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need to rebuild our chevy 350 in our 1988 chevy blazer. need some advice!

R

riv1973

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hey all!

so the engine in our 1988 blazer is way worse than expected and it looks like a rebuild is in order. the motor has heads that are leaking oil past the valve guides or something and causing smoking at start up. not while running that i can notice. so i would think that at least a rebuilding of the heads are in order.

we have a LQ9 and 4L60 trans we were planning to stick in the truck but i think we are going to back burner that and focus on the 35o in the truck.

it is a TBI engine and is stock. we want to get 300 hp and 400 lbs of torque eventually from the motor as a goal.

was thinking we could start with the top end of the motor and just either rebuild the heads or get a set of Vortec heads. i know that the intake would have to be changed to accept the TBI unit and bolt to the heads since the vortec heads won't bolt to the stock intake. i was also looking at upgrading to another throttle body unit to flow more CFM ( i heard the stock one is 500 cfm and is only good for about 275 hp max).

any ideas on some set ups we could run? like i said, our LS swap will be on hold....

john
 
a few questions, how many miles are on the engine/heads? Could be heads or rings that is causing the smoke. How much smoke in the morning? Just a brief poof of smoke in the morning and I'd be.."eh, run it" 2 or 3 seconds and I'd be digging into where it's coming from. How are your spark plugs, black, brown or crusty? Carbon deposits, fuel deposits/normal running, or crusty equals oil intrusion. Oil pressure high or low? Too much oil pressure can cause oil to get into places it shouldn't. Low oil pressure, probably looking at a rebuild anyways. How is your oil? does it smell like fuel, how long between oil change intervals? Fuel leaking by the rings can cause the rings to wear out prematurely. No oil wedge on the rings means metal on metal wearing which can lead to excessive smoke and or fouling of plugs. Check your PCV valve and air cleaner too. If the engine can't breathe properly, then you can get oil in places it doesn't belong. Start small, start cheap and go from there before you jump to the engine swap or rebuild. Vortecs are pretty tough engines and will last a long time if properly maintained.
 
are the 350 TBI engines in these trucks the first start of the Vortec engines? also are they four bolt mains?

john
 
No

Not necessarily 4 bolt. That said, a 2 bolt block will take 500+ HP. I wouldn’t worry about it
 
all the bolt on TBI mods in the world wont make a BIG difference unless something else changes- whole system is kind of power restricting and difficult to work with.

the smoke on start up is common and probably not a big deal. before doing anything, get a compression check. make sure you have all the spark plugs out, and the throttle all the way open before cranking the engine for each cylinder.

if it runs well, and compression is reasonable, the valve stem seals are an easy afternoon fix (as long as you don't drop a valve). the seals get old and dry and worn, and allow oil to seep down the valve - when its parked, it accumulates, when you start it , it burns off and the rate at which it gets into the chamber is so slow that you wont see it coming out of the tail pipe and/or the catalytic converter is burning it off.

Ive had to replace the valve seals on 3 of these engines now. all were done with the engine in the truck, with less than 75 bucks worth of tools?
-crappy valve spring compressor
-the air tool that threads into the spark plug hole and helps to keep the cylinder pressurized (and keep the valve from falling out)
-new seals
-tube of assembly lube to help keep the keepers keeping while the retainers go back together?

-edit- 10/26/22 i had to do some valve stem seals recently, and the comppressor avail did not have enough air to keep the valves up... tried the "rope" method, and I think I like it better. I took some 1/4 camo lashing cord that was on the wall at home depot... (rocker arms and pushrods removed) shoved as much as I could into the spark plug hole, and then gently turned the engine over until the wad of rope compressed against the valves a little bit... when done, back the motor off a little bit, and pull all the rope out. Easy.
 
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the mechanic and i both think it is the valve seals so that seems consistent with what you are saying.

i will do as you suggest with the compession check. the car has been out of our possesion having other issues handled. we are hung up now on getting a stock steering arm since we took the 4" lift out of the truck. when we get it back a full engine eval will go on.

we are looking to put headers and a full 2 1/2" exhaust on the truck to help it breath. if the motor is in good shape and just needs valve seals then i will go with that.

any idea who makes a good exhaust set up for this truck with headers? and any header suggestions? do they make short headers for this vehicle?
 
Sanderson makes a shorter header, which has the collector close to the factory collector. Part CC17

Clears all the factory stuff
 
if it has an auto trans, you should have options for headers. but "opening it up" is going to take more than bolting headers on... and if you uncork something else to make use of your new headers, you may cause TBI fueling issues...

have I mentioned that my stock cast iron manifolds do not need gaskets? therefore have never had an exhaust gasket leak?

when I was doing more work on the truck years ago, I would have PROBABLY tried headers, but they don't make emission compliant ones that will fit a manual trans here in CA...
at this point, I prefer my stock manifolds (I have seen the Sanderson ones though- interesting)
 
riv1973 said:
the mechanic and i both think it is the valve seals so that seems consistent with what you are saying.

