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6-71 or NA advice

11K views 89 replies 15 participants last post by  bygddy 
#1 ·
So I made the deal, I swapped my Comet for the junk Vette with the blower motor. Here is my dilemma, the motor was put together about 6 years ago, dyno'd, then put on an engine stand in a heated garage. 2 summers ago it was put in the car, the wiring was a disaster so that was cleaned up and the motor was fired. It ran for a few min in my laneway, float sticking issues made us shut it down, then a dead battery prevented a restart and the owner had to go. The car sat with a cover over it, and a seperate cover over the motor, outside in the snow, then in the spring was towed out. Went to its "new" resting place and sat again untouched for the summer and this past winter.
Now its coming back here.
I can install it as it sits in my Monte, run new braided line and hope the Holley red is still OK after 6 years of sitting, hope the motor is OK etc etc, or
I can pull the motor down, sell the blower crap, replace the blower pistons with good forged pistons, install a big solid roller, a VC Jr and and an 850 and shoot for 500hp NA
It has forged internals, VC Jr heads as it sits.
TH400
3500 stall
4.11 gear.
So do I run fuel lines, bolt the thing in and see what I have? Or do I take it apart and redo it, as usual money is an issue, I can sell blower stuff to fund cam and pistons, or I can spend very little and install it with the blower.
 
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#2 ·
id go blower!!!

if money is an issue why not try to work with what you already have? worst case scenario it comes back out of the car then you can sell and rebuild an n/a motor. plus if i remember from your previous post this was making big power without much boost?

are you racing the monte?

ive never owned a s/c car, but i would love to.
 
#13 ·
I have to agree,all you have to lose is your time to install the engine and firing it up.If it's not OK,just tear it down and rebuild it the way you want.I have been playing with blowers for many years,no racing,just street driving.I have had a 6-71 on my 39 chevy for 35 years,on various small blocks.I have a 4-71 on my freshly built T-bucket.The blower cars are lots of fun to drive. That being said,I also follow NMCA and other drag racing,and the Turbo cars definately make extreme power.If it becomes financially feasable,I plan on replacing the 4-71 with a twin turbo setup on the T-bucket.
 
#3 ·
Swap

Why not sell the whole thing to somebody that knows how to tune a blown motor? Theres a lot of good parts in there to just tear it down and rebuild. Take the money and build something your more comfortable and can tune within your capabilities. Seems less complicated, anyway Good Luck./
 
#4 ·
I'm not conceremd with the tune aspect of it, its more the fact that its been sitting so long, that's the only thing I'm overly worried about. I wouldn't sell it as it sits, I would keep the blower pistons and cam aside and go turbo at a later date if anything. It had Carb and timing set up with several dyno runs and nobody has touched it since. No racing really, it will see a track a couple times a year, and lots of street miles. I'm going to swap the gears to 3.55 if it stays blown.
 
#5 ·
I would pull the heads and look inside. I would also take the heads apart to check spring pressures.maybe flip over and pull a couple bearing caps( one crank,one rod)If all looks good,it cost you gaskets.The knowledge of whats inside will lower the guesses when you tune,,,,,
regasket the carb and clean any glazing(you would have done that anyways)
afternoons work for piece of peace

go blower,lol
 
#6 ·
You know what, that makes sense, I'm likely being overly paranoid, I was conceremd about the springs from sitting, and will have them checked, but its a small roller so hopefully they aernt a huge spring. I assume I'm going to have to switch pans anyways from the C3 to a Gbody so will peak at the lower end while im there. Carbs will need cleaning, they were brandnew but the floats were stuck the last time we fired it. Ihad the boost number wrong, it is pullied for 9psi and that's where the dyno runs were done. With 110 and 36* it made its biggest number. Then it was set up with 20* initial and 32* total for 92 where it made 650hp
 
#7 ·
at 650 hp the torque will be huge by fat.If you get tired of breaking things or buying tires the blower can come off and sold....
then the bad part as your brain contemplates a turbo,,,,,
I watched a bunch of videos today with turbo cars making so much power that they power wheelie about 150' down the track,,,,!!!!
 
#8 ·
I spend way way too much time watching turbo car vids, and reading on turboforums,
The bad news is, I think that the wee 7.5 won't live long, even with upgraded axles and posi as it sits. The good news is if I keep the Drag radials aired up it will never hook so maybe that will help driveline longevity.
Anything else I should be looking at from sitting so long? I assume new braided line for fuel? should I bother with a new pump? This one has virtually zero run time on it. Should the trans have anything done to it? It made a couple short drives behind an 850hp BBC and then was bolted to this motor and hasn't moved since.
 
#11 ·
It has brand new MT drag radials, 275/60's
But they tend to hook with a combination of a decent burnout and having them aired down. Your right, what some of the turbo guys are doing on small tires is unreal.
The PO had an AFR headed 406 in the car with a T56 and he beat it hard with no breakage. It regularly saw the strip and many third gear burnouts on the street. I'm amazed its lived this long. I will see how gentle I can be until I can afford a 9"
 
#10 ·
just make sure the seals dont leak for the trans,,,
When putting the engine back together slap assembly lube on cam if you can. I used to pour STP in back in the day and or E.O.S. from GM.
Change the oil after a day and have fun.The 7.5 will grenade when you step into it even on a roll
you have a lot of straws and a very small camel
 
#12 ·
I'm going to talk to my tranny guy tommorow and see what he will charge me to go through the thing and replace seals.
Yah, I don't know how much, if any help the upgraded axles and posi will be.
Thanks for the e.o.s tip for the cam while its apart, I wouldn't have thought of it.
 
#15 ·
New toy arrived. Going to pull it this week or next, get it on a stand, every nut and bolt is crusty and rusty. Going to pull all of them and clean and paint them. Rebuild the carbs, replace vacuum lines, replace plugs, figure out how to change the supercharger oil, replace engine oil. Then install in the Monte and see what I have. Should be entertaining.
 
#17 ·
Check the blower belt at a minimum, if not replace it entirely. Pop the distributor cap and take a peek in there. My friends dirt track car had a VERY rusty MSD distributor after about a season...One of the blower guys here can probably talk to you about hot start issues and blowers, may or may not be a problem for you.

NO ONE regrets getting a blower...
 
#18 ·
Small update
Blower is off and sold
Weld wheels are off and sold
C3 exhaust is off and sold.

I have ordered and paid for the following
76mm GT45 Turbo
Large by huge front mount intercooler, charge piping, couplers etc.
Oil feed and drain lines.
Forward facing turbo headers.
Complete fuel system including twin Walbro 255's, sump for tank, 8AN and 1/2 hardline feed and return, aeromotive bypass reg.
Assortment of vband clamps and flanges.
I still need to order the Carb and Carb hat.
Will have the motor out of the Vette in a couple weeks, then I have the shell sold for 1500.
That 1500 goes to the CSU Carb ($1000.00 jeez us) and Carb hat.
Goal is a 700rwhp street car
Stock appearing right down to wheels
Only non stock is 2" lowering and small cowl hood.
 
#23 ·
So, fuel system all here minus the stupid expensive filter, boost guage here, UMI heater delete plate here, intercooler, BOV and WG all at customs, should be here Friday/Monday, headers are backorderded 6 weeks, no biggie, lots to do between now and then, but at least this arrived today!

Its sxy, and one big heavy mother
 
#25 ·
Have tyou looked into EFI. You are not too far off for what parts you have. EFI will make tuning so much more stable, i.e. the tune is only as good as the EFI tuner and dyno operator.

I did an EFI BBC 871 project for my Jet boat. After the dyno session this thing started and idled rock solid, no surging or anything. It had 12psi of boost and was a violent ride. After a hard run I would idle it to the sand bar where the hang out was. Never stalled, never sputterd or nothing.
Since sold the bolt and parted it out. To many other projects. However if I were to do it again it would be a turbo. Blowers look cool but...
 
#27 ·
I did consider it briefly, but I'm completely mentally challenged when it comes to injection.
And tuning along with the initial cost of getting started made me stick with a Carb.
For the most part I have heard nothing but amazing things regarding CSU carbs in regards to power as well as driveability. I do want to go with an injected LS at some point when this either breaks or gets boring but have a ton to learn before that happens.
 
#29 ·
If you know someone with a radiator shop, or its cheap enough, have that pressure tested before you do the install. Its probably fine, but a few pinholes can drive you nuts, especially after you do your best IKEA impression and pack 5 pounds of crap in a 3 pound bag.
 
#34 ·
bygddy,
Sorry I may have not followed this post all the way through. What are you pressure testing?

What process are you using to join your turbo tubes/pipes? Are you planning on pressure testing those too? I have done quite a few of turbo tube welding for people as well as blow off valve flanges and I always pressure test when complete. Regardless of how well a TIG welder you are, the naked eye cannot see tiny tiny holes. Some turbo people on other forms just slap stuff together with bird poop flux core MIG welds and wonder why their boost and performance is so poor. Over the years I have made many pressure test adapters and JIGs. Here is just a small sample of what I have, mostly home made cobbled stuff.
 
#36 ·
piece of pvc pipe with a cap on it make 2 of them then drill and tap the ends one for a guage and one for a air fitting , put aregulator in the line and test away

word of advice do not point the caps at yourself or anyone else i had a friend helping me presure test some of my pipes and he forgot to tighten the clamp all the way lets just say getting hit with a cap with only a few psi behind it really sucks
 
#37 ·
So I currently have an MSD 6AL in the car, I need the ability to retard timing obviously.
I was looking at just using an add on MSD 8762 for boost retard and keeping my current box.
The other option is the MSD programable 6AL2 which seems to do absolutely everything and more.
My concern is I'm more then slightly inept with all things computer related and not sure if I could get the thing right.
I don't really need the 2 step, launch control etc. I need boost retard, and start retard would be nice.
Opinions?
Thanks
 
#39 ·
That's kinda what I'm leaning towards at this point, I can run a normal advance curve, and use the BTM to pull timing under boost, no hassle there. If I upgrade next year then I can look at something more advanced. I was concerned about possible failure with the BTM and hurting something with full timing and boost but I have to hope the quality is better from the earlier timing retard boxes.
 
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