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96' LT-4 Ladies & Gents; Plz chime in.

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Old 07-17-2018, 11:52 PM
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GG's70YellowConv
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Default 96' LT-4 Ladies & Gents; Plz chime in.

Hello fellow C-4 forum members!

Next week I will be looking at an LT-4 with about 73,000 miles. Being a C-3 enthusiast but wanting to step up to a C-4 or C-5, I no nothing about what normal maintenance, inherent weak factory issues that should have been addressed/replaced, if any. "I do know" that this is the engine to have if U seek performance! IMHO, every year corvette seems to have something/some part that can be improved upon. Just seeking your input for the sake of knowledge to educate myself on what questions to ask B4 I view the car.(P.S.--This car is not a GS.)

Sincerely,
Gene
Old 07-18-2018, 12:25 AM
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Originally Posted by GG's70YellowConv
Hello fellow C-4 forum members!

Next week I will be looking at an LT-4 with about 73,000 miles. Being a C-3 enthusiast but wanting to step up to a C-4 or C-5, I no nothing about what normal maintenance, inherent weak factory issues that should have been addressed/replaced, if any. "I do know" that this is the engine to have if U seek performance! IMHO, every year corvette seems to have something/some part that can be improved upon. Just seeking your input for the sake of knowledge to educate myself on what questions to ask B4 I view the car.(P.S.--This car is not a GS.)

Sincerely,
Gene
Be prepared to deal at some point with the OPTI spark distributor, although the 95 and 96 OPTIs are far and away the best of the lot, and if yours is an oem they can go in excess of 100,000 miles easy with maybe a rotor and distributor cap change (same as any distributor, just harder to get to); other than a fancy water pump, it's basically a Chevy small block...I know, with reverse cooling. So nothing much different than any other C4. One GREAT advantage is that an LT4 "Hot Cam" is a direct drop in without any other changes...just something to think about.

After working on those C3s, the first time you open that clamshell hood, it will be love at first sight.

Last edited by mtwoolford; 07-18-2018 at 12:26 AM.
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Old 07-18-2018, 12:42 AM
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OH THREE Z
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Since you are looking at a 96 it is highly likely the forward facing HVAC vents wont operate properly. Most 96's suffer from a poorly redesigned vaccum module that controls which vents the air comes out of. There is a fix but it requires you to be a contortionist.
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Old 07-18-2018, 09:50 AM
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Make sure the car has had the rocker recall done. You'd have to look up the break point vin, but there was a recall done because the roller rockers would drop a retaining ring/pin and explode. If it was under the recall, ones that have already had this done will have a sticker in the engine bay letting you know the work was performed.

Cheers,
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Old 07-18-2018, 10:01 AM
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If the LT4 fit the VIN 'restraints' a phone call to a local dealer would validate if the recall was thought to have been accomplished. It would mean at least the 'paper' was done. The work? Most likely.
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Old 07-18-2018, 11:47 AM
  #6  
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Originally Posted by RandomTask
Make sure the car has had the rocker recall done. You'd have to look up the break point vin, but there was a recall done because the roller rockers would drop a retaining ring/pin and explode. If it was under the recall, ones that have already had this done will have a sticker in the engine bay letting you know the work was performed.

Cheers,
Do you know where exactly in the engine bay this Sticker would be located? I bought a LT4 a few months ago and never knew there was a rocker recall.
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Old 07-18-2018, 01:47 PM
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Make sure its a real LT4 and not an LT1 that someone took red paint to the intake.
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Old 07-18-2018, 02:37 PM
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Originally Posted by RandomTask
If it was under the recall, ones that have already had this done will have a sticker in the engine bay letting you know the work was performed.
Wasn't aware of a sticker but...
Subject:
PRODUCT CAMPAIGN 96-C-07(a) - INADEQUATE RETAINING LOAD
HOLDING ROCKER ARM ROLLER PIN IN PLACE -- REISSUE --
---------------------------------------------------------------------------------------------------

Model and Year:
1996 CORVETTES WITH LT4 ENGINE
--------------------------------------------------------

To:
All Chevrolet/Geo Dealers
------------------------------------

General Motors has decided that CERTAIN 1996 Chevrolet Corvettes equipped with 5.7L engines (RPO LT4 - VIN Code "5") may have been built with rocker arms that have inadequate retaining load to hold roller attaching pins in the rollers. When there is inadequate retaining load, the pin may back out, with a resultant engine failure likely to occur.
To correct this condition, dealers are to replace the rocker arms.

