: REPLACING 4100 WITH A CHEVY MOTOR,I GOT A FEW Qs



85 FLEETWOOD COUPE
06-05-11, 06:56 PM
ok well got my 85 fleetwood im working on replacing the old bs 4100 motor and trans to a 305 chevy with a 700r4 thats comming out of my parts car thats a 91 fleetwood.the motor is carbed and i know if i put the motor in place the crossmember will hit the manual fuel pump on the motor, should i just raise the motor mounts some to clear the crossmember or should i just use a electric fuel pump and cap off the manual fuel pump?? and would you guys think a 600 edelbrock carb would be to much for a 305 chevy?

cadillac kevin
06-05-11, 07:21 PM
can't you swap the crossmembers too? as for the 600 cfm carb, no I dont think thats too much. but I'm wondering why you wouldn't put a quadrajet on it (a bit more fuel efficient)

85 FLEETWOOD COUPE
06-05-11, 07:27 PM
no the front crossmember thats part of the frame, the tranny crossmember you can move because its bolted, i would do a QJET BUT I HEARD THERES DIFFERENT CFM`s??

85 FLEETWOOD COUPE
06-05-11, 09:28 PM
theres only 1 bolt holding the trans together right and thats on the tranny crossmember correct?

cadillac kevin
06-05-11, 10:27 PM
IIRC there is a quadrajet thats 600cfms. you can make any quadrajet put out however much fuel you want. you just need to change the metering rods. most carbed chevy pickups with 350's came with 480-600 cfm carbs. I believe 305's came with 600 cfm quadrajets (but dont quote me on that)
I'm not sure what you mean by 1 bolt holding the trans together.

85 FLEETWOOD COUPE
06-05-11, 11:00 PM
yea thats what this older guy told me to about the q-jets ,im meaning the trans is mounted to the motor right? but theres only 1 bolt holding it to the tranny support right?

csbuckn
06-05-11, 11:54 PM
The rear tranny mount is kinda two pieces. The tranny bolts to a mount and the mount bolts to the crossmember. But yes, you can take the one bolt out and remove the tranny. Am I the only one that thinks 600 cfm is small? Not too small, it will work fine but I would want at least 650.

sven914
06-06-11, 12:39 AM
^You have a 500. Small to you is irrelevant.

If your '91 parts car had the 305 in it, you can take the computer and keep the engine TBI. That way the fuel pump will be in the tank and you won't have to worry about clearance issues. Otherwise, installing an electric fuel pump to the carburettor would work; you would just need to play with it because it can cause engine flooding if the calibration is off. I personally wouldn't change the engine height, because it can cause more clearance issues on the top of the engine (but I don't know if it will for sure).

85 FLEETWOOD COUPE
06-06-11, 12:51 AM
o sorry i 4 got to say im not using the stock motor out the 91 im just using the transmissin,i got another 305 chevy thats out of a firebird that is carbed thats why i wanted to keep the manual fuel pump,i had bad experiences with the electric fuel pumps, when i went to the edelbrock website they say the recomended carb for a 305 chevy is a 500 cfm?

cadillac kevin
06-06-11, 01:22 AM
go for a 600 cfm.

85 FLEETWOOD COUPE
06-06-11, 01:29 AM
i already got a holly but was thinking a edelbrock 600

85 FLEETWOOD COUPE
06-06-11, 03:17 PM
http://http://www.layitlow.net/pics/1005/0524124524_01[1].jpeg

85 FLEETWOOD COUPE
06-06-11, 03:19 PM
http://www.layitlow.net/pics/1005/0524124524_01[1].jpeg

cadillac_al
06-06-11, 08:13 PM
It sounds like the motor mounts are supposed to be moved forward so the fuel pump can clear. That is a pain so I would be very inclined to use an electric fuel pump. I'm always on the lookout for cheap low pressure pumps for carbed cars. They are everywhere but GM makes a pretty nice one in the GMPP catalog. I'm not a fan of aftermarket carbs on GM street engines because you just can't beat a good working Q-jet

85 FLEETWOOD COUPE
06-06-11, 10:12 PM
But if i moved it up that means i would have to extend my drive shaft?,i think if i just lifted up my motor mounts 1 inch it should clear,id used those electric fuel pumps that they sell at auto zone when i put a 350 in my 90 fleetwood but it needed a regulator and i hated messing with that to!!

