Throttle Body Coolant Bypass installation notes

[Idaho Slim]

Thanks Mad-Mic!!

I was hoping you might reply, I follow your performance posts, & I want the best I can get also, but keep it a daily driver to where my wife wont beotch, if ya follow

I may be paranoid, (And yes, I am going to try and find a Vette enthusiast shop for my vette work ), but it seems that after the work I had done, the car just did not have what it had B4 I took it in, and it should have ran better, since my plugs definetly were bad and i had them replaced, plus put in a 160. It felt like it was slow off the line, and was not consistent when i punched it anywhere along 25-40 , sometimes it would get full power & passing gear, sometimes it wouldn't, i could sometimes trick it to kick down by shifting out of O/D into drive manually at the same time as I punch it. They say all 160 related, which i have a hard time believing. For most of the simple stuff I am going to doo it myself, but as time & ability dictates will have to find a shop.

 

[warren s]

Slim-


The shop sounds like they are full of sh*t. I have done the 160 them ,TB bypass and the fan relay switch on about 8 C4s, all have run better both on the street and at the track. My own 95 C4 automatic runs a 13.4

I think they may have left a vaccume line off or somthing like that. The passing gear kick down is a strange one. The therm change should in no way affect your performace as you describe. Using that logic of the 160 therm causing the problem , your car should never run right until it gets hot?

 

[KANE]

I performed a similar mod on a 1993 Z28 with the LT1.

Now, on the F-body there is a bypass line that comes out of a really nasty pre-fab aluminum and metal hose that runs from the heater to the radiator and throttle body. I changed over to regular rubber hoses and used upper and lower radiator hoses without the plastic elboes and hoses.

The bottom line here is that if you want to bypass the coolant passage, then take it completely out of the loop.

I personnally have little faith in cheap kits.

 

[TODD L GRIFFITH]

Strange, I never had a performance problem after doing the coolant by-pass. I would think that maybe something did happen while they were replacing the plugs. Hopefully the used the correct plugs with the right spark gap. Also in addition, I would check all the vacuum hoses to ensure one isn't off. There are also two hoses located in the rear of the intake plenum, very hard to get at. You may be able to get a finger in there to check and see if they are connected. If someone was trying to get at the plugs closest to the firewall, they could have disconnected these inadvertantly. From my memory, one hose is around 3/8" and the other is 1/8" small. Something to check. I also would refer you to c4c5specialist who is a member here. Maybe you can PM him and ask if he has any thoughts regarding your power loss.

 

[Skant]

That shop is feeding you a line about the 160 degree stat causing the problems you've described. That couldn't possibly be true. That they told you that means they're either incompetent or lying. If they're lying, it may mean that they know they botched the job in an expensive way. The housing for the thermostat is directly over the optispark.. and if they dumped coolant down the front of the engine while they replaced it...

That could be the cause of irregularities in engine power, but I don't think that theory matches up with shifting problems, too. There are some vacuum lines that get yanked when you replace the thermostat. Messing those up could cause all of your symptoms.

In any case... the 160 degree stat isn't going to be the cause of your troubles. There are some differing opinions about whether 160 or 180 or even the stock 195 degree stats are the best. But we're talking about marginal differences in horsepower between them... less than you could feel in the seat of your pants. Certainly nothing dramatic. And unless you also reprogrammed the computer to change the temperature the aux fan turns on at, the difference they'll make is zero.

- Skant

 

[Chetzki]

Hey Skant!

I finally got my TB by-pass done on my LT4. Just like you said, but I did cut my hoses off. I'm not done with all my repairs yet and I have not bought the plugs to cap the tubes, so I don't know how she goes yet. I replaced my 180 deg thermostat with another 180 OEM thermostat (yes, it was $21 with tax!!!) since I am flushing and replacing the coolant (with the orange stuff). The TB by-pass was easier with the air intake hose off the TB. BTW, after seeing the MAF, there is no way I would take the screen off!

See ya!
Chetzki

 

[WNH]

Bottom Line::: The 1st time you do a TB Bybasss, you might buy a kit.

But, if you do it a second time, you will spend about 1 Dollar on parts .

Its experience & No-How.

Experience Rules With C4's

 

[mullu]

Thank you, I have been looking for your type of instructions for a week. I am going to do my 95 tomorow. Thanks again for sharing.
Bill

 

[KANE]

I have a version of the same mod- if you are willing to do it... best of all- it is free.

Drain and remove enough coolant from the engine in order to pull the throttle body. Then remove the water passage / IAC from the throttle body by removing the allen screws.

Using a dremel, cut the water passage out from around the IAC leaving three of the screws to hold it in place. Clean up the cut with a small grinding wheel.

You'll need to make a new gasket that accounts for the smaller size and then install the assembly.

When you are done- it will look like you never had a coolant passage.

I've done this on both of my C3 TPI swaps.

 

[fatboyreyn]

tb coolant

That run down of the procedure was fantastic but I remember seeing pictures of the modification.Does anybody remember this or did I dream it up?....I'm planning to do this mod real soon.I took my vette out of storage just today and I would like to do the mod before anything else.....TIA....P.S...I love this site

save your money on the kits. they are all a ripoff. just get a longer pc of hose and connect directly from one port to the other, and bypass the TB passageway completely. no need to cap ports on throttle body passage.

 

[CAJUN C4]

Slim-


The shop sounds like they are full of sh*t. I have done the 160 them ,TB bypass and the fan relay switch on about 8 C4s, all have run better both on the street and at the track. My own 95 C4 automatic runs a 13.4

I think they may have left a vaccume line off or somthing like that. The passing gear kick down is a strange one. The therm change should in no way affect your performace as you describe. Using that logic of the 160 therm causing the problem , your car should never run right until it gets hot?

I definatly agree. Idid my 95' and noticably more HP

 

[Hib Halverson]

I definatly agree. Idid my 95' and noticably more HP

Please define, "noticably" more HP, that is: does "noticeably" mean 5 more, 10 more, 50 more....what?

Also, how did you measure the improvement?