i will do as you suggest with the compession check. the car has been out of our possesion having other issues handled. we are hung up now on getting a stock steering arm since we took the 4" lift out of the truck. when we get it back a full engine eval will go on.

we are looking to put headers and a full 2 1/2" exhaust on the truck to help it breath. if the motor is in good shape and just needs valve seals then i will go with that.

any idea who makes a good exhaust set up for this truck with headers? and any header suggestions? do they make short headers for this vehicle?
Click to expand...
May not need 2 1/2" exhaust. Or at least not 2.5 dual exhaust. Your muffler will make a difference in sound and performance and dual exhaust will too but may not be necessary, depends a lot on your engine performance level and pocket book. No sense in throwing money after something that won't matter for the way you drive. Just keep in mind you need to think of the engine as an entire package, not just air in or air out but all together. You may not get the full extent of your headers without improving other components as well. Heads, intake, fuel, etc. Now if you are working in steps towards a final goal and can only afford some much here and there, that's different. If you want a stock or sleeper look, look into what was offered in your model years in the Camaro or Corvette.
 
300hp and 400tq is going to require mods that the stock TBI computer will not like. You can get chips burned or got to an aftermarket setup. Just keep in mind making it run right is usually more difficult than bolting in a new higher horsepower engine.
 
scouthead said:
if it has an auto trans, you should have options for headers. but "opening it up" is going to take more than bolting headers on... and if you uncork something else to make use of your new headers, you may cause TBI fueling issues...

have I mentioned that my stock cast iron manifolds do not need gaskets? therefore have never had an exhaust gasket leak?

when I was doing more work on the truck years ago, I would have PROBABLY tried headers, but they don't make emission compliant ones that will fit a manual trans here in CA...
at this point, I prefer my stock manifolds (I have seen the Sanderson ones though- interesting)
Click to expand...
Kinda surprised that the Corvette manifolds don't work. The ones I have set up and machined will pass the physical test at least. Smog tubes, manifold, donut gaskets and all. Havent been able to get underneath and pull the old 2" exhaust and get it to the muffler shop and get it sniff tested. I think mine are from an 82 or 83 Vette.
 
Joel Wilson said:
Kinda surprised that the Corvette manifolds don't work. The ones I have set up and machined will pass the physical test at least. Smog tubes, manifold, donut gaskets and all. Havent been able to get underneath and pull the old 2" exhaust and get it to the muffler shop and get it sniff tested. I think mine are from an 82 or 83 Vette.
Click to expand...
cant get to the sniffer test unless there is a plate welded to the header that have the exemption order number on them... smog tech needs to be able to run that number and see your vin number match to the vehicle list that EO# is good for...

same mentality as the pistol drop test and roster... if the manufacturer makes the headers and submits them for testing, and pays the whatever the fee is - lets just call it $20,000.00, the state MAY issue an EO# covering it for the vehicle... but, not all similar vehicles will be able to use that EO#. If manufacturer submits for the EO for a 1/2 ton suburban with LO5, and 700r4... that order will not usually be useable for a 3/4 ton, or a 1/2 ton with a manual trans... or for a truck (even if the truck has the same Lo5 and 700R4), or for a blazer, etc, etc, etc...

sometimes if the manufacturer wants to keep popping out wads of cash to add other vehicles to the list, they can, but they usually wont if there isn't going to be a return on that investment...

In my case, there was only one option for my 1988 blazer -short tube header that bolted in to the same place as the factory manifold, AND had the air injection fittings for the smog pump... only problem was it was made for a truck with an auto trans and the header and the slave cylinder on my trans needed to be in the same place at the same time. no modifications allowed!

Oh well. I'm not loosing 50HP because of the lack of headers. (and I've never had an exhaust leak!)
 
I wouldn't waste my time or money on ANY modifications. Do what you need to do to keep it running. If it's valve seals, your solution is easy.

You have an LS to swap in, it makes zero sense throwing money at intakes, heads, exhaust, and a host of other things that will be discarded when that swap happens. Save the money for the LS swap.

Don't get me wrong, if the LS wasn't already sitting at your house I'd say otherwise. New heads, probably aftermarket induction setup, SINGLE 3" exhaust, and so on. But the LS is the way to go.
 
thanks for your help guys!

yes after thinking about it i think the LS swap will be best. i have the engine already and the trans. and it makes the power i want in stock form. i plan of getting a test stand and getting the LS motor running on the stand and then doing the swap after i make sure it runs well.

thanks guys!

john
 
Blue85 said:
Goal met! https://www.summitracing.com/parts/nxo-50-10103-2-5
Click to expand...
Very nice...I'm still holding out for a supercharger. Just a little one then maybe spray it with some meth to keep things cool. I just need to come up with a way to have it removable every 2 years for smog.

Where are you going to put the switch? Gotta be in a cool spot to keep the cool points....12voltguy.com can make you a custom switch plate to put wherever you want.
 
Why not ditch TBI and throw a quadrajet on there, stock manifolds to a single exhaust? :eek::eek:
 
Leaking valve seals doesn't really hurt anything, especially on an engine you are not keeping.

Martin
 
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