You know what they say about opinions? Well, I'd like to know yours.

[jgrote]

Well, I can't leave well enough alone. I have a "problem" and I'm going to throw money at it. Currently, my truck has a 350/350 combo, and no telling what gear in it. (None of the running gear is original.) It has an Eddy carb, and electric FP on it. It also has some HEI in it, but it looks like it's probably an Amazon special. (Works fine though.) It's running way too rich, and gets terrible mileage. like5-6 MPG. And it stinks like gas a lot. (Not leaking anywhere.) The motor seems sound, but definitely isn't new. I was having some dieseling issues, but some Seafoam, plugs, and a good Italian tune-up seems to have fixed it.

So... My options.

1) Holley Sniper and a rear mounted tank. This is the easiest option, as I can do most of the work in stages, while still able to use the truck. (Tank, wiring, fuel pump, etc.) I could be down for a weekend or less. But, I still would have a old engine, 3sp trans, and a reasonable top speed of about 65. Anything more, and she feels wound to the moon. But, suspension and braking also limit this as well.

2) 5.3 and 4L60 swap. Money isn't THAT tight, but I'd still have to go the JY route. In my area, everything is 4wd, so I'd need to do a tailshaft swap. I would do a minor refresh on the motor, but I'm not interested in rebuilding it. If the one I find has DOD, I'd obviously do a cam and lifters to do away with it. I'll probably run Holley for management. The biggest downside is down time. I'm afraid this can turn into a boondoggle that takes me months to finish. I don't have months. I know I can gather parts, clean and modify the engine/trans, and get the fuel system in place first, but it is still a lot of work. And I don't own an engine hoist anymore (and don't really want to.) I feel like this is the better way to spend my money, but I think it may be too big a job for me right now.

3) And out of left field, there's one more option. I happen to have a 57 Belair that is sitting in my garage, with the front clip already removed. It's been parked in a garage since the early 70s. It has a 1969 327 in it, which I did get running not too long ago. It built oil pressure, and didn't smoke at all. I pulled the valve covers, and it honestly looks like it's brand new in there. So, should I throw the 327 in the truck, and then EFI that engine? The only downside I see in this choice is that it's a little more work (2 engine swaps), and it doesn't get me an extra gear on the trans. The 57 is for sale, so I need to make a decision before I sell it.

[notsolo]

Maybe a quick fix for now, pressure regulator and gauge, if you don't have 1.... I ran into similar problems and a leak across the head gasket. 5.3 4L60 swap was well worth the time and effort.18-20 mpg with regular gas.

[Grumpy old man]

Option - 4 ) Get rid of the Eddy and put it back to the way it came with a Quadra jet and mechanical pump , All the other options are time consuming and costly , Be done on a Saturday project . How much do you actually drive the truck that you would have to spend BIG BUCKS AND TIME to justify the gas milage ?

I'd be looking at how that electric fuel pump is wired , if it's direct wired to the ignition it's not going to turn off in a crash and will keep pumping fuel .

[jocko]

from a math perspective, you'd have to drive the truck 30 miles every day until you're 120 years old to recoup the investment in the Sniper setup such that you would then be saving $ on fuel. Just kidding, I have no idea how old you are - but you get the idea. I'd submit that you have many more options that your 3 or Grumpy's #4. And of the 4, I definitely align to #4. Your gas smell may be totally unrelated to your engine - what's your fuel tank setup - vented, unvented, relocated, EEC, etc? You pose a good question and it's one many folks deal with at one time or another - dump the old and somewhat unknown engine for something you'd rather have - or make what you have better. I have the same dilemma - I have a mid/late 70's 350 in my truck that I "want" to replace with an L31R. Haven't done it just yet because I'm cheap There can sometimes be more satisfaction in making something you already happen to have work better than in just replacing it. Having said that, I'm still leaning toward the L31R (which I will propose as option #5 since you seem to be considering engine swaps as an option). But it'll still need an induction system - which is what it sounds like may be your problem - a problem that could be solved on your current engine. Bottom line - if you'd be ok with your current engine if it didn't exhibit all the current issues you're concerned with (except the fuel economy), then I'd just fix it - if you actually want to replace it, then don't waste $ on the current one and make plans for a swap. If you do any highway driving - your fuel economy is probably more related to your trans/rear end combo than the engine. If fuel economy is your biggest concern, I'd swap to an O/D trans and just get your current engine running more efficiently. Your fuel economy won't improve drastically with the Sniper setup if you keep the TH350.

