1978 Rebuilt corvette will not start

I bought a 1978 corvette with small block cehvy 350 - I changed the
cam, heads, manifold, timing chain and gears, carburator, new headers
and exhaust, alternator, battery and starter - now I am trying to get
it started - I tried all the TDC with the spark plug and still nothing
- I get spark, I can see fuel, and sometimes it backfires so I get
combustion -

Any ideas

Recheck the distributor and make sure you didn't re-install it 180 degrees
out.

"database-consultant" > wrote in message
ups.com...
>I bought a 1978 corvette with small block cehvy 350 - I changed the
> cam, heads, manifold, timing chain and gears, carburator, new headers
> and exhaust, alternator, battery and starter - now I am trying to get
> it started - I tried all the TDC with the spark plug and still nothing
> - I get spark, I can see fuel, and sometimes it backfires so I get
> combustion -
>
> Any ideas
>

I left the distributor in and clicked over the engine until it pointed
toward cylinder #1, then I tried the same thing the other way - Can you
explain in laymans term what 180 degress out is for us geeks



Tony wrote:
> Recheck the distributor and make sure you didn't re-install it 180 degrees
> out.
>
> "database-consultant" > wrote in message
> ups.com...
> >I bought a 1978 corvette with small block cehvy 350 - I changed the
> > cam, heads, manifold, timing chain and gears, carburator, new headers
> > and exhaust, alternator, battery and starter - now I am trying to get
> > it started - I tried all the TDC with the spark plug and still nothing
> > - I get spark, I can see fuel, and sometimes it backfires so I get
> > combustion -
> >
> > Any ideas
> >

>I left the distributor in and clicked over the engine until it pointed
> toward cylinder #1, then I tried the same thing the other way - Can you
> explain in laymans term what 180 degress out is for us geeks
>
>
If you don't understand that ....
put the wrench down and step away from the car


kickstart

"database-consultant" > wrote in
message
oups.com...
>I left the distributor in and clicked over the engine until
>it pointed
> toward cylinder #1, then I tried the same thing the other
> way - Can you
> explain in laymans term what 180 degress out is for us
> geeks
>
>
if this is not a bait post ?
wouldn't think ya done all ya said ya did,
if ya don't understand "what 180 degress out is" ...
get ya some help, timmy...

my2¢
--
"Key"
=====

> Tony wrote:
>> Recheck the distributor and make sure you didn't
>> re-install it 180 degrees
>> out.
>>
>> "database-consultant" > wrote
>> in message
>> ups.com...
>> >I bought a 1978 corvette with small block cehvy 350 - I
>> >changed the
>> > cam, heads, manifold, timing chain and gears,
>> > carburator, new headers
>> > and exhaust, alternator, battery and starter - now I am
>> > trying to get
>> > it started - I tried all the TDC with the spark plug
>> > and still nothing
>> > - I get spark, I can see fuel, and sometimes it
>> > backfires so I get
>> > combustion -
>> >
>> > Any ideas
>> >
>

On Tue, 19 Sep 2006 18:06:18 UTC, "database-consultant" >
wrote:

> I bought a 1978 corvette with small block cehvy 350 - I changed the
> cam, heads, manifold, timing chain and gears, carburator, new headers
> and exhaust, alternator, battery and starter - now I am trying to get
> it started - I tried all the TDC with the spark plug and still nothing
> - I get spark, I can see fuel, and sometimes it backfires so I get
> combustion -
>
> Any ideas

I'd have to agree with Kickstart. You could have made any number
of mistakes at this point. You changed the cam so it could be
out of phase with the rest of the system. Are you sure that
before putting on the timing chain that everything was lined up
properly?

David

database-consultant wrote:
> I bought a 1978 corvette with small block cehvy 350 - I changed the
> cam, heads, manifold, timing chain and gears, carburator, new headers
> and exhaust, alternator, battery and starter - now I am trying to get
> it started - I tried all the TDC with the spark plug and still nothing
> - I get spark, I can see fuel, and sometimes it backfires so I get
> combustion -
>
> Any ideas
>


Your problem sounds as though the ignition timing is incorrect...
although the cam timing
could be off, I suspect that would cause more problems than just not
starting (for example,
pistons hitting valves, which means it wouldn't crank for long!).

