New motor time (suggestions please)

I've got an itch to do something better in the engine-tranny department for my stock '81. I've got the rearend in the shop right now getting 3.55:1 installed. I'm afraid the gas mileage is going to be bad when I get it back in and installed. I'm getting 13-15mpg now with the 2.87:1 and I took it to the local 1/8th track and pulled consistent 10.1@70mph in 3 passes.

I want decent power - stock c5 performance is what I am aiming at. I would also like decent gas mileage (20-24 is ideal). I have about $4000 left to spend. I don't want to rebuild my current engine either.

I've been watching these auctions on ebay-
http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW
This is for an 89 TPI corvette motor and 700r4. It was buy-it-now for $1900+~$500 shipping. It didn't sell. I could do the TPI, but I'm not sure what kind of mileage I'd get. It seems like it might have enough power to get me by. With the tall gearing of the 700r4, I could probably 1/8th mile pretty fast. This particular one has a few miles. I'd try to find a younger copy.


http://cgi.ebay.com/ebaymotors/ws/eB...RK%3AMEWA%3AIT
This is for a complete LS1 and 4L60E out of a late model firebird. I think I'd REALLY rather have this, but there will definitely be some teething problems and I hope it won't sink me too much into the ground financially trying to get this to work. I know the motor mounts are different, but I believe a certain company sells the adapters to make it fit right. I know the speedo will probably have to be changed (analog to digital). There's no telling what other problems I may run into. It also removes something from the current car that I really like - noncomputerized stuff is way easy to work on. 45k isn't too much mileage - it should last a long time, and get great performance and mileage. Best of all worlds. Highest buy-in cost. Highest risk in not working right, although I've seen it done by somebody on CAC.

OR

Would anyone recommend a 350HO or ZZ4 from GM Performance parts? I have a new Holley doublepumper and Victor Jr. intake to stick on the car. Like I said, I really don't want to build my own engine or tweak the original engine. From the looks of Summit and Jegs, the cost of heads and all the bits of hardware to do it myself, I can get a crate that puts out a bit less performance than these theoretically, but then I get a warranty.

I'd also entertain the Holley or Edelbrock MPFI systems. They run about $2000-2500 and if they do as good of a job in mileage as the LS1, I'd entertain that on the stock motor. I can't afford to get a crate motor and the MPFI. I'd even also entertain a supercharger on the stocker (although that probably gouges the mileage).

Anybody have any horror stories of buying used engines and sticking them in the car as-is and having them thrash apart after a few miles? I really need someone to talk me out of that LS1. I'd rather have new, but LS1 is really tempting. Can I ever hope to get 20-24 out of a ZZ4 or 350HO, knowing that I have 3.55:1 and want a 700r4 or 2004r?

[black_81_vette]

Hello,I just replaced the engine in my 81.I went with a short block from comp pruducts out of oshkosh WI and some 305 heads that have been ported and fitted with bigger valves.I am also running the same gear you are now but I am running a four speed. The cam I am running is a 488 lift 292 duration grind and a wieand action pluss intake with a well set up Q-jet.I dont have any milage figures as of yet,but the performance is awsome! And as far as I can tell even with a fresh engine im using less fuel .BTW I was getting about 20-22 mpg highway before and about 15-17 city.I have a friend with a 79 with nearly the same set up as mine and he pulls low 13s in the 1/4 and he is getting 18-20 mpg on the open road. Good luck on whatever route you go!

[norms72]

Well, you could go with the ZZ4 350/355 for about $3600.00. It already comes with an intake and Demon makes a carb specifically set up for that engine. Bolt in/on and go. The people in this forum that have them really seem to like them. Save up for the 700r4/2004r and you're set.

Originally Posted by norms72

Well, you could go with the ZZ4 350/355 for about $3600.00. It already comes with an intake and Demon makes a carb specifically set up for that engine. Bolt in/on and go. The people in this forum that have them really seem to like them. Save up for the 700r4/2004r and you're set.

Would this engine suck way more gas than an 8.5:1 or 9.1:1? I know gearing plays a ton in gas mileage, but how much can the engine itself contribute to overall mileage? I feel like I know a bit about cars, but this is stuff I haven't delved in to.

[81 Corvette]

imo, an overdrive tranny and fuel injection is need for good gas mileage. keeping the lead out of the foot helps as well

[Evolution1980]

Originally Posted by dfw81shark

I want decent power - stock c5 performance is what I am aiming at. I would also like decent gas mileage (20-24 is ideal). I have about $4000 left to spend. I don't want to rebuild my current engine either.

So you want your cake AND the ability to eat it? On $4000??? You've heard the old saying..."How fast do you want to go? How much money do you have?"

IMHO, the only way you are going to take $4000 and turn it into C5 performance is to go with some type induction or nitrous setup. I guess I should ask though, what part of C5 performance? 1/4mi times? Top Speed?

Using the 1997 base model, it was spec'd at 13.36s @ 109.4mph. That can be acheived with a ZZ4, headers, and a 700R4 trans. However, that's gonna set you back more than $4000, unless you do all the labor yourself. Since you are already going with the 3.55 rear, you could do a 200R4 instead and save yourself the hassle of the custom crossmember required for the 700R4. A 700R4 + the 3.55 would give you a very steep first gear. The 200R4 would be more practical.

However...Before I had my 700R4 trans, I had the ZZ4 mated to the stock (and very worn!) TH350. I pulled a 13.4 in the quarter. So quite possibly with just the ZZ4 and headers, decent ignition, and the 3.55 rear, you could pull the same numbers or better.

With the overdrive on the 700R4, I have no doubt my highway mileage is in the 20's somewhere. Hell, it might even be that in the city. I don't keep track though. When the tank's empty, I fill it.

dfw, just don't count on those high dollar fuel injection systems to give you gobs of power. they only support that kind of power that the engine components build. they do however give you better driveability and easier cold starting with usually improved fuel mileage. if you look around for old conversion vans 87 and newer, good chance they can be bought cheap. get your tranny there and scrap the rest. I am doing that as my winter project. Good Luck!

Originally Posted by Evolution1980

IMHO, the only way you are going to take $4000 and turn it into C5 performance is to go with some type induction or nitrous setup. I guess I should ask though, what part of C5 performance? 1/4mi times? Top Speed?

I'm definitely not looking for top speed. I'd like to get 0-60 down into the low five second area and the quarter in 13 at about 110. After that, the requirement is just gas mileage. I'd like to be able to go from Fort Worth to Eureka Springs and back without spending $150 in gas.

I think what I am going to do right now is completely scrap the ls1 idea. It is too risky. I'm very leery about buying used engines off the internet from wrecked cars. I know I am asking for trouble. Therefore, I am pursuing just the transmission right now. I will also probably buy a nice set of headers and intake to go with the motor, as these will bolt on to a new motor should I decide that later. I'll take it as slow as I can, so I try not to don't regret a hasty decision down the road.

Thanks,
Michael

[Glensgages]

At one point in it's life, my '79 Z28 ran 14-thirties at 97+ MPH, and got 17+ MPG highway;
NOT the numbers you speak-of, but in those days, we didn't have the luxury of A/OD transmissions, all the performance advances made in the 20+ years since then, either.

It was based-on the stock '79 LM-1 short-block (very similar to the L-48), the original THM350, and original 3.42 gears;
if that'll tide you over, and want some info, let me know.....

GLEN!!!!!

[photovette]

I put a Grooms Engines 355 Perfomance Plus motor in my '77. It has a no questions asked lifetime warrenty. I also can whoop C5's on a regular basis now even with all the original emissions equipment. I have a 3.55 rear end and a TH-350. I get 17mpg in town and on the highway. Fairly inexpensive too.

