[Brody]

Hey folks, wrapping up my restoration which included a new crate motor from Blueprint. Got it running with no issues, and set the total and initial timing as per Blueprints recommendations. When I turn the car off it will keep running/sputtering for like 10-15 seconds then shoots a little gas out of the carb. What’s the issue? I haven’t called Blueprint yet, thought I might get a quicker reply here.

 

[Brody]

Idle rpm is around 900, what should it be at?
I did talk to Blueprint, they said the float levels are probably too high. I adjusted them and she still did it after a quick test drive.
No vacuum leaks.

 

[Brody]

Try dropping your idle to 750 and see if that helps. Automatic or stick?

Tremec 5 speed. Brand new motor, might only have 2 gallons of 93 through it.
I’ll play around with the idle tomorrow. When I first got it fired it didn’t do it the first few times it ran and was shut off.

 

[Brody]

Set the idle to around 750. Also picked up a vacuum guage and tuned the idle mixture screws. It helped a lot but still runs on for 2-3 seconds, I will tune it a little more and see where that gets me.

 

[Brody]

Both timing and carb settings issues here.

Please outline for us,

INITIAL timing setting at 650 rpms, vacuum advance disconnected, in degrees DO NOT USE A DIAL BACK FEATURE ON THE TIMING LIGHT

When connected to full manifold vacuum, same idle speed, where do the degrees go to

ow many degrees of TOTAL TIMING, INITIAL, and mechanical advance, vacuum advance disconnected, and at what rpms

Where are the idle transfer slots set to at IDLE

View attachment 747180

The engine manufacturer stated to set the timing as follows: Disconnect and plug the vacuum advance line. Get the engine up to operating temp. Then dial in the curb idle screw so it’s idling at 3500 rpm to eliminate any mechanical advance. Then set total timing between 32-34 degrees. Return the idle speed to desired idle speed then check initial timing, if it is between 10-16 degrees they advise it’s ok. I followed this procedure and set total
Timing to 32 degrees. Initial timing was right at 10 degrees.
is that picture how the idle slots should appear at idle? I have not checked them.

 

[Brody]

Yes, I have seen more than I care to of parts that literally "flung themselves right out of the engine" using that method.

Let me guess, you will be using the "Dial-Back" settings on your timing light to test all this, right?????

Be it as it may, do as you see fit, hope the engine warrantee is good, and in effect.

Please enlighten me…

 

[Brody]

So here’s the update. I had the car at my local restoration shop to have them tune/adjust the carburetor and attempt to solve the dieseling issue. The mechanic, working in conjunction with a master tech from Blueprint were unable to solve the issue. Here is what was attempted:

• set total and initial timing as per Blueprints specs. (They played with this as well)
• set fuel levels and adjusted idle mixture screws, curb idle
• removed, cleaned and reinstalled spark plugs
• swapped out carburetors from another mechanics vehicle that was running fine
• changed distributors
• used seafoam engine spray

Currently all attempts have been unsuccessful. The only other pertinent information is that we’ve deduced the motor does not do this when cold. When it gets up to operating temperature is when the dieseling will begin.

Where to go next folks? I spoke with Blueprint today and we discussed an idle stop solenoid?

 

[Brody]

If you really don't want to do it better, right, do it the way the engine blow up experts outlined.

Ask them what the "quench distance" is, please post back here (we have a reason).

Dieseling, too hot, timing better suited to a Top Fueler, NOT a street engine, carburetor too far open at idle, exposing too much of the Idle Transfer Slots. VERY common problem, comes from WRONG ignition and carb setups. Alternate reason, top tuner has "dyno tuned it, directly to absolute oblivion.

View attachment 748797

I will look at the transfer slots. Should they be exposed or should the throttle blades cover them? It’s my understanding that Blueprint puts the Holley carb on straight out of the box and doesn’t tune it at all.

 

[Brody]

I assume we are talking about a big block here? What is the actual cubic inch? If we're talking big block, IMHO 10 degrees initial timing is a little low. I'd try bumping in a minimum of 14 degrees (and would prefer to see upwards of 18 degrees) and reset your idle setting. Don't wing the engine to see where the mechanical is at, it'll most likely be too much. Just let it come up to temp and see if it still diesels when you click it off. Should this remedy the problem, you'll then have to see where the mechanical is at and limit it to what the manufacture recommends is the max safe total timing. Personally, I've found big blocks to be in the 36 degree range give or take a couple degrees.

It is a small block stroker motor. I am going to check the transfer slots and see where they are at.

 

[Brody]

As I have outlined previously, the PICTURE OF THE IDLE TRANSFER SLOTS is above. Now, pulling the carb off to see them is not the way to do it.

So, here is a way too see where the plates are when the ITS is in the correct place. With the carb off the manifold, set the slots to the picture. Now, use a scribe, and from the top of the carb, make a scribed line over the front of each primary throttle plate in their throttle bores in the base plate. Put the carb back on the engine.

NOW, you can look down the primary bores, and SEE the lines you made in the base plate at the front of each throttle plate, where the ITS are in the proper position.

I’m not quite tracking the scribe part, but I will pull the carb and set the ITS based on your picture. Youll have to bear with me as I am new to this.

 

[Brody]

Pulled the carb off yesterday. As it was the primary ITS were spot on to your picture. The secondary ITS were not visible. I set them to match the primary ones. Reinstalled and fired it back up. It then idled around 2k so using the curb idle screw brought the idle down to about 750. Still dieseled upon shut down.
Today I pulled it back off and set both primary and secondary ITS so I could barely see them. Reinstalled and fired it back up. Idled around 1k. Adjusted curb idle screw back down to 750 and it still diesels. What else ya got for me?

 

[Brody]

I dropped the idle down to 600-650, I’m using the factory tach so it’s hard to see exactly what it is but I believe it may have fixed the issue. Two times after dropping the idle it shut right off. I will have to drive it some more today and see.
I know when it was in the shop the mechanic attempted this but hadn’t adjust any of the ITS.

 

[Brody]

So with the ITS of the primary and secondary TBs set so they were just visible and the adjusting idle down to 600 it seems to have done the trick. Been driving it for the last few days and all is well.

 

[Brody]

Nice to hear there has been positive response with the changes, keep going, sir.

No, thank you. Blueprints “master tech” couldn’t figure it out. I appreciate all of the responses.