i just purchased a Scat balanced 331 kit and what i recieved was a crank for a 347 and pistons for a 331. my question is: they want to swap out the pistons for the correct ones that will make it a 347. what problems will i need to be aware of if i do this. will it still be balanced? should i send it all back and have a new kit sent out? thanks for the help
331 or 347?
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What rods did you get... I or H?
Lightweight/ultra-lightweight or standard?
You should ask the Dealer you bought them from the same question (knowing what you have in your hand) and comparing that to what they tell you.
Your paperwork should include the bobweight and total weight removed or added to attain the 28oz imbalance.
Lightweight/ultra-lightweight or standard?
You should ask the Dealer you bought them from the same question (knowing what you have in your hand) and comparing that to what they tell you.
Your paperwork should include the bobweight and total weight removed or added to attain the 28oz imbalance.
The 347ci pistons with that stroke (3.4") require a CH of 1.090". That will be the difference in weight.
That should change your bobweight imbalance correction, but since I don't balance rotating assemblies, I don't know to what extreme.
The choices you have are;
1. return the whole assembly for the unit you requested in the first place (best option IMO)
2. have them send you the 5.315" rods, have everything balanced locally (oiling ring not in the pin)
3. have them send you the 1.090" pistons, have everything balanced locally (oiling ring in the pin)
Get some sort of refund on the balancing because it's going to cost you about 300.00 to have that done @28oz imbalance.
Did you buy this kit from Coast High Performance?
That should change your bobweight imbalance correction, but since I don't balance rotating assemblies, I don't know to what extreme.
The choices you have are;
1. return the whole assembly for the unit you requested in the first place (best option IMO)
2. have them send you the 5.315" rods, have everything balanced locally (oiling ring not in the pin)
3. have them send you the 1.090" pistons, have everything balanced locally (oiling ring in the pin)
Get some sort of refund on the balancing because it's going to cost you about 300.00 to have that done @28oz imbalance.
Did you buy this kit from Coast High Performance?
Kdubslugga
Active Member
I did a lot of research on this topic myself. I opted for the 331, simply because my car is street car. Not to say a 347 cant be a street car but from what i found, 347s prefer naturally aspirated and high compression, 331s like boost. If a 347 is not what YOU want id send it all back!!!!
Dealing with Coast High Performance is a GOOD THING!
I cannot believe they sent you that FUBAR setup without going through QA first.
Don't be afraid of the 347 over the 331.
They cost the same to build, yet the 347 will absolutely walk away from the 331 in an acceleration competition.
Kdubslugga
Active Member
Yeah not buyin that statement. At the time I bought my 331 the 347 was 200 more, they are now the same price. Anyway, the guy I talked to on the Phone at DSS Racing highly recommended a 331 even though the 347 cost more.. Simply because they last much longer and make more horsepower all the way up to 6500 rpm, at 6500 its nearly 40 more HP than a 347. Now obviously the 347 makes up for this with more low end torque. You cant go wrong with either, and this is just 1 company telling me this but hey, they know more than I do! If its gonna see more street than the track id def stick with the 331
Thanks 347HO for the great info.
CHP has been great and are willing to do what ever i want them too. they suggested to just swap the pistons but i was not sure what that would do to the balance. they told me today that as long as they wieght the same as the ones i'm returning it should be fine. if this is true then Hello 347.
CHP has been great and are willing to do what ever i want them too. they suggested to just swap the pistons but i was not sure what that would do to the balance. they told me today that as long as they wieght the same as the ones i'm returning it should be fine. if this is true then Hello 347.
Lemme ask my dealer if those pistons weigh the same.
I'm inclined to say "not" due to the fact the taller compression height piston has more piston above the and below the pin.
The guy you talked to at DSS obviously has no clue.
He probably thinks an engine doesn't need air and fuel to make power either.
At say 6000rpm, which engine do you think is moving more air/fuel per cycle?
Now, if you want to talk about acceleration... that is a whole different subject which can be applied to the 331 vs 347.
Okay, here's what my dealer posted to me for you;
[quote author=woody link=action=profile;u=1 date=1282967271]
let me go weigh each right now.
[/quote]
[quote author=woody link=action=profile;u=1 date=1282967627]
435 on the 1.175 and 442 on the 1.090, on this batch anyways, they vary, if there is a larger discrepency simply get the weight needed by changing the pins
[/quote]
So, as you can see, it's opposite what I had thought.
[quote author=woody link=action=profile;u=1 date=1282967271]
let me go weigh each right now.
[/quote]
[quote author=woody link=action=profile;u=1 date=1282967627]
435 on the 1.175 and 442 on the 1.090, on this batch anyways, they vary, if there is a larger discrepency simply get the weight needed by changing the pins
[/quote]
So, as you can see, it's opposite what I had thought.
so with that info it's seems that CHP was right ands they could match the weight of the pistons they already sent me. do you know if there is any room for fluctuation in that number or does it need to be exactly the same. I'm going to double check the weight of the pistons i have current a the new ones when i get them.
Kdubslugga
Active Member
Agree to disagree. I get it, your proud of your 347. More power to ya! "pun intended"
I now understand why you're proud of your ignorance, and heading toward stupid because you refuse to learn, even when faced with facts and proven with physics.
Here's another clue for you;
What's easier and cheaper to accomplish, 1.35hp per ci or 1.29hp per ci?
The target is 450hp @ the wheels N/A.
I wouldn't accept a rotating balance error of .5grams and higher.
Most average machine shops can get inside of .3 grams easily.
CHP is REALLY good with Customer Service. Just drop your questions on them, and someone who "knows" will have the answer, or someone will get you the answer as soon as possible.
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