Turbo on a 235 inline. ?'s what does close tolerance mean?

Guys I have a 235 i am building for a 49 chevy. I was considering a turbo system. I figured it would be perfect. These motors already have low compression, inline6 gove easy intake, exhaust feed plumbing. I was going to look for fast spool no lag small turbos or something of a small diesel since these are low reving motors.

I was talking to some of the techs at cliffords performance and mentioned it and he said "you really don't want to force induct these motors, they are a close tolerance (.030") motors". I didn't want to go into it with him and make him think I was questioning his knowledge. What was he talking about, valve to pisiton tolerance? Rod/Main bearing tolerance? Piston ring gap? just curious. I alreay did a search and didn't see many of these engine force inducted so maybe it was a bad idea. Just saw some blower setups and a 261 on youtube where someone had it running on a stand with a ratty turbo setup.

Thanks!!!

 

I had a turbocharged 270 GMC and later a 302. Worked great. I have no idea what this guy means by "Close tolerance" .030 may be close tolerance when you are building a house but it's pretty sloppy in an engine. You might want to look at turbos from a V6 Buick. As new as you can find. I used Corvair turbos. A friend has a turbo from a 2.2 Chrysler he thinks is great on a flathead.

 

I picked up Leo Santucci's 'Chevrolet Inline Six-Cylinder Power Manual' and decided to build a turbo I6 as well. My original plan was a 235 but I got lucky and found a 292 to use instead. I'm not too sure what the tech was talking about because my research (as well as yours I'm sure) has showed these are great motors for boost. Either way, good luck on your build!

 

Close tolerance could mean many things, but if you are going to turbo this (which I highly recommend!) you need to open up your ring gap.

There are a few threads on www.theturboforums.com relating to how much you should do this. It's a cantankerous site that requires some reading before you throw questions around, like the HAMB used to be.

Other sites that can help you choose a turbo:

http://www.turbofast.com.au/javacalc.html (measurements are in metric)
http://www.not2fast.com/turbo/glossary/turbo_calc.shtml
http://www.squirrelpf.com/turbocalc/index.php

I would recommend a Master Power T70 with a .68 AR housing, 15 psi should net you close to 400 Hp provided you build it right.

 

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If you want a cheap and 'near bolt on' turbo set up
for your 235, maybe think about a complete set-up
off of a late '70's carburated turbo-Buick V6.
These were used on 3.8 itre V6's in late 70's. I
picked up one in a boneyard a few years ago from
a '78 Buick Regal and put it on an otherwise stock
slant-6, in an in O.T. '81 Dodge D100 pick-up. The
late-'70's Buick set-up is a 'draw through' system,
with a Rochester Q-jet mounted to the inlet of the
turbo, via a cast aluminum adaptor.The size and
layout of the Buick turbo set-up happens to be
just about perfect for adapting to an inline-6. To
fit it to the Dodge, I used short piece of 2-inch
diamiter stainless steel exhaust tubing, with
flanges welded on the ends. The turbo mounted
to the stock slant-6 intake manifold, sitting just
above it, with the stainless exhaust tubing
connecting the turbo's compressor outlet to
the carb mounting pad on the slant-6 intake. For
the exhaust, I had another piece of stainless
exhaust tubing - this time 2 1/4 inch diamiter
- bent in a "U" shape, with flanges welded on
the ends to connect the outlet on the stock
slant-6 exhaust manifold to the inlet of the
turbo's exhaust turbine.

For an an exhaust system, I had a 3 inch diamiter
'downpipe' made up, that went from the exhaust
outlet on the turbo and connected under the truck
ito to a homemade 3 inch inlet and two - 2 1/2
inch outlets "Y" pipe that fed into a pair of
2 1/2 inch inlet & outlet X 30 inch-long resonators
and a pair of turnouts, exiting just ahead of the left
rear wheel. Even with two side by side, straight-through
resonators and turnouts, the turbo acted enough as a
miffler, that until you were really on it and making
boosrt, the system was still resonably quiet and not
a whole lot louder than stock.

