Custom 454 won’t idle.

[Hipster]

I've only bought one Weiand manifold in my life. Took it out of the box and said "Oh hell no" and sent that POS back. Had a guy give a dual carb tunnel ram,got a couple bucks for it at the recycler.

Never been a fan myself.

 

[Scooterwrench]

The port surfaces on the one that I bought was machined so poorly it would have taken a caulking gun to seal it and the gaps at the front and rear were about 3/8". The dual ram had decent machining but I never figured I was going to build and engine that would only make power in the 4000+ range. Huge plenum! Both were for small blocks.

 

[Supercharged111]

Back around Y2K I bought a Weiand Stealth intake for a F*Rd 289 and it didn't suck. They must have off shored manufacturing since then.

 

[Jeepwalker]

Interesting thread. If you DO end up modifying your fuel pump situation and add a fuel pressure regulator ...get a good quality one:

Car Caught On Fire. Fuel Regulator malfunction. - CorvetteForum - Chevrolet Corvette Forum Discussion

C3 General - Car Caught On Fire. Fuel Regulator malfunction. - Boy what a scare I had today. I was just starting the car to go take it for a spin and then I saw something like this...

www.corvetteforum.com

 

[Erik the Awful]

Just this last week I was helping my buddy get his '64 Mustang running again after installing a new fuel pump. It was shooting fuel out of the vent just like that post describes. I took a fuel pressure reading and it's running rock solid at 5 psi. The needle and seat in the cheapo replacement carb isn't sealing the bowl off.

 

[Scooterwrench]

I remember those Tomco carb kits that used a wafer instead of a needle to "control" the inlet fuel. Whoever designed that POS should have been strung up by his skadeechies. Chinesium parts are killing us in money and down time. I think our rebuilders are probably doing the best they can with what they can get. Time to get that senile idiot(and all his puppeteers) out and our own people back to work!!!!!
Probably not the correct thread for this rant but I just couldn't help myself.

 

[Erik the Awful]

About half the Chinese parts I've bought have been great. It's the other half that's killing us, and that lack of quality control is what's giving them a bad repuation. I bought a $30 Chinese carb for the Chinese Predator generator we use at the race track, and it worked flawlessly. My buddy's Chinese carb is junk. I buy Chinese Haisstronica-brand heat-shrink butt connectors in bulk, and they're great. Then I bought a bluetooth amp from another company and it arrived DOA.

I'm a capitalist. If you find a Chinese brand that makes a good product support them. If you get garbage, air out their name so everyone else can avoid it. I'm old enough to remember when we were having these same debates about Japanese products.

Time to get that senile idiot(and all his puppeteers) out and our own people back to work!!!!!

Let's keep the politics off the forum.

 

[Scooterwrench]

Let's keep the politics off the forum.

Sorry man,I was having a bad morning,pissed off at the world.

 

[Moofus02]

Greetings Cookscustoms,

I've got an idea, but first I wanted to recap/comment on the good troubleshooting steps you've taken to date.
First, setting your timing light to 32° advance & then setting the timing mark to 0° at 3000 rpm was a good move
to combat not being able to set the timing at idle speed. (As far as I'm concerned, the base timing should be close
enough at least to get the engine to idle. (Depending upon how much total timing curve is in the distributor it could be
close, or still need a small handful of advance.)

Also, substituting a 'known-good' carb just to cross-check the idle fuel delivery was very good -- that takes a *lot*
off of the troubleshooting table.

****

OK, punchline first, followed by the theory after. Here's a passage from page 5 of the Comp Cams installation guide.
Check out what I underlined:

You must be registered for see images attach

(credit: Comp Cams installation guide .pdf (LINK)


The older 454 big blocks used an adjustable valve lash setup, via studs & self-locking nuts. On the other hand, the
'99 L29 454 did come with factory roller lifters, but at the same time a non-adjustable valve train setup is
employed, replacing the studs with bolts torqued to 40 ft/lbs to hold the pivot balls/rocker arms in a set position.

We haven't discussed pushrod length yet, but IF you used the ones that came with the engine then the following
might be the key to the no-idle mystery:


^^^^^^^^^^^^^

IF you are still running the non-adjustable valvetrain AND the stock length pushrods,
then if the heads and/or block were decked a sufficient amount, *then* you now have
effectively even longer than stock pushrods, which would lead to excessive hydraulic
lifter pre-load. Which, according to Comp Cams, will give you "low manifold vacuum."

Again, your willingness to temporarily swap in a known-good carb, install a new
fuel pressure regulator and measure the output PSI, and get the timing set at
32° at 3000 rpm are solid troubleshooting steps. In addition, the compression
test you made at *cranking speeds* tell us that the basic valve seal & piston
ring seals are good enough to support a running engine.

So, it really looks like the only variable is that when the engine is no longer
cranking over at 150+ rpm, but is now (trying to) run at 1000-3000 rpm,
now the oil pressure is way up, and with too much lifter preload the valves
are being held just far enough off the seat to cause the low vacuum that
Comp Cams warns about? (Either loss of dynamic compression from
the intake valves not completely closed, or dilution of the intake charge from
uncontrolled EGR from non-seating exhaust valves...or some combo of both?)

****

This is a tough problem. And for all I know the machine shop already measured
everything during assembly and had to order a set of custom-length (shorter)
pushrods in order to make the non-adjustable valvetrain work with the 'decked
heads' and/or block. OR they upgraded to the adjustable old style screw in
studs...yet still managed to set the preload too tight? It happens.

Q: Does all this make sense? I'm hoping that I am describing all this clearly.

The bottom line is that the factory length pushrods are correct for the L29
motors being built to stock specification on the original assembly line. But as
soon as any changes are made to any of the parts involved, then pushrod length
checks are a must.

You know the old truism -- "Spark + Fuel + Compression = it has to run."

The fuel delivery looks good enough to idle. Assuming the spark system
is good & a set of fresh plugs still don't cure the no-idle issue, then all
we have left is compression. And the basic mechanical setup is healthy...
we just gotta figure out the lifter preload per the Comp Cams installation
manual.

Best of luck sorting this out...we're rooting for ya!

Had a 351w that had that problem. Ran like **** couldn't tune it or keep plus in it. Non adjustable rockers with decked block and head