85 FLEETWOOD COUPE
06-06-11, 11:31 PM
http://i52.tinypic.com/308wk9d.jpg heres the car im working on, my 85 the last year rwd they made as a 2 door

cadillac_al
06-07-11, 10:13 AM
Now that's a labor of love. Old school back yard shade tree mechanic work. I must say, I don't miss those days. Keep us posted and I hope you can bring that "diamond in the rough" back to a beautiful gem.

If you have to wire in and plumb an electric fuel pump it isn't that much more work to add the regulator. If I had the choice, I think I would rather pay to have the driveshaft lengthened or find another one before unbolting the frame mounts. Some people cut them off and weld them in place.

85 FLEETWOOD COUPE
06-07-11, 03:18 PM
thanks,its a learning experiance plus im trying to save money at the same time lol i never heard any 1 putting it foward, ok if i did use a electric fuel pump put it to the rear close to the gas tank right? where would i put the regulater at? in front of the fuel pump or in the engine capartment for easy ajusting? what setting do i set the regulater at? if i used the q jet or a 600 edelbrock

cadillac kevin
06-07-11, 08:15 PM
aside from needing a paint job, that car actually looks pretty good.
I'm a shadetree mechanic myself (just theres no tree or shade in my yard . lol) Its good to know that some people are keeping these behemoths on the road instead of taking the easy road and junking them.
as for the driveshaft go to the junkyard and buy a driveshaft off a 1991-1996 fleetwood brougham with a 305 or 350 chevy or an LT1. all 93-96's have the driveshaft you will need (direct bolt in for the 700r4 trans) as will 91 and 92's.

85 FLEETWOOD COUPE
06-07-11, 09:38 PM
thanks keven,i love cadillacs especialy the 2 door rwds, i already got a drive shaft from a 91 cadillac thats where i got the tranny from to, in the pic is a 91 the blue one,a 90 the brown one and the 2 door a 85 fleetwood 2dr in the back http://i52.tinypic.com/jhxbw4.jpg

85 FLEETWOOD COUPE
06-07-11, 09:42 PM
the interior is mint, dash real nice to just need to replace the dash pad that got the normal crackshttp://i51.tinypic.com/2mhsc29.jpg

85 FLEETWOOD COUPE
06-07-11, 10:16 PM
heres the chevy motor im putting inhttp://i56.tinypic.com/13z0tnn.jpg

cadillac kevin
06-07-11, 11:24 PM
the interior is mint, dash real nice to just need to replace the dash pad that got the normal crackshttp://i51.tinypic.com/2mhsc29.jpg


I have an affinity for the 2 doors as well, but they're really rare around here (most got junked about 15 years ago when the 4100s blew). most of the ones I've seen have been made into lowriders or donks with the euro front clips and candy paint. I'd love to get one, but I have a shoestring budget and my caddys sat for almost 6 months. I have worked on it quite a bit(body and interior work) but it still only moves 20ft at a time (drive it forward and back and side to side to cut the grass)
btw your interior is the same color as mine. Its gonna be hard to find a dash top thats the right color since IIRC thats an uncommon interior color. I really like the light woodgrain too.

85 FLEETWOOD COUPE
06-07-11, 11:32 PM
the dash pad aint no big deal, i can always dye it to match. a donk is a 71-76 chevy so it cant be a cadillac i know what you saying though a cadillac on big rims right lol

BIGBODYBEAR
06-08-11, 01:40 AM
any pics?

