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Old 09-24-2010, 06:36 PM
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Headgasket Change In Sbc (350)

What is all involved in changing a head gasket in a 93 350 TBI and should both be changed for good measure or just the bad side? And well the heads are off what should I be checking for damage wise? Also well they are off what could I do to "freshen" the heads up?

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Old 09-24-2010, 06:54 PM
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Quote:
Originally Posted by 350chevypower
What is all involved in changing a head gasket in a 93 350 TBI and should both be changed for good measure or just the bad side? And well the heads are off what should I be checking for damage wise? Also well they are off what could I do to "freshen" the heads up?
Something caused the pooched head gasket. Normally you would think that excessive heat played a role. Or perhaps the motor has been down before and the assembler improperly torqued the head bolts or maybe used gaskets that needed re-torquing after a heat/cool cycle and didn't bother to re-torque them.

I don't like to do the same job more than once, so the least I would do is to disassemble the heads, freshen the valve job, check the guides for proper clearance and test the springs for proper installed height and pressure on the seat. I would take a very light cut on the surfaces of each head. Just enough to get the warp out of them if there is any.

I would then make sure what the procedure was on re-installing with the gaskets you will use.....do they need re-torquing or not? Then I'd re-install the heads with new head bolts and waterproof goop on the threads. I would then install the proper heat range thermostat (using a fail-safe design) and make certain that there is a spring in the lower radiator hose to prevent collapse. You didn't say that overheating was involved, I'm just thinking out loud about some of the more common causes of overheating.
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Old 09-24-2010, 06:56 PM
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Quote:
Originally Posted by 350chevypower
What is all involved in changing a head gasket in a 93 350 TBI and should both be changed for good measure or just the bad side? And well the heads are off what should I be checking for damage wise? Also well they are off what could I do to "freshen" the heads up?
You will have to drain the radiator
Disconnect the TBI wires, cables and hoses
Remove any brackets that are bolted to the intake and heads
Remove the distributor
Remove the intake
Remove the exhaust manifold bolts
Remove the valve covers
Loosen the rocker arms and remove the push rods
Remove the head bolts and remove the heads

I would suggest replacing both head gaskets since you're that far into it anyways. I would take the heads to a machine shop and have them checked out. At the least, I would have them surfaced. This insures they are flat for a good sealing surface when you reinstall them.
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Old 09-24-2010, 09:09 PM
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alright thanx. The truck itself is a 89S-10 with the 350 in it. The reason I asked is beacuse I have been having a misfire issue. I have replaced everything to do with ignition and fuel and I still have the misfire... mind you no codes are coming up. I even changed the O2 sensor beacuse t he motor is running rich also. Now it ran a little better after I changed the sensor out but again started misfiring. Now since I bought the truck it has always pushed out a little water from the exhaust and smoked white a bit when cold. I just thought it was condensation in the mufflers. (I have true duel from headers back... no cats flowmaster 40 series mufflers.) And my coolant was always a little down but i would just top it back up. Now what gets me is it blows water out of BOTH exhaust pipes... not just one or the other... hence why I thought condensation. But now the other day after I changed my plugs i checked my oil and it was almost halfway up my dipstick. Well i thought what in the hell? beacuse its not milky in color at all it looks normal the level is just raised. But putting 2 and 2 together i figured could coolant be getting past through the cylinders JUST enough that it is shorting out a plug causing my misfire? Beacuse the white smoke out BOTH exhaust is very miniscle just a few puffs here and there and once it warms up it doesnt smoke at all.... its just running like crap after a few min of running. but when first started runs ok? Thats why I hin towards it being a head gasket... but what are the chances of having 2 blown gaskets? I am very lost....

