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Ask Gm Tech (Cam) Your Own Question
Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1667
Experience:  GM Grand Master Technician 2007. 14 year experience.
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I have a 1989 Chevy S-10 and rebuilt the engine. I am

Customer Question

I have a 1989 Chevy S-10 and rebuilt the engine. I am thinking it is one tooth off on cam. As I drive at normal speed it seems ok, but when I try to accelerate it backfires through the carb
Submitted: 10 months ago.
Category: GMC
Expert:  John Bryant replied 10 months ago.

Hi, thank you for posting your question to Just Answer. I am John, an ASE Certified Auto Technician with over 45 years of real world experience in dealerships and the aftermarket. I was the owner/operator of a facility for 20 of those years. So I am confident we can resolve your problem together. Please remember I do not know your skill level. I cannot see, smell, hear, or touch the vehicle so it may take a few back and forth replies or a phone call to get to a satisfactory resolution. I will make every effort to get you all of the information you may need with the expectation you will give me a positive rating once you are satisfied. Please be aware that I am usually working with a few people at a time so occasionally it may take a few minutes to respond.

Customer: replied 10 months ago.
I have a 1989 Chevy S-10, 2.5 Eng. I rebuilt and put new cam and cam brs in. I replaced the fiber gear with a steel one. However the steel gear the marking was on the tooth instead of the valley. The truck runs and can drive but, when I try to accelerate too fast it runs terrible and backfires through the carb. I need to know the setting for the closing and opening of the intake and exhaust vale so I can use a degree wheel and check the cam
Expert:  John Bryant replied 10 months ago.

This is a throttle body 2.5 engine?

Expert:  John Bryant replied 10 months ago.

I have attached a document that will help you verify if the timing marks are set correctly. If they are than we should be able to run through some basic diagnostic tests to isolate the problem OK.

Customer: replied 10 months ago.
Not what I am looking for. I need the degrees....When the exhaust valve closes after TDC and when the intake valve opens BTDC
Customer: replied 10 months ago.
The mark on the cam is wrong. It is on the tooth not the valley. I want to degree the cam in
Expert:  Mike S. replied 10 months ago.

That information is usually not found in repair manuals, although it might be found with the manufacturer of the camshaft. Which camshaft did you install and where did you purchase it from?

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