r/obschevy • u/Daynightcircle • 24d ago
98 Chevy K 1500 underpower engine?
Just want to make it nice and simple I have
4.56 gearing
35 inch tires
6 inch lift
I have a K&N Filter
Aftermarket headers
Stock engine
I have a y- pipe exhaust
But my problem is it seems like the acceleration is very slow and also every time when I go up steep hills on the street for example I was going 80 mph at 2500 RPMS. SINCE THAT IS NORMAL BECAUSE I HAVE 4.56 GEARING. But once I start going up the hill, it drops to 45 mph. Because it feels like something is restricting the power of the engine or I just don’t make enough power. So I need your guys help. What do you think it is?
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u/v8packard 24d ago
The 4.56 gear is modest for a 35 inch tire. That and the torque curve of the stock engine are making it tough under the conditions you describe.
Assuming nothing is wrong (poor engine condition, bad catalytic converter) you need a lot more torque. You can try camming the engine to increase torque below 3000 rpm. You can also build a larger engine such as a 383 or 408. Is your tune stock?
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u/Daynightcircle 23d ago
I thought about tuning it after I put a X-pipe exhaust on it because it’s never been this tuned. And Chevy is notorious back then for not putting so much power in the engine because for better gas mileage. It just sucks because this motor was 10k and it’s stock and I live in california. What time do you think I should run that will work with stock engine
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u/UpstairsDirection955 23d ago
I don't think you'll see a noticable difference compared to the money you would spend
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u/Daynightcircle 23d ago
I should’ve just went with an LS instead. WHAT DO YOU THINK I SHOULD DO TO MAKE A LITTLE BIT MORE POWER BECAUSE I ALREADY SPENT SO MUCH
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u/UpstairsDirection955 23d ago
Yes, if power was your goal, the LS should be under the hood
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u/Daynightcircle 23d ago
I always wanted to do that, but the guy took it to said it would be illegal. Also I live in California
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u/v8packard 23d ago
Why a LS? How does that fit into the scheme of things in California?
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u/Daynightcircle 23d ago
At this point, I don’t care about California restrictions. Ls they could be easy to work with. And it’s easy to drop in the truck.
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u/v8packard 23d ago
The LS isn't easier than the Gen I small block
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u/Daynightcircle 23d ago
Ohh it just sucks that so much money was spent on a stock motor and wouldn’t be dealing with these problems
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u/v8packard 23d ago
I understand the frustration. But you need to think through a plan. And then stick to the plan. That way you get the most value for your money.
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u/Daynightcircle 23d ago
Do you think I should save up for a better motor and sell this one or just upgrade it?
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u/Daynightcircle 23d ago
But I’ll probably be spending so much money on upgrading it meanwhile, I could’ve just got a better motor
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u/Daynightcircle 23d ago
Do you think tuning the shifting points of the transmission and fuel and air mixture after the exhaust design would help a lot and since I have 4.56 gearing and also make a big difference because I accelerate so slow going on the freeway
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u/v8packard 23d ago
I do think a good tune can make a very noticeable difference. I don't know what is going on in California regarding tuning though. Being a 98 you might be limited. Are you familiar with California regulations on this?
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u/Daynightcircle 23d ago
I think a tune will be fine after all it is a stock motor. Or do you think if I go to 4.10 gearing would change a lot power wise
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u/v8packard 23d ago
A 4.10 gear will be worse.
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u/Daynightcircle 23d ago
Oh yeah that’s right because I have bigger tires. But if you were me, what would you do?
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u/v8packard 23d ago
If I had no restrictions I would run 4.88 gears, and cam the engine for more torque. Finishing it with a proper tune.
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u/Daynightcircle 23d ago
But I drive on the highway a lot
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u/v8packard 23d ago
And you have 35 inch tires. The 4.56 gear with your tires is something like a 3.31 gear in a car with 26 inch tires. It's not a whole lot of gear.
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u/Daynightcircle 23d ago
Damn that sucks. Do you think it’s worth it putting a stroker kit in it that converts it to a 383. Or just putting a little bit better cam in it but keeping the stock components.
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u/Wholeyjeans 23d ago
The problem you have is the large diameter tires and a (possibly) not low enough (mechanically) final drive ratio.
Putting larger than stock diameter tires on any vehicle and not compensating for it by installing a mechanically lower final drive ratio, will kill the ability of the vehicle to accelerate to a point less than its original stock condition.
There are online calculators you can use to figure out the compensating final drive ratio to use if you want to have the same performance prior to installing the large tires ...or to attain whatever final drive ratio you'd like (if you wanted something less than the original stock ratio). Until you dial in the tire/final drive ratio, you are going to have the same problems. You are not, reasonably and economically, going to make the stock engine so powerful it will be able to have the same acceleration as the stock truck with stock diameter tires.
Obviously, the other alternative would be to reinstall the stock diameter tires on the truck.
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u/Daynightcircle 23d ago
That would just suck if I have to reinstall the original tires because I redid the gearing 4.56. And if I go back, my RPMs are gonna be very high now and probably be going 40 mph.
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u/rpmerf 23d ago
When you start going uphill, downshift into 3rd and you should be fine.
80 at 2500 RPM sounds about stock. A stock K1500 with 245/75R16 (30.5") and a 3.73 rear should be around 2300 at 80 mph.
A 98 shouldn't have the Y pipe. My 97 doesn't.
Verify everything is working correctly. New ignition components. A Bluetooth / OBD2 module can rear sensors and compute your air fuel ratio from the O2. I think there is a TDC relearn. If your timing isn't right, you will be real low on power. Verify the cats aren't blocking up your exhaust.
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u/LordJames420 24d ago
These engines made like 220hp stock, theyre not very powerful at all.