Also on a side note I sea foamed my motor and while it was running I really noticed alot of water coming out of the exhaust ALOT more than ever and it was almost oily feeling but after it ran for awhile it stopped?
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Old 09-24-2010, 10:42 PM
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Quote:
Originally Posted by 350chevypower
alright thanx. The truck itself is a 89S-10 with the 350 in it. The reason I asked is beacuse I have been having a misfire issue. I have replaced everything to do with ignition and fuel and I still have the misfire... mind you no codes are coming up. I even changed the O2 sensor beacuse t he motor is running rich also. Now it ran a little better after I changed the sensor out but again started misfiring. Now since I bought the truck it has always pushed out a little water from the exhaust and smoked white a bit when cold. I just thought it was condensation in the mufflers. (I have true duel from headers back... no cats flowmaster 40 series mufflers.) And my coolant was always a little down but i would just top it back up. Now what gets me is it blows water out of BOTH exhaust pipes... not just one or the other... hence why I thought condensation. But now the other day after I changed my plugs i checked my oil and it was almost halfway up my dipstick. Well i thought what in the hell? beacuse its not milky in color at all it looks normal the level is just raised. But putting 2 and 2 together i figured could coolant be getting past through the cylinders JUST enough that it is shorting out a plug causing my misfire? Beacuse the white smoke out BOTH exhaust is very miniscle just a few puffs here and there and once it warms up it doesnt smoke at all.... its just running like crap after a few min of running. but when first started runs ok? Thats why I hin towards it being a head gasket... but what are the chances of having 2 blown gaskets? I am very lost....

Also on a side note I sea foamed my motor and while it was running I really noticed alot of water coming out of the exhaust ALOT more than ever and it was almost oily feeling but after it ran for awhile it stopped?
By "true dual exhaust", do you mean you have no crossover or H pipe in the system? Your problem could be a leaking intake gasket in a water port also since it is smoking from both exhausts. What color are your plugs when you removed them? You need to keep track of any different coloring as that will be a good indication of what cylinder needs attention. Before you tear it apart completely, I would suggest removing the valve covers and re-torquing all the head bolts to see if that helps. If not, it's time to tear into it and get it fixed.
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Old 09-25-2010, 12:10 AM
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thnx s10racer,
the color of the plugs were...well destroyed haha...they were burnt and pretty carboned up.... i dont think they were ever changed by the guy who had it before me... actually # 6 and # 8 cyl still had the original ac delco plugs from factory i take it the res were bosh platinums..reason being the header pipe is basically in the way and he didnt bother to try and change them....but anyways they didnt feel wet or anything which is a good sign right? no wetness= no coolant?.... its at my buddys/mechanics right now hes gunna do a compression test in the morn and let me know cus hes changin my header gaskets out anyways.... ill mention that intake gasket thnx again

And to answer your first question no it does not have a crossover pipe in the exhaust system its one pipe fromeach header to a muffler then out the back... ill post some pics up here of her she really is a diamond in the rough i get compliments all the time but all these issues just brings a guy down u know.. p***es a person off lol

Last edited by 350chevypower; 09-25-2010 at 12:18 AM.
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Old 10-26-2010, 11:17 AM
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i completely understand the frusteration

I too have a SBC 350 that i have put alot of time and money into. It does help to know where to put the time and money tho and what to pay special attation to. After getting this motor all put together and thinking i was gonna be able to drive the car today well that just wont happen. Instead when it was put back together i started it this morning to find out that water is just pouring our of the driverside exaust. After all the battles i have had with this car it makes me want to just give up. other then a warped head or cracked head could it be anything else? Someone told me if it was a cracked block that it would most likely leak water right out of the motor its self. Is it pretty safe to assume that? i do know that water is getting in the oil. Is there any suggestions on what i should check or look for? Its just the driver side exaust and like you i have true duals no connector pipes. frusterated is an understatment actually.
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Old 10-26-2010, 09:09 PM
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I understand your pain creoo! frustrated is indeed an understatment! Now about your water issue. Did u assemble the motor yourself? If so did u tourque your head down right? you could have a leaky head gasket thats not seated right. Theres a certain tourque pattern you gotta follow. OR a intake gasket leaking? If u didnt assymble the motor yourself ask the person who did. You also could be on the money with a cracked/warped head. Just some suggestions. I know for my motor Im giving up with the stock heads and cam and looking into the TBI Performer package from Edelbrock. I to was also having water coming out of the exhaust but its on both sides not just one or the other. It did get hot once so I could of warped the heads but instead of guessing I am gunna start tearing into it... Its a daily driver until the snow starts falling then its parked for the winter so time for a rebuild!
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Old 10-27-2010, 06:22 AM
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Sounds like those "destroyed" and burnt and carboned up plugs could very well be the misfire issue, causing the engine's PCM to think it is rich. If it were mine, I'd put a fresh set of plugs in, check the plug wires and then see where you are with the heads.

