Poppets!

[Pinger]

For another project I'm researching (I'm trying in essence to build heavier duty poppets) and looking for info on GM poppets to begin with to get a rough idea for the spring. Has anyone ever taken a poppet apart? Does the spring release to a longer length (ie, is it pre-loaded when installed)?

I found this >>
https://www.instructables.com/Poor-Mans-Repair-Guide-For-ChevyGMC-Vortec-Fuel-I/
but it doesn't take any poppets apart but it does have a cut-away diagram but it's not very clear. I found a schematic drawing (see below) but a schematic is all it is.

If anyone can answer the spring pre-load question, has photos of a stripped poppet, or spring dimensions or any info at all - it'd be much appreciated. The dimensions of the pintle part (with the ball at the end) would be useful (so I can calculate its mass).
One more question. Am I correct in thinking that between injection events there is a 'solid' line of fuel between the injector and poppet and when the injector next opens it is that fuel that is forced through the poppet (at least initially)?

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[Ricky8680]

I have no info to help with,except for the fact that when I do my mpfi upgrade/intake gaskets,I'll happily send you my poppets for research purposes if you'd like,free of charge.

 

[Erik the Awful]

How to rebuild your poppets:
1) Remove upper intake
2) Replace poppet spider with MPFI spider
3) Reinstall upper intake
4) Throw poppet spider in the trash can

There is no good reason to try and rebuild the poppets. It was a bad idea. When GM comes out with a counter-measure that eliminates the original engineering, you know it was really bad. GM will throw stupid money at propping up bad ideas like side post batteries and non-standard-sized 3-piece stereos, but they ditched the poppets just like they ditched the Vega's aluminum block and the Cadillac 4-6-8 injection. There's a reason.

 

[Pinger]

I have no info to help with,except for the fact that when I do my mpfi upgrade/intake gaskets,I'll happily send you my poppets for research purposes if you'd like,free of charge.

I might take you up on that - cheers!
(I'd pay postage as it would be to Scotland).

 

[stutaeng]

I remember there was a thread where it was mentioned that they do take in the cores of these, presumably to get rebuilt? I wasn't aware of this when I upgraded to the MPFI. And later I did see some reman. single poppets on RA that resembled the original...Maybe around $35 each?

But I agree, just upgrade them and move on. Being under the upper plenum is a bad thing for diagnosing them in itself!

Is this related to your LPG setup?

 

[HotWheelsBurban]

Had a couple poppet injectors replaced on the other 99 vortec Burb, was around $75 each for parts IIRC. I don't think the spider was available then, it wasn't offered as an alternative by the shop. Spider and FPR are probably in my Burb's near future. These are in the upper part of the manifold, correct? I don't have to take both parts of the intake off? Thanks in advance!

 

[stutaeng]

Had a couple poppet injectors replaced on the other 99 vortec Burb, was around $75 each for parts IIRC. I don't think the spider was available then, it wasn't offered as an alternative by the shop. Spider and FPR are probably in my Burb's near future. These are in the upper part of the manifold, correct? I don't have to take both parts of the intake off? Thanks in advance!

Correct, just the upper. I think it took me like 2 hours on my 5.7/K3500. Distributer cap comes off, but not distributer. All you really need is a ratchet and a few sockets. Disconnecting the fuel lines is probably the most difficult thing. A pneumatic/cordless ratchet will speed things up.

 

[Pinger]

Is this related to your LPG setup?

Related to a LPG setup - but not the truck's. A 2T project that I need a poppet valve for - but it will see combustion so have to be more substantial. Figuring out the spring is the tricky part. Stiff enough to control the poppet and with the correct pop pressure.

 

[Pinger]

Whatever anyone is doing - it's always worth looking at how others have done it - then crib from there.
What I want my poppet to do is so similar to what a GM poppet does the only real difference is scale.

 

[LC2NLS6]

Look at GM's high pressure direct injection injectors perhaps? For fittings, just use quality AN fittings to connect hoses to things.