I need help with 350cid noise!!

CoyCaller · 08-17-2007, 01:32 AM

I put a 350 (only 3,000 miles on overhaul but has been sitting for 3 years in a shed) into a pick up this week. It runs great but has a little tick while idling. (maybe a rocker, not sure) When we took it out on a test drive we could no longer here the tick. But when we accelerate hard there is a very loud chatter from the same side of the engine that we suspected the loose rocker arm. When we let of the of the accelerator the noise stopped and is not heard while maintaining speed at any RPM.

When we stopped the pick up and put it in park we revved the engine and could not make it chatter. It only chatter under fast acceleration when a load is put on the engine.

It doesn't seem to miss on a cylinder when the noise is heard either.

Could it be that a lifter is stuck after sitting for so long?

If so, what do I do?

If not, what is it?

silicon212 · 08-17-2007, 10:36 AM

Unfortunately, if it's only making this noise under load, I would suspect a wrist pin issue with the piston on the offending cylinder. You might want to take it easy on this engine, lest it grenade on you.

777stickman · 08-17-2007, 10:46 AM

Could it be an exhaust leak? With help put it in gear with the brakes set and apply some throttle (not a lot) and see if you can pin point where the noise is coming from.

silicon212 · 08-17-2007, 11:34 AM

You know, that's another possibility. Come to think of it, I once had an EGR valve gasket leak that produced a similar sound under similar conditions.

CoyCaller · 08-17-2007, 01:18 PM

I don't think that it is a wrist pin.

It's more of a loud dieseling noise than a chatter.

It is not an exhaust leak, I am sure of that.

It could be that it is not a one cylinder issue. It was really hard to tell while my brother was power stalling the pick up so that I could get a better listen while the hood was up.

I had a guy in town that said it could be a timing issue. He told me to try and retard the timing and see if that eliminated the noise.
I'm going to try that tonight.

We have a stock pick up mud drag tomorrow so I doubt that we are going to take it easy on the engine. If it is a wrist pin, we may be the star of the show when she "Grenades". We'll just start over.

Thanks for the input guys.

silicon212 · 08-17-2007, 02:01 PM

Quote:

Originally Posted by CoyCaller

I don't think that it is a wrist pin.

it's more of a loud dieseling noise than a chatter.

That's exactly what a wrist pin sounds like.

maxwedge · 08-17-2007, 03:00 PM

Kill 1 cyl at a time se if the noise goes away this will pinpoint which one, if it changes, usually the problem is a rod bearing or if it is worse cold then a wrist pin.

CoyCaller · 08-20-2007, 12:31 AM

Sorry Silicon,

I'm a rookie. I haven't heard all of the noises an engine can make. Sorry for the bad noise description. My brother and I were getting a super stock class pick up ready for the local mud drags and ran into this problem. He is no better at these things than I am and we agreed that dieseling is what it sounded like.

Anyway we figured it out. We retarded the timing and it ran great on Saturday. We got smoked but we were still proud of what we accomplished in the amount of time we had to work on it.

Any ideas on getting more power with a small budget.

We are running a 1986 Chevy 1/2 ton 4 wheel drive. We have a 350cid engine, turbo 350 transmission, and 4:10 gears. The pick up has a 10 suspension lift and a 4 in body lift and we are running 35x12.50x15 tires.In order to stay in the super stock class we have to pull at least 13lbs of vaccum.

Our runs will inprove a lot when we get a narrower tire but we are lacking a little in power. We are thinking of putting a stock 454cid but we don't know if we will lose the rpms we are getting from the small block. From what we have seen, the high rpm small blocks are holding there own with the big blocks. The tracks are only 150 feet long so a snappy start is always a plus. A staller would help there but my brother likes to drive around town and thinks that a staller on the pickup would ruin his cruising experience.

What do you think.

silicon212 · 08-20-2007, 01:28 AM

Quote:

Originally Posted by CoyCaller

Sorry Silicon,

I'm a rookie. I haven't heard all of the noises an engine can make. Sorry for the bad noise description. My brother and I were getting a super stock class pick up ready for the local mud drags and ran into this problem. He is no better at these things than I am and we agreed that dieseling is what it sounded like.

Anyway we figured it out. We retarded the timing and it ran great on Saturday. We got smoked but we were still proud of what we accomplished in the amount of time we had to work on it.

Any ideas on getting more power with a small budget.

We are running a 1986 Chevy 1/2 ton 4 wheel drive. We have a 350cid engine, turbo 350 transmission, and 4:10 gears. The pick up has a 10 suspension lift and a 4 in body lift and we are running 35x12.50x15 tires.In order to stay in the super stock class we have to pull at least 13lbs of vaccum.

Our runs will inprove a lot when we get a narrower tire but we are lacking a little in power. We are thinking of putting a stock 454cid but we don't know if we will lose the rpms we are getting from the small block. From what we have seen, the high rpm small blocks are holding there own with the big blocks. The tracks are only 150 feet long so a snappy start is always a plus. A staller would help there but my brother likes to drive around town and thinks that a staller on the pickup would ruin his cruising experience.

