open lm motor?

[racin6mod]

looking to build a new motor for our lm wounding what's the most common cu in. and heads I'm thinking about and 18 degree,LS or maybe sb2 377 up to 430. just looking for ideas for now not looking to buy someone else's motor at this point.

[grt74]

if you can get it hooked up bigger is better from my experience,we have a 450 and everyone has said it would be too much,its the easiest driving engine we have and all the national guys have 415 or bigger,I've seen some really good running 430 sb2's,where we race its all about qualifying and heat races,feature time 600 to 700hp is all you need,if you have options,i would build a 415-430

[sj valley dave]

We run a 421" with SB2's and we really aren't down on HP on the heavy tracks in qualifying. Our problem is when it drys off and goes slick, our driver has a heavy foot...

[powerslide]

We run a 421" with SB2's and we really aren't down on HP on the heavy tracks in qualifying. Our problem is when it drys off and goes slick, our driver has a heavy foot...

get on the dyno and learn what to change to kill off some torque

[mab475]

Better fix is disconnect the secondaries.

[drtrkr244]

A lot of touring drivers are using two ignition systems. The second one has timing reduced 4-6 degrees, used for slick track conditions.

[Matt49]

Another quick fix that a lot of people don't think about is moving the throttle linkage down on the pedal assembly. It slows down the motion ratio of the drivers foot. Quick to change and can be pretty effective.

[Brian Gray]

If your running eldora. 500+ inches if your racing local around 410 will get it done. I've seen much less do well also. Opt on the side of durability isy opinion . 430's are probly the best all around option but larger strokes mean more fatigue on critical parts.

[Necrosis]

Big inch, small manifold, and 2 different carbs. One for hammer down, and one for slick. And I cannot stress enough, the importance of smooth, linear linkage that suits the driver. It's even money if you went with a 377 SB2, as it is to build a 440. No replacement for displacement.

[SS Motorsports]

Exactly. There is no substitute for cubic inches.

[7uptruckracer]

Most big companies got away from the big cubic inch motors for driveability issues. You want it right when its time to win the money. I've driven monsters that where fine and dandy and all the sudden would blow the tires off halfway down the straight with no pedal modulation. It's not all about the HP number or the torque number on the dyno its when and where the numbers are. The 415 IMO is a great all around good power for Qual, and really manageable in the slick. We had a ridicously big Draime motor that was the worst driving thing I've ever seen but it had an awesome HP number!

Exactly. There is no substitute for cubic inches.

[hpmaster]

Most big companies got away from the big cubic inch motors for driveability issues. You want it right when its time to win the money. I've driven monsters that where fine and dandy and all the sudden would blow the tires off halfway down the straight with no pedal modulation. It's not all about the HP number or the torque number on the dyno its when and where the numbers are. The 415 IMO is a great all around good power for Qual, and really manageable in the slick. We had a ridicously big Draime motor that was the worst driving thing I've ever seen but it had an awesome HP number!

First I know people will disagree, that's ok. Torque peaks over a small RPM range not horsepower is what blows the tires off. In the past 3 years we have built and extensively dynoed several engines. In several different sizes of engines with different head designs we worked to get a very flat torque curve and have had success to make torque lines vary only 20 ft pounds in the entire usable RPM range. It is a combination of heads, intakes, cam designs, cam timing, headers and carbs. Often very popular and also expensive headers only make to problem worse, when tested on a dyno and some parts cost far more than the gains you get. Dyno testing, retesting is the key and it isn't cheap. The stroke of an engine is an aspect the builder has the least control of in developing torque. You can make a long stroke motor have a very flat torque line the problem is it makes a lot of torque to start with. When it comes to engine part selection monkey see monkey do is not at all the way to go. Drivers love hammer down tacky tracks the problem is how many nights do you really get that? Things like disconnecting the secondaries and adding restrictors will kill power but simply do no address at all what the problems are. JMHO

[sj valley dave]

Over time, we have figured out some ways to make it easier for him. We run 2 ignition boxes, one from the crank trigger and the 2nd box retarded 5*. Also use a throttle stop. Going to play withe linkage next year to increase the amount of distance he will have to move the throttle..

[zeroracing]

Honest question regarding open LM motors, what hp are the big guys honestly topping out at? Hear crazy numbers but anybody actually know an honest number?

[Brian Gray]

Dynos are relative but 1000/1000 is not a problem now days.

[go2fast]

About 870 @ 7,400 rpm and 705 tq @ 5600 on a 438 wide bore with a race carb with a big carb you can add 10 more horse to that and that is on a new dyno

[hpmaster]

Big numbers are always impressive to look at on a dyno sheet but it's drivability that wins races.

[go2fast]

Brand new out of pro power shop last week

[hucktyson]

Go fast Brian Gray would have squeezed another 295 ft lb of torque out of it no problem lol

[grt74]

About 870 @ 7,400 rpm and 705 tq @ 5600 on a 438 wide bore with a race carb with a big carb you can add 10 more horse to that and that is on a new dyno

agree with above,a good rule of thumb is 2 hp for every cubic inch,thats from your top engine builders,and yes they are getting them very drivable

[SLM98]

New dyno or not they can make the numbers what ever they want. Big numbers sell engines.