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Rebuilding Suburban 350

  
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Rebuilding Suburban 350

 
beaukulele beaukulele
New User | Posts: 27 | Joined: 06/11
Posted: 06/12/11
12:14 PM

I'm new to the forum but I come seeking some advice about what I should do in regards to rebuilding the 350 in my '95 K series Suburban. Please feel free to comment if I say anything ignorant. After researching a little I believe the truck has an L05 model 350 because GM didn't implement the Vortec motors until 96. What I'm curious about is the top end of the motor. As soon as it is financially available to do so I'm looking into rebuilding the top end of the motor in hopes of getting more MPG and a little performance boost. The original motor is still in the truck 230,000 miles later. It still runs fine due to good maintenance, but it's far from stellar in performance and also usually gets single digits in MPG. I plan on getting this a top end kit from Summit Racing. The kit includes heads, cam, lifters, gaskets, etc.

Obviously with this kit I would be dropping the TBI setup and switching to a carburetor. The old TBI setup is junk anyway, so if nothing else I'm gaining performance for roughly the same fuel economy. Thoughts?

Also, I am of the understanding that those heads should bolt up fine. But I'm not sure. I've read some things about the L05 having garbage swirl port heads? What I'm simply asking is should the bolt patterns for those heads work?

If anyone has done this swap before I would love to hear your pros and cons of it. It would be exceptionally useful information for me.

I'll also probably go ahead and replace the main bearings, rod bearings, piston rings, and all of the essential "overhaul" parts. Please note too that I'm not building a drag motor, or any high-performance engine, but just a solid street motor with normal power. Thanks for your input!  

redneckjoe69 redneckjoe69
Addict | Posts: 2337 | Joined: 03/10
Posted: 06/12/11
02:32 PM

230,000 miles is a long time, musta been good maintinence.  Cool     i think you should slow down, take it all apart, inspect everything.   honestly with that many miles you may be into some machine work.   start with the short block first.   is it the original timing chain?    come up with a solid plan first, it will pay off in the end.       welcome to chp.  

waynep7122 waynep7122
Guru | Posts: 1130 | Joined: 08/09
Posted: 06/12/11
03:08 PM

i have a great idea while you are saving......

check the operation of the TBI... if its only getting single digit MPG...  something is really wrong....

is the check engine light on....   its a 95 model...  under the dash board...  does it have this 12 cavity connector..  

or does it have an OBD2 connector..   94 and 95 gm trucks and cars usually have OBD1.5...   some OBD2 scan tools will pull codes and show live data from these..

TBI systems have problems with engine coolant temp sensors... where the sensors go bad and sometimes the connector pigtails...

Su102

they are also problems with air injection diverter valves leaking uncommanded air into the upstream tubes that are connected to the exhaust manifolds...  if air leaks into these.. it will dilute the exhaust stream.. causing the oxygen sensor to set the fuel mixture incorrectly...

tuning the carb and new vacuum advance HEI.. to get the same fuel economy as a properly working TBI is going to take a LOT of doing....

and.. people remove TBI units all the time... as they don't understand them ..

there are a with 200,000 miles some things that probably need to be changed...  

waynep7122 waynep7122
Guru | Posts: 1130 | Joined: 08/09
Posted: 06/12/11
03:13 PM

see if you can find somebody with a scan tool that will at least display codes...  

if they have one that will show live data stream from this system and some will.... print this chart...

go over it one line at a time only...   start with a cold engine, key on only..  write the values from the scan tool on the proper line .. then with the motor at normal temps and running...  

Scandata

post what codes you get...

and something that might show up on your truck..  engine off.. grab the throttle lever.. open it slightly..  see if the throttle shaft wiggles in the bore..   if it does.. with the scan tool hooked up..  you might also with the key on.. engine off.. look at the TPS voltage..   work the pedal a few times...  each time it should come back to the exact same minimum voltage...


warn throttle shaft bore will cause all kind of problems.. as the ecm never knows when you actually have your foot off the gas...  as the TPS minimum voltage keeps changing..  it will keep the injectors pouring fuel in.. like you are starting to accelerate..  

beaukulele beaukulele
New User | Posts: 27 | Joined: 06/11
Posted: 06/12/11
04:08 PM

I actually own my own scanner. I just ran it and got no codes. I think right now its just that it could use a tune up, and the fact that brand new it only got 15 MPG highway. I'll probably change the plugs, plug wires, oil, etc. this weekend, but that will only bring me to about 12 MPG highway I think. The main reason I want to get rid of the TBI is the heads that come with it. Those swirl port heads are terrible. If I'm not going to get much different fuel economy than I am now, I'd love to get a performance boost out of what I have right now. Also, I'm sure you're right about the machining. I have a buddy who is a machinist who I'm going to have take a look at the block when I'm ready. Unfortunately I don't have the luxury of tearing it apart right now as it is my daily driver at the moment. In a few months i'll have another vehicle to drive while I'm working on this. The other reason I want to drop the TBI is I'm just a little partial to the old school setup with a carb. I've never been a big proponent of fuel injection just because I think you get a small performance gain whilst adding a lot of points for failure (Electrical lines, fuel pump, so on and so forth). Is there any way you all could affirm for me whether or not the heads would indeed bolt up? That's really all I'm curious about. Also would there be many sensors that I would have to block?