Engine Basics and Selection

Ahh, now we get to the heart of the race car.   The  engine.   Engine selection is pretty important.  The biggest baddest engine you can find might not be the right choice.  The  Flyin’ Miata XXXocet   used a supercharged LS3.  Cool, great power, but presented some interesting problems.  Take a look at their build to see what I mean.

Later engines have a little more displacement, but are also more complicated.  DBW throttle, VVT, etc.   Choose wisely, Weed Hopper.

I needed a simple and inexpensive engine that I can beat on lap after lap, day after day, and season after season.  When it finally blows up, it should be easy and inexpensive to replace.  the 5.7L LS1 really fills this slot nicely.  It’s also aluminum.  Adding lightness is always a good thing.

I purchased a stock LS1 and transmission through E-Bay.  water pump to shifter, intake to oil pan, wiring harness, ECU, even had the pedals.   All for $3,500 delivered to my driveway.  Came out of a 2001 Firebird, with 49K miles.

Engine Delivery
Engine Delivery
Engine Unwrapped
Engine Unwrapped

Mostly, I wanted to leave the short block alone.  But more power is more better.   I added an ASA cam, which is probably good for 40-50 hp.  And a set of used worked over stock GM heads.  Increased compression and better flow.    I also added a set of beehive valve springs to match the cam.  Maybe not the most power to be had from a cam swap, but easy on the valve train.

I try to be fairly meticulous about engine assembly.  I tested every valve spring before installation, used a valve spring micrometer and shimmed all the springs exactly to specs.  And I clayed every piston – all 8 of them.   I was also very careful to measure for proper push rod length- critical in a LS engine.

Valve spring testing
Valve spring testing
Claying the pistons
Claying the pistons
Timing chain support kit
Timing chain support kit
New timing chain
New timing chain

For the short block, I replaced the stock oil pump with a good Melling unit; and the timing chain with a GM heavy duty part.  The LS1 does not come with a provision for a timing chain support.  But that’s easy to add.

For road racing, oil control is critical.  This oil pan from V8 Roadsters should work nicely.  Notice that there are no provisions for an oil filter.   It’s also a steel pan.  I would prefer aluminum, but that pan isn’t baffled as well.   More on that later.

oil pan interior
oil pan interior
Oil pan, exterior
Oil pan, exterior

I installed a used LS6 intake (also from e-bay), and an LS6 PCV valley cover.   Good bang for the buck, there.  Have you priced an aftermarket intake?  Yikes!    Because I will be using E-85, I installed some 45 pound injectors into the stock fuel rails.   I drilled some of the bolt heads and safety wired them.  This OCD is really costing me a lot of time!

LS6 Intake and fuel rails
LS6 Intake and fuel rails
LS6 PCV valley cover
LS6 PCV valley cover

The rest of the assembly is pretty straight forward;  TTY bolts, stock gaskets, etc.  I did not replace the rings or bearings – a decision I might regret.

Mostly complete, and ready to install
Mostly complete, and ready to install

ENGINE DETAILS

Updated  2/17/16

So, a few more details.   As I said before, the big goal with this engine is not maximum power.  Yes, I know it’s a race car.  But sometimes max power won’t get you where you want to be.    I wanted solid power, with a broad flat torque curve, and – above all – reliability.  This needs to run lap after lap, week end after week end, season after season.   I want to go 3 seasons between overhauls.

The cylinder heads are Chevy 5.3L LS1 862 castings that have been slightly worked.   The ports had a mild CNC job, and the deck is shaved for more compression, with a polished 58cc chamber.   That calculates out to about 10.5 static compression, I think.    Remember that I live at 6,200′ ASL, and I’m running E-85.  More compression is a good thing.    I added a set of PAC 1218 Beehive springs with steel retainers.   The rocker arms have upgraded trunion bearings, but otherwise stock.   Nothing fancy here, either.   Head gaskets are – once again – stock GM MLS replacements, which should give me a 0.40″ quench.    Head bolts are stock GM TTY single use bolts (see a trend here?)

The short block is mostly stock.  I added a good oil pump, and a pan to match the chassis.  The rotating assembly is untouched from original factory install.

The camshaft is Howard’s Cams version of the ASA cam.  Decent duration, low lift, aggressive ramp rates:  .525/.525,  274/285, 113* LSA.    Nothing too radical at all.   Makes pretty good power, and sounds good, too.

I took the car over to Under Pressure Performance this week for a dyno tune.    They specialize in custom built turbo installations, but they can tune almost anything.    I could get the car to idle, and move around the neighborhood a little.   But it needed a real tune for the track, and I just didn’t have time to do it on the street.

They did a very nice job, and I got exactly what I needed; 417hp, 405 ft/lbs.  Pretty flat torque curve, too.   Really no need to run it above 6,000 rpm’s.    We did some very nice donuts in the parking lot before loading it back onto the trailer.   🙂

On the Chassis Dyno
On the Chassis Dyno
Dyno Tune 2/16/16
Dyno Tune 2/16/16

When I put the car up on the rack last night, I noticed some oil on the left side of the oil pan.  Not good.  I’ll have to take  some time to track that down before doing anything else.   I was going to do corner weights and alignment this week end, but might not get time.  If I have to remove the pan, the subframe probably has to come down.   That’s a big job.   We’ll see what happens.

Compression

Cylinder pressure makes power.  That’s the bottom line.  The more fuel:air you can cram in to that tight space, the more power you will make when it explodes.  As Bill Nye said, “An explosion is when something gets really big, really fast”.    But, there’s a limit.   Mostly, that limit is set by the fuel being used.   As you know, too much compression with crappy fuel, and things go bang when they’re not supposed to.  And that’s a bad thing.

Lots of people think that using E-85 is the panacea for compression and detonation.  That’s only sorta true.   E-85 is 85% Ethenol, and 15% gasoline.   The octane rating is about 105’ish.   And the intake charge is significantly cooler than E-10.     Which would make you think you can run insane cylinder pressures without detonation.

But, that is not exactly true.  The 15% of the mixture that is gasoline is some of the worst and cheapest dregs of gasoline left over at the refinery.   Probably has an octane rating of 82-84.     Unfortunately, that part of the mixture likes to get underneath the first ring land and detonate there.  The piston looks like a scene from “Alien”.

I took this piston – and a couple others that looked just like it – out of my 427W engine.   Static compression was a little over 12, and dynamic compression was about 8.5.

427W piston
427W piston