350 that hesitates when its cold- anyone have any ideas

Ok, your ECM is located behind the glove box. If you remove the glove box liner you'll have easy access to it. AFTER unplugging the battery, remove the ECM. There will be two access covers, one for the CALPAK, one for the PROM. The PROM is a standard ROM chip so it'll be easy to recognize. You need to get the P/N off of it and post it here.

Doc

"\"Doc\"" wrote in news:5oGdnT3PhrKMtU snipped-for-privacy@adelphia.com:

Can you also look up the engine block # 0100793 to see if its a 350 I'm working on(I hope that is the engine block # it came off the back of the block). All I know is what the owner told me. For all I know he could be lying to me.Thanks for all the help!

Kev

That isn't the block number (or if it is, it sure ain't in my master listing). The block number should be just before the bellhousing on the back of the motor, almost directly below the distributor. It will be

8-digits long and should begin with the number 1. Sometimes the last 3 digits of the block casting # are stamped into the side of the block, right below where the heads bolt up. The last 3 digits will suffice if you can't find the entire casting #.

I can't find my listing of PROMS for your year, sorry. Call your local Chevy dealership and give him the P/N (the number is 192981397, the first digits are unimportant AFAIK) and see what he comes up with.

Doc

"\"Doc\"" wrote in news:GvmdncpJYcozzE snipped-for-privacy@adelphia.com:

"\"Doc\"" wrote in news:GvmdncpJYcozzE snipped-for-privacy@adelphia.com:

Is any place else on the block where you can get the number. Its a real pain in the ass to get the number off the back?

Kev

Nope, that's it. If you get up on a step ladder just beside the driver's side fender with a flashlight you get a real nice angle to see it.

Doc

"\"Doc\"" wrote in news:q8idnchY2Jib9k7dRVn- snipped-for-privacy@adelphia.com:

I told you the number backwards the block is a 350. I met up with the guy I bought the truck from and he told me the block is a 350 out of a 79 van. The heads intake and throttle body are off the old 305 that was orignally in the 88 truck. The computer is from the 305 as well. The tranny is not the orignal either it's a turbo 400 out of god knows what and has no kick down. I'm really confused now. Do you think this can work. Or is there something they might have done wrong? Or doesn't match up.

kev

Awww hell you're in bad shape man. The 305 heads will NOT work with the 350 block. Combustion chamber is too small as are the valves. What's happening is the increased compression due to the teeny combustion chambers is causing spark knock, which in turn is causing the ECM to retard the spark, giving you the hesitation and shitty performance. Add the fact that she's not getting enough gas due to the smaller injectors and it's going to run lean and make the spark knock even worse.

The chip inside the ECM (PROM) needs to be reflashed for the bigger motor, different tranny, etc. and you need bigger injectors.

Easy fix: Find a decent set of 350 heads, an intake for a 4-barrel carb and a 4 barrel carb and run her carbed. You'll never get that thing to run right with EFI.

The TH400 transmission doesn't have a cable kickdown like the TH350 or the TH700R4, just a lone vacuum line running from the intake manifold to the vacuum modulator on the tranny.

Sorry to be the bearer of bad news, but that thing is a giagantic cluster f**k.

Doc

The TH400 has an electric detent:

You'll need a switch for it to go into a lower gear at full throttle, or downshift as it's called.

Refinish King

"Refinish King" wrote in news:yJoCc.65$ snipped-for-privacy@fe39.usenetserver.com:

Well it can't be a turbo 400 than because there is a spot to hook a wire up. Its a flat connection and I believe its a green wire with a female connection that slips right on. I did this and it kicked down but it when it jumped into 3rd it would jump back down to 2nd when I let off the gas. Also if the engine was made to have a higher compression should it still read about 120 for a compression test. I'm also going to check the fuel pressure what should it be running at?

Kev

Kev,

Let's take a simple approach at this:

1. Count the number of transmission pan bolts and post the number here. Ten bucks says it IS a TH400.
2. 120 psi of compression is shit on that motor and indicates it's time for a rebuild. 150 psi is healthy.
3. Fuel pressure should be 9-13psi.
4. Too late to get your money back?

Doc

"\"Doc\"" wrote in news: snipped-for-privacy@adelphia.com:

There are 13 bolts. I don't know what the compression is yet I was just wondering what it should be at. Tomorrow a friend is stopping by with a computer to pull the codes off the engine then we are going to check everything possible. I'll let you know what we find. Is the throttle body for a 350 different from a 305? If they are can i just change the injectors? The body and interior are mint so even if I have to drop a new engine in it's still worth it. Be sides I'm a diehard chevy fan that doesn't give up easily. Thanks for all your help so far! Kev

That's a TH400.

Compression should be at or above 150 psi. You might be pushing 170-180 with those heads though.

You can check your codes with a paper clip:

TB is the same on 305 and 350, but the 350 injectors are bigger.

Doc

"\"Doc\"" wrote in news:Nqqdnff snipped-for-privacy@adelphia.com:

So can I change them. Or do I have to get the TB replaced. Its probably easier just to change the whole TB. I have tried the wire trick but my friend has the computer which is easier hopefully. What is the wire connection for on the tranny, its on the drivers side and when hooked up make the tranny kick down when I step on the gas. Kev

Detent/Kick down/Passing gear:

Instead of a cable, the TH400's had an electric kick down.

Refinish King

"Refinish King" wrote in news:a38Fc.491$ snipped-for-privacy@fe39.usenetserver.com:

Can it be replace if its not working right or is it something inside the tranny that screwed up causing to shift wrong.

Kev

Check the vacuum line from the back of the intake manifold to the vacuum regulator on the passenger side of the transmission case. If the vacuum line is old/cracked/leaking it'll mess with your shift points.

Doc

"\"Doc\"" wrote in news:sZ6dnS6YrNWqR3jdRVn- snipped-for-privacy@adelphia.com:

Looked into truck specs it had a tranny with overdrive that wire is more than likely hooked in to the computer and the computer thinks 3rd gear is overdrive and shifts down to 2nd thinking its 3rd. I need to find something that had a 350 with TB and 400 turbo tranny that is run by computer so it can send the right signals. Any ideas?

Kev

Kev,

The computer doesn't have anything to do with the transmissions on these older trucks. The ECM didn't start becoming involved in transmissions until

1993 in full-size GM trucks.

The cable that on the truck when it had the 700R4 was just a simple cable that ran from the throttle linkage to the tranny; no sensors, no computer "knowing" what gear it was in, etc. The computer could guess what gear it was in based on VSS, TPS and MAP sensor signals and distributor feedback, but it never "knew" 100% what gear it was in.

Did you check the vacuum line? How's the fluid level and quality in the AT?

Doc