I had the downpipe and turbo mounting and exhaust
tubing bent up for me at a local mufler shop and a
little trick I used to get the bends right, was to use
exhaust 'flex flex pipe' to mock everything up. When
I had the flex pipe bent the way I needed it, I
brushed on some epoxy cement and let it harden. Then
I took the pieces of flex pipe to the muffler shop and
got them to rplicate them in stainless steel exhaust
tubing. I made the flanges up myself at work, from
some scrap 5/16 304 stainless plate

To lube the turbo,I found an unused oil port on the
side of the block. I plumbed into it by removing the
stock pipe plug from it and replacing it with an NPT
to AN adaptor fitting. Then I used a length of braided
hose, -also from work - to connect to the oil inlet on
the turbo. For the oil outlet, I simply ran a line from
the turbo into a brass hose fitting that I epoxyied
into the the side of the valve cover. The only other
even 'semi-major' mod I made was changing the carb.
The stock Buick Q-Jet is an electronic "feed-back" carb
and used a computor.whiich I didn't have and wouldnrt
have wanted to try messing with anyway. Probably any
old style 'non-feed-back' Q-Jet could be made to work,
but I had a 'Holley 'list 80552' 650 cfm 'sreadbore
replacement' marine carb collecting dust on a shelf that
I rebuilt and used. The carb worked great almost
'as is' with only some linkage fabrication and
going 3 jet sizes richer on the secondaries required.
I also added an electric fuel pump at the back of the
truck to push fuel up to the stock slant- 6 mechanical
pump , "just in case" to ward off any chance of fuel
starvation and lean-out under boost. After a bit of
tweeking with the timing to limit the total advanvve
to 30 degrees, the system worked great. With the
turbo, at low speeds, the truck drove pretty much
as stock. In fact you'd hardly know that it had been
modified. But when the scondaries kicked and it
started making boost, hang on! I kept the boost
limted it to 6lbs, which was probably about the
mazimun safe limit for the stock cast pistons and
stock, 80,000-plus mile slant-6 bottom end, but
what a difference even just 6 lbs. made!. I never
tried dynoing it or running it at the track, but
just 'seat of the pants' guesstimating from driving
it, I'm sure the stock 115 horsepower was at least
- and probably more than - doubled! Besides
everything being basically "bolt on", it was cheap too.
Including buying the complete Buick turbo set-up from
a boneyard, having the tubing bent at a muffler shop
and buying or making the assorted small bits and
pieces, I still had less than $350 tied up in the whole
system. I''m sure that you could adapt the Buick turbo
set-up to a 235 Chevy - or any other any similarrly
sized inline-6 - and have simillar results.

Mart3406
===============================

 

Guys, I have got more then expected from this thread and have read some of the links posted. I have a Buick Regal T-Type setup already with a t3 style air research turbo on it no carb. I was going to try with it first since it didn't cost me anything. I like it pecause of no plumbing for lag. It won't be running I/Cooler so i doubt I will be running 15 psi. I have to find some old Kaiser boost gauges so they don't look out of place in the car.

I may be able to get a nice 261 this weekend also which I would like to use over the 235. Thanks for the gret lenghty responses and keep them coming. I have learned lot.

Ray

 

The Buick turbo can be made to work well, it's just a bit old these days and the T3 turbine housing might be a tad restricted if you want to turn it up past 200 HP.

Don't be too concerned with lag, those blower guys don't know what their talking about

 

yeah what mart said..

 

What he meant was he didnt want you to do it. He was frightened by the idea seeing as how it is out of the usual and also he hadnt thought of it. I did a 170 /6 back about 1970. it worked great. When your engine was built close tolerance meant about an inch. Now it means .0001".
Do i sound Jadded? I am . It is because SO many good projects dont get done because someone pours water on the fire. Turbocharging is easy and quick. A few years back some fellows were running a Desota Airflow wth a Chrysler Flathead straight 8. i am glad they didnt ask but just did it. I believe they ran it both a Bonneville and some drags as well.
A 235 is a decent motor, quite tough and reliable. I remember when I first worked in the machine shop trade they were a very popular power plant for 6 cyl stock cars. They are hard to hurt. Go for it. Only thing with a turbo conversion is the power circuit in the carb. It cannot always sense engine vacuum to operate it when a turbo is there(turbo is always creating vaccuum when it is spinning under the carb even if the engine isnt) We used to run a line from the power piston or valve externally around the turbo to the intake down stream of the turbo or block the power circuit open if a race only deal.
Don
here is the turboed /6 170 cu inch

 

6ck pony, exactly the pic I was looking for!!!! What size and type carb? I was told some carbs have to be made for suck through applications? I had in my mind mounting it length ways with the valve cover but that looks like a better mount. Have you any way to monitor EGT's or is that even a concern? What PSI are you running? Do you have any power #'s. I amy be PM ing you for some other questions. the only thing that has me concerned is getting that height crammed under a 49 chevy hood. I have a predator carb which is already tall, so that may have to go.
Thanks for the pic!!!