[dmjlambert]

Others have mentioned an option 4... That's what I would do. A remanufactured Quadrajet for cheap from National Carburetors, new Auto Zone store brand mechanical fuel pump, bend yourself a steel fuel line to go from the fuel pump to the carburetor, original intake bought used and cleaned up, and verify the gears by lifting a back wheel off the ground and count the turns of the wheel compared to turns of the drive shaft, and change it to 308 economy gear if necessary. I'll bet somebody would trade rear ends, and you can give your highly desirable (for some reason) launching to the moon gear to somebody for their economy gear.

[kwmech]

What are the driving needs for this truck---daily driver, occasional jaunts here and there, plan on keeping it long term, hauling/towing?

[Don Brace]

My 71 C30 Longhorn gets 15 mpg on the road. I switched to a 3speed overdrive on the column ten years ago. I drive it 70 mph. The OD is a truck OD but a car OD will work fine.

[LS short box]

I'm a LS guy but I think I would do option #4 assuming the engine is in good shape. I'd run a compression check.
Keep in mind if you go FI you will need to add a high pressure fuel pump, regulator and assorted parts to support the FI system.
No reason the eddy carb won't work if its in good shape and is well tuned. Quadrajet is also a choice but again may need to be tuned to match your engine.

[jgrote]

Lot's of great questions and advice here. Thank you guys! To clarify a few things:
1) I drive it almost daily, but not far.
1b) I do occasionally use it for truck stuff. (camping, HD runs, dump runs, etc.)
2) MPGs are not my biggest concern.
3) I like F.I. better than carbs, and I will be adding F.I., one way or the other.
4) This is a toy, not a financial decision.

I have considered the Sniper, a 700R4, and keep this motor, but I'm not sure I'd be as happy with that as I will a full swap.

*And for the last consideration; the WIFE! Since it is our money, she gets veto power, and some kind of vote. (Not as heavily weighted as mine, but a vote.) Her vote is to swap to the 5.3/4L60

[dmjlambert]

The clarification helps. It sounds like you and the wife would both be happiest with option 2, that's a win-win, so I change my opinion to option 2 full speed ahead.

[jocko]

Well in that case... swap in that 5.3 4L60 and take that wonderful wife on a vacation wherever she wants to go!

[LS short box]

Well LS it is.
Hope you have good luck with your project.
Maybe a 6.0 instead of a 5.3?
On my LS swaps I've used the stock GM ECM's. I typically go small cam. I haven't done any big power LS swaps. I like using as many stock GM parts as I can in case I need replacement parts in the future.
On the older LS engines (24 tooth crank reluctor) uses one ECM for the engine and trans. The newer LS engines (58 tooth crank reluctor) use one ECM for the trans and one for the engine. Either work well.

[cbeerman]

Personally I'm not a big 4l60 fan. I've spent more money on them than I care to mention. Granted they were behind some built motors but they just don't hold up. Any thoughts about a 24x LS motor and a 4l80? You still can run a 0411 pcm with a stand alone harness.

[jgrote]

After many minutes of research, price checking, and schedule checking, I (we) have changed my mind. I'm gonna go with sniper. The biggest reason is time. I'm a one man show, with no friends willing to put in that much time into wrenching. I'm gonna throw a sniper and bed mounted fuel tank for now. 4 speed auto will come later. I'm not sure if I'll do 700r4 or 4l60 yet. I know they're pretty similar.

[chevy72blu]

As the owner of an LS swapped truck, you should fix what you have.

You seem to be throwing up your hands about fixing the carb and mistakenly think that EFI will solve all of your problems. We havent even really dug into what your problems are yet.

EFI can be costly and painful too. Power gains will be minimal, if there are any at all. EFI will not make the truck significantly more reliable. A well tuned Holley or Q jet will get your truck back to decent mileage much easier, less expensively, and with fewer headaches than anything else.