" I tried all the TDC with the spark plug"

I don't understand what you mean by this... ignition TDC is when the
#1 piston (front cylinder on the driver's side) is at top dead center
(top of the stoke)
AND both valves in that cylinder are closed. When the engine is in that
position, the
distributor rotor should point at the distributor cap post holding the
spark plug wire
from that #1 cylinder. Determining that correct #1 piston position first
requires that the engine
was correctly assembled (crank and cam are correctly aligned). You can
determine the
firing stroke TDC by removing the driver side valve cover and making
sure both valves in the
#1 cyl are all the way up (closed) as the zero-degree crank timing mark
line aligns with
the timing pointer. OR, you can remove the spark plug from the #1
cylinder and place a
finger firmly over the hole while someone bumps the engine with the
starter until the timing
mark aligns with or passes the pointer... when the piston is on an
exhaust stroke as it reaches
TDC, you will feel air pressure pushing against your finger, but when
the piston is on the
compression stroke the air pressure will FORCIBLY push your finger OFF
the hole. You
want the latter situation: TDC on a compression stroke... when you find
it, leave the engine
in that position while you shift your attention to the spark plug wires
and the distributor.

The spark plug wires must be positioned in the correct order in the
distributor cap:
1-8-4-3-6-5-7-2 clockwise when looking down on the distributor...
( http://modeltech.tripod.com/wiring101.htm )
If the distributor is 180 degrees out, the rotor will be pointing at the
cap post for
#1 wire, but the #1 piston is at TDC on the exhaust stroke, not the
compression stroke,
so the plug fires on the wrong stroke.

To get the distributor in the correct position, one must ensure that the
timing pointer
is pointing at the 0 degree timing mark on the flywheel and that the #1
piston chamber
has both valves closed... the position I told you to leave it.
Then adjust (remove and re-seat) the distributor so that it is seated
properly on the block...
a cross-pin at the bottom of the distributor shaft will only allow it to
seat properly (insert
all the way so that the "land" on the distributor case is down flush
with the block) when the
matching notch on the oil pump shaft top meshes with that cross-pin as
the distributor is
lowered into the block. The distributor shaft will turn, clockwise, I
think, slightly as the
driven gear on it slides/meshes with the corresponding drive gear on the
camshaft, so you
need to allow for that by pre-positioning the oil pump shaft notch so
the shaft cross-pin
drops/slides into it during that slight rotation as you lower the
distributor. You will need to
use a long screwdriver to reach down and turn the oil pump shaft a bit
to pre-set it so that
the distributor will drop & settle into the correct position as it's
lowered... this takes some
trial-and-error repeated attempts to get it right.
You want the wires positioned on the distributor cap as shown in the
diagram in the link
above, such that when you have it correct, and the distributor
drops/settles into position,
the distributor rotor will be pointing at the front of the passenger
side head, corresponding
to the correct position of the #1 cylinder wire on the cap (as in the
diagram shown at the
link above).

This all assumes, of course (as someone already mentioned), that you
correctly aligned
the crank and camshaft when you put the engine together.