 

-----------------------------------
If you're using the relatively small, stock Buick set-up
and you're keeping the boost in the 6 to 10 ilb. range
I doubt egts will be a big concern.. If you plan to crank
the boost up or are concerned, you can always install a
pyrometer. If you shop around you can probably find one
new for about $100-125. A while ago, I picked a NOS
Stewarrt-Warner pyro stil in the box, complete with
temperature probe and cable, on ebay for 40 bucks
to use on a buddy's 2.3 EFI- turbo-Pinto project. .
About the carb - for a draw-through set-up, other than
maybe jetting jetting the carb a bit richer *if required*,
there's not really much to do or change - at least not
just because tha carb is going on a turbo . A carb works
because when the engine is running, there is a lower
than atmospheric pressure below the carb, causing air to
be drawn through it. It's the same on a 'draw-through'
turbo set-up - the carb doesn't know or care whether
that pressure differential is caused soley by the engine
itself, or by a spinning compressor wheel 0 and when the
compressor wheel is spun up and making boost - the
pressure differential below the carb is just that much
greater and carb just 'acts' as those it's on much larger
displacement engine than it really is. When I built my
Buick-turb'd slant-6. the 650 cfm Holley (List 0-80552)
spread-bore carb I used, - just because I had it and
it fit - and acording to the Holley catalog - originally
calibrated for a 350- 454 Chev marine engine - and it
worked 'as is' with no other mods other than richening
up the secondaries up a bit . Perhaps if I was going
to build a carb specifically for a draw through turbo
system there's a few tweeks and mods I'd like to
try, but at least on with a more or less stock Buick
set-up on an also more or less stock inline 6,
running limited boost you don't really need a
tricked -out carb to make it work.


Mart3406
==========================================

 

it is a 600 edelbrock and running at 5 psi I have a 9lb spring I need to try. Not really concerned about egt's. I liked it mounted over the cover cause when you look at it from the front or back the carb looks centered on the car. You can plumb it almost anywhere you want it. I've seen some nice under the hood set-ups with custom intakes. Good luck to ya.

 

hello im am new to the site and joined due to this post. thank you all so much because i am atemting to do the same thing in my car ,250cui 6 nova. one question i have though is, is it safe to run boost on these motors with no bov or waste gate? i ask because the t70 turbo i have requires an external bov and wastegate, and if i can run it with out them i will so i dont have to spend anymore money haha. thank you very much

Customnova

 

Wastegate is intended to regulate the boost pressure, so if your turbo can make more boost than your engine can handle this is going to be a good investment. Some diesel guys ran without wastegates on early 6.9 ford's. BUT, I think that turbo maxed out about 8-10psi on that engine.

A BOV vents the high boost pressure out of the intake system when you slamm the throttle closed. I think you can run without, but depending on your setup I believe you may cause some damage over time... maybe some with some greater turbo knowladge can confirm or correct me.

cheers
g

 

What that means is the Tech guy doesn't know anything about the subject.
Go with something guys here suggested,buy some books and try to make up a system.I think it was Ak Miller that said something like " if you haven't burned up pistons,you haven't done turbo supercharging"
Some guy in the 50's had a turbo kit for the dipper 216 engine,made 150 real HP back then.
Some one previously said 400 hp at 15 PSI.Not with a 235 or 261,probably need 30 psi and the lower end is no where robust enough for 400 hp in my opinion.Remember,if mechanical strength is no issue the only limit to boost is detonation.

 

If you limit the amount of air that goes in the turbo that will limit the amount of air that comes out. If you are going with a suck through that works fine. On mine I started with a fairly small four barrel and went larger after deciding it was going to live. That is what GM did with the Corvair except they started with a 1 BBL. and never went bigger. and it sorta worked for them.

 

Just do it. You have the only opinion that matters. Here is mine back from the machine shop (final mock-up). Its a ford 223, t3/t04E with a holley 500. Going to run about 8 psi. Read all you can and get the corky bell "Maximun boost" book.

 

Cool turbo set up, like the exhaust manifold. Rich Fox, I was wondering about you "limiting air" comment. I am picking up a good 261 tomorrow and the build will be similar to 6ck pony picture. I have the same regal t-type turbo setup. I was wondering though... should i spend the money on the clifford 4 barrel intake?, because when i put my carb on the 4 barrel turbo manifold the turbo necks down to about the size of a 1 barrel carb (look at his picture) and then attaches to the four barrel plenium on the clifford intake. I have also heard that your intake/heads flow only as well as your weakest/most resitricted link. Didn't know if I would feel the effects of the $300 plus intake, or if I should just pressurize my stock one barrel intake.

I have also been told by turbo heads that the rules of "porting-polishing" change from naturally aspirated heads and intakes to turbo heads and intakes and that pressurized systems overcome restrictions easier. To some all of that up I am just asking if you guys thing I should spend the money on that clifford 4 intake since the turbo necks it down?

I am going to run a predator carb...didn't buy it so don't get excited. I have heard plenty of horror stories about them, but I like the therory of never being overcarbureted and I think they just look badass. If it doesn't work I will throw something else on.

 

I made my own intake from exhaust tubing. But the port runners were stock 270 (the early small port) size and went 158.914 in the car pictured here. At wide open throttle it would pull 17 pounds mainfold pressure. By swapping carbs I could raise that to 22 pounds but the motor didn't like that. If it was me I would start with a two bbl carb and work up from there. But it's you so just have fun and maybe get an EGT. I got mine from Westach.

 

Wow that car is awesome!!! I looked at your profile to see if you had an album. If you get a chance load some pics of that thing! I would love to see some close ups of the engine and your setup. May have to PM you on specifics.

If I actually have to buy a carb I was leaning towards that Weber 38 two barrel unless someone has better experience

 

thank you guys for all your quick responses.

my motor however is all stock, so does this mean i should run a bov and wastegate then?

if so whats the max psi i should run?

i plan to use a 650 for a carb

 

You really don't need a BOV unless you are running a manual trans or making over 8-10 PSI. And without going through the bottom end I would stay under that range.

Waste gates are a must. Some are built in and most every aftermarket turbo requires an external waste gate. If you do something like a T04B from Ebay you will need an external waste gate.

The smaller A/R turbine housing will help you spool up quicker but choke off the engine at higher RPMs, which you should probably keep under the 5K mark on a stocker.

http://cgi.ebay.com/ebaymotors/T04B...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

http://cgi.ebay.com/ebaymotors/SUPE...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

http://cgi.ebay.com/ebaymotors/SUPE...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

 

I would think something in the 8 to 10 pounds at WOT would be the max you would want in your setup. If you use the Buick V6 turbo the waste gate is built in. Also the Chrysler turbo and I guess other OEM parts. If you are going to build a suck through system you need a turbo with seals made for that use. Most newer turbos and diesel parts were not made with the idea that they will ever see vacume and will suck oil from the bearing into the intake not a good thing.

 

i already have a t70 turbo that requires an external wastegate and or bov.

what size wastegate should i get?

also my turbo is only oil cooled. what is the best way to get oil to it? i really dont know where to begin on the oil issue.

also am i going to have to change anything spark wise because i have a completly stock points type system, it is very well woorking though. the only thing i know ill need to do is tighten up the gap on the plugs.

any help is very apreciated!!!!!!!!!

 

36 to 40 MM waste gate should be sufficient. The XO brand is a knock off of the Tial piece, so parts are interchangeable.

Oil comes from any pressurized port on your engine. #3 AN line and some fittings should be just fine to feed it. And you want the turbo to be higher than your oil pan if at all possible to promote good oil drain back. I run a #8 return line with no problems, some suggest #10 but I think that is a bit unnecessary.

Cooling shouldn't be much of a problem, change your oil frequently. I suggest a synthetic oil rated for turbo engines if you are concerned about it.

 

im planning on buying an oil filter relocation kit. so the oil will be pumped out the engine to the oil filter (mounted below the turbo) then come out of the oil filter in to the turbo, then out of the turbo and then drain down into the oil pan.

sound good? my only concern is that my oil pump isnt strong enough to pump the oil all that way.
to solve this, if it is a problem, should i just buy something like this?... http://www.amazon.com/DC12V-Brushless-Water-Heating-System/dp/B002PH4994

and another question i have is, is that i dont have the time or tools to pull my engine to remove the oil pan and tap a hole for a fitting so the turbo can drain back in so i was wondering if i could maybe just buy a fiotting that is the exact size of my oil drain plug and basically just replace the oil drain plug with the return line of the turbo.

what do you think?

haha sorry for all the questions as i am sure they could be somewhat annoying to someone of your knowledge.

 

to richfox

i decided that due to the fact that im guessing that my turbo since it is aftermarket is not built with seals that are usable with a draw through system , ive decided to do a blow thru, and this way if i ever weanted to i could run a bov and intercooler.
thank you for your concern though

 

I would vote "no", on the return oil through the drain plug scheme................Doesn't that inliner have removable side covers on it, ( where the lifters live)???????

Remove one, drill and tap for return, and bolt it back on, as long as , it's lower than the turbo..............

 

Oil feed for the turbo should be taken after the filter. It is really common to branch off the connection for your oil pressure gauge. This will supply more than enough oil. In my case, I have very high oil pressure and to restrict it down I machined some stainless AN adapter fittings to accept 0.060" Nitrous jets. Since you are using a stock oil pump, you won't need to do this.

Return line needs to be above the oil level in your pan, so the drain plug is not so good. A port in your side cover or in the oil pan as close to the top and behind a main cap where there it would be out of the crank windage is preferred. A fitting like this is easy to install, just drill your hole and put it in.

http://www.summitracing.com/parts/SUM-220882/