Throttle Body Bypass??

Thinking I may do this at the same time I do the Vette fuel rail covers since I'll have all this stuff off the engine anyway.
Found this online:
This is pretty cool. Easy 6-hp update, lots of the folks on the Impala and Z28 clubs have done this.
GM piped coolant through the throttle body on LT1 engines. Stupid, you want COLD air going into the engine. All you have to do is unplug the hose going into the intake and the one coming out of the intake and splice them together, and then cap off the intake fittings with rubber caps. Done.
FAQ's about the lt1 throttle body bypass
Question 1 Is this hard to do?
Answer No only takes about 20 to 30 minutes
Question 2 Why did the Chevrolet design it the way they did?
Answer The reason for the coolant running through the throttle body is to heat up the incoming air slightly reducing emissions and for fast start up in extremely cold conditions only problem is once the engine reaches operating temperature the coolant keeps pumping through up to 225 degrees warming the air to reduce horsepower. Every racer knows that cooler air is more dense then warm air equaling more horsepower .

I did this on my SS. It is quite easy to do. Need to do this on the Caprice at some point.

Did you see-feel any difference? Don't really need a heated throttle body in Texas. ; )

No, I don't think I did. But I also didn't drive the car a whole lot so it's quite possible I just missed it. The car already had an aftermarket cold air intake though. Even if there wasn't a difference, I still think it a good mod to do, especially as you mentioned, in the southern climates.

I'll be right there this weekend. Will most likely just do it and see.

This is fine during the summer, but as soon as the temps drop below freezing, if the intake air has any moisture in it, then the venturi effect through the throttle body will cause it to ice up. The heat shed rate through the throttle body is not that great so keeping it connected for daily use won't make that much difference. Yes it will improve all out performance but I find it hard to believe 6 HP. It would all depend on ambiant temperatures.

Bill

Interesting. Not a huge concern down here in Austin.

And did I read your post right....6.2 Diesel Roadmaster Wagon? That's wild!

I too have done the bypass mod. Not really noticed a change in performance...but it looks cleaner. I drove cars in the winter in Louisville, KY (and now in SC) with no problems. But I am with Bill, if you live somewhere where it gets pretty cold....leave it as it. Throttle blades sticking due to ice does not sound fun.

A tip when removing the hose clamp from the hardline above the passenger side valve cover....take a small hacksaw and cut the clamp. Then pop it off and replace with a nice worm clamp. I really hate those little factory clamps, but that one is really a PITA to get to if the prongs are facing the wrong way. You can move that little pipe up a touch to get the new clamp to clear the valve cover too.

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I agree with Bill - what GM did was most definitely not "stupid" - there are very valid reasons for having this function. Horsepower means nothing when your throttle blades stick.

The only reason I have removed the functionality from mine is that I developed coolant leaks after some throttle body work and it was easier just to bypass it.

81X11 wrote:

Interesting. Not a huge concern down here in Austin.

And did I read your post right....6.2 Diesel Roadmaster Wagon? That's wild!

Did a write up last year on it:

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Now using the Caddy as my daily, and still doing some fix ups (finally got over 28 MPG on the last haul into southern Ontario ) and unfortunately the locomotive has been sadly neglected. Going to have to re-do the exhaust (again), freshen up the interior and give it a new pump and injectors. Was really hoping it had the needed humph to pull our new trailer but sadly that wasn't the case.

Back to the thread topic, it would be interesting to see what the temp difference is before and after the TB with and without the heater connected. Can't see it being a significant difference.

Bill

That's pretty amazing! I have many non-fond memories of working on the old 5.7 GM diesels when I lived in New Jersey in the late 80's, early 90's. I worked at a full-service gas station...and basically bothered the mechanic there until he taught me something. I remember working on an 84 Eldorado diesel...it kept blowing head gaskets. We put new bolts and thicker gaskets and still it kept coming back....still have nightmares...."shudder".

For some reason there were still a lot of those diesels up there....have not seen one in Texas....ever. And have not missed them!

That being said, the GM truck diesels got much better, so I'm sure that made good sense to do all that work on yours. Really neat and you are very talented!!