"WayneC" > wrote in message
news:2y1Qg.1991$HZ5.333@trndny08...
> database-consultant wrote:
>> I bought a 1978 corvette with small block cehvy 350 - I
>> changed the
>> cam, heads, manifold, timing chain and gears, carburator,
>> new headers
>> and exhaust, alternator, battery and starter - now I am
>> trying to get
>> it started - I tried all the TDC with the spark plug and
>> still nothing
>> - I get spark, I can see fuel, and sometimes it backfires
>> so I get
>> combustion - Any ideas
>>
>
>
> Your problem sounds as though the ignition timing is
> incorrect... although the cam timing
> could be off, I suspect that would cause more problems
> than just not starting (for example,
> pistons hitting valves, which means it wouldn't crank for
> long!).
>
> " I tried all the TDC with the spark plug"
>
> I don't understand what you mean by this... ignition TDC
> is when the
> #1 piston (front cylinder on the driver's side) is at top
> dead center (top of the stoke)
> AND both valves in that cylinder are closed. When the
> engine is in that position, the
> distributor rotor should point at the distributor cap post
> holding the spark plug wire
> from that #1 cylinder. Determining that correct #1 piston
> position first requires that the engine
> was correctly assembled (crank and cam are correctly
> aligned). You can determine the
> firing stroke TDC by removing the driver side valve cover
> and making sure both valves in the
> #1 cyl are all the way up (closed) as the zero-degree
> crank timing mark line aligns with
> the timing pointer. OR, you can remove the spark plug from
> the #1 cylinder and place a
> finger firmly over the hole while someone bumps the engine
> with the starter until the timing
> mark aligns with or passes the pointer... when the piston
> is on an exhaust stroke as it reaches
> TDC, you will feel air pressure pushing against your
> finger, but when the piston is on the
> compression stroke the air pressure will FORCIBLY push
> your finger OFF the hole. You
> want the latter situation: TDC on a compression stroke...
> when you find it, leave the engine
> in that position while you shift your attention to the
> spark plug wires and the distributor.
>
> The spark plug wires must be positioned in the correct
> order in the distributor cap:
> 1-8-4-3-6-5-7-2 clockwise when looking down on the
> distributor...
> ( http://modeltech.tripod.com/wiring101.htm )
> If the distributor is 180 degrees out, the rotor will be
> pointing at the cap post for
> #1 wire, but the #1 piston is at TDC on the exhaust
> stroke, not the compression stroke,
> so the plug fires on the wrong stroke.
>
> To get the distributor in the correct position, one must
> ensure that the timing pointer
> is pointing at the 0 degree timing mark on the flywheel
> and that the #1 piston chamber
> has both valves closed... the position I told you to leave
> it.
> Then adjust (remove and re-seat) the distributor so that
> it is seated properly on the block...
> a cross-pin at the bottom of the distributor shaft will
> only allow it to seat properly (insert
> all the way so that the "land" on the distributor case is
> down flush with the block) when the
> matching notch on the oil pump shaft top meshes with that
> cross-pin as the distributor is
> lowered into the block. The distributor shaft will turn,
> clockwise, I think, slightly as the
> driven gear on it slides/meshes with the corresponding
> drive gear on the camshaft, so you
> need to allow for that by pre-positioning the oil pump
> shaft notch so the shaft cross-pin
> drops/slides into it during that slight rotation as you
> lower the distributor. You will need to
> use a long screwdriver to reach down and turn the oil pump
> shaft a bit to pre-set it so that
> the distributor will drop & settle into the correct
> position as it's lowered... this takes some
> trial-and-error repeated attempts to get it right.
> You want the wires positioned on the distributor cap as
> shown in the diagram in the link
> above, such that when you have it correct, and the
> distributor drops/settles into position,
> the distributor rotor will be pointing at the front of the
> passenger side head, corresponding
> to the correct position of the #1 cylinder wire on the cap
> (as in the diagram shown at the
> link above).
>
> This all assumes, of course (as someone already
> mentioned), that you correctly aligned
> the crank and camshaft when you put the engine together.
>


yea, that's right !
exactly what I meant to say :-)

no real pun intended...

g'day all
--
"Key"
=====

You've had lots of help. If you are real, let us know how you did.

Simple method.

Remove the driver's side valve cover.

Roll the engine to where the harmonic balancer mark comes to TDC, watching
the two front rockers.

If you are at TDC for #1, both should be up and not moving. If the exhaust
is closing (end one going up), you are TDC on #6. In many small blocks, the
two end ones will even be slightly loose, such that you can wiggle them
easily at TDC for #1.

Install the distributor so the rotor points to the #1 plug wire position,
moving the distributor shaft as needed like Wayne said.

Snug the distributor hold-down bolt enough it won't move on its own but you
can move it.

Attach your timing light.

Wedge a 10 inch wide piece of cardboard along the lower edge of the rockers
to keep oil off the exhaust and let you see the valves work.

Pour a tablespoon of gas down the carb throat or pump the accelerator
linkage a couple of times while watching to see that gas actually pumps.

Get someone to crank the engine.

Make sure the front two valves are closed (rockers up) each time the light
flashes and when the engine fires, immediately check the timing and adjust
as needed. I believe 4 degrees BTDC is what you need, but check a book. 4
BTDC should make it run regardless.

After you time it, shut it off and install the valve cover.

!!! Don't look down the carb while trying to start it. !!!

"database-consultant" > wrote in message
ups.com...
>I bought a 1978 corvette with small block cehvy 350 - I changed the
> cam, heads, manifold, timing chain and gears, carburator, new headers
> and exhaust, alternator, battery and starter - now I am trying to get
> it started - I tried all the TDC with the spark plug and still nothing
> - I get spark, I can see fuel, and sometimes it backfires so I get
> combustion -
>
> Any ideas
>

Keep a fire extinguisher close by..a backfire can really wreck your day...