Plastic Liner inside tank??
Thread Starter
Melting Slicks
Joined: Apr 1999
Posts: 3,264
Likes: 3
From: Toms River NJ
Plastic Liner inside tank??
I heard some c3's have a plastic liner inside the tank? I was curious if '74's had this liner or if its just all steel. I wanna know cause I am planning on welding in 2 fittings as new pickups.
Thanks
Chris
Thanks
Chris
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
Re: Plastic Liner inside tank?? (QuickVet)
This might be useful.
In 1975 the Chevrolet Corvette was unable to meet FMVSS 301 and not leak more than one ounce of gasoline a minute after a 30 mile per hour rear end moving barrier crash. GM's solution was to introduce a rubber bladder which provided the necessary protection against gas spillage inasmuch as the tank is located in the crush zone approximately 8 inches from the rear bumper. The history of bladders in competition race cars and in aircraft has been well documented with a variety of problems: deterioration, condensation, folding, cracking and the like. General Motors in 1978 introduced one of the safest gas tanks in the U.S. in its Corvette line by replacing the problematic rubber bladder with a High Density Poly-Ethylene ["HDPE"] liner.
HDPE is a common material for gas tanks today and an overwhelming number of safely positioned tanks on the road today are made of this plastic. It is capable of taking heavy blows and is slow to burn. It has proven itself as an automotive construction material in a number of applications.
Because the gas tank on the Corvette is directly in the crush zone for a rear impact, General Motors engineers encapsulated the HDPE tank within a standard metal tank and created a double-walled tank that has performed extremely well since 1978.
Based on the absence of fire claims from rear-end collisions suffered by Corvettes, and the vehicle's ability to be repeatedly certified by General Motors in compliance with FMVSS 301 for every production year since 1978, there is good reason to believe that a similar style HDPE/metal tank would enhance fuel system integrity of GM pickups with side saddle tanks.
In 1975 the Chevrolet Corvette was unable to meet FMVSS 301 and not leak more than one ounce of gasoline a minute after a 30 mile per hour rear end moving barrier crash. GM's solution was to introduce a rubber bladder which provided the necessary protection against gas spillage inasmuch as the tank is located in the crush zone approximately 8 inches from the rear bumper. The history of bladders in competition race cars and in aircraft has been well documented with a variety of problems: deterioration, condensation, folding, cracking and the like. General Motors in 1978 introduced one of the safest gas tanks in the U.S. in its Corvette line by replacing the problematic rubber bladder with a High Density Poly-Ethylene ["HDPE"] liner.
HDPE is a common material for gas tanks today and an overwhelming number of safely positioned tanks on the road today are made of this plastic. It is capable of taking heavy blows and is slow to burn. It has proven itself as an automotive construction material in a number of applications.
Because the gas tank on the Corvette is directly in the crush zone for a rear impact, General Motors engineers encapsulated the HDPE tank within a standard metal tank and created a double-walled tank that has performed extremely well since 1978.
Based on the absence of fire claims from rear-end collisions suffered by Corvettes, and the vehicle's ability to be repeatedly certified by General Motors in compliance with FMVSS 301 for every production year since 1978, there is good reason to believe that a similar style HDPE/metal tank would enhance fuel system integrity of GM pickups with side saddle tanks.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: Plastic Liner inside tank?? (74VETTE)
I took the bladder out of my 75 and left it out. I silver brazed 2 half inch outlets to the bottom of the tank. I ran each of the outlets to a large filter then into a high pressure holley pump. I have 2 of everything just in case one fails.
Silver brazing is the easiest to do for installing outlets.
If you need the procedure just ask
Silver brazing is the easiest to do for installing outlets.
If you need the procedure just ask
Melting Slicks
Joined: Feb 2003
Posts: 3,053
Likes: 4
St. Jude Donor '03,'11
Re: Plastic Liner inside tank?? (paul79)
Sounds like we should upgrade to a 78 or later tank when the old one goes.
There has been some discussion here about going to a racing type fuel cell. I notice there are 16gal circle track aviation foam filled fuel cells in the Jegs catalog for $210. I wonder if this would be even safer.
Dieing in a fire because some soccer mom in a minivan rear-ends me is an extremely scary proposition.
[Modified by turtlevette, 4:39 PM 4/5/2003]
There has been some discussion here about going to a racing type fuel cell. I notice there are 16gal circle track aviation foam filled fuel cells in the Jegs catalog for $210. I wonder if this would be even safer.
Dieing in a fire because some soccer mom in a minivan rear-ends me is an extremely scary proposition.