Yeah I'm definitely interested in some info. The stock Z28 came with 3.42s? I think the upgradable option on the vette was only 3.15. I am really inexperienced when it comes to how the carb, intake, and engine play together to suck down fuel. I understand past the flexplate.

One good question I can come up with now is: am I right to think a 600cfm carb always uses less gas than 750cfm carb? Or is it correct to think the a 750cfm has the potential to suck more gas than a 600cfm? Is it a jetting issue and not the cfm number altogether? How does a "doublepumper" differ from a standard carb?

That's it for now. I can make my messages quite lengthly with tons of embedded questions. I am really interested in how you tweaked the Z28.

Thanks,
Michael

[Glensgages]

Originally Posted by dfw81shark

I am really interested in how you tweaked the Z28.

Really, it wasn't much;
in the 23 years since, there is probably even better combinations offered.....

Car was 2 years old, with 20,000 miles on it:
removed everything from the cylinder heads up, and the camshaft.

Replaced same with:
Holley #4777 650 dbl-pump carb
Chevrolet dual-plane intake (327/365 HP from the mid-sixties we had just laying around)
a pair of 1.940"/1.500", 64cc heads from the same era
hydraulic cam, lfters, and springs (SUMMIT Racing house-grind, .450", 218* @ .050" lift, 114" LSA)
ACCEL HEI ignition and Super Coil adaptor
"on-sale" headers (BlackJack? ), and straight 2.250" pipes (no cat) to the OEM resonators (mufflers)
B&M shift kit

As above, car would run 14.40s @ 97 MPH, shifting at 5500, and trapping at approx 4500 in 3rd gear, with open headers, on 225/GR70-15 UNIROYALS, thru the 'one-wheel-peel' open rear end.

Car maintained OEM short-block, with standard crank, 'junk' rods, and cast pistons;
with 64cc heads, it made 9:1 cr, which'll probably run on any gas you choose.

Other than shift kit, trans was un-touched, using OEM GM 12" converter (I added the Hurst Dual-Gate II shifter 'cause it was neat, and it's still there to this day).

Car idled a bit 'lumpier' than usual with the cam, but didn't over-heat, and the A/C ran fine, too.
On a 680-mile round-trip with the car, I got 17.8 MPG:
almost 19 at 60-65 MPH on the way, but only 16+ on the return trip (at speeds WELL-over the limit...)

I would think that with the technological advances since the early-'80s, you could easily duplicate those numbers, and even better them.

Similar carb, Edelbrock Air-Gap intake, Edelbrock aluminum cylinder heads, any similar camshaft (268H, ground at 114* LSA?), and today's exhaust/mufflers offer performance equal-to the open-pipes of yesteryear (but not as-much fun).

If you'd use a prepared 700R4/200-4r OD transmission, with both a lower First Gear, and OD, I'd think you'd easily beat BOTH the ET/MPH and MPG figures, if it hooks at the track.

[70 LS1]

The LS1 will set you back between $5000 and 6000 by the time you are all done. I was able to hang with a Z06 from a rolling start and I still get 26 ish mpg.

Originally Posted by 70 LS1

The LS1 will set you back between $5000 and 6000 by the time you are all done. I was able to hang with a Z06 from a rolling start and I still get 26 ish mpg.

That's awesome. I just don't have the cash to do that right now. I think I'll table the fuel injection for the next project. Hell, I may even own a C5 one of these days...

I think I'm going to try to set up like Glengage's for now. I'm going to wait for motor work until I get the rearend, transmission, and headers done. Then I'll gauge where I need to go. Depending on how things go, I may just leave the motor alone for now. I'll keep you guys posted as this monster progresses... Thanks!

[Blue82]

Try these guys out of San Antonio http://www.fuelinjection.com/. They buy low mileage, wrecked sports cars and remove the motor, trans, wiring harness, radiators, air purge components for reverse flow systems , etc... Basically everything you need to install them in another vehicle.

I called them when I was debating a rebuild / swap.