85 FLEETWOOD COUPE
06-08-11, 08:41 AM
pics of what????

brougham
06-08-11, 01:18 PM
Between the parts car and the millions of GM cars that came with 305 and 350s this should be a pretty straight forward swap. There should already be a lot of info out there on carb size and all that stuff also.
If the rear axle isn't the same size as what the parts cars is chances are the driveshaft will be different length then what you need.

85 FLEETWOOD COUPE
06-08-11, 03:40 PM
so you saing my driveshaft i got from a 91 wont fit my 85 rear end?????

brougham
06-08-11, 06:43 PM
You'd have to find out what axle your coupe has and see if there's a difference in size between it and whatever the 5L 91 has.

85 FLEETWOOD COUPE
06-08-11, 09:49 PM
so it wont bolt up???? and what you mean by what axle? like bolt pattern or what?

csbuckn
06-08-11, 11:52 PM
The 7.5 rear end is very close/same to the 8.5 so you should be alright there. The main issue to pay attention to is where the frame mounts sit. Hopefully the mounts for the 4100 will be in the same place as the sbc.

85 FLEETWOOD COUPE
06-08-11, 11:57 PM
i already know that the motor mounts aint in the same position, when i had my buddy install a 350 in my 90 fleetwood at his shop he had to move it back some and thats why the manual fuel pump hits the frame,so thats why i was thinking just extend the motor mounts 1 inch up and it should clear?

csbuckn
06-09-11, 12:08 AM
If you move the engine up, you may run into clearance issues with the valve covers. Have you thought about notching the frame to make the pump fit?

85 FLEETWOOD COUPE
06-09-11, 12:14 AM
i dont think it would hit, im looking at my 90 and how the 350 sits and it gots plenty of room, it only needs just a inch maybe less for it to fit, o dont want to have to cut the frame, or was just thinking of electric pump lol,

csbuckn
06-09-11, 11:40 AM
Well, I had the same issue on our build and we went with an electric pump. Kinda wishing we would of found a way to fit the mechanical pump. Make sure you can get it in and out without lifting the motor.

85 FLEETWOOD COUPE
06-09-11, 03:03 PM
yes that is true , i want it in a position that if something happend i could replace the pump with no problem ya know

85 FLEETWOOD COUPE
06-09-11, 07:26 PM
Question,i 4 got to ask this, what do i have to do if i o go with electric fuel pump, do i have to do anything to my gas tank on my 85 fleet? Or i could i just bolt up the pump to the inside of my frame rails next to the tank?? Im using a 700r4 out of my 91 should i use the tranny support bar from the 91 or will the tranny support bar in my 85 work??

csbuckn
06-09-11, 08:00 PM
Isnt the 4100 fuel injected?

85 FLEETWOOD COUPE
06-09-11, 08:31 PM
Im not really sure i think so?

cadillac kevin
06-09-11, 08:39 PM
it is fuel injected. it has a throttle body w/ 2 injectors.
I dont recall if the pump is mounted to the engine or on the tank itself.

Stingroo
06-09-11, 08:41 PM
Greencadillacmatt should know. I'll bug him to view this thread when he gets online.

85 FLEETWOOD COUPE
06-09-11, 08:47 PM
Thanks stingroo do that 4 me

greencadillacmatt
06-09-11, 10:26 PM
If the vehicle in question is HT4100 powered, then it has a very rudimentary form of throttle body fuel injection. That means it has an electric fuel pump. The pump is located in the gas tank, and there is a feed and a return line going to and from the throttle body, respectively. Since it's OLD fuel injection, and throttle-body injection at that, the pump only puts out about 13psi. You should be able to get a fuel pressure regulator and install it before the carb you will be using to knock the pressure down to about 5 or 6 psi. Then run the fuel line from the regulator to a T-line, with one end going to the carb, and the other connecting to the return line to the tank. Good luck!

85 FLEETWOOD COUPE
06-10-11, 12:07 AM
So you saying use the fuel pump thats already in the tank and just use a regulater?

csbuckn
06-10-11, 12:20 AM
It should be in the tank, just run a regulator to get it down around 5psi.

