I'm having trouble getting my truck to run right, this is my first attempt at tunig a carb. It's a 91 s10 with a crate 350, th400 trans. Summit hei vacuum adv., and a edlebrock 1806 thunder series carb. The engine was dynoed at 390hp at the crank, it's got a mild cam 9.5:1 compression.

I did have a lot of timing issues, switched between ported and intake vacuum. It pulls good vacuum(15-20in) at idle. I set my total timing at 38deg at 3k rpm with the vacuum plugged. I've been playing around with it, with the vacuum not hooked up to the distributor and it has been running better. Guys have told me they have ran their vac adv. distributors with the vacuum not hooked up, is it a bad idea to be running it like that? From how I understand it, the vacuum advance only works during part throttle, but when the engine reaches a certain rpm it's at it's total advance and stops?

The reason I put this in the carb section is I think my main problem is the carb. When I adjust the idle mixture screws, nothing happens. The engine doesn't slow down or speed up. When I hit the gas off of idle, it hesitates very bad. Even at part throttle to wot it stumbles. It's lacking power for sure.

I have a stock style carter fuel pump, with no regulator. I'm thinking that could be an issue. Every part on the truck is new, the carb was re manufactured. Sorry for the dumb questions, I'm new to this and want to learn.

Thanks for any help!

 

With the vacuum advance hooked up, the engine will have less timing at start up (easier to start). 38deg without advance is ALOT of timing for your combo. I'd pull 10deg out of it and hook up the vacuum advance.

As for your carb, I personally can't stand the Eddie carb. They are a pup to tune. I find it easier to tune a Rochester or a Holley. Just my two cents.

BTW, if your looking for a good deal on a carb go to Allstate Carbs. I bought a reman 600 vac secondary marine carb for a buddy's boat for half price and it works GREAT!

http://www.allcarbs.com/

Good luck!

 

Well it was 38 total timing, initial was around 14-16. I don't like the idea of running it without the vac hooked up. Ill set the initial around 10 and try that.

I forgot to say, when I hook the vacuum advance up, I have to have the idle high to keep it running, if not it stalls.

Yeah I was always told how simple the edlebrock carbs were, I'm thinking otherwise. I have a new Holley quadrajet knock off on the shelf, but it might sit too high with the spread bore adapter. Honestly I just want to throw a mpfi system on it, carbs seem like rocket science compared to that.

Thanks for the quick reply!

 

Couple of things.
Which "crate 350"? They make like a hundred of them.
Also did you change the springs in the summit distributor? If not when you set the timing to 38 at 3000 (which is actually too high especially depending on which engine you have) it is still advancing past 3000. So you timing is well over 40 at 4000! Way to high. get the spring kit if it didn't come with it and install one light and one medium spring then set total to 34 @ 3000.
As far as the vacuum can. There is really no reason to not run it at least on ported vacuum for better fuel economy. It has no affect on performance. Depending on the cam size it can be beneficial to run it on full vacuum to get extra timing at idle, but with smaller cams you don't really need it.
Now if the carb is not taking an adjustment with the screws then either you idle screw is in to far which i don't think or there is something wrong with the carb.

 

There is no way it should want to stall when you hook up the vacuum can. Just by hooking up the can to full vacuum the idle should go higher and smoother.
Something else is wrong. I would double check tdc with a piston stop and try another timing light.
I just recently had someone with weird timing issues and realized his new inexpensive balancer was 9 degrees off from tdc brand new!

 

This is the engine I have,

http://blueprintengines.com/index.ph...base-bp3550ct1

I think you are right, I will re check tdc. I have an adjustable pointer, and we set it before installing the engine but that doesnt mean it couldnt be off.

 

yea recheck tdc. Also 38 degrees is way to high for those heads. I am surprised it's not knocking under wot. Should be 32 to 34 total.

 

I'm not sure the easiest way to check it with the engine in and everything on it? It's pretty tight on the front of the engine with the fan and shroud. I just ordered a flywheel turner, and a piston stop, that seems like the easiest way for me to check it right now.

 

yea a piston stop and either a degree wheel or mark the balancer and measure the middle of the 2 marks to find tdc is the only way.

 

I had a good friend of mine eat a cam in a Blueprint engine. We ended up building a 427 SBC and sold the block.

Here's the engine and the car it's in.

 

As previously discussed in a thread you were part off ;
https://www.thirdgen.org/forums/carb...m-vs-full.html

it depend on what the dist /vac can is calibrated for; smog or not
many have unwittingly connected to wrong vac source and not been happy with the results

 

Usually SBC like 34* advance, at MOST. You really gotta use a timing light and tach to dial in your engine.

 

Sorry to hear that man. Was he racing it, or just running it on the street. That's the blueprint engine he had?

My truck,



Only pic I have of the engine on my phone,



Thanks for the help!

 

No we hated the Blueprint engine. That engine in the picture is a Dart black 427 pushing 600 hp.

 

I verified tdc , and got my timing all straightend out with the vac advance hooked up. I too it out and ran it a little and I have some questions. I had the idle set at 8-850 rpm, if I lay into the throttle off of idle, it bogs down and will stall if I stay in it. If I go from 1500-2k rpm to wot it Boggs down for a second and then picks up. If I roll into the throttle it revs up fine.

