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TBI Chevy Rebuild

 
beaukulele
V-6 Camaros rule!
Posts: 27
Joined: 06/11
Posted: 02/10/12 07:08 AM

I have a '95 Suburban with the TBI 350 that is tired. It has around 225,000 miles and has become a real dog lately. I know a fair amount about this motor and I think that I'm going to rebuild it this summer. I just have a few questions before I do so.

First, it has the L05 swirl-port heads that I know are garbage except for low end torque. I have a feeling these may be a culprit in my engine being tired. I don't really have the money to buy a new set of performance heads or I would. However, I have a couple of sets of pre-86 heads and I'm wondering if these would be better for overall performance?

Also, I have a Holley Pro-Jection Throttle body that I think I will use as it has a rated flow at 670cfm and I feel like that should improve performance.

I know you can't use the old style heads with a TBI intake manifold but I think I'm going to purchase an Edelbrock Performer EPS spread bore and an Adapter plate for my TB.

I also know that the camshaft in this motor is quite small for this application. I want to run something with good duration but I also don't want to over cam the motor either. Any suggestions?

Thanks for any advice.  

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waynep7122
I mow my lawn and find Chevys
Posts: 1130
Joined: 08/09
Posted: 02/10/12 07:58 AM

GM performance  and several others have TBI / vortech intakes.. that allow you to install Vortech heads..  a vast improvement.  not cheep.. but it keeps your engine fuel controls in place..  

F20043939

notice the angle of the intake mounting bolts are straight down.. not off at 45 degrees or so...


you can go 100 different ways from there...

i saw that you read the other post.. be sure to take some readings with a proper scan tool prior to tear down..

so you know what your base line live data should be on start up..  

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waynep7122
I mow my lawn and find Chevys
Posts: 1130
Joined: 08/09
Posted: 02/10/12 08:18 AM

oh.. before you invest in a motor swap..

please examine the ignition coil for signs of high voltage leaks...  i have had to change almost every coil i have come across on these...

you will also want to remove the distributer cap...   remove the rotor...  check carefully for cracks..

Smallcapheicracks

please also check the distributer shaft for movement.. it should NOT wiggle ...  i have found them so bad that the tips of the reluctor are banging the tips of the pick up coil...

there are REman distributers that look like this...  this is a V6 version.. the V8 versions are similar..

4Pointthreetbidistributer

you won't believe how much better the engine runs with just a distributer change..

don't worry if the module says transpo.. its still a quality unit..  these are just over 100 bucks at many parts stores.. and come with usually a lifetime warrantee..

if you preset the engine.. so the tips of the reluctor line up with the tips of the pick up coil..  then note the timing marks.. you can remove and install the new one..  and get it to start on the first try...

i normally do this with the rotor pointing toward the # 1 wire cap position..


more this evening..  

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beaukulele
V-6 Camaros rule!
Posts: 27
Joined: 06/11
Posted: 02/10/12 09:29 AM

will be sure to check the distributor. but the other reason I would prefer to swap to old style heads is price. Everything Vortec that I've looked at has been incredibly expensive. Also, this is also hopefully a stepping stone to a carburetor swap and a TH400 swap. Frankly, it isn't worth the extra money to me to go with Vortec Equipment for what appears to be nominal performance gains over the old style equipment which is priced much more conservatively. As previously stated I don't have a ton of money to spend and was merely asking if there is anything I would have to do to switch to the pre-86 style heads. Also, I said that I was planning on getting an adapter plate for the throttle body which I know will work on the intake I want to get.  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 02/10/12 09:36 AM

When you have everything together, try this. With the distributor cap off and #1 cylinder on its compression stroke.  Mark the #1 to a reference on the firewall.

Rotate the engine by hand, by the crank bolt,and see how much it moves before the distribtor moves. Then read the balancer.I'll bet its quite a bit. Unless you've replaced the timing chain at any time. Confused  

With that many miles on your engine you maybe surprised at the amount of total degrees, between the crank balancer and the #1 timing mark at the cap.

Yeah the cams for any trucks and Suburbans are made to have some low end torque and keep emissions in check. When you replace your cam try to stay in the area of .210 to .214 degrees duration. Lift .450 to .460 and LSA of about 112 to 114 degrees. Those numbers are estimates, but the LSA is wide so you will have a broad power curve. Thats what you need with a heavy vehicle. Grin  Cool
Thanks
Bob  

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beaukulele
V-6 Camaros rule!
Posts: 27
Joined: 06/11
Posted: 02/11/12 07:09 PM

thanks for that information. big helper. I know you do not have any specific number for those old heads so you can't know exact specs, but generally do you think the old style heads flow better than the stock L05 heads?  Confused This thing isn't going to be a performance machine just rebuilt. Also, would using a carb'd intake with the adapter plate be bad for flow? As I stated before I plan on switching to a carb sometime later but I would like to keep the TBI for now in effort to save money.  

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waynep7122
I mow my lawn and find Chevys
Posts: 1130
Joined: 08/09
Posted: 02/11/12 09:21 PM

yes.. you can use the carb intake.. with the TBI...   since you seem to want to switch to an earlier head..

be sure to check the intake bolt pattern when selecting heads and intakes..

there are 6 in a row...    or 2 then 2 at an different angle then 2 more ..

the TBI intake has a rather large puddle of HOT coolant under the floor of the intake manifold.. this heats the incoming fuel and air charge to better vaporize the fuel ..

carb intakes do not have this feature..

fixing the fuel and ignition systems problems... like are described above.. are a great place to start..   before tossing motors at it..

but i only fix them for a living..    replace them when there is damage like a bad rod bearing.. blown head gaskets.. burning oil... after i have verified that the PCV system is actually operating properly..  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 02/11/12 10:56 PM

If you have the part numbers off them it maybe possible to find information on them.  

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