85 FLEETWOOD COUPE
06-10-11, 12:27 AM
First thing is to replace it because i know it old as heck lol i wonder how much they cost hmn got to look it up threw autozone,then where should i place the regulater at? By the tank or under the hood??

cadillac kevin
06-10-11, 01:02 AM
do not get an autozone fuel pump. I've never had good luck with autozone anything. personally I'd spring for an AC delco fuel pump. at least you wouldnt have to replace it in a year when it goes bad.

csbuckn
06-10-11, 02:10 AM
I have my regulator under the hood.

sven914
06-10-11, 02:15 AM
Advance Auto should sell the AC-DELCO parts you need.

85 FLEETWOOD COUPE
06-10-11, 08:43 AM
Like?

85 FLEETWOOD COUPE
06-10-11, 03:16 PM
If the vehicle in question is HT4100 powered, then it has a very rudimentary form of throttle body fuel injection. That means it has an electric fuel pump. The pump is located in the gas tank, and there is a feed and a return line going to and from the throttle body, respectively. Since it's OLD fuel injection, and throttle-body injection at that, the pump only puts out about 13psi. You should be able to get a fuel pressure regulator and install it before the carb you will be using to knock the pressure down to about 5 or 6 psi. Then run the fuel line from the regulator to a T-line, with one end going to the carb, and the other connecting to the return line to the tank. Good luck!regulators will only regulate around a couple psi. i put the low psi regulator on it and it did absolutely nothing. Even talked to the tech guys at jegs and speedway and they said a low psi regulator will regulate 4-8psi or so and 15 is just too much for them to handle.

sven914
06-10-11, 05:09 PM
Like?

Small AC DELCO electronics that are OEM for your car. They don't have everything, but they should stock a fuel pump for the 4100.

brougham
06-12-11, 08:15 PM
The 7.5 rear end is very close/same to the 8.5 so you should be alright there. The main issue to pay attention to is where the frame mounts sit. Hopefully the mounts for the 4100 will be in the same place as the sbc.

From what I can find the driveshaft for 7.5 rear is more then an inch longer. That's enough to cause problems.

sven914
06-12-11, 11:11 PM
^But what transmission is that going into? The difference in length could be because they are for different transmissions.

brougham
06-13-11, 01:19 AM
That difference is just for the axle. The transmission would affect the length again.

cosmo
06-21-11, 10:54 PM
Here's another, easier thought. Get the TBI from a 305, and leave all as is. All the sensors will work. None of the wiring need be changed, though a lead or two might need lengthening/shortening.

Why would I suggest this??
A) It's easier than changing to carb.
B) It's cheaper, too. Chevy TBI intake and injectors are dime-a-dozen.
C) The engine will run better AND get better mileage.
D) Probably more horsepower, too.
E) Might even pass emission testing.
F) Can't think of a downside.

Cosmo

sven914
06-22-11, 01:06 AM
^That was my suggestion...

csbuckn
06-22-11, 02:26 AM
Here's another, easier thought. Get the TBI from a 305, and leave all as is. All the sensors will work. None of the wiring need be changed, though a lead or two might need lengthening/shortening.

Why would I suggest this??
A) It's easier than changing to carb.
B) It's cheaper, too. Chevy TBI intake and injectors are dime-a-dozen.
C) The engine will run better AND get better mileage.
D) Probably more horsepower, too.
E) Might even pass emission testing.
F) Can't think of a downside.

Cosmo

Could you do this with a TBI 350 if you just grab the computer too? Should plug right in.

brougham
06-22-11, 10:53 PM
Getting the TBI to work would be a mess. It is far easier to get the carburetor to work on it. Just have to get gas to it and change the distributor. Unless one of your parts cars has fuel injection. Then just move everything over and hope you didn't miss anything.

csbuckn
06-23-11, 02:37 AM
The 4100 is TBI fuel injected so would you be able to plug a small block in and hope the computer can get it right. I would think it would be able to since it has an 02 sensor and should correct the fuel mixture.

sven914
06-23-11, 02:38 AM
His donor car was a '91 Brougham...