[Modified by turtlevette, 4:39 PM 4/5/2003]
Thread Starter
Melting Slicks
Joined: Apr 1999
Posts: 3,264
Likes: 3
From: Toms River NJ
Re: Plastic Liner inside tank?? (norvalwilhelm)
norval....if you could explain that procedure, id really like to hear it in case I can do it myself rather than let someone else do it :cool:
when you say silver brazing, do you mean by using acetyline and the brazing rods used in refrigeration pipes of air conditioning?? if so, im set to do it cause my dad owns a HVAC company and know how to do all the stuff.
thanks
chris
when you say silver brazing, do you mean by using acetyline and the brazing rods used in refrigeration pipes of air conditioning?? if so, im set to do it cause my dad owns a HVAC company and know how to do all the stuff.
thanks
chris
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Race Director
Joined: Apr 1999
Posts: 11,520
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From: CORVETTE 77 385 C.I. TEXAS
Re: Plastic Liner inside tank?? (74VETTE)
Starting in 75 Corvettes used a heavy rubber bladder like those used in race cars encased in a ribbed steel housing.
Remember race cars have safety equip.!
:cool:
Remember race cars have safety equip.!
:cool:
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: Plastic Liner inside tank?? (74VETTE)
74vette Gas tanks can be safely welded with an open flame if you take percautions. First of course is to remove all cover plates and the fuel filter and of course drain all gas from the tank.
I then take the shop vac and turn the hoses around so it blows instead of sucks and put it in the tank. You can let it pump air through the tank for as little as 5 minutes but to be really safe leave it 1/2 hour.
It is now safe to use anything you want on the tank. Pass a open flame in the opening and I guarantee if you did the vacuum thing nothing will happen. My son worked for a summer term at a gas tank repair shop and they thought 5 nimutes was more then enough.
To install a new fitting drill a hole in the tank, clean the area to be welded very clean with emery paper, install the fitting in the hole and then using either oxy acetaylene or just a plumbers acetaylene tank braze it with the same stuff that air conditioners use. I persoanlly use silver braze wire and flux but the stuff used for air conditioners works fine.
I have done both my corvette and the mustang's tanks with dual outlets at the lowest corners on each without a problem.
I have also repaired many tanks over the years with a penny and a open flame.
I then take the shop vac and turn the hoses around so it blows instead of sucks and put it in the tank. You can let it pump air through the tank for as little as 5 minutes but to be really safe leave it 1/2 hour.
It is now safe to use anything you want on the tank. Pass a open flame in the opening and I guarantee if you did the vacuum thing nothing will happen. My son worked for a summer term at a gas tank repair shop and they thought 5 nimutes was more then enough.
To install a new fitting drill a hole in the tank, clean the area to be welded very clean with emery paper, install the fitting in the hole and then using either oxy acetaylene or just a plumbers acetaylene tank braze it with the same stuff that air conditioners use. I persoanlly use silver braze wire and flux but the stuff used for air conditioners works fine.
I have done both my corvette and the mustang's tanks with dual outlets at the lowest corners on each without a problem.
I have also repaired many tanks over the years with a penny and a open flame.
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
Re: Plastic Liner inside tank?? (RUXperienced)
That is correct. But it was a major upgrade in 1978. There is a world of difference between rubber and HDPE.
http://www.plasticsmachining.com/mag...06/omnium.html
[Modified by paul79, 4:50 PM 4/6/2003]
http://www.plasticsmachining.com/mag...06/omnium.html
[Modified by paul79, 4:50 PM 4/6/2003]
Race Director
Joined: Jun 2001
Posts: 16,483
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From: The Only Corvette in Gila Bend, Az.
St. Jude Donor '09
Re: Plastic Liner inside tank?? (paul79)
Do the HDPE liners collapse like the rubber ones did?
I remember seeing everyone removing their liners awhile back. I don't want to unless it will solve a problem.
I remember seeing everyone removing their liners awhile back. I don't want to unless it will solve a problem.
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
Re: Plastic Liner inside tank?? (page62)
That is correct. It is a rigid plastic composite. And to remanufacture a tank using it/around it would be very expensive. The rubber insert is more pliable: moldable. This thread is instructive as it explains why all the Corvette catalogues list tanks to 1977 and then....stop.
Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
Re: Plastic Liner inside tank?? (Ganey)
As long as we are talking tanks, what years have that sock or so called filter on the pickup that plugs with sediment etc. and cut down the fuel flow. I have a 73. Can the sock be cleaned or pulled out without droppoing the tank? Thanks for the advice.
JP
JP
Race Director
Joined: Jun 2001
Posts: 16,483
Likes: 1
From: The Only Corvette in Gila Bend, Az.
St. Jude Donor '09
Re: Plastic Liner inside tank?? (bigvette1)
Yes the sock and pickup can be removed right through the top of the tank, without removing the tank from the vette. The sock is easily replaced. and after 20 plus years, its a good idea to do it...
I think there is a tech article somewhere. But right now I can't find it...
I'm glad to hear the the later years, liner is rigid, that means that I don't need to remove it for fear of it collapsing. :cheers:
I think there is a tech article somewhere. But right now I can't find it...
I'm glad to hear the the later years, liner is rigid, that means that I don't need to remove it for fear of it collapsing. :cheers:
