completing a 3800 conversion

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completing a 3800 conversion

Unread postby jaymaechtlen » Sun Feb 23, 2020 4:02 pm

A friend has an 85 Lesharo with an unfinished Buick 3800 conversion.
He started it a number of years ago, and got stalled. Recently he enlisted me to get the beast running.
So far, I have some of the engine wiring done, working on clogged fuel tank supply line and some odds and ends.
For brakes, the Renault power booster got lost, the master cylinder is rusted up, and brake lines aren't connected to Buick calipers.
That's fine, I can flare brake lines and will fit some kind of (probably) US booster and master cylinder.

I have a fuel pump connected, drives through fuel rail and out the return.
Oddly, I don't see a fuel return to the rear tank, only the front. Any thoughts on that? Is there a return to the rear tank?
I've done 3800 swaps (an '87, then an '02) into another car, so I have confidence that I can figure out the wiring. And I can fix the hacked firewall, etc.
fun, fun, fun!
Jay Maechtlen
Main project is a 3800-powered Corvair, runs great!
Located in sunny SoCal
www.laserpubs.com
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Re: completing a 3800 conversion

Unread postby hasben » Mon Feb 24, 2020 11:06 pm

3 out of 4 of my conversions used GM booster and master cylinder. The rear fuel tank was intended for generator use only, many have removed the generator and added another pump to transfer the fuel to the main tank.
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Re: completing a 3800 conversion

Unread postby jaymaechtlen » Wed Feb 26, 2020 12:15 am

- generator only - interesting.
This one had an electric valve to allow running from the rear tank, but the fuel return goes only to the front tank. That makes sense - this lets you run from the rear in an emergency...
A GM booster and master cylinder?
Ok, sounds good.
Did it take anything special to get decent stopping power?
This has the GM FWD brakes up front, I haven't measured the rotors yet. They look about the same as the brakes that were in the 87 Olds I used for a swap some years ago. Aha! I'll have to check, as I still have those brakes in good shape!
Jay Maechtlen
Main project is a 3800-powered Corvair, runs great!
Located in sunny SoCal
www.laserpubs.com
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Location: About 20 miles East of Los Angeles

Re: completing a 3800 conversion

Unread postby hasben » Wed Feb 26, 2020 5:08 pm

That dual tank valve is probably worthless, I had one like that, never worked, so I switched it to a transfer pump. The rust and sediment in the rear tank is the biggest problem so deal with that first. As for the brakes, 15" versions are adequate, 16" slightly better. Keep plenty of space in front of you. I did have to replace a pair of nearly new 15" front tires with flat spots after locking up in a panic stop.
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Re: completing a 3800 conversion

Unread postby jaymaechtlen » Fri Mar 06, 2020 2:24 am

re the brakes - what did you mean 15" vs. 16"?
Flat spotting would be from locking up the wheels - that would be less likely if the front/rear balance is set up well, and with good/big tires it should be less likely.

Something that isn't always distinguished - even smallish brakes might be capable of locking up an axle, but might get too hot on a long downgrade.
A bigger brake setup (larger diameter rotors and maybe wheels that let air through?) can dissipate more heat and handle the long downgrades at a higher speed.

Also, bigger rotors place the calipers farther from the axle center, so the same size caliper pistons would provide more stopping force (due to moment arm of the clamping/friction force) for any given brake line pressure.
Jay Maechtlen
Main project is a 3800-powered Corvair, runs great!
Located in sunny SoCal
www.laserpubs.com
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Re: completing a 3800 conversion

Unread postby jaymaechtlen » Fri Mar 20, 2020 11:51 pm

We came up with the booster and master cylinder from an 86 LS, so that removes one set of cut/weld operations. Just need to plug two of the outlets, since the Buick brakes only have one fluid connection per side.
The fuel outlet from the main tank was solidly plugged, so we got a replacement flange mount pickup and I installed it in the tank.
- I filled the tank with water all the way to the top, then drilled the necessary holes for the pickup and screw holes. The water floated out an amazing amount of slime - this was the residue of gasoline that had been in the tank when it was parked. Nasty stuff.
I will definitely have a filter on the inlet side of the electric fuel pump!
Jay Maechtlen
Main project is a 3800-powered Corvair, runs great!
Located in sunny SoCal
www.laserpubs.com
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Location: About 20 miles East of Los Angeles


Re: completing a 3800 conversion

Unread postby jaymaechtlen » Sat Jan 09, 2021 1:59 am

Well- I goofed on the fuel pickup and had it too far from the floor of the tank. We could have fixed it, but were able to get the standard plastic fuel tank and went with it for now.
Got the extra brake line outlets plugged, and have brakes working.

The fuel system was a very nice puzzle - I had spark, and fuel to the fuel rail at the right pressure - it would start on starting fluid but not keep running.
Eventually I discovered that the engine had sat for so long with fuel lines not sealed, that the injectors had all stuck. I was able to flash 12 volts across them one at a time repeatedly until they unstuck, all but one. I stethoscope helped - you can hear a click when an injector actuates. Five click, one doesn't. If you have the fuel pump running, you can hear the 'click-shhhh' as the injector opens and the fuel sprays.

Ok, have an injector and a set of o-rings and retaining clips coming from Rockauto. It runs, just has a hard miss on that one cylinder. Progress!
Need to move wiring from temporary-under-the-hood to actual ignition switch on the column or dash.
Got exhaust system pieces, need to patch together.
Got the steering working smoothly, need to tidy up and secure. (owner's first attempt had issues...)
fun, fun, fun!
Jay Maechtlen
Main project is a 3800-powered Corvair, runs great!
Located in sunny SoCal
www.laserpubs.com
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jaymaechtlen
 
Posts: 12
Joined: Sun Feb 23, 2020 12:30 am
Location: About 20 miles East of Los Angeles



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