It is your money but in my opinion it is a waste.

Going LS/4l60E/EFI tank is a bigger project but it would also yield actual results. I'd do one or the other, not a half measure.

[cj847]

I am an "LS everything" guy, but I agree with chevy72blu. Unless your engine is smoking like crazy and obviously on it's last leg, fix it and drive it.

1) Eddy carb adjustment instructions are available on line. It is highly unlikely that anyone has changed the jetting, so an idle mixture adjustment is likely all you need.
2) Gas smell can be fixed, but most don't even when moving the tank to the back.
3) Determining rear gear ratio is a simple task. Instructions available on the internet. But, regardless what factory ratio it has you will likely get a max of 12-14 mpg.
4) After that start saving for your future LS swap.

[jgrote]

I fully understand that the carb is work-able. I.... just don't like carbs. I'm not playing with an old truck because it makes sense. I play with my old truck because I enjoy it. And, I've never done an EFI swap into a carb'ed car before, so this should be fun. I've done a couple engine swaps, a harness merge, and other crazy stuff for no good reason. My biggest build was shoehorning an EG33 out of a Subaru SVX into a Forester. I was the first one to figure out how to make the auto trans work, and keep AC. It took me about 18 months to build it, and I was a lot younger then. So, really, my decisions are being made mostly by considering the time this will take. I don't have very much of that. Once my kid is out of the house, a full drive train swap will be more possible.

[tutone]

I have a good friend who built a 69 swb for his son a couple of years ago. Turned out to be a neat little rig. He sourced a salvage low mile vortec 350 from a 98 chevy and used his already bought 700r4 (pre elec shift).
He retained the computer and sent it and had part of the harness deleted and added a pressurized tank. All this was around 1500 bucks. The truck already had 3: 73 gearing. After reading your thread over the last few days, I called him for an update on it. He said even with his son's driving habits ,the truck gets a solid 15mpg around his area and will get 16-17 on the highway at reasonable speeds. The best thing he noted was the trouble free aspect. Cold starts are better and the truck has plenty of power. I think at this point, anything you do will be an improvement. Good luck and let us know how this turns out.

[A1971Blazer]

The Edelbrock carb is really finiky about fuel pressure...about 5 psi is all it wants, otherwise it cannot handle the pressure and will run super rich, you mentioned that you have an electric fuel pump....do you have a pressure regulator in the system?

[biketopia]

If you're thinking of going with an electric OD trans in the future, which i would do over a 700, I would highly suggest you look into the terminator x max stealth system over the sniper. I had a sniper and ran into a lot of RF feedback issues that just made my car not fun to drive at all. The terminator x stealth uses a similar throttle body either one that looks like a carb, or just a TBI unit, but the ECU is separate. It's also the same ECU as their other terminator x kits, so if you want to go LS one day, your management is all there, just swap harnesses. You could even just go with the X not the X max and forgo the expense of having trans control for now, and down the road sell the x and buy just the x max ECU. With the terminator kits you also get a lot more tunability with that ECU, more inputs and outputs, for example you can run a dual sync distributor and then run 8 LS coils.

That's what I have on my SBC in my camaro, a terminator stealth system with trans control, which the non X stuff is their top of line ECUs, so I have a dominator ECU which is way over kill but the price was right I couldn't pass it up. My car hasn't ran this great in years, the LS coils are plentiful if you'd ever have one fail you just have miss not a dead engine, the benefits are huge. If you have any questions I'd be happy to help answer them.

[1970 CST Short Wide]

I went back and forth about going LS for a long time. Went from 350/350 to 454/350 then this LS1 with 6 speed manual with ~ 40,000 miles came along for $2500. I took a leap of faith and didn’t look back. Best move I’ve ever made. I drive it anywhere and everywhere with NO problems. Dependable,Fast and Fun
Just my 2c

[jgrote]

Thank you everyone for your responses. Your experience helps me quite a lot. I was taught long ago that learning from the mistakes of others is way less painful than learning them yourself. At this point, I think I'm going to go with the sniper, just as a stop-gap. When time and budget allows, I'll switch to LS and OD trans. (Probably a 4L60, since they're a dime a dozen.) My local JY sells engines for $200, and trans for $90, and the Tahoe is the #1 thing in the JY. If I can finally get someone to buy my 57, I would have time/space to start collecting parts for the swap.