NOTICE: Previously recieved rocker arms P/N 12551311 must not be used. The rocker arms previously received should have been returned to GMSPO (reference GMSPO Information Bulletin #96-128). Any vehicles previously repaired with P/N 12551311 rocker arms as a result of the canceled Campaign No. 96-C-07 must have new rocker arms installed.
VEHICLES INVOLVED
Involved are certain 1996 Chevrolet Corvettes equipped with 5.7L (RPO LT4) engines built within the following VIN breakpoints:
YEAR MODEL PLANT PLANT CODE FROM THROUGH
1996 Y-Car Bowling Green "5" T5100052 T5111116

1996 Y-Car Bolwing Green "5" T5600012 T5600363

Involved vehicles have been identified by Vehicle Identification Number Computer Listings. Computer listings contain the complete Vehicle Identification Number, owner name and address data, and are furnished to involved dealers with the campaign bulletin. Owner name and address data furnished will enable dealers to follow-up with owners involved in this campaign.
These listings may contain owner names and addresses obtained from State Motor Vehicle Registration Records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this campaign. Any dealer not receiving a computer listing with the campaign bulletin has no involved vehicles currently assigned.

PARTS INFORMATION

Notice:

A pre-shipment of part numbers 12557779 (Rocker Arms) and 10108625 (Rocker Cover Gaskets) will be sent to involved dealers of record the week of May 6, 1996. Pre-shipment will equal parts for approximately 40% of the number of assigned vehicles to be repaired. Pre-shipment parts will be charged to the dealers open parts account.

Parts are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "Involved Vehicle Listing" prior to ordering requirements. Normal orders should be placed on a DRO = Daily Replenishment Order. An emergency requirement should be ordered on a CSO = Customer Special Order.

Part Number
Description
Quantity / Vehicle

12557779
Rocker Arm Assembly
16

10108625
Gasket, Rocker Cover
2


OWNER NOTIFICATION

Owners will be notified of this campaign on their vehicles by Chevrolet Motor Division (see copy of owner letter included with this bulletin).

DEALER CAMPAIGN RESPONSIBILITY

All unsold new vehicles in dealers, possession and subject to this campaign must be held and inspected/repaired per the service procedure of this campaign bulletin before owners take possession of these vehicles.

Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward.

Owners of vehicles recently sold from your new vehicle inventory with no owner information indicated on the dealer listing, are to be contacted by the dealer, and arrangements made to make the required correction according to the instructions contained in this bulletin. This could be done by mailing to such owners a copy of the owners letter accompanying this bulletin. Campaign follow-up cards should not be used for this purpose, since the owner may not as yet have received the notification letter.

In summary, whenever a vehicle subject to this campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle.

SERVICE PROCEDURE

ROCKER COVER REMOVAL

LH SIDE

1. Note setting of all electrical devices and then disconnect battery.
2. Remove fuel rail beauty cover.
3. Remove booster vacuum hose from intake manifold.
4. Remove distributor vent hose from intake manifold.
5. Remove fuel rail cover attaching studs.
6. Remove hoses (2) from A.I.R. check valve.
7. Loosen A.I.R. check valve tube at exhaust manifold and pivot away from rocker cover.
8. Remove air cleaner assembly.
9. Remove accessory drive belt.
10. Remove generator bolts and rear bracket and lay generator aside.
11. Remove rocker cover bolts (4) and cover. Both rocker cover gaskets should be replaced with new gasket P/N 10108625.

RH SIDE

1. Remove fuel line beauty cover.
2. Remove PCV fresh air hose.
3. Remove rocker cover bolts (4) and cover.

ROCKER ARM REMOVAL AND REPLACEMENT

1. Rotate engine clock wise to TDC number 1 cylinder firing position. This can be done by watching number 1 cylinder valves as crankshaft balancer hub arrow approaches the 12 o'clock position. If a valve moves as arrow moves to the 12 o'clock position, the engine assembly is in the number 6 cylinder firing position. Crankshaft must then be turned one more revolution to reach number 1 cylinder firing position.
2. In this #1 firing position the following rocker arms should be replaced with new rocker arms P/N 12557779:
Exhaust: 1, 3, 4, 8
Intake: 1, 2, 5, 7
3. Loosen rocker arm nut and lift rocker arms from stud.
4. Install new rocker arms P/N 12557779. Be sure push rod is properly seated in the lifter and rocker arm.
5. Install nuts and torque to 25 Nm (18 lb. ft.).
6. Rotate engine clock wise one more revolution until hub arrow is again at 12 o'clock position. This is a number 6 firing position.
7. In this #6 firing position the following rocker arms should be replaced with new rocker arms P/N 12557779:
Exhaust: 2, 5, 6, 7
Intake: 3, 4, 6, 8
8. Repeat steps 3 through 6.
9. After rocker arm installation be sure that the roller tip of the rocker arm is squarely seated on top of valve stem. (Refer to 1996 Corvette Preliminary Service Manual Section 6A1B-13, Figure 14).

ROCKER COVER INSTALLATION

RH SIDE
1. Install rocker cover and bolts (4). Torque bolts to 12 Nm (106 lb. in.). New rocker cover gaskets P/N 10108625 should be used.
2. Install PCV fresh air hose.
3. Install fuel line beauty cover.

LH SIDE
1. Install rocker cover and bolts (4). Torque bolts to 12 Nm (106 lb. in.). New rocker cover gaskets P/N 10108625 should be used.
2. Install generator, generator bolts, and rear bracket. Torque front generator bolts and bolt with nut to 50 Nm (37 lb. ft). Torque rear bolts and bracket bolt to 47 Nm (35 lb. ft).
3. Tighten A.I.R. check valve tube at exhaust manifold and torque to 55 Nm (41 lb. ft).
4. Install hoses (2) from A.I.R. check valve.
5. Install booster vacuum hose to intake manifold.
6. Install distributor vent hose to intake manifold.
7. Install fuel rail cover attaching studs. Torque studs to 12 Nm (106 lb. in.).
8. Install fuel rail beauty cover.
9. Install accessory drive belt.
10. Install air cleaner assembly.
11. Connect battery and reset all electrical devices as noted in Step 1.
12. Install Campaign Identification Label.

CAMPAIGN IDENTIFICATION LABEL

Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label".

Each label provides a space to include the campaign number and the five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or a ball point pen.

Each "Campaign Identification Label" is to be located on the radiator core support in the area which will be visible when the vehicle is brought in for periodic servicing by the owner. When installing the new Campaign Identification Label, be sure to install the clear protective covering. Additional Campaign Identification Labels can be obtained from VISPAC Incorporated by calling 1-800-269-5100 (Monday-Friday, 8:00 a.m. to 4:30 p.m. EST). Ask for Item Number S-1015 when ordering.

Apply "Campaign Identification Label" only on a clean, dry surface.

CLAIM INFORMATION

Submit a Product Campaign Claim with the information indicated below:

REPAIR PERFORMED
PART
COUNT
FAILED
PART NO.
PARTS
ALLOW
CC-FC
LABOR
OP
LABOR
HOURS

Rocker Arm
Replacement
18
12557779
**
MA-96
V9790
1.1*

* For Campaign Administrative Allowance, add 0.1 hours to the "Labor Hours".
** The "Parts Allowance" should be the sum total of the current GMSPO Dealer Net Price plus 40'6 for the rocker arms and rocker cover gaskets needed to complete the repair.

Refer to the General Motors Corporation Claims Processing Manual for details on Product Campaign Claim Submission.
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Old 07-18-2018, 02:42 PM
  #9  
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Originally Posted by cuisinartvette
Make sure its a real LT4 and not an LT1 that someone took red paint to the intake.
Good Point also.

Besides them all being manual transmissions only, check the 8th character of the VIN
P = LT1
5 = LT4

People have made fake LT4 and even fake GS cars.
But it is much harder to mess with the VIN

This is one of the main reasons the GS cars have a unique VIN also.
12th character: 1 = Regular corvette , 6 = Grand Sport
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Old 07-18-2018, 03:13 PM
  #10  
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Originally Posted by GG's70YellowConv
Hello fellow C-4 forum members!

Next week I will be looking at an LT-4 with about 73,000 miles. Being a C-3 enthusiast but wanting to step up to a C-4 or C-5, I no nothing about what normal maintenance, inherent weak factory issues that should have been addressed/replaced, if any. "I do know" that this is the engine to have if U seek performance! IMHO, every year corvette seems to have something/some part that can be improved upon. Just seeking your input for the sake of knowledge to educate myself on what questions to ask B4 I view the car.(P.S.--This car is not a GS.)