What do you think.

Ok, I know the noise you're talking about now. It's called detonation and if it's that bad - it's usually not good for the engine (broken spark plugs, broken piston crowns/rings/lands, damaged rods and wrist pins and bent valves. It's not a good thing, but happy to see you got it figured out.

As for the transmission, if you run a TH700R4, you can use a wicked high stall converter and still get good cruising economy due to the torque converter clutch (removes the stall speed from the equation).

As for RPMs, the rule is the shorter the stroke, the higher the windup.

GreyGoose006 · 08-28-2007, 09:22 AM

Quote:

Originally Posted by silicon212

As for RPMs, the rule is the shorter the stroke, the higher the windup.

within reason...
and there are exceptions as well, as with any rule.

silicon212 · 08-28-2007, 10:48 AM

Quote:

Originally Posted by GreyGoose006

within reason...
and there are exceptions as well, as with any rule.

No, it's pretty steadfast. A larger stroke gets you more torque for a given displacement, while a smaller stroke gets you better revs. It's about leverage - with a longer throw, you get more torque but also a higher moment-of-inertia which in itself consumes more power, thus limiting the longer stroke RPM in two engines of otherwise equal displacement.

Perhaps 'consumes more power' is incorrect, however it will require more power to get it to a particular RPM than the shorter stroke will. Something about that gosh-darn flywheel effect.

Perhaps, over time, both engines can achieve the same RPM - however the shorter stroke gets there FIRST and leaves FIRST. Again, due to the flywheel effect.

GreyGoose006 · 08-28-2007, 04:58 PM

Quote:

No, it's pretty steadfast

well i was thinking more about the effect of lightweight pistons ect...

Quote:

Perhaps 'consumes more power' is incorrect, however it will require more power to get it to a particular RPM than the shorter stroke will. Something about that gosh-darn flywheel effect.

that and higer piston side loads.
of course there is the whole offset crank theory (i forget the exact term) where the crank is offset to minimize side loads on the power stroke.

Quote:

A larger stroke gets you more torque for a given displacement, while a smaller stroke gets you better revs.

while this is true, and i am not disputing this statement, i would more easily accept the statement that a longer stroke gets you more torque for a given displacement, while a larger bore gets you more power.

at least in my mind that makes more sense.

power follows revs and torque. more specifically, power is a direct function of torque * RPM.

to say that bore is the key to power implies that you need to have a high rpm to acchieve it, whereas to say that torque is the key to power is to imply that you are not revving high

silicon212 · 08-28-2007, 07:22 PM

Quote:

Originally Posted by GreyGoose006

power is a direct function of torque * RPM.

More specifically, horsepower is torque * RPM / 5250.

Engines, or any methods of rotational power generation, are measured in torque. This goes for dynamometers as well - dynos do not measure horsepower in the strictest sense - they measure torque and convert that number, along with RPM, to horsepower. Pure power is torque.

Also, to clarify something, a longer stroke in and of itself, will not cause additional piston side loading. Short rods with a long stroke, however, will. A prime example being the Chevy 400 SB. This had a 3.75" stroke, coupled with 5.565" rods (measured center to center, small end to big end). This is also why people who make stroker motors tend to want to run special pistons with longer rods - either 5.7" or 6" on these stroker motors.

Lightweight pistons can help counteract the effect of stroke on RPM, but the same pistons on a shorter stroke engine will run higher RPM. It is what it is.

Remember the golden engine rule - torque is power. Horsepower is torque over time. Without torque, there's no horsepower.

GreyGoose006 · 09-04-2007, 08:52 PM

the way i think about it is this.

torque (think big inline-6 diesel) can get a lot of work done slowly

power (think F1) can do less work, but can do it extremely quickly

silicon212 · 09-04-2007, 10:57 PM

Quote:

Originally Posted by GreyGoose006

the way i think about it is this.

torque (think big inline-6 diesel) can get a lot of work done slowly

power (think F1) can do less work, but can do it extremely quickly

You're getting the concept of power wrong.

Torque is what gets your vehicle started from a standing stop. It's what provides burnouts. The amount of available torque directly determines how fast your car accelerates from 0 to whatever speed. More torque, quicker acceleration. Remember, you don't swap gear ratios to get more HORSEPOWER - you swap them to change the amount of available torque, measured at the wheels. Horsepower is what maintains vehicle speed, while torque is what gets it there.

Remember - power = torque. Horsepower = torque*rpm/5250.

A way to look at it is this - take a car with a 400HP engine, and put it up against a Chevy Silverado with the Duramax engine which produces 300HP. If the car had the same weight and gear ratio as the Silverado did (hypothetically of course), the Silverado would eat your car for lunch. Even though it has 100 less HP, it has 670 ft.lb. torque, nearly double what your 400HP engine would likely have. It just peaks at a lower RPM (high compression diesels won't spin as fast as a lower compression gasoline would).

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