heavy engine loading or at higher rpm. If your stock ignition is kept in
good repair and adjustment, it should be more than sufficient (and
efficient) for normal driving. When an engine is modified to run at
higher compression ratios and higher rpm, then the ignition system might
need to be upgraded to handle that.
You are definitely reading too much advertising. MSD is good in the right
application, but for yours, you don't need anything more than a good stock
The stock HEI will saturate somewhere around 7500-8000 rpm, depending on the
parts. Really around 7000 rpm it is not very dependable, but then, are you
revving your L48 to 7000 rpm? :-)
The HEI kicks out a great spark. The MSD has the advantage to fire under
adverse conditions, in that if the first fire does not jump across the gap,
then the second or third might. Also, the high dollar (not basic) will use
rev limiters and such that can be very beneficial to keeping your engine
alive in the event of missed shifts.
The L48 will begin to float valves before you rev high enough to break it.
As soon as that happens, it stops revving. With a high compression race
motor, floating a valve could be disastrous in that the valve and piston
would probably hit, but the dished pistons of an L48 won't.
In motors we kept under 7000 (basically set for 6500 and hope we didn't push
that too much), I've run fresh HEI setups and had no ignition problems.
It is possibly one of the best things GM ever did, and may have been if they
had put a tach drive on it.
Thanks Tom. You know, when you have an L48, even a nicely rebuilt 350 like
mine, you always have time to wonder how you can get it to kick out a bit
more. That's what I do in the rest time from 0 - 60. Well, kidding, sort
of. It's a really nice piece of equipment, and it makes daybreak tolerable
knowing I'll be driving it, but it would be nice to find a way to put a
little more zip in it without spending way too much.
I keep reading on here about the C5 and dream about having that, and keeping
the one I've got (because I built it; every piece of it, and learned on
every nut and bolt). I don't know how the guys afford them though. Or
maybe most just have a more lucrative occupation than teaching high school.
Unless I can find one hellofa hellofa deal, I will be happy with what I've
got and proud of it, but always be trying to find a way to zip it up a
Anyway, thanks for the input. There is so much I don't know yet.
Two things make an engine run - spark and fuel. After that, what determines
how it runs is how fast it can take fuel in, process the fuel, and then get
rid of the waste. It is really very simple.
If you built your L48 stock, then you should have the 333882 heads on it.
These are not a performance head, known as lightweights due to how the
casting cuts back in between the lower row of head bolts, however, they were
used with the L82 also and should flow up to 6000 rpm with no problem. What
will stop you from having some snap are:
1. cam profile
2. ignition map (ignition timing curve)
3. exhaust system configuration
If you still have the original exhaust, then you have a good chance your
original catalytic converter is nearly plugged. If you have no emissions
testing, you have a few options. First is a new factory exhaust with a new
catalytic converter. Second would be true dual exhaust, ordered for a '74
Corvette. Of course, this isn't PC as there is greater emissions. The
third would be true dual exhaust with new style small performance cats that
do not restrict the exhaust flow. Fourth option would be headers and dual
exhaust, even headers with sidepipes. The fourth option would permit the
If you have emissions testing, you would be stuck with the first but you
might get away with the third. It depends on if they do configuration exams
or just check that there is a cat.
Timing on the stock L48 isn't that great. However, it should be matched to
your engine, gearing, and cam, so with that information, you can probably
get any local speed shop to recurve your distributor to improve things.
Cam profiles we went over on Larry & Michele's '79 L48 and the same would
apply to you.
Also, be sure what you have is working. The number of Quadrajets running
around with sunken floats is incredible. The composite float develops a
leak, fills with gas, and then sinks. This leaves the needle open on the
seat and allows the bowl to overflow with gas at low speed, creating an
overly rich condition. Usually, your tailpipes are black and you see black
smoke at low speed if you goose it a little. Your mileage is probably
What Tom meant to say was "three" things make an engine run - spark,
fuel and air - the more the better. After that, what determines
how it runs is how much air it inhales and how fast it can take fuel in,
process the fuel, and then get rid of the waste. It is really very
simple. An engine is basically an air compressor.
Not within the RPM range your engine will live at.
MSD does have a multiple spark but you won't see
enough benefit to justify the cost. The multi spark
and larger Zaaaap of the MSD helps at high RPM
and very high cylinder pressures i.e. high compression,
nitrous, turbos or blowers, yada yada.
If you were building a vette o hotrod around in I'd go with a MSD.
a club member that has (had) it on his '77. On one of our club trips it went
south and there was no fixing it. It was replaced with stock Chevrolet parts
and the trip went on without a hitch. Why pay a premium for an
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That was one worry about my '32. The mismash of parts on it
and repairs on a road trip.
Although any speed shop will have MSD stuff in stock, but finding
a speed shop in many small towns is futile.
While a agree that an MSD will give little back on a stock engine for the money
(but not that it will give nothing). However I
totally disagree with the comment on "repair". I have found that MSD is a very
reliable system. The fact that someone has
experienced a failure doesn't mean that they're all bad. In fact I don't care
who the manufacturer is... they will have failures,
including GM stock components.
As far as upgrading the ignition system, I recommend getting top of the line
solid core wires with shielding and avoiding the carbon
core stuff. Use good quality spark plugs and upgrade to a high performance coil
and then gap the plugs just a little wider. You
should take your distributor down and have it spun up and checked for wabble and
runout. Some the the factory distributors have some
bearing slop (especially after a some miles) or shaft warp which can throw off
individual cylinder timing slightly at higher RPMs
(usually greater than 4500 RPM). You want everything to be as "clean" as
possible. The hypertech coil is a good choice (about $100).
The key is to make everything work together and not just upgrade on component
and ignoring other things, especially those things
that will get in the way of what you upgraded.
If you're going for show looks an aftermarket distributor can look really good,
if that's also what you want try the Mallory HEI
(about $200). Its a direct replacement (no mods).
to get yours running, anything can be fixed and everyone that carries stock
GM parts has MSD parts. Spend the extra money for the upgrade (?), and then
put another one in the back so you can keep it running if it goes down in
the hills of Pennsylvania. Of course now you have 3 systems, the one you
took off, the one running and the one for a spare that may never be used,
not a efficient use of money for a minimal gain. Maybe you could put the old
GM in the back to fix the better ignition, less cost and you have one you
know will work.
in, it drops in and you can replace it with a
factory distributor if it fails (including the one you took off). What's the big
deal? As long as you wire the new ignition system
so that a factory unit can replace it easily, you're no worse off than if you
had a factory unit that failed. Been there done that...
Besides, on customized cars there are normally lots of things that fall into the
"you can't get one of those here" categories. I've
driven with groups where one of the roadsters with the Jaguar rearend broke and
there was no place close to get one even looked at.
If your afraid of that sort of thing... be sure your car is absolutely stock. No
higher quality aftermarket for you...
The whole point of driving a Chevy is that you can get parts for it
anywhere. (At least until they started those LT and LS motors.) Remove the
Chevy and you remove that advantage.
Just crossed into Tennessee from Kentucky about midnight one trip and
suddenly the motor in the van sounded like a you'd stuffed a potato in one
exhaust and trying to backfire out the carb.
Pulled into an all-night station under the lights, the only light around for
as far as you could see, pulled both valve covers, and found two broken
rockers. A guy in getting cigarettes and beer told me he had an old Monte
Carlo sitting in a field about a mile down if I needed parts.
I thanked him, told him I had all the spares I needed, and pointed to the
two engines I had in the back. But the point was, you wouldn't find an MSD
on that Monte, I'd bet a paycheck on it.
The old saying "if it ain't broke, don't fix it" really applies here.
I'll bet that ol' Monte wouldn't have had any parts for my factory Opti-spark
ignition system either...
Or any parts that would work on my TPI (injectors, throttle body parts, etc...)
Tom in Missouri wrote:
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