Big CI motor small carb.

[7uptruckracer]

Roller Cam
Gross Valve Lift - Intake 705 - Exhauat 667

Duration at .020 Tappet Lift - Intake 287 - Exhaust 291

Valve Timing @.050 - Open Int 22BTDC - Exh 58BBDC
Close Int 56 ABDC - EXH 24 ATDC

Lobe Sep. 107 Intake CL 107 installed 3* Retarded

Duration @50 258 Intake - 262 Exhaust

Could not open the attachment for some reason. but Honestly, I have never heard of rules saying that you have to run more carb. Its usually how much restriction they put on the induction system to even the field. That's just crazy.
Regardless, you can put an out of the box 500cfm 4412 on it or a more restrictive intake. If you have a nice carb you are running now, you could lose about 20ftlbs and 15-20hp by going that route alone and the intake might take away another 10hp and 15ftlbs of torque if you have a " good one " on it now.
All else being said, having too much power is one of the best problems you can have unless the power is like a light switch ( either on or off ).

[hpontap]

427 cubic inches and a 14.5:1 compression ratio with that camshaft. That combination with the big 4" stroke crank and the compression is going to make a lot of torque. It is screaming cylinder pressure. You could widen the lobe center out to a 110 or 112 as suggested earlier and more duration would also help raise the rpm that the camshaft makes power at. Should take away some of the abruptness. Good luck with it.

[7uptruckracer]

Thanks for the good advice! One question though why do I want to raise the RPM it’s makes power at? Wouldn’t that make my problem worse being I operate in the 5700 to 7200 range? It makes peak TQ at 4500 now. It got better or more manageable adding gear so I was farther on the backside of the curve?

427 cubic inches and a 14.5:1 compression ratio with that camshaft. That combination with the big 4" stroke crank and the compression is going to make a lot of torque. It is screaming cylinder pressure. You could widen the lobe center out to a 110 or 112 as suggested earlier and more duration would also help raise the rpm that the camshaft makes power at. Should take away some of the abruptness. Good luck with it.

[hpontap]

Typically, adding duration will raise the effective rpm range is all that I meant by that. The camshaft you are running looks small to me for such a large cubic inch engine and the compression ratio along with that is going to make a lot of cylinder pressure which makes it harder to control. Changing the timing events with the camshaft, you can lower the dynamic cylinder pressures at given rpms.
You are correct about turning engines past the curve, we used to turn one of our dry slick motors 9,200 so it was easier to drive when the tracks slicked off. Talk to a good cam grinder and give him all of your information. He can put you on a cam that will calm it down.

[7uptruckracer]

Ah ok I follow you now it will move the whole band to wider ends and spread it out. My builder is very good but has not built many of the mod motors to these rules and he did exactly what I told him but I should have been more specific I told him I wanted to kill power until certain rpm but didn’t know the track wouldn’t handle it later period so I should have done what you said and stretched it out through the whole band. This was a custom Comp I usually use Schneider out west but went with what the builder wanted to put in per my Info we knew we might have to change it we knew we were getting a repave but they didn’t do what we thought so we can’t use the power like we thought! Thanks this gives me a good idea what I need to look at.

Typically, adding duration will raise the effective rpm range is all that I meant by that. The camshaft you are running looks small to me for such a large cubic inch engine and the compression ratio along with that is going to make a lot of cylinder pressure which makes it harder to control. Changing the timing events with the camshaft, you can lower the dynamic cylinder pressures at given rpms.
You are correct about turning engines past the curve, we used to turn one of our dry slick motors 9,200 so it was easier to drive when the tracks slicked off. Talk to a good cam grinder and give him all of your information. He can put you on a cam that will calm it down.

[hpontap]

Good luck and update us on what you did and how it works out.

[fastford]

have you tried taking a few degrees of ignition timing out of it? reason i ask is we use to run a unit inside the car that you could adjust the timing while on the track , until they banned it , best trick we ever tried to reduce wheel spin on a slick track......

[7uptruckracer]

Yes 7 degrees lol

have you tried taking a few degrees of ignition timing out of it? reason i ask is we use to run a unit inside the car that you could adjust the timing while on the track , until they banned it , best trick we ever tried to reduce wheel spin on a slick track......

[fastford]

wow , that should have knocked it in the head.......

[7uptruckracer]

I run up front but I’m going to work on setup too. Balance rear drive better. A combo of all the advice should take care of it

wow , that should have knocked it in the head.......

[7uptruckracer]

No update yet car has been out on the jig!

[50j]

Be cautious with the slower timing, that can be hard on the engine. EGT readings will change.

[stock car driver]

No update yet car has been out on the jig!

On the jig since March when you started this post? So zero races this season?

[7uptruckracer]

Started this post while I was racing Car got destroyed May 26th, running up front but someone dive bombed me, and junked it head on into the wall. Well known chassis guy in this area and he still has it as of today....Only ran 6 races I believe this year.

On the jig since March when you started this post? So zero races this season?

[hpontap]

Hate to hear that. I know how it is to lose a good car.
Did you ever make any changes to it and if so, how did it do?