X-heads / 6 Barrel combo porting

72bluNblu said
Decent numbers on the heads!

I'd be careful with the cam if you're going to run 3.55's, especially with tall rear tires.

I ran 3.55's in my Duster for awhile, with a larger cam than what you're looking at, and 26" tires. I went with the 3.55's because with the 26" tires that was about the best I could do and still manage decent freeway speed without running around at 4k+ rpm all the time with the 833 4 speed I was running. Anyway, the 3.55's and clutch slip to take off got old after not very long at all. Sure, if you drive it like you stole it and drop the clutch at 3k all the time it's fine, but that doesn't exactly work in traffic.

Anyway, my set up is with a stock stroke 340, .060" over, with a Lunati HFT with duration @ .050 (Int/Exh): 234/242; Gross Valve Lift (Int/Exh): .513/.533; LSA 110. Lunati recommends 3.73's, all I can say is I'm a lot happier with my current 4.30's, 27" tires and T56 Magnum. Advertised RPM range is 2200-6400, I think 2200 is a little optimistic. Below 2,500 there isn't a ton of power. Over 3k and she's a beast, pulls all the through to 6k+.

Compression is 9.8:1 with 308 heads, ported and flowing what you see below. Just the intake side, I don't have the exhaust numbers
LiftIntake Flow CFM@28”
0.200165.7
0.250184.3
0.300202.2
0.400243.8
0.450258.7
0.500263.9
0.550257.2
0.600252.7

So anyway, long story short if the plan is 3.55's and any rear tire 26" or taller you want a smaller cam than what I run for sure, unless you like pedaling to get it going.
Click to expand...
Thanks for the input.
This engine build is going to be a replacement in my Dad's 70 'Cuda. Currently 440 / auto. The rear is a Dana. My 70 'Cuda is donating it's TKO (old Keisler kit) and since it is a small block and Dana (S60) we can even use the driveshaft. I am going to be using the T56 that I have for a defunct Valiant project. Currently his car has 295/50's (26.8") but he wants to go with a 255's (27").

TKO ratios:
First Gear Ratio: 3.27:1
Second Gear Ratio: 1.98:1
Third Gear Ratio: 1.34:1
Fourth Gear Ratio: 1.00:1
Fifth Gear Ratio: 0.68:1
*in post #1 I mistakenly referred to the trans as a TKO-600

Tremec's calculator says the 1:1 cruise speed will be 50 mph on a 27" tire. With the .68 OD he will be at 73 mph. That is going to be perfect for him as he lives in an area where he will predominately drive 55 for about 10 miles, hit the interstate for about 5 miles, and then he's in town. If he wants to drive to Oklahoma City it's 20 miles on the interstate.

My 'Cuda has the same gear ratio, the 408 has a 224/228 @.050 cam, and currently has the TKO in it. When I had it on the road it drove beautifully. I have 335/35-19's on the car and their at 26.89"

After taking into consideration Rumblefish's cam recommendation I am still leaning toward a cam like what's in my 408 for my Dad's 340 but just a touch less at ~218-222 @ .050". Dad wants a stock stroke and mine is a 4" arm. We are still working on finding him a 340 at the moment but it sounds like @coloradohill has one that may be just right with this build.