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86 El Camino

 
mrbigA47
I love my Chevy Chevette!
Posts: 10
Joined: 12/12
Posted: 12/15/12 09:56 PM

What's the best 305, tranny, and differential setup that will yield power (min: 250 HP) and at least 20+ miles to the gallon for a limited slip daily driver? This is my first restore, so I am trying to do this with minimum modifications to the stock configuration.  

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waynep71222
My first time was in a Chevy
Posts: 218
Joined: 04/12
Posted: 12/16/12 01:01 AM

in reality.. you can create a 305.. that will get decent fuel economy...

that year el camino came with and without electronic control of the carb..

if everything is working perfectly.. you can get great mileage with the absolute stock system.. but it all has to operate perfectly...

so where you go from here depends on which system you have...

as far as i can recall. there were also 2 models of transmissions available in el caminos that year..

the TH200C  3 speed with an 11 bolt pan and the 200-4R.. with a 16 bolt pan..

car manufacturers have spend billions of dollars on R & D and testing to try to get what you would like.. but also have it put out as clean an exhaust as possible.. but also have it be able to bolt together hundreds of  thousands of them and they should all run the same..  

talk about variables..   if you want decent mileage.. don't try to outthink the professional engineers by removing components that might offend you..    ah.. i don't need that part..  i wonder why my car does not run as good as it used to .. well.. lets take another part off.. that should fix it..  nope..

the bone stock 305s if in proper tuning should get over 20MPG..

if you have a FEEDBACK CARB system... please.. don't tear into the carb or try to adjust anything on it.. until you understand exactly what needs to be done to it..

if you do not have a feed back carb...  please don't get into it until you know that there is one adjustment that will make or break your rebuild... and its not mentioned in the paperwork..
so..  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 12/16/12 03:06 PM

I agree with Wayne on this.
 
  I have a 1986 Monte Carlo SS with a 305 HO. With a 2004R trans, and a 3:73 rear Gear. I could never get more then 20 MPG. I put a 260/350 Crate engine in a friends MC exactly as mine, and he gets 25 MPG. Thats 80 more stock HP, 45foot lbs. of torque and the same ECM. OBD1 is a little more forgiving....

The 2004R Trans. with O/D has the following gear ratio's. 1st gear 2.74, 2nd gear 1.57 3rd gear 1.00 and O/D is .067. Put a shift kit in it so its a firmer shift and also a quicker shift. Install a Seperate Trans Cooler. Don't put it in series with the radiator.

So my suggestion. A 2004R trans and a 3:50 rear gear. You will have some horse power and MPG.

Bob  

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mrbigA47
I love my Chevy Chevette!
Posts: 10
Joined: 12/12