Engine swap gone wrong !

[87 Z TRUCK]

I have an 87 Chevy R-10. It had a 305 til i found out it had 2 burnt
valves and leaks everywhere. After much thought and research, I
deceided to by a Crate motor from Mr. Goodwrench thourgh
Summitt Racing. I had a local mechanic install it for me, I would
have loved to have done it myself but just didn't have the time.
Since it was installed, It has been in the Shop for 2 months!!!
I have not got it back yet !!! The truck has a Some type of Air/
Fuel problem. It sits at idle and it surges. Idle goes up and down
like it running out of fuel and the computer compentates by trying


to bring the idle up. It also acts like a vacuum leak somewhere on the
engine. The mechanic has been so discourged with it. We have gone
as far to removing the whole top end and replacing the intake, He
thought the old one had a crack in it. All sensors have been replaced
We swaped the TBI with another one to see if it would make a change.
New EGR and Idle air control valve. I even replaced the chip with one
i bought from HYPERTECH, I bought with the engine for later use. Now
6 different mechanics have looked at it, 1 from the Chevy Dealership,
and have come up ZERO soultions. I am here now to ask you all for
help. I love my truck but it is getting closer to becoming a FLOWER POT !!!

Thanks,
From the Future Gardener!

[leolkfrm]

Welcome to the forum.....
have you talked to summit racing, maybe it needs to have a carb, they might haved modified it for racing, with a cam or whatever

[76silverado]

Sounds like a computer problem to me. Disconnect the negative terminal only and leave it off for about 1 min. That will reset the computer and maybe solve your problem. I would put a scanner on it first though and see whats going on. Good luck and welcome!

[87c10slammer]

i would definitly say it has to be a fuel problem.. have you rebuilt the tbi or checked the injectors... why not just switch it to carbed and solve all your problems.. if you get a new intake and a 750 carb you should have plenty of fuel for that motor

[75K30]

How does it run when the throttle blade is open? Does this situation improve or does it become worse?
Is this situation in "open loop" when the temps are down or have the temps been allowed to increase?
What was the part number for this chip?
Which injectors are you running? You did change the TBI to a larger TBI right? Even the 350 TBI might be a little small for a larger displacement engine, and I am fond of the 454 TBI even with larger injectors.
How is that exhaust? Did you leave the puny stock manifolds on this thing?
Does it run an EGR system?
Gonna need some specifics, but I am positive that gettin you on the right track is easy.
TBI systems can be a little tricky, but work reasonable well.

[PAPA BEAR]

has any one tried hooking up a vacume guageit can help a lot some times good luck

[87 Z TRUCK]

First,
I would like to Thank all of you for Welcoming me to this forum.
I am still a novice to the game, Hopefully i can catch up to
to you all in the ALL MIGHTY CHEVY KNOWLEDGE. Thanks
for all the replys and I will try to answer them.

I have not contacted Summitt about the problems i have
been having. I only ordered a stock engine from them, If
i remember correctly, It is a 92 model block. I will call.

We did change the computer from another chevy to see
what affects it would do, No change. It was out of a 91
Sub. with a 350.

About switching to a carb system, Before i bought the motor,
My thoughts were trying to keep the truck as original as possible
with just a few modifications. WHAT WAS I THINKING!!!. Had i
known i was going to run into these problems, I would have bought
a different motor all toghether. I was told that because of the
heads being for FI and the mounting, I cannot use a carb system
on this motor. I will have to look into this matter further.

On the " OpenLoop ". We have not tried that, Interesting.
The chip is a Street Runner, HYP-127111. The TBI has not been
Changed at all. When i did look up injectors on another website,
I noticed that they are different for a 305 and 350 by item numbers.
I wonder if it makes a difference by CFMs or some other matter.
I had planned in the future to buying headers after i got it running.
So Yes, PUNY MANIFOLDS. It does have an EGR system, I did replace
it as well with the sensors. I would like to here more about your ideas
on the injectors.

I am not sure about the vacuum gauge, but i will ask the mechanic.

Thanks again to you all. I look forward to seeing your replys.

Have a good night.

[75K30]

OK, now we have some interesting pieces of information, and it appears that the calibration is off.
Your injectors are way too small, as well as you TB. The throttle body is far to small, and this just wont flow enough air (CFM)
The injectors are also undersized and do not have the ability to flow enough fuel (lbs of fuel per hour)
Well now that we have a computer that is for the 350, and a TB for a 305 also having small injectors, and such small exhaust manifolds, you have develpoed a surge.
The ECM is searching for something that it cant find, and since you have upgraded the "chip" it is even worse.
The 454 TB is a subtle upgrade as well as the larger 350 injectors. For now the injectors are most important.
Now if you have a problem with the O2 sensor, and it does not reach temp, and actually control the engine, the ECM will search for an optimum mixture and continue to do so until it sees correct data. IN this case it will never come. For the most part I believe you have a cold surge problem, so we will look into this later.

Knowing that the TB itself is nothing more than a controlled vacuum leak, I believe that there is a simple solution.
However, it sounds to me that you have a problem with mix-and-match parts. It's great that you went with a chip to move your calibration up to the 350-cid engine. Is it a custom chip or an off-the-shelf chip for a 350? This makes a huge difference when you go to order or re-install any TBI unit. If the chip is an off-the-shelf 350 chip, it is probably calibrated to the LO5 350 TBI injector size. (I think) The injectors in your throttle body are different sizes between the 305 and 350. The proper PN for the 350 injectors is 19110538, and you will need two. You can easily swap them out, and this should take care of your cold start surge (lean condition) and your lean "check engine" light going down the highway. (I suspect it is doing this also) Start here, and see if this helps.
I think this should take care of it.
Might even be willing to bet a cold adult beverage!

[gmctrucks]

SUPER good info I have an idea why don't you fly 75K30 over there and pay him to fix it might be cheaper in the long run hey im not kidding I bet it will be cheaper.

[Case 7230]

Originally Posted by gmctrucks

SUPER good info I have an idea why don't you fly 75K30 over there and pay him to fix it might be cheaper in the long run hey im not kidding I bet it will be cheaper.

Couldn`t agree more.