Hello out there,

This is my first post here, and I am paitently waiting on the return of my 400 from my engine builder and I would appreciate some input. The motor will have TMI (kieth black hyperutectic) pistons with stock heads, producing 9.4:1 comp. The heads have been ported and polished, stainless steel valves with 3-angle grind, and running comp roller-tip rockers. Wieland intake with Holley 670 cfm carb. The cam is a comp custom grind, full roller conversion with hardend push-rods and guide plates. 268 degree with .520/.520 lift. 110 degree lobe seperation with 7 degree overlap. This is basically a roller version of the cam in the Hod Rod "down and dirty" article from 1998. My engine builder contacted kieth black to ask about ring gap placement, the head tech on the phones that day highly recommended running a water/methanol injection set up to avoid dentonation, and recommended never exceeding 33 degrees total advance. Acording to kieth black, the kb-2347-30 model piston that TMI sells is a circle track piston designed for high octane racing gas. Now, a good NA methanol kit is only $300, a small price to save an expensive engine build. I am wondering if anyone has set up such a kit, and if it is really nessasary? Seems like alot of peole on this site have used this piston.
Thanks in advace,
Cody

 

A Compression ratio of 9.4:1 is not so high as to require Water/Methanol injection with a cam that has a late Intake Valve Closing angle like an XE268.

If you will post the full cam spec with Seat-to-Seat duration as well as duration @0.050 and the intake valve center angle, I can calculate the Intake Valve Closing angle. Or you can simply supply the IVC and I will calculate the Dynamic Compression Ratio.

My estimate is that this cam has an IVC of 64 Degrees ABDC (Advertised), and the DCR is about 7.6:1. That is well within the limits for pump fuel, possibly midgrade fuel.

 

If you need it I recommend the Snow Performance injection kit. New motors may take a while to start needing higher octane.

 

comp camshaft spec card:
GRIND #: FC 5433 /5216 H 110.0
SPC INST 1:
SPC INST 2:
J. DIAM: STD INT EXH
VALVE ADJUSTMENT HYD HYD
GROSS VALVE LIFT .525 .529
DURATION @ .006
TAPPET LIFT 267 280
VALVE TIMING OPEN CLOSE
@ .050 INT 6 38
EXH 49 1
SPECS FOR CAM INST. @ 106.0 CENTERLINE
INT EXH
DURATION @ .050 224.00 230.00
LOBE LIFT .304 .306
LOBE SEPARATION 110.0 FIRING ORDER STD
ROCKER ARM RATIO 1.73 1.73
Thats all the info I have on my cam
Thanks
Cody

 

Based on the above cam spec, the Intake Valve Closing angle is 59.5 degrees ABDC. In a motor with 9.4:1 Static CR, this cam will produce a Dynamic CR of 7.8:1. This should run good on 92 or 93 Octane fuel. I would recommend a 180 degree tstat if 91 Octane fuel is to be used.