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post #1 of (permalink) Old 03-17-2000, 12:23 PM
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Torque and Power Curves for S-10 4.3L

Does anybody know of a website that shows torque and power curves for a 4.3L Vortec engine? I want something like the graph on this website for Scouts

http://www.binderbulletin.org/images...b/345graph.gif

The main reason I'm asking is because when my S-10 is cold, it makes a really loud knocking noise around 2000-2500 rpm in second to fifth gear (and a little in first gear). The noise goes away once my truck warms up, but I hate hearing the knocking until then. Based on the graphs for the Scout 345, it looks like my problem might be related to higher torque output at around 2000-2500 rpm, but I want to make sure the 4.3 also has a similar maximum torque in the same rpm range as the Scout does.

Also, assuming higher torque is what causes my engine to knock (very loudly I might add), anybody have ideas on how I could remedy the situation and/or what might be the cause?

[img]/wwwthreads_images/icons/cool.gif[/img] Steven Fairchild [img]/wwwthreads_images/icons/cool.gif[/img]
[img]/wwwthreads_images/icons/wink.gif[/img] <font color=green> 96' S-10 4x4 </font color=green> [img]/wwwthreads_images/icons/wink.gif[/img]
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post #2 of (permalink) Old 03-17-2000, 12:50 PM
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Re: Torque and Power Curves for S-10 4.3L

Is the Knocking noise consistant throughout the rpm curve? starting at or around 1500 to 2000 and up? and you said it goes away after warmup or can it still be heard faintly. I have heard that some of the 4.3 vortecs had wrist pin problems similar to the small block of the same era(ie 95-up LT1). it had something to do with the pistons used in the motor.

1985 S-10 Blazer


post #3 of (permalink) Old 03-17-2000, 01:42 PM
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Re: Torque and Power Curves for S-10 4.3L

Does it sound like a spark knock? Do you have any trouble codes? my buddy had a bad knock sensor in his truck(chevy 1/2ton 4.3) and when the truck was warming up it would spark knock but only when under load (like starting out or trying to accelerate in 5 gear) because the computer was messing with the timing. but his had a trouble code. How is your oil pressure when the truck is cold? I have also heard about the wrist pin problem in 94' chevy pickups but not in the 4.3 although it is very possible.
hope this helps some.
good luck

nick


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post #4 of (permalink) Old 03-17-2000, 06:08 PM
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Re: Torque and Power Curves for S-10 4.3L

Thanks for the great leads. I think I can honestly say the combined knowledge of Chevy owners on this web site greatly exceeds that for my local Chevy repair shop.

Here's the requested info. The knocking occurs under normal acceleration between 2000-2500 rpm, but only when the engine is cold. Also, oil pressure seems normal (averages around 40-45 psi although I think it might get up to 60 psi at high rpm).

My problem could be faulty wrist pins, but it seems like this would be noticeable at any engine temperature(?).

Also, I can't really say if it sounds like "spark knock" because I have never heard an improperly timed engine knock as loud as mine does (although I'm sure it is possible). I have always had the feeling, though, that my computer is messing with my engine's performance when the engine is cold. Also, the check engine light has never come on since I've had the truck. Of course, it the knock sensor is faulty, then I guess that would mean the truck would be knocking w/o the computer knowing anything about it. Hmmm.......If I run down to my local Chevy dealer's diagnostic machine will they be able to tell if I have a faulty knock sensor just by hooking it up to the diagnostic machine? Also, any other ideas as to what would make my S-10's computer @*#! with the performance at low engine temperatures? Thanks again for the help.

[img]/wwwthreads_images/icons/cool.gif[/img] Steven Fairchild [img]/wwwthreads_images/icons/cool.gif[/img]
[img]/wwwthreads_images/icons/wink.gif[/img] <font color=green> 96' S-10 4x4 </font color=green> [img]/wwwthreads_images/icons/wink.gif[/img]
post #5 of (permalink) Old 03-17-2000, 09:07 PM
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Re: Torque and Power Curves for S-10 4.3L

From what i have heard about the problems that the small blocks had it only made the knocking when it was cold and they were really bad thi time of year when the temp was below 40 degrees. If the noise is that loud then it is probably not a spark knock. My friend has a 98 sonoma with a four cylinder thats makes a knocking when it is cold but it not that loud but it has done it since the day he bought it the dealership told him it is nothing to worry about.(so he does'nt but any noise on a new truck would bother me.) If there is a bad sensor it should throw a code but a computer maybe still able to help you.
other then that i have know idea without hearing it.
best of luck with it
nick

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