Compression Ratio for a 347 Stroker w/ Vortech S-Trim

We've run 9.5:1 on pump gas with over 12psi on boost however we are using a tuner, PMS, etc...to keep track on the timing and fuel. It also denpends how efficent the chamber in the heads are, etc..

Probe makes a nice 4cc flat top

With a 61cc chamber STOCK for a TFS you get 9.2:1 with a o deck, if the pistons are in the hole .010" it is 9.0:1. With a 58cc head (NOT KNOWING EXACTLY HOW FAR YOUR WERE MILLED) it will raise it .34 to 9.54:1 at a o deck.

cro699 said:

So, just use the 306 engine I have now, add the heads and supercharger, and then install 42's instead of using the FMU? I want whatever will work best and still allow it to be somewhat streetable.

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Yes the FMU is an annoyance at higher RPM's it tends to cut out. So the idea is getting bigger injectors to eliminate that issue completely and just have the car tuned after with the 42lb injectors. It will be a sweet set-up, I would not worry about the cam at all. The only worry is making sure you get the right piston for those heads. Trickflow makes a good head but those rotated valves only give you so much to work with as far as pistons. I would go with Forged Probe pistons they make a great piston and fairly cheap for the twisted wedge heads.

Here's a pic of a 14.2cc dish Probe from one of my customers blower motors, you can see it is cut for both inline and twisted valves.



I would also go with a 42# inj although with a 36#-38# you can make 450RWHP+ reliably with a blower, no FMU with only a 255lph intank and a T-rex.. This is keeping the FP at 36psi and the injectors are running well under 80% duty cycle. The larger inj and no FMU is a better set-up in the long run.

I tend to put 42# inj on most of the street cars I build with stroker, aftermarket top ends and blowers. If it is a 94-95 car and they want to run a stock EEC with no chip then I use a 36# or 38#.

Check out motorsportsdigest.com It will tell you all you need to know.

65ShelbyClone said:

Seriously, that guy would start spinning as soon as he got into boost(just past the tree) and it wouldnt stop until after the traps, even when he was pedaling it.

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Never understood the point of having a car like that, pretty useless with that much power.

I expect it had stock suspension and the 17" street tires werent helping either. I saw some road racers over the weekend that could use power like that....with 12" wide slicks. I have probably 275-300rwhp and its more than enough with 205s .

Well you really need to find out the cc on the heads, however with a 3" stroke, 5.09" rod 8.2" deck (pistons are .010" in the hole) and a 1.600" comp height piston, 60cc CHAMBERS you are 9.289:1 with a 4cc flat top PROBE SRS SERIES 10682-.030 If you decided to need a set of those I deal with Probe pistons Even if the heads have been milled down to 58cc chamber you would only be 9.5:1. You do realize that you will need to have the rotating assembly balanced with the new pistons, rings, etc...

I would use a Fel-Pro 1011-1 head gasket NO ORING, head studs.

Bore Size: 4.030
Gasket Bore: 4.100
Piston Top Land Dia: 3.995
Stroke: 3.000
Connecting Rod Length 5.090
Compression Height: 1.600
Deck Height: 8.200
Ring to Top of Piston 0.250
Gasket Thickness: 0.040
Valve Notches Volume: 4.00
Dome Volume: 0.00
Volume Head: 60.00
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:COMPRESSION RATIO: 9.289
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calculation variables:

Piston to Deck: 0.010
Crank Throw: 1.500
Vol. Above Top Ring: 0.90 cc
Piston to Dec Vol.: 2.09 cc
Gasket Volume: 8.65 cc
Volume Clearance: 75.65 cc
Cylinder Volume: 627.08 cc
CID: 306.014