1970 454 4- speed engine runs rough

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Golf - 24 Jun 2006 12:32 GMT

I have completely rebuilt my 454 engine, including a mallory
breakerless distributor, no vacuum advance. I have a ballast resistor
in line with distributor. Engines idles smooth at cool temp. When
driving, I can not rev up past 2900 RPMs in first. Once engine is
warmed up and I attempt to rev engine, it begins running rough & tries
to stall, and diesels when I shut it off. On going problem for 2 years.
Using a Carter 4-bl carb.

I have new plugs , wires. Any ideas?

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dave - 24 Jun 2006 13:26 GMT

I have a Mallory 9000 electronic module Distributor (breakerless) on my
1970 BB and it doesnt have a ballast resistor ; better check with
Mallory to see if its even needed. I suspect it isnt.

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Salvatore Giomarra - 24 Jun 2006 16:46 GMT

> I have completely rebuilt my 454 engine, including a mallory
> breakerless distributor, no vacuum advance. I have a ballast resistor
[quoted text clipped - 3 lines]
> to stall, and diesels when I shut it off. On going problem for 2
> years. Using a Carter 4-bl carb.

What I would do:

1) I would pull off the heads and see if there was any weird carbon built
up on the pistons that get red hot and cause early fuel detonation and
dieseling on shut-off.
2) I would look at how my fuel is going to the carb - if it gets really
hot then it turns to a vapor (which it should not do) and that's not how
it's designed to work.
3) I would rebuild the carb (easy to do and quite inexpensive to get a
felpro rebuild kit)
4) I would take it to a mechanic if the first 2 observations came up empty.

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WayneC - 24 Jun 2006 17:18 GMT

> I have completely rebuilt my 454 engine, including a mallory
> breakerless distributor, no vacuum advance. I have a ballast resistor
[quoted text clipped - 5 lines]
>
> I have new plugs , wires. Any ideas?

Sounds like an ignition problem to me, too, but there are other
possibilities.
Shouldn't be too tough to stick a Chevy HEI distributor in it for a test
to find out
if it's the distributor. Likewise for a carburetor... doesn't have to be
the exact
correct replacement carb just to run tests.

Only happens in FIRST gear??? What about in other gears? Neutral?

Does the engine rev up OK when it's still cold?
Are you running the right heat range spark plugs?
What do the plugs look like when you pull them?
Hi-test gas?
Does engine run at normal temp once it's warmed up?
Decent spark plug wires, correctly routed and separated?
Double-checked all the spark plug wires are connected to the right
cylinders?
Double-checked valve/lifter adjustments?
Carb secondaries open OK (ie, no linkage problems)?
And is the Carter carb (it's not the original) adequate?
Is it possible you have a stuck heat riser valve (or that you
re-installed it upside down)?

If it were mine, I think after 2 years I'd take it to a tune up shop
and let a pro have at it..

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Tom in Missouri - 26 Jun 2006 07:50 GMT

I vote with Wayne. You can swap out the distributor and the carb in such a
short time, it is the best way to find this in a hurry.

Dieseling is most likely timing. Use an adjustable timing light to see what
your timing is at 3000 rpm while sitting in the garage. It should be
somewhere around 32-34 degrees. You could have even 38, but other than
those, you have a problem. No vacuum advance is a racer toy and not good
for the street. You'd have much better performance with a good tuned HEI
plus you can buy parts for it anywhere in the US of A, if you actually ever
had to buy parts.

Carb. By Carter, I assume Carter Q-Jet or similar replacement, not the
Carter AFB. Replace the bronze filter in the inlet? Are the secondaries
opening? With it warm and the air cleaner off, open the throttle and see if
the secondaries open. The choke could be adjusted wrong and holding the
secondaries closed.

>> I have completely rebuilt my 454 engine, including a mallory
>> breakerless distributor, no vacuum advance. I have a ballast resistor
[quoted text clipped - 32 lines]
> If it were mine, I think after 2 years I'd take it to a tune up shop
> and let a pro have at it..

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Tony - 25 Jun 2006 00:01 GMT

Check to see if distributor was installed 180 degrees out. It can be done
and it will run.

>I have completely rebuilt my 454 engine, including a mallory
> breakerless distributor, no vacuum advance. I have a ballast resistor
[quoted text clipped - 5 lines]
>
> I have new plugs , wires. Any ideas?

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Kickstart - 25 Jun 2006 00:47 GMT

>I have completely rebuilt my 454 engine,

. On going problem for 2 years.

> I have new plugs , wires. Any ideas?

you do know 454 are externally balanced ???

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BottleBob - 25 Jun 2006 04:15 GMT

> When
> driving, I can not rev up past 2900 RPMs in first. Once engine is
> warmed up and I attempt to rev engine, it begins running rough & tries
> to stall, and diesels when I shut it off.

Golf:

Sounds like a compression check might be in order. Could be a head
gasket, burned valves, or a valve not closing completely if it's a solid
lifter cam.

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