mjgord51

I am working with a 68 C10 long bed (V8) now. The truck originally had a 6 cyl. with the 5/16" fuel hard line. The fuel pump connection area the line was right behind the engine perch and motor mount making it real hard to service, thinking that line was for a 6 cyl. and not for a V8. I will add more info if needed.
Now here's where I am now. I bought 3/8" fuel lines & sending unit from Classic Ind. Huntington Beach, CA and the line from sending unit & the short line going through the floor at the sending unit connection doesn't line up so they are going back for return.
I was always told if you have a V8 you need 3/8" line & the 6 cyl's would use a 5/16" line. On the other hand some say the smaller V8's can use 5/16" lines & sending unit. Not sure what to believe now.

thanks in advance.

Gumby22

I’m not too familiar with the set up on the 68 pickups and I don’t have the exact answer for you, but it’s a matter of volume. A V8 requires more fuel to meet the proper air-fuel ratio, so the volume is easier to move through a larger line.

Chances are good you’ll need 3/8” line, but the carb should meet the demands of engine displacement, and the pump should be able to meet the fuel demand of the carb. If you’ve already selected a carb and pump setup, check the manufacturer specs for volume - over 35 gallons per hour and 3/8” is a better size to meet the demand.

I think no matter what, you’ll probably have to either make your own line or adapter fittings to get everything lined up the way you want.

mjgord51

Volume "may or may not" have a part in this as I have seen from different Catalogs for Restoration Parts for these trucks (50-59) - (60-66) - (67-72) one of them list 50-59 "all same" same catalog 60-66 "all same" that being said both grouping years of trucks have 6 cyl's to V8's all of different cubic inch's and using 2 & 4 bbl carbs, for the 60-66 group the 327 c.i. motors did have a 4 bbl carb requiring more fuel than the 2 bbl usages but still listing it with "all same". On the other hand I have seen some Catalogs clearly stating 2 bbl or 4 bbl differences with No Foot Notes indicating something special used.

My actual question was leaning more too about the fuel line fitment at the fuel pump area (frame & eng.perch area) as well with the Sending Unit fitment with the line coming out from the floor not matching or inline with each other at the sending unit connection fittings. Catalogs are not all the same even though they sell Restoration Parts with in the end sometimes needing a "tweak" here and there for the part.
My purpose for my question was to see if anybody else has had the same problem I am having (68 c10 V8) for fitment and having a solution for the Correct Lines and Sending Unit needed to get me back on the road using a catalog for the parts needed.
Thanks again in advance

Gumby22

Fair enough - I guess I was understanding your question as needing to know if you had to install a 3/8” supply line from the tank.

As for volume, I was looking at it from a purely mathematical standpoint - a larger engine requires more fuel, plain and simple. Therefore, the carb - regardless of the number of barrels - has to be able to meet that demand, which it can only do if the fuel supply is adequate to keep the bowl from going empty. That means the fuel pump has to be capable of doing so, and in terms of mechanical work, it’s easier to move a larger volume of fuel through a larger line.

I promise that’s all the more I’m gonna say about it. I don’t have the time or energy to start crunching numbers just to prove my point.

Are you restoring this truck or just replacing the engine? Pics?

kevinkpk

We did a 71 replacement tank, and unit, I don't remember other than it (sending unit) installs with a lock ring, and gasket (O ring). Small block chevy with an edlebrock 650 square bore. I had a 69 caprice with a 327 quadra jet years ago, as far as tubing diameter it was 3/8.

kevinkpk

mjgord51

Actually the part with 3/8" line was about I bought for my 68 C10 V8 the fuel lines and the sending unit as a matching pair and when installed they didn't line up to one another, with the sending unit with the short line going down through the floor at the sending unit it wasn't lining up to each other like the old line & sending 5/16" did, the line coming out of the sending unit was at a different clocking or not at all lining up with each other (new 3/8" line) and they were confirmed over the phone by a representative of Classic Ind.they are a matching pair. All of what I have seen on everybody's online catalogs with pictures shows the sending units line coming out of it all are clocked the same just like what I bought.
I even watched a YouTube video with Kevin Tetz showing how to replace your Sending Unit for 67-72 Chevy trucks with parts from LMC but in the first part of that video it did show the- - -SAME MISSED MATCHED lines with screw in connectors but as the youtube video goes on it changed to showing the two line having different line setups with then changing out to having slip on hose connectors. Kinda Stupid starting out with one kind of setup of lines and ending up with a complete different Solution Fix, but then again the parts did come from LMC.

Kinda curious you end with a statement like your all done and haven't any more energy left to crunch numbers- - - - what for it - - - what for it - - - then you ask me more about what I am doing with the truck, and then wanting pictures. You made your point for fuel volume with a good story then you puffed your chest out again in one more post about the volume thing again, I get it that larger motors that Pump Out Tremendous Volumes of Horse Power like upwards of 400+ and beyond but we are talking about stock small block motors like 250 esh horse power at best.
Actually now I don't have the energy to keep this conversation going with you. Have a good day guy.

mjgord51

Your picture show the same problem I had with the sending unit Not lining up to the fuel line coming out of the floor, seems as you also bought your stuff from Classic Ind. How did you get the two lines to line up?

Gumby22

All I meant was I didn't want to turn this thread into a long, drawn out argument over exactly how much fuel your engine was going to need because it distracts from the original intent of your post - then your question may never be answered. I've seen it dozens of times on auto forums where guys will start nit-picking and bickering with each other and throwing equations into their posts to prove exactly why they are right - that's what I don't have the time or energy for.

Absolutely no "chest puffing" intended - I only wanted to clarify why I brought up fuel volume to begin with, which was because I misunderstood your original question. Clearly we don't know each other personally and I've no idea what level of experience you have in automotive repair, so how would I know whether or not the carb and pump set up you have is adequate? I don't, and if you're certain that it'll work for you, I'm not going to try and convince you otherwise.

I asked what you were doing with the truck and if you had pics out of pure curiosity. Rebuilds and restorations are interesting to me, but if you don't want to share, that's absolutely your choice.

Good luck.

kevinkpk

The sending unit has a lock ring with o ring seal. Rotate the locking ring counterclockwise, rotate the sending unit to align with the tube connector, then lock it back down. I'd recommend little bit of grease on the O ring as it won't grab on the lock ring.
Side note, we all are tired, and tired of this coron crap, just take it into consideration, enjoy your project!