Andrew crabtre 2011-06-13 01:31:13
’74 C20 w 292ci inline 6, manual 4, no idea of miles on the engine.
When I got it ~2 months ago it was getting approximately 5MPG City. I
removed the addon rack (original listed weight was 4600, now probably 4300),
replaced points with pertronix, new plugs, wires, cap, rotor, coil, battery,
and retimed the engine. City mileage is now just shy of 11.
How does this compare to others with a similar engine? I’m presuming best
case you don’t get much above this. I’m thinking maybe rebuild the carb and
possibly change the gearing in the back axle, but those are both low
priority for now.
John alt 2011-06-13 01:31:17
Sure you can. Next step, carburetor. Keep your timing as advanced as you
can without the engine pinging. Which plugs did you use, btw?
Andrew crabtre 2011-06-13 01:31:19
I timed it per the sticker on the air intake. 8 BTDC @600RPM. Are you
suggesting to try to advance furthur?
That was a big pain. I went to Autozone without a plug in hand and just
trusted their system to give me the right thing. What I got had 1/2 the
thread depth I needed. Except for 1, which apparently was a screw up by the
manufacturer. So went back and pulled one of the old ones and of course
that crossed to something they don’t stock. I can’t remember the exact
numbers, but they are Bosch Platinums. The too short ones were 4806 maybe,
the one that matched the old plugs was 4835, and the ones I put in were
4805. It appeared to have the same temp range from visually inspection but
I need to pull one to check how it is wearing. I gapped the plugs at .044
(spec says .035), since I have the pertronix Ignitor and coil, and it seems
to be working fine so far.
Andrew crabtre 2011-06-13 01:31:21
I forgot to mention, the original plugs were 13/16th, and the ones in their
now are 5/8th. I am hoping that is the only difference in spec.
John alt 2011-06-13 01:31:23
Timing lights are almost useless on high mileage vehicles because of slack
in the timing chain and other components. Bump it up 2 or 3 degrees, and
see if it pings. If it starts to be hard to start (firing too soon makes it drag), it’s too much.
Repeat after me: I will never, never, EVER use bosch platinum’s in my
Chevy. They are c***. The correct plug is the Delco R44T. They stock them,
at least around here they do. Very common plug. Buy a set of those. Enjoy.
I wouldn’t go much over the stock gap even with the high perf coil. Try
..038 to .040 for starters.
Whitelightning 2011-06-13 01:31:34
292 straight six is gear to gear drive, no chain, no belt, no slack. things
to check, vaccum signal to advance unit on distrib. The port sometimes
gunks up on the carb, the base of the carbs underside does the same blocking
vaccum passages. Find an electronic igniton distrib from a later model and
ditch the points. Make sure the carb screws are tight, the screws that hold
the base to the center part of the carb get loose with age as the gasket
shrinks. Quick check grab carb firmly and GENTLY try to twist back and
forth. If there is movement, they need tightening.
I will agree here, Bocsh, NGK, Nipsendenso have no place in GMs, some fords
(only some because so many are more Mazda then ford these days) and even
Now then if you want to have some real fun, first make sure compression is
good, as its a good indicater of the general engine health. The intake is a
bolt on unit. Clifford has a real nice four barrel intake for this engine
and even nicer exhaust headers.. If you really want to go, there is tri
power set up..They also have a far superior two barrel manifold for use with
350, 500 cfm holly 2 barrles, or 370cfm weber. for really sweet there is a
dual two barrel set up using webers. Clifford also has some nice cam
shafts. Isky makes numerous cams for it..
Only thing better than a 292 is an OVC Pontiac straight six.
Sarge 2011-06-13 01:31:50
I agree 100% that Bosch is c***. I had one blow the electrode clean out the
metal threads. The electrode was still attached to the wire so the plug did
not go flying through the hood. It destroy some other wiring under the hood
causing 435 dollars worth of damages and towing. Photos were taken of the
damages and the plug. Removed the rest of the plugs and found spots where
compression was leaking through the and they were about to blow out. Sent a
bill for damages to Bosch and long with the plugs, a receipt for new Delco
plugs and all eight of their crappy plugs.
I received a letter from them three months latter stating that they did not
believe that the plugs were defective that I installed them wrong. They
were either over torqued or under torqued and that is what cause the damage.
I had an attorney friend write back along with a sworn affidavit form the
friend that put them in that they were installed correctly. A month latter
they offered to pay for the plugs only. My attorney friend reply back “SEE
YOU IN COURT”. Their reply was a check for the plugs and damages.
Andy crabtree 2011-06-13 01:31:52
Judging only by the picture at Delco’s website this plug won’t fit. It
looks exactly like the one autozone crossed to for the engine, but the
threads are not long enough. On a vehicle this old who knows what
happened in the 30 years between manufacture and me getting it, but
perhaps the head has been replaced with a different unit. I will try
to make that determination once I clean things enough to get numbers
off of them.
The nolalu bar 2011-06-13 01:32:25
On 22 Jan 2005 09:12:31 -0800, “Andy Crabtree”
I bought an ’82 Chevy 4×4 350 and am working on it to put on the road
this spring. The previous owner put plugs from a Ford in it and the
reach was unreal. I knew right away that the plugs were wrong when I
saw how much thread there is and some time on GOOGLE told me where the
plugs really belong. Exposed thread, glowing red, can make for a lot
of pre-ignition. Always use what is recommended. The Platinum’s,
4-gaps, etc. are just marketing successes to make money from you and
me. They don’t and cannot work any better and sure as h*** are not
worth the extra green.
Santa 2011-06-13 06:15:44
R44TS Resistor Plug ( R) Plus Long Hot Tip 035 is the gap!
Are you sure your old Plugs were not # 45 plugs ?
By the Way .. A 292 6 cyl Had GEARS for Timming ,, Their is NO CHAIN
I got 20 mpg with My 1 ton 1970 Chevy Tow truck with Well over 90K
They stock them,
Santa 2011-06-13 06:15:46
you forgot to Mention that The HEAT RISER Butterfly Freezes up also,
Make sure it works freely..
Brianorion 2011-06-13 06:17:08
you didn’t mention a new air-cleaner.You did check/replace that I
hope.Also check that the vacuum advance diaphragm isn’t broken.This
happens and will wreck your mileage.Disconnect the hose at the carb and
apply vacuum(suck on it).You shouldn’t get a mouth full of air.
Even if it’s good I would invest in an adjustable vac.advance which
will allow you to set it for max possible advance.They are about $25 and
come with 3 sets of springs to set the centrifugal advance as well.It
really helps your mileage to get the timing dialed in as close to knock
Best …Brian O.