Sincerely,
Gene

I own a C3 (71 LS5, auto) and a C4 (96 LT1, auto). You will notice the handling is night & day. My 96 does have C6 wheels & tires but the thing eats corners for breakfast with no noticeable body roll, unlike the '71. I think without a doubt it's easier to work on the C3. Computers & electronics are great but after 20yrs computers break, sensors fail, the dashboard lights up like a x-mas tree. The clamshell hood is nice but deceiving, you would think a simple tune up (plugs, wires, cap/rotor, fuel filter) would be easier, nothing could further from the truth. My C3 will come out of the hole a little better, big block torque. The C4 will take an off ramp at 85mph easy without a squeal where the 71 would be in the weeds.
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Old 07-18-2018, 05:27 PM
  #11  
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LT-4 tid-bits. When you open the oil fill cap, shine a flashlight in the oil fill opening, you will see “LT4” stamped into the head. Also, LT-4s had a crossover balance tube (runs transversely) that is just ahead of the spare tire carrier. I believe the rocker recall affected early LT-4s, but as others have mentioned it would be prudent to confirm either the recall had been performed, or, that the car was built after the fix was applied in production. Per Corvette Fever, February 1997; page 40. Authored by Hib Halverson: “LT4 also had two sobering downsides. Rocker arm failures caused by roller tip pins falling out developed into two recalls of a large number of LT4s during 1996. The initial fix did not solve the problem, so the the second recall affected all the cars of the first. We know that customers were told not to drive their LT4s because of an initial shortage of recall repair parts saw little humor in the situation. GM eventually fixed all the sick-rocketed LT4s at no charge. Those and the ones built after the solution were found were quite reliable.”

I have a late build LT-4 that was built in the last month of C4 production. Before purchasing my car 20 years ago, I was aware of the recall back then. I had the dealer verify my VIN was not part of the recall as it was resolved earlier in the production run. Good luck on your hunt!

B17Crew
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Old 07-18-2018, 06:04 PM
  #12  
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Originally Posted by bac22
Wasn't aware of a sticker but...
YEAR MODEL PLANT PLANT CODE FROM THROUGH
1996 Y-Car Bowling Green "5" T5100052 T5111116

1996 Y-Car Bolwing Green "5" T5600012 T5600363
Sorry, Im an idiot.

The last 5 digits of my VIN for my LT4 is 13,924. This means this car was the 13,924th vette made for model year 1996?.. and based on the aforementioned, came AFTER this rocker recall fiasco, right?
Old 07-18-2018, 08:32 PM
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Originally Posted by AgentEran
Sorry, Im an idiot.

The last 5 digits of my VIN for my LT4 is 13,924. This means this car was the 13,924th vette made for model year 1996?.. and based on the aforementioned, came AFTER this rocker recall fiasco, right?

yes and no. 13924 plus the 400+- grand sports that woukd have been built by then. if you ever got a chance to look at your build sheet my guess is that your job number would be around 14300

job number = total production to that point
Old 07-19-2018, 08:22 AM
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Originally Posted by AgentEran
Sorry, Im an idiot.

The last 5 digits of my VIN for my LT4 is 13,924. This means this car was the 13,924th vette made for model year 1996?.. and based on the aforementioned, came AFTER this rocker recall fiasco, right?
Might this be your VIN? 1G1YY225XT5113924 Might be easier for you to compare using the last 8 of the VIN vs attempting a match of just the last 5. It was quite easy to build a coupe VIN with an LT5.. A 'vert would look like this I believe 1G1YY3252T5113924

13924 doesn't mean sequence !

Last edited by WVZR-1; 07-19-2018 at 08:30 AM.
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Old 07-19-2018, 11:52 AM
  #15  
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Originally Posted by WVZR-1
Might this be your VIN? 1G1YY225XT5113924 Might be easier for you to compare using the last 8 of the VIN vs attempting a match of just the last 5. It was quite easy to build a coupe VIN with an LT5.. A 'vert would look like this I believe 1G1YY3252T5113924

13924 doesn't mean sequence !
Great.. now the whole world knows my VIN...

But, yes Sir that is indeed it.
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Old 07-19-2018, 04:12 PM
  #16  
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Check for broken gears in the electric seat functions. Also look for loose door panels.
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