Trying to build a 408 and can't seem to get anything going. My block has been at the machine shop for 1 month and so far nothing has been done. I stopped in 2 weeks ago and asked about the progress, and nothing. They blamed this on Scat and said that Scat wasn't responding. 2 weeks later I stopped in and again they blamed Scat again. I gave them a WTF or two and asked if they were too busy for me. Is something up with Scat, or do I need to find a new machine shop?
Is something up at Scat?
- Thread starter Leadfoot
- Start date
-
I’ve never put my machine shop in a position where they ordered the parts. I ordered and pay for my desired parts and drop them off for balancing and sizing. I don’t trust people enough to follow through so I do the leg work.
Must be something up with Scat. Summit usually carries rotating assemblies for building a 408. It appears as if 90% of the kits they offer are backordered and won't ship until October 2nd.
Scat Engine Rotating Assemblies DODGE 5.9L/360 Mopar small block LA - Free Shipping on Orders Over $109 at Summit Racing
Scat Engine Rotating Assemblies DODGE 5.9L/360 Mopar small block LA - Free Shipping on Orders Over $109 at Summit Racing
Once again you can not go by summits shipping date. You must call the manufacturer
Jax340Dart
Well-Known Member
I bought a rotating assembly from Scat late last year with the same problem. They had everything in stock but were waiting for the crank to be made. I think it was 2 or 3 months later that I got everything
@PROSTOCKTOM sells molnar rotating assemblies and usually seems to have stuff ready to ship... should talk to him...
Slow boat from Chy-na?
replicaracer43
Grumpy Old Man
- Joined
- Oct 10, 2008
- Messages
- 6,051
- Reaction score
- 7,867
I could have built you one and shipped it to you by now! Still can if you are interested!
RCR, you ever do a 426? I don't get the 408 thing when a 426 is around the same price... That's my goal once i find a 360 roller block
replicaracer43
Grumpy Old Man
- Joined
- Oct 10, 2008
- Messages
- 6,051
- Reaction score
- 7,867
Yeah, but in my opinion, I dont see any real advantage over the 4" stroke, and it also increases rod angle, thrust load on the cylinder and a shorter piston comp height. Most ALL of the stroked sbm builds are cylinder head limited anyway. But again, that's just one guys opinion!
You are the first person to give me a legit answer to that question
Everyone acts like 408 over 390 is a MASSIVE difference.. but 408 to 426 doesn't matter at all.. but without much backup as to why. Thanks
mcodecuda
Senior Member
I waited over a year for a custom ground flat tappet solid lifter cam. Now I’m hearing that the manufacturers are no longer offering them and the cost of the lifter has almost double.
If I'm not mistaken, with the additional stroke to make the 426 sb the rings are up into the wrist pin area, requiring support rails, possibly not ideal for a car that is driven. As @replicaracer43 has stated, less than optimal rod angles, short piston, side loading, and limited cylinder head architecture. If you have ever been in a 408 without W2, W5, Indy, or seriously worked standard port LA heads, they nose over fairly quickly in the high 5, low 6000rpm range. If you add more cubic inches the rpm limitations become more pronounced. Something that can't be measured on a dyno is an engines rate of acceleration, when strokes get very long, engines don't gain rpm as quickly as one with a shorter stroke. Though I don't really race, I've seen at the track where shorter stroke engines can get of the line quicker than some of these really big stroker. I feel the 408 is a nice balance with good heads.
Last edited:
well.. i know it's a .180 extra stroke (i think it was) nothing mentioned bout oil support rings or anything.. was just thinking if i was gonna spend the money to go 408 why not go bigger, just wanted legit reasons why people don't
Bigger isn’t always better.
Been told that a lot have you?
The 408" vs 426" debate!
I can give you two of the most important reasons why to stay with a 408" aside from the rod angle debate.
1. A 426" cost more to build than a 408" because they require custom pistons ($600-$700 over the 408" cost). If you need a replacement you'll wait months to get it over a shelf piston.
2. There are very, very few heads available that can properly provide the air flow a 408" needs, so when you build a 426" all you do is lower the potential RPM range the engine can make power at.
3. Having sold Molnar parts for 13 years and K1 prior to that I can tell you most guys just want a 426" because it sounds cool. Build the 408" and tell your friends it's a 426"
I'll sell a customer whatever they like, but I would never sell them a 426" without first explaining why a 408" is a much better engine combination.