-Mike

well,.i gotta add my 2 cents real world observations,.
as most of you have seen it gets interestng here in the winter,. the old gold run of the mill rusty roady, has had the tb bypassed since i got it in the winter 5? 6? years ago,. its had cone filter straight in,. a k+n filter in a cheesed box,. also had a flexible hose thingy for a short while ,. bottom line is its never and i mean NEVER ever had the tb stick,.its been to soo,. ottawa,. ny all in the winter,. cruise on ,. interstate driving,.
never a problem,.
I have never heard of anyone with an lt1 tb bypassed ever having this happen,.i believe it to be another of those internet bogus facts,. kinda like the antifreeze spilled on the sealed opti spark causing it to malfunction,.i put an opti in a bucket of antifreeze with the vent hoses out,. left it there for a couple of weeks,. washed it with water blew it off,. and its still working on the rusty roadyt to this day,. (3yrs??)
rochester quadrabogs were famous for freezing,.

Nick

I've been too lazy to do this mod, mostly as CHris mentioned that clamp is a PITA, and by that point I just wanted to finish putting it all back together.....maybe on my '94 DGGM as that's going to be my hot rod wagon...one day

Nick:

Ever hear of a guy called Bernoulli? Push air through a venturi and both pressure and temperature drops. Air going through a throttle valve creates a venturi. In other words, the throttle body could be susceptable to icing up, especially within 5 degrees of freezing. Cool damp air, drop in temperature going through venturi equals ice.

Having said that, maybe theres enough residual heat under the hood of these cars or the intake is hot enough to keep the TB above freezing, or the air intake picks up enough heat off the rad...don't know. Had no problems this winter with the Caddy and I have by-passed the TB because of leaks but that does not mean it couldn't happen given the right set of circumstances. The guys at GM aren't total dolts and are not in the habit of installing stuff just because it will cost more. They must have had their reasons.

Either way, the little amount of coolant running around the throttle bore doesn't amount to a hill of beans. If it raises the intake air temperature 3 degrees I would be suprised. The point is to keep the bore warm enough not to let ice form should the conditions be there to form ice.


Bill

Hmmm...thanks for all the comments. I'm planning to start the Vette fuel rail cover mod tonight and while I have it apart I'll look at the hoses and decide if I want to mess with bypassing. I may just leave it alone, this car is not a hot rod, just a daily driver and it doesn't sound like it makes much difference. Being a '96 from what I've read the hose on the passenger side is even more of a bear to get off.

We'll see.

Anyone want to give me a quick lesson on uploading pics? I'd like to show off my big toy, but when I click on Host an Image above it seems to lock up on me.

Thanks again all for the warm welcome and good advice!

-Mike

Get a Photobucket account (or someplace similar) and upload your photos to it. They give you all the required links for posting those pics to message boards, websites, etc. Copy the required link and paste it in your message/reply and voila, you have pics.

The required link to copy/paste has [You must be registered and logged in to see this image.] surrounding it.

Hi Mike:

You first have to establish an account with one of the on-line photo storage sites. I use Photobucket. Upload your pics to the new account and then just do a cut and paste of the address into your thread.

Bill

........

If I lived in Round Rock Texas all year I wouldn't worry about it. If the car comes of the road for winter, I would,'t worry about it then either. The only reason mine is still on is that I'm spending time fighting larger issues. I'll get around to it, but it's on the back burner, and there are other more urgent issues to resolve.

If Nick can make it through Ontario winters, and I'm 150 miles south of that, and don't use the car in winter anyway, it won't be an issue to get rid of it in the long term. *( hell, I'm lucky when I get it running... period)

convert2diesel wrote:

Nick:

Ever hear of a guy called Bernoulli? Push air through a venturi and both pressure and temperature drops. Air going through a throttle valve creates a venturi. In other words, the throttle body could be susceptable to icing up, especially within 5 degrees of freezing. Cool damp air, drop in temperature going through venturi equals ice.

Having said that, maybe theres enough residual heat under the hood of these cars or the intake is hot enough to keep the TB above freezing, or the air intake picks up enough heat off the rad...don't know. Had no problems this winter with the Caddy and I have by-passed the TB because of leaks but that does not mean it couldn't happen given the right set of circumstances. The guys at GM aren't total dolts and are not in the habit of installing stuff just because it will cost more. They must have had their reasons.

Either way, the little amount of coolant running around the throttle bore doesn't amount to a hill of beans. If it raises the intake air temperature 3 degrees I would be suprised. The point is to keep the bore warm enough not to let ice form should the conditions be there to form ice.