Sounds like you also have some gasket problems. If I suspect a head gasket is leaking water, as a quick check I start the cold engine with the radiator cap off and watch for air bubbles coming up in the coolant. Also a compression check might indicate a leaky head gasket, especially a lower compression reading on two adjacent cylinders. I'd try re-torqing the head bolts if you see this. I once had a head bolt that was leaking fluid because of a thread sealer fault and fixed by merely removing the head bolts in the area that was leaking, re-apply sealer, and install/torque (one at a time, of course). If okay, I then suspect the intake gaskets and will check the torque on the intake bolts. If that doesn't make it better, then I'd be looking at some disassembly. All IMHO, but based on experience.
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Old 10-27-2010, 04:20 PM
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Thanks for the input cucumber.

Ya I did change out the plugs, fixed the miss a great deal... until my dizzy went on me.Found a big crack in the magnet.. a few actually. Replaced that ran great now its doing it again. I also noticed when i had it on the scanner that it was staying in closed loop even with engine at temp (195'F). As for the coolant I actually just had to change the bottom rad hose.. (Left me starnded on the highway with a big hole in it and coolant p***ing everywhere!) so i filled it with the cap off until it was full, started it let it warm up then just topped up what was needed. As it was warming up I did notice air bubbles coming up but i figured that was air just being purged from the system? I dunno i bought the truck used supposdly from the 2nd owner. he said there was only 140,000km on motor and tranny but who knows right? I already had to put a fair amount of money into it fixing these unexpected problems popping up. So the way I see it is I work in a mechanic shop why not over the course of winter go into the motor and do some replacing. Then I have the reassurance of knowing that I will have a fairly "fresh motor" and go from there!
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Old 10-27-2010, 06:03 PM
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Well, good luck to you and hope you find the problem when you take it apart.

As an aside, my '97 Explorer and wife's '01 Honda Civic stay in closed loop all the time, including prolonged idling - with one exception. While coasting (no throttle) down some of the larger hills in central PA for a prolonged time I noticed that the Honda's system went to open loop, especially if down shifting to take advantage of some engine braking. Makes sense.

Based on what I see other than that, I would think your truck staying in closed loop while idling would be proper operation.
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Old 10-27-2010, 09:06 PM
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I think you might be right on that one. When I shut it off and turned it back on it was in open loop then immediatley went to closed again.... now that i think about it until I held steady throttle it stayed closed... tho Im not sure cus I thought closed loop meant that the computer was keeping it in "cold mode" till it warmed up thus turning it to open loop?
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Old 10-27-2010, 09:25 PM
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Actually, I believe you have it backwards. Closed loop means the system is reading the O2 sensors that are on either side of the catalytic converter - certain components have to be up to temperature before the system will go into closed loop. Until those temps and other conditions are met, the system will be in open loop. For example, my Explorer goes into closed loop about 20 seconds after cold startup, sooner if the engine is already warm.
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Old 10-28-2010, 12:12 AM
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Ohhhh ok.. Thanks for the correction! so then staying in closed would be normal then. basically worried bout nothing there then haha!
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