Tom
I can give you two of the most important reasons why to stay with a 408" aside from the rod angle debate.
1. A 426" cost more to build than a 408" because they require custom pistons ($600-$700 over the 408" cost). If you need a replacement you'll wait months to get it over a shelf piston.
2. There are very, very few heads available that can properly provide the air flow a 408" needs, so when you build a 426" all you do is lower the potential RPM range the engine can make power at.
3. Having sold Molnar parts for 13 years and K1 prior to that I can tell you most guys just want a 426" because it sounds cool. Build the 408" and tell your friends it's a 426"
I'll sell a customer whatever they like, but I would never sell them a 426" without first explaining why a 408" is a much better engine combination.
Tom
Last edited:
Thanks Tom
Are you set on using Scat parts? If not, I might suggest as has @PROSTOCKTOM , Molnar parts. In my 408 built in 2015, K1 was used, these are top shelf parts. Scat I beam rods with Chevy Journals, and Diamond piston. A quick look around and it seems these parts might be available, plus it gives you a lighter wrist pin. As @pittsburghracer stated, collect your parts yourself and bring to a competent shop. You save the markup this way also.
I apologize to the OP for posting this, but it seems relevant if you're parts shopping.
If you plan on using a 360 block Molnar only offers two crankshaft strokes 3.79" and 4.00" both are only available with the stock 2.125" rod journal size.
Therefore you have to use a 6.123" rod with the stock .984" wrist pins. This is great since most of the off the shelf pistons are made for the .984" pins.
When you use a 340 block the options open up. You can choose 4 different strokes. 3.58", 3.79", 4.00", and 4.125"
The first 3 can be had in either the stock 2.125" rod journal or 2.100" SBC rod journals. The 4.125" is made to use 2.00" SBC journal rods.
I sell all my kits using the 6.123" 4340 H-beam rods for both the 340 and the 360 blocks because of ICON piston availability. This holds the cost down and allows for easier piston
replacement down the road should you damage one. With custom pistons now costing $1600 to $2800 a set using an off the shelf piston makes the most financial sense.
Tom
If you plan on using a 360 block Molnar only offers two crankshaft strokes 3.79" and 4.00" both are only available with the stock 2.125" rod journal size.
Therefore you have to use a 6.123" rod with the stock .984" wrist pins. This is great since most of the off the shelf pistons are made for the .984" pins.
When you use a 340 block the options open up. You can choose 4 different strokes. 3.58", 3.79", 4.00", and 4.125"
The first 3 can be had in either the stock 2.125" rod journal or 2.100" SBC rod journals. The 4.125" is made to use 2.00" SBC journal rods.
I sell all my kits using the 6.123" 4340 H-beam rods for both the 340 and the 360 blocks because of ICON piston availability. This holds the cost down and allows for easier piston
replacement down the road should you damage one. With custom pistons now costing $1600 to $2800 a set using an off the shelf piston makes the most financial sense.
Tom
replicaracer43
Grumpy Old Man
- Joined
- Oct 10, 2008
- Messages
- 6,051
- Reaction score
- 7,867
I personally like the 3.79 stroke combos, good ballance of extra stroke but not excessive. Add a set of W2s or indy heads, it's a great combo
Then you have to buy custom made pistons.
The beauty of the 4.00" stroke crankshaft is you can get 3-4 different dished choices, flat top, or domed pistons off the shelf and they are readily available.
Using the KISS Method is good for the bank account and it always allows for ease of replacement parts should they be needed.
Tom
Last edited:
replicaracer43
Grumpy Old Man
- Joined
- Oct 10, 2008
- Messages
- 6,051
- Reaction score
- 7,867
I agree with everything your saying
I would like to see how fast an “all out “ or semi all out 360 could go. Matt ran 6.54 with a stock crank 360, flat top pistons, ported open chamber Edelbrock heads, 727, 4.10 gears, ported victor360 intake but nothing like I’m doing now, 750 alcohol carb, .620 roller cam, and I think he babied it and was shifting at 6400 rpm. Car race ready was 3200 pounds.
I'm going to go talk to the machine shop this week and see if this could be a viable option.
-
