speedj2

I'm hoping to get some pearls on racemotor care from both a mechanical standpoint as well as from a drivers perspective.

I'm fairly new to high horsepower roadracing and have had more than my share of broken parts. I'm starting to wonder if it is my design and set-up that's flawed, or if it's my driving.

Is a 400 sbc too large a stroke to rev consistently to 7400... over a 30 min race?

How long can you keep the motor at or near redline?

Is a large mechanical roller camshaft just too hard on the valvetrain to allow a motor to last over the course of a season? (approx 10 30 min races, 20 20min warm up sessions.

Are there any driving techiques that might help the equipement last? Presently, I've gotten beond banging the gears or stabbing the throttle. I do think that I'm staying reasonably with-in the rev limit, perhaps exceeding the limit at the end of a long straight stretch by 1-200 revs, ... unknown about the downshift though...

Is feathering off the throttle near the end of a long straight, (after you've hit redline), better than keeping your foot into it for another second or two?

thx for your perspectives. cj

Too me, it seems that my engine is running at or near red-line for too long. Can a SBC reliably do this?

Slalom4me

Respondants might consider posting to the OP's existing thread
over in C4 Tech to keep everything together.

Advice on care of racemotor

.

AU N EGL

Speedj what gears are you running??

DREGSZ

Can a 3.75" crank, solid roller motor run at 7400 rpm all season?

Maybe it can, maybe it can't.

with 3.73 ratio in 4th gear, you are talking about an extended stay at 149 mph.
What track are we talking about??

Nuts and bolts?
Having blown a few 415 CI solid roller motors and retired from racing due to the cost of new motors.

I would never build beyond a 10:1 CR, Hyd roller motor at 450 +/- hp motor. and I'll win on my driving ability.

Yes I would stay in it rather then shift at the end of the straight but usually I will shift around 5300 rpm, as soon as the torque in that gear drops off.

I used to race all the way around the track w a 377 and 4.10 rear gears at 7400 rpm, all race long. that motor lasted 2 seasons.
which was 2 seasons longer then my 415ci

The answer is it may last, but I doubt it, and if it does, you are definitely tearing down in the off season
good luck

speedj2

Thank you for your responses and patience:

I do have another thread on the C4 tech board... they suggested that I also ask here.

When I pull onto the grid, I notice right away that there's no one else running a 400 sbc. I was hoping that it was because of class regulations... but I wonder if its more a reliability question?

I see that you are from Gig Harbor, so you know my local track, PIR.

My car's pretty light, and the big motor makes it quick enough, even if I am a little green. So far the fastest lap is a 1: 12.5 non-chicane... and I'm running DOT's, so it's quite a handfull.

But, I'd sure like to know if it's the set-up or the driver that's wrecking all those shiney race parts.

I've noticed twice when reviewing the video that the motor seemed to start going south on T-6, it would send out a brief gasp of blue smoke from under the hood and then would loose a rod bearing by the end of the back straight (T-10). From t-3 to t-8 I'm up in the revs some, but only part throttle. Could this be a problem?

I'd be happy to mail you a video if you had a moment.

Thanks craig johnson

DREGSZ

It's always the driver
I've only instructed at PIR once, every other track day or race I've had is in California at Laguna Seca, T Hill, Sear's, Button Willow and once at Reno Fernly.
Even though I'm in Washington I directed 8 days at T hill and 2 at Laguna last year.

Revving shouldn't kill a 406. My 415 (Dart) w 3.875 stroke revved to 7200 (I couldn't find my 7400 pill it went in the previous motor) but I still shifted at 5300. (it didn't live out a season, but that was the last time I'll use a solid cam, too finicky)

I think the reason you don't see GM 400s is they aren't that plentiful anymore, they were popular with circle track guys and now scarce, and the center bores are pretty close together and have overheating issues. Actually, overheating of 400s w the center cylinders is a big bone of contention among 400 fans. it's a split opinion.

I had one destroked to 377 with a Crower solid flat tappet cam and 6.2" rods for torque, before my dart solid roller motor. My water never got hot, but my oil temps were insanely high. I'm guessing in retrospect maybe a manifold vacuum leak but no oil dripped?

My 377 finally laid down to cracked internal webbing in the second main.
I drove from a 14th place rain qualifyer into a second place finish w no oil pressure and the crank walking all over the place. (that was after nearly 3 seasons without a freshening)

If the motor goes south and the block survives, build a 377. you give up a little torque but they spin to the moon and love it It's a totally different feel then a stroker, it feels like a race motor should feel.

There was a guywith a motor done at the same time as mine, from the same builder with the same setup and a bigger cam spinning 9000 in a drag car. that was my builder's "thing"

My next motor will probably be a 355 or 383 stroker w hydraulic roller cam and nothin fancy. I'd like to see 400-450hp and worry about the driving not the motor.
After having 600 hp, I think 450 is about right for balance of speed and handling in a C4. There were so many seconds per lap left on the table even with the 377, I had no business going to a 600 hp motor, it just made the car harder to drive, (but shockingly fast in the straights)

I hope that helps.

Why would you lose a rod bearing? bottom end oil? or rod bolt/torque issues? were you using a Canton pan? I used a Canton 3rd gen Camaro pan. it was a 1/2" deeper and narrower then the vette pan. We had to clearence the front crossmember diagonals, (with a mallet) but it sat further away from the headers because it was narrower.
Also, I've heard that Hi Volume oil pumps put too much oil on the top and don't leave enough in the pan creating cav on the pickup and maybe bottom end oil issues, but I'm not an expert on this stuff.

