Engine power gain question!

[pfd60]

I am looking to get more power for qualifying. I am looking for advice on what my best route is for power and financially. ? Put a new 13* top end on my existing aluminum 403 18* Chapman headed motor or, put a higher lift stroke crank and get more HP/ TQ that way if its worth it, or sell my motor and look for something with more power. I think my motor is fine after qualifying but that is a very important part of the night where I have been racing. Thanks for your thoughts in advance.

[let-r-eat]

I'd sell what I have and build another. There is a big misconception out there about stroke and hp. Stroke with just allow you to reach the HP potential of the heads sooner. You could put a 3.2 stroke crank or a 4.0 stroke crank in your 18* engine and make the same hp.

The difference is where it makes it. The 3.2 stroke may have to turn 9500 to reach hp potential of heads and the 4.0 stroke may reach it at 6500.

[MasterSbilt_Racer]

I'd sell what I have and build another. There is a big misconception out there about stroke and hp. Stroke with just allow you to reach the HP potential of the heads sooner. You could put a 3.2 stroke crank or a 4.0 stroke crank in your 18* engine and make the same hp.

The difference is where it makes it. The 3.2 stroke may have to turn 9500 to reach hp potential of heads and the 4.0 stroke may reach it at 6500.

True, but low end torque will get you off the corner!

[pfd60]

Thanks for the input. So would I gain a decent amount of power from putting a brodix 13 * top end on my existing 403? Or like Let r eat said just sell it? So heads make most of the power??

[powerslide]

I would say keep the 18 degree as a spare and build a new wide bore motor. Used engines rarely bring anywhere near what you have in them is why I say hold on to it.

[hall99]

i would say that you top end is gonna be better with the 13* heads but your probably gonna require more gear to get you off the corner.

[pfd60]

Thanks for the input. I really appreciate it

[Brian Gray]

Easiest most full proof way to gain power. Add more compression . If you just need to boost the power and and you like the way the current motor performs, just add another point on the CR!

[pfd60]

Thank you guys for the suggestions. I do like the smooth power of the motor. I'm going to make a gear change to help get through the corner while its heavy. I have a few more races this year until I do anything. Turn it 8200 ish instead of 77-7800.

[fast_crew]

Add gear to it and tighten valve lash .004"

[let-r-eat]

Thank you guys for the suggestions. I do like the smooth power of the motor. I'm going to make a gear change to help get through the corner while its heavy. I have a few more races this year until I do anything. Turn it 8200 ish instead of 77-7800.

"Easiest most full proof way to gain power. Add more compression . If you just need to boost the power and and you like the way the current motor performs, just add another point on the CR!" ~~Brian Gray


That's not always true. Big misnomer actually.

[Matt49]

Thank you guys for the suggestions. I do like the smooth power of the motor. I'm going to make a gear change to help get through the corner while its heavy. I have a few more races this year until I do anything. Turn it 8200 ish instead of 77-7800.

"Easiest most full proof way to gain power. Add more compression . If you just need to boost the power and and you like the way the current motor performs, just add another point on the CR!" ~~Brian Gray


That's not always true. Big misnomer actually.

I'm no engine expert but I know enough to know that if you add compression and use the same fuel, you could actually lose power.

[let-r-eat]

Matt 49,

We'd all be running diesel's, lol. You are correct that fuel requirements change for sure when raising compression. Meltdown city could soon be at the end of the next very short road.

[save the racers]

14.2 is what alot of people are using as the upper limit on c/r.If you are using a 3.75 crank switching to a 3.875 will get you 20 to 30 ftlbs of torque and 10 to15 hp.I would talk to a head expert and see if you can get any more from what you have.

[pfd60]

Ok thanks guys for the input. I know I need some more power to qualify but I don't know if my budget will allow me to do it! . I know my best option would be to buy I wide bore but I can't afford one.