Bill

i don't deal in theory,. just real world observtions,.MY real world observations,.nuff said.
YRMV

Without theory in physics, chemistry, engineering stc. you wouldn't have anything to observe except maybe the stuff that happened by accident or by natural selection.

Bill

While I understand the concepts of the discussion, I have issues with the "first start" conditions. Coolant is ambient, air is ambient. Coolant doesn't warm up until the block does. After warm up, the block itself should radiate enough heat.

81X11 wrote:

Anyone want to give me a quick lesson on uploading pics? I'd like to show off my big toy, but when I click on Host an Image above it seems to lock up on me.

Here you go...very simple


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convert2diesel wrote:

Without theory in physics, chemistry, engineering stc. you wouldn't have anything to observe except maybe the stuff that happened by accident or by natural selection.

Bill

bullshit,. you,ve got the horse before the cart,. people had real world observations then the physicists, chemists,and engineers came along and wrote down why it was happening,. then expounded on their theories and added a lot of possibles, variables etc,.
real world is just that,. no theories,. just experiences,.
as i mentioned too many theories and half facts on the internet suddenly become gospel after being repeated enough times,..

nick
Still learning real world lessons,. not fancy book learnin ,.

Now that was just plain rude.

In no way am I denigrating your abilities nor your knowledge. Your mechanical capabilities and your ingrained intutition rank up there with the best of them. The big difference here is I tend to ask WHY. In order to effectively answer that question, I first try to understand the principles and how it works. That means taking it apart and applying my book learning to see. If you find that frivilous then so be it. To directly address the original thread in a way acceptable to you:

Observation 1. I have taken the TB off the Caddy three times now for various reasons and have looked at the coolent channel a number of times. There is insufficient swept area to impart enough heat to the air to amount to anything (sorry I had to apply a bunch of bullshit book learning about thermodynamics, heat shed and heat transfer to come to this conclusion)

Observation 2 Having experienced the same problem as many with these engines, I by-passed the TB coolent passage due to leakage. To date have not experienced, nor observed, any iceing of the TB, but then again it may be because I just didn't experience the set of circumstances that would cause iceing.

Observation 3 This engine does not employ anywhere near the amount of airflow, air fuel, heating that has been common in all gasoline engines for the past fifty years (sorry more direct experience/book learning here). This leads me to the conclusion that iceing was not their only concern in the past, but rather maintaining a constant intake temperature. It would seem that when they designed this engine they decided that TB heating was all that was needed (if at all)

Observation 4 No automobile manufacterer increases their cost/vehicle unnecessarily. There must be a reason, ergo asking WHY.

Observation 5 As long as the heat stove is hooked up and the flapper valve is functional, in over forty years of running Quadrajets, I have never experienced one that froze up. A few that boiled the fuel in their bowls causing vapor lock but never one that froze up.

Observation 6 Most people around here when faced with a Quadrajet, promply ripped out the heat stove and jammed the butterfly open assuming that it was useless and then had the carb freeze up the first cold morning, immediately concluding that the carb was junk and then replacing it with a Holley double fuel dumper and remained utterly amazed that their car now uses twice the fuel, won't idle properly and really only turns on when the throttle plates are vertical. Must have been that crappy quadrajet.

Nick it is not my intention to turn this thing into a pissing contest, just illustrating that there is always more then one way to look at a problem. You are absolutely correct in that the whole thing starts with observation but it does not stop there. All too often observation is just not enough. You have to figure out why and then act.

Bill

convert2diesel wrote:

Now that was just plain rude.

Quote :

convert2diesel wrote:
Without theory in physics, chemistry, engineering stc. you wouldn't have anything to observe except maybe the stuff that happened by accident or by natural selection.

Bill

I felt the same way about your post,
stuff that happens by accident or natural selection is always investigated and explained later by some egghead, then accolades are bestowed and somebody gets credited with "discovering" something,.
meanwhile other folks just work around the problem and find fixes for it,.

convert2diesel wrote:

In no way am I denigrating your abilities nor your knowledge. Your mechanical capabilities and your ingrained intutition rank up there with the best of them.

your above post reads otherwise,.

convert2diesel wrote:

The big difference here is I tend to ask WHY. In order to effectively answer that question, I first try to understand the principles and how it works. That means taking it apart and applying my book learning to see. If you find that frivilous then so be it.