Good Luck
Evan

davidfarmer

unlike the trans and brakes, the engine doesn't care how hard to stab it, or about feathering on/off. Obviously, feathering could be easier on the drivetrain, especially the trans.

1. If you are using forged parts, 7400rpm is NOT a problem. Warm the oil up before revving, and warm up the drivetrain a lap or two also before hitting them hard.

2. Get an accusump. Even if it doesn't help with starvation (which I think they do), it is great to be able to pre-lube your engine at every startup. Eliminating a second or two of dry running with EVERY start is extrememly valuable for engine life.

Slalom4me

From the 'Analysis' feature of Engine Analyzer Pro V3.3 regarding
a 3.875" stroke at 7,400 RPM

The refererence to drag racing & F1 suggests aluminum or titanium
to me.

.

Slalom4me

It might spin as a result of elongation of the big end of the rod,
rod bolt stretch or breakage.

Evan. In looking back, do you have any other thoughts about your
engine durability besides the possibility of a vacuum leak and the
high oil temperatures?

What was the cracked webbing of the mains attributed to?

377 ci = 4.155" x 3.480". 7400 RPM => 4292 FPM

415 ci = 4.125" x 3.875". 7200 RPM => 4650 FPM
415 ci = 4.125" x 3.875". 5300 RPM => 3423 FPM

.

Slalom4me

While poking around in Engine Analyzer Pro, I came
across specs for '98 Winston and Busch engines. I
do not follow these series and do not know what RPM
the engines are run up to these days, so I use 8500
& 9000 RPM redlines below for sake of illustration.

This compares with speedj2's engine

I believe the principal issue is fatigue life of the
components or their time-to-failure. Busch and Winston
engines receive a greater measure of preparation and
maintenance than a privateer (which I assume speedj2
to be) may be able to muster.

However, I feel I need to hush now. I've never built
an engine to run over 7000. Theory is great but experience
is what counts.

.

DREGSZ

Great info, I had the 3.875 crank in the 415, he , (the poster) has a 3.75 crank in a 406.
does it say the same thing for him?

Deakins

If you are taking out rod bearings you are either starving for oil, or running too much timing. Both of these things will cause the rod bearings to fail prematurely. Just for reference on the ability if the combination; a 410 sprint car engine will have the same stroke and a good one will pull nothing less than 7400 in the turns and 8200+ in the straits. Now these are maintained very well and contain some very good parts but do kill rods that quickly! If you have not destroyed any connecting rods why would you think that the architecture can not sustain under these conditions? The rod bearing problem stems most likely from an oiling issue; if you are as serious as it sounds and rules permit, run a dry sump system and the bearing problems will go away if you are tuning the engine right. Have you tried pulling a degree or two of timing out of it? What are you running for total timing now? I am a big inch, big power guy and have found that if you spend the money they will hold up just fine heck; a good drag engine of almost any size leaves the line at or above your redline!

DREGSZ

I think there was a problem with the main cap or bearing, can't recall

DREGSZ

That is great information, bear in mind the Nascar teams are running superlight rotating assemblys, the crank alone probably costs $5k and weighs less then 38lbs,

AU N EGL

and are frequenlty rebuilt, i.e. after each race.

DREGSZ

While this is true, dry sumps are expensive to buy, expensive and timely to install, and complicate alot of things that would would be much simpler if it was a wet sump, like changing the oil or pulling the motor.

While it's true you would have positive oil flow at all times,
and possibly negative crank case pressure which builds lots of power, (hard to fit more then a 3 stage pump in a C4, need a 4 stage or bigger for neg crankcase pressure)

That is the point at which Big Red started to be too much car for me to handle mechanically...

DREGSZ

With all new parts and the old ones are all on Ebay

Slalom4me

Yes, I believe EAP merely looks at the projected piston speeds and
pulls comments from the appropriate cells of a look-up table. Speeds
in a similar range will generate similar comments.

I reversed the Peak HP and Max Rpm parameters to be more
appropriate. Included two additional paragraphs.

.

speedj2

Thank you again for both your acedemic information and your experiences.

I dug up my racing log and have all of the correct engine specs, instaed of just by memory.

The camshafts that I've tried were: first a 258/268 @.050 605/605 on a 108 lobe separation. I found this too hard to drive because of the too much torque... the car wouldn't hook up off the corner. The current cam is a: 269/277 @ .050 .661/.620 on a 106.5 lobe separation. This cut down the torque substantially.

Evan: I do have a dry sump and an oil cooler, however, since it's installation I've never kept track of my oil temps... but I will in the future.

Aunegl: The gearing is: 1.94, 1.29, 1.13, 1.0. The rear gear is a 3.33 OEM Dana 44.

Slalom: Thanks for the info on the piston speeds. I'm using flattop pistons, so the bob weights are pretty light @ 1789 gr. Still, the rods that I'm using might not be up to the task. (?) These are a forged H-beam 6" rod (Lunati Pro-Mod). I chose them because of the favorable pricepoint and because the cap cleared my block. After the bearing failures, the rods were disgaurded. I wonder if you could tell if the rod was the instigator of the failure after the fact? Do I need to use better rods?

Also, the bearings used were a standard federal mougle camphered bearing. The clearances were: .0030 mains, .0020 rods, rod side clearances were .015 to .016. Oil was a 15-50 synthetic. I know that they make different bearing materials for special circumstances... would any different bearing material be appropriate?

Decans: The total timing was set at 38 degrees. When we tried advancing the timing more, we lost power. Even with the bigger cam, the final torque curve was impressive, coming up to more than 500 ft/lbs at 4500 and staying flat until 6000. Would less timing be easier on the engine?

Slalom4me

Did the TQ/HP curves kind of look like these ones?

.