On a side note: I turned both idle screws down a quarter turn, and she's a much happier engine. If I find a good deal on a wide band, I'll do a little more tuning. I have a tuning kit for the Eddy, just no real good way to measure AFR. And I'm not old enough to tune a carb with just a vacuum gauge and a timing light. (I miss you, Grandad!) At this point, I'm probably just stalling a little, hoping that the right deal will come along for a swap.

[biketopia]

If you're on FB I would 100% join the group "holley sniper efi owners and tech" there is a lot of good info on what will hinder your outcome and success with the sniper. There's a lot of complaints on there, but you gotta remember you look for help when there's a problem, not when things are good. I was not a fan of my sniper, but my camaro caused all kinds of havoc with RFI. My buddy has one on a SBC gremlin, and its the most trouble free thing there is. You'll need to factor in the fuel system upgrades, a throttle cable/kick down bracket that fits, and few other misc items. I would piece together my own fuel kit vs buying holley "complete kit" you can build it to reliably support the LS down the road. I would 100% look on that FB group for someone selling a take off before I bought new at full price if you're looking for just a stop gap. Second option would be to get a refurb unit https://www.holley.com/products/fuel..._-_sniper_efi/ Last bit of advice, ignore the quick start guide with any EFI. Download and read, reread, and read again the full install book and follow it to a T. Here's the link to the snipers, https://documents.holley.com/199r11031r.pdf

[garyd1961]

Originally Posted by jocko

from a math perspective, you'd have to drive the truck 30 miles every day until you're 120 years old to recoup the investment in the Sniper setup such that you would then be saving $ on fuel. Just kidding, I have no idea how old you are - but you get the idea. I'd submit that you have many more options that your 3 or Grumpy's #4. And of the 4, I definitely align to #4. Your gas smell may be totally unrelated to your engine - what's your fuel tank setup - vented, unvented, relocated, EEC, etc? You pose a good question and it's one many folks deal with at one time or another - dump the old and somewhat unknown engine for something you'd rather have - or make what you have better. I have the same dilemma - I have a mid/late 70's 350 in my truck that I "want" to replace with an L31R. Haven't done it just yet because I'm cheap There can sometimes be more satisfaction in making something you already happen to have work better than in just replacing it. Having said that, I'm still leaning toward the L31R (which I will propose as option #5 since you seem to be considering engine swaps as an option). But it'll still need an induction system - which is what it sounds like may be your problem - a problem that could be solved on your current engine. Bottom line - if you'd be ok with your current engine if it didn't exhibit all the current issues you're concerned with (except the fuel economy), then I'd just fix it - if you actually want to replace it, then don't waste $ on the current one and make plans for a swap. If you do any highway driving - your fuel economy is probably more related to your trans/rear end combo than the engine. If fuel economy is your biggest concern, I'd swap to an O/D trans and just get your current engine running more efficiently. Your fuel economy won't improve drastically with the Sniper setup if you keep the TH350.

I have the L31-R in my truck and couldn't be happier with it.

[mr48chev]

Looking at the local price for regular today 3.85 if he gained 4 mpg he would save 109 dollars every thousand miles. Meaning going from 10 to 14 mpg. That would take 14,250 miles to have the Sniper pay for it's self.

Still it would be prudent to figure out why it is doing so badly right now.
I did pretty much the same thing on my 71 with the 350. Hei from Skip white on Ebay, new Edelbrock carb on a performer that I have owned for 35 years running a mechanical pump in the 71 3/4 ton with turbo 400. I picked up two mpg with the Hei swap and 2 or 3 with the carb swap. I was driving the truck 50 miles a day to go to work and back.

I'd either invest in a good quality pressure regulator or spend about the same money and change to a mechanical fuel pump. If you have any sort of ricky racer pump it is probably putting out way too much pressure for the needle and seat.