I was told that it is normal for the engine to hesitate from 800 rpm to wot. Is that normal? What rpm should the idle be at? I increased it to 950-1k rpm and that helped the idle to wot acceleration, but not by much.

I'm worry for the dumb questions, just trying to Learn. I'm considering going fuel injected with the engine this winter.

 

Don't worry your not asking any dumb questions

As far as idle rpm there is no correct number, just set it where it likes to be. Just keep in mind to always set idle and a/f screws with the car in gear. It makes a big difference. Idle speed in park is meaningless.

What is your timing at idle with the vacuum can disconected?
Also try moving the accelerator pump rod all the way inboard like this pic and see if that helps. If its better but still not right then contact edelbrock because i don't know how to get more pump shot put of it unless someone else knows.


And no it should not bog off idle. If the timing is right, it is probably the carb doesn't have enough pump shot. Not a fan of those edelbrock carbs.

 

Ah I've always set the idle in park. I will set it in gear tomorrow. The idle mixture screws, run them in until the rpms drop, then back them out until the engines rpm is as fast as it will get and stop?

Initial timing is 12deg. With the vac disconnected and plugged.

I will move the accelerator pump rod tomorrow also. Honestly I'm not much of a fan of them now lol, I shouldn't say that though I can blame its poor performance on my lack of tuninbtb abilities.

Thank you for the help!

 

No problem. Most of us here enjoy helping people get their cars running right.

 

Here's a question....

What are you using for the fuel line? If its too small you will have a starvation issue. I had this issue with the El Camino I had for a week. I got it running good, but when you'd lay into it, it would stall at the top of 1st, just before the shift. I ended up finding a buch of fuel lines crunched in areas and so forth. Before you bend that rod. Just be sure you have adequate fuel. If its a 5/16 line it's too small.

Hope this helps!

 

Fuel cell is in the bed with -6an going to the fuel filter and -6an going to the 3/8 hard line running the length of the chassis, -6an from hard line to pump, and from pump to carb is 3/8 hard line. All the bends in the hard line are not too sharp or kinked.

The only thing in the fuel system I question is where the fuel filter is at. It's before the fuel pump mounted under the bed. I contacted tech support at summit, jegs, and edelbrock. I know I can't rely on the mail order tech support but edelbrock said it was ok. That could be an issue?

 

U always want to protect your pump. My system will have a pre and post filter.

Your line size is adequate. Maybe the filter is the issue? Hmmmmmm

 

Thats definetly possible, its only had about 20 gallons of gas pass through it. Its a large screw on fram filter.

 

More problems,

I moved the rod on the accelerator pump to the upper hole, and tried to fire it up. It ran for a few seconds and shut off. The carb was dumping fuel into the engine even after it was done running. Fuel was even coming out of the bowl vents. I pulled the top of the carb off to check the floats and they were working fine. They were adjusted to 7/16 like the manual said they needed to be. The accelerator pump looked good also.

Im lost? I called edelbrock tech support and they were not much help, he said the float needed adjusted.

 

I think you may have found the problem! Carb is dumping fuel.
What is the fuel pressure?

 

I don't have a gauge on it. It never started doing that until today. It's got a stock type mechanical fuel pump. I cranked it for about 10 seconds and fuel poured out of the bowl vents. Enought to puddle up under the carb in the air gap.

 

Well I think you were right jabot, fuel pressure is most likely the problem. The pump I got puts out 7.5-9 psi. Edelbrock recommends 4-5.5, so I ordered a regulator. It will be here today. From what I've read, it could be the cause for most of my problems.

 

It's most likely the cause of the fuel overflowing into the engine. There is a slight chance you may need a new needle and seat, but it should be ok once the pressure is down.
If that fixes the fuel dumping problem then get the msd hei spring and weight kit. Put weights and the 2 light springs or 1 light and 1 medium spring in.
Set total timing at 3000 to 34 degrees with the vacuum can unplugged (if you are only using 91 octane 32 may be better, but I don't have much experience with that). Hook up the vacuum can to full vacuum. then adjust the idle and idle a/f screws in gear.
With the quicker advance rate and the idle adjusted right it should feel like a different truck.

 

I got the fuel pressure reg installed, fuel is still leaking out in the primaries. Not nearly as bad though. I may have to get a new needle and seat, I was thinking that the seat was brass? Ive never tore into the carb enough to find out. Thats my next step I guess.

I bought a nice nitrous express fpr with a gauge, but it is big, and I couldnt plumb it into my fuel system and it look good. I got a Mr. Gasket regualtor with 11 clicks on it, in .5psi increments. Not sure how accurate it is?

 

One of the floats was bad. I dont know how I missed it before, but I did. I put the cheaper fuel pressure regualtor on, but I honestly couldnt stand how cheap it looked, and I question the accuracy of it.

 

Changed the float, replaced the air horn gasket, and installed a nitrous express fpr. Runs better, but still a hesitation from off idle. Its not nearly as bad, it does not stall now, but its still there. Accelerator pump is in the top position.

One problem I have had, Ill set the fuel psi at 5-5.5 at idle but after I run it for a little while the pressure just drops off to 0 on the gauge. Ive tried re adjusting it and it doesnt want to change.

Any thoughts?

 

The hesitation is a comon problem with those carbs and if you have the rod in the top hole i don't know of any other way to fix it. I know quite a few people who got rid of those carbs for holley style carbs because of the same problem.