more problems building motor
07-06-2007, 03:24 AM
#1
1st Gear Member
Thread Starter
Join Date: Jul 2006
Posts: 57
more problems building motor
Got a call from my dealer and they were told by Scat that they dont have any 6.0 inch rods available but they can substitute 6.2 inch rods and then a piston with a pin higher up to compensate. Is this possible on a 393 kit (not that I m into the idea). I think the 408 uses the 6.2 rod. But then they would need a different crank also. I may just get 6" rods form someone else, have them ship the remainder of the parts and then add them to the kit. The kit is supposed to be a balanced assem. but then with different rods i suppose I will have to have the entire kit rebalanced. Im new to a bunch of this aftermarket stuff. I normally only build stock engines. I will never get this engine together.[:@] to top it off my current 5.0 is dieing a horrible death. Verege of overheating all the time. No power, Crappy mileage. Anyone herd them trying to sub parts like this? And will it work?
07-06-2007, 10:34 AM
#2
Join Date: Jun 2007
Location: South Jersey
Posts: 25
RE: more problems building motor
Longer Rod Pros
•
Less rod angularity
•
Higher wrist pin location
•
Helps resist detonation
•
A lighter reciprocating assembly
•
Reduced piston rock
•
Better leverage on the crank for a longer time
•
Less ignition timing is required
•
Allow slightly more compression to be used
before detonation is a problem
•
Less average and peak piston velocity
•
Peak piston velocity is later in the down stroke
•
Less intake runner volume is needed
Longer Rod Cons
•
Closer Piston-to-valve clearances
•
Makes the engine run a little more cammie at
low rpm
•
Reduces scavenging at low rpm
Shorter Rod Pros
•
Increased scavenging effect at low rpm
•
Helps flow at low valve lifts (a benefit if the
heads are ported with this in mind)
•
Slower piston speeds near BDC
•
Allows the intake valve to be open longer with
less reversion
•
More piston-to-valve clearance
• Can allow for a shorter deck height
Shorter Rod Cons
•
More rod angularity
•
Lower piston pin height (if the deck is not
shorter)
•
Taller and heavier pistons are required (again, if
the deck height is not reduced)
•
More ignition timing is required for peak power
•
In general, the pistons are heavier
• More intake runner volume is needed
07-06-2007, 11:18 AM
#4
1st Gear Member
Thread Starter
Join Date: Jul 2006
Posts: 57
RE: more problems building motor
I already have a custom cam built for the build with the 6.0 inch rods. I wonder if the 6.2 inch rods may interfere with the piston to valve clearance. Shouldnt if I can get the same compression ratio. I was told the the ratio will not change. Maybe I will go with the longer rods just to get the engine built.
07-07-2007, 05:46 PM
#10
1st Gear Member
Join Date: May 2007
Location:
Posts: 140
RE: more problems building motor
ORIGINAL: roblarss
Got a call from my dealer and they were told by Scat that they dont have any 6.0 inch rods available but they can substitute 6.2 inch rods and then a piston with a pin higher up to compensate. Is this possible on a 393 kit (not that I m into the idea). I think the 408 uses the 6.2 rod. But then they would need a different crank also. I may just get 6" rods form someone else, have them ship the remainder of the parts and then add them to the kit. The kit is supposed to be a balanced assem. but then with different rods i suppose I will have to have the entire kit rebalanced. Im new to a bunch of this aftermarket stuff. I normally only build stock engines. I will never get this engine together.[:@] to top it off my current 5.0 is dieing a horrible death. Verege of overheating all the time. No power, Crappy mileage. Anyone herd them trying to sub parts like this? And will it work?
Got a call from my dealer and they were told by Scat that they dont have any 6.0 inch rods available but they can substitute 6.2 inch rods and then a piston with a pin higher up to compensate. Is this possible on a 393 kit (not that I m into the idea). I think the 408 uses the 6.2 rod. But then they would need a different crank also. I may just get 6" rods form someone else, have them ship the remainder of the parts and then add them to the kit. The kit is supposed to be a balanced assem. but then with different rods i suppose I will have to have the entire kit rebalanced. Im new to a bunch of this aftermarket stuff. I normally only build stock engines. I will never get this engine together.[:@] to top it off my current 5.0 is dieing a horrible death. Verege of overheating all the time. No power, Crappy mileage. Anyone herd them trying to sub parts like this? And will it work?
Big problem if you are building a 393 then you don't need a 6 inch or a 6.2 inch rod.A 393 is a stock 351 rod 5.996a stock 302 piston and a scat 3.85 stroke crank Ive build many like this and have had no problem and only cost about $750 for every thing.Who ever told you to use a 6 inch rod is not that very knowledgeable and should not be putting motors together.If you use a 6 inch rod your crank jornals need to be turned down smaller and a lot of other things need special detail,andalso if you use an early block that has been decked more then 5 thousands your piston will pop out above the deck and then custom head gaskets are needed.I could go on forever but I dont want to confuse you or get you lost on the topic.
Thanks Matt