on carb ect.
But start where I sid to know if the motor is still alive
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Old 10-28-2012, 02:22 PM
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do you think the assembly lube was still good,or did you prime the oil pump before starting? pull both valve covers after making sure electrical is all good. run the engine and make sure you do not have a wiped out cam.You didnt say what cam is in it.
A cam gone flat can still show good CR.
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Old 10-28-2012, 03:37 PM
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Alright well after alot of diagnosing, trial runs, and only on the road for a month, I got some nasty sounds in the bottom end after my last rip up the road. I did prime the oil system prior to starting though. This things getting pulled out, time for a new heart.

thanks anyways
Ryan350 :thumbup:
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Old 10-28-2012, 03:45 PM
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350 chev, confusion

When you get to the timing, start by setting the initial timing about 18*-20* at idle. If the idle is too high adjust the curb idle screw out until it idles about 800 rpms. The mechanical timing need to be set to 16*. Have someone hold the rpms steady about 3000-3500. Use a timing light with an advance knob. Unplug the vacuum hose from the distributor and plug it. Point the timing light at the scale. Turn the knob on the back of the light until the line on the balancer lines up on zero. You need a reading of no more than 36*. Loosen the distributor and adjust to 36*. Lock it back and reinstall vacuum hose. Make sure the vacuum hose is plug into full time vacuum. The port on the right side of the Edelbrock 600 is full time vacuum. Test drive it. If you hear any pinging sound back off the timing about 2* and test again. Here is a good article to read before you start tuning. http://www.crankshaftcoalition.com/w...EI_distributor
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