Now you're adding your own inflammatory assumptions here

convert2diesel wrote:

To directly address the original thread in a way acceptable to you:

Observation 1. I have taken the TB off the Caddy three times now for various reasons and have looked at the coolent channel a number of times. There is insufficient swept area to impart enough heat to the air to amount to anything (sorry I had to apply a bunch of bullshit book learning about thermodynamics, heat shed and heat transfer to come to this conclusion)

Observation 2 Having experienced the same problem as many with these engines, I by-passed the TB coolent passage due to leakage. To date have not experienced, nor observed, any iceing of the TB, but then again it may be because I just didn't experience the set of circumstances that would cause iceing.

Observation 3 This engine does not employ anywhere near the amount of airflow,
air fuel, heating that has been common in all gasoline engines for the past fifty years (sorry more direct experience/book learning here).

well better head back to the books then, this'd be a magic engine if it produced more horsepower from less airflow than any other 5.7 cube motor,

convert2diesel wrote:

This leads me to the conclusion that iceing was not their only concern in the past, but rather maintaining a constant intake temperature. It would seem that when they designed this engine they decided that TB heating was all that was needed (if at all)

Observation 4 No automobile manufacterer increases their cost/vehicle unnecessarily. There must be a reason, ergo asking WHY.


Observation 5 As long as the heat stove is hooked up and the flapper valve is functional, in over forty years of running Quadrajets, I have never experienced one that froze up. A few that boiled the fuel in their bowls causing vapor lock but never one that froze up.

rochester called their carbs quadra jets the 4gc's then the 4mv's
not all quadrabogs had a heat stove, all early ones relied on a heat flapper(fancy name is actually a "heat riser") in the exhaust to put hot air under the carb,(66-68? i can't really remember).the same ones that the gasket would fail and then the exhaust would boil the carb,.
In a very humid area (west coast for me) holding the throttle steady in the right temp was guaranteed to freeze it up,. so much so,. there were even printed up caveats for drivers of early quads not to be alarmed if it happened to them, and how to shift to neutral, stop the car, and shut off the motor wait a short while yada yada,..so it would seem to me your real world experiences have gotten mixed intogether over time,.40 yrs of running quadrajets? 1966 was the first year,.....
my first ones came along in 74-5? i was done with them by the early 90's as i was eager to get into the new fangled fuel injection so i only had 20 some odd years of them, but did have to learn how to make them work when i raced the olds, i,ve worked my way around just about every oem carb (and distributors and points) known in those years, and aftermarket stuff too,.and i,m damn glad those days are gone,.

convert2diesel wrote:

Observation 6 Most people around here when faced with a Quadrajet, promply ripped out the heat stove and jammed the butterfly open assuming that it was useless and then had the carb freeze up the first cold morning, immediately concluding that the carb was junk and then replacing it with a Holley double fuel dumper and remained utterly amazed that their car now uses twice the fuel, won't idle properly and really only turns on when the throttle plates are vertical. Must have been that crappy quadrajet.

Nick it is not my intention to turn this thing into a pissing contest,

if thats the case then neither your above post or mine is rude,.

convert2diesel wrote:

just illustrating that there is always more then one way to look at a problem. You are absolutely correct in that the whole thing starts with observation but it does not stop there. All too often observation is just not enough. You have to figure out why and then act.

Bill

you are correct,. and I do,.sometimes not in a way that pleases chemists,. engineers or physicists,..

Nick

To set the record straight, in observation 3 I was referring to the method used to heat the intake air and the air/fuel mixture...not the volume of same.

The first time I encountered what I define as a Qjet (small primarys with stacked venturi and large vacumm secondaries) was in 68 on an OHC 6 in my neighhbors Firebird. Never could get it to work right without bogging unless you got it up over 4,000 RPMs. They must have fixed it by 69 as I had the same engine in my Firebird and the thing went like hell. My last encounter was two months ago with a friends 86 Cadillac, complete with the electronic mixture control. As I have been a GM guy since the late 60s it is the carb I am most familiar with. I do agree though, the demise of the carb and mechanical ignition was a long time coming and good ridance. Mind may be playing tricks on me but I seem to remember a heat stove on the 69.

Your right, the climate on the west coast would indeed be the perfect set of circumstances for iceing. No different then flying a piston aircrafft through a cloud bank on a cool day. Have seen iceing at 45 F ambiant.


As far as the other stuff is concerned, at the end of the day it doesn't really matter. We both approach the problem in different ways. As long as the results are the same, and we are happy with the results, then there should be no problem. Sorry for any percieved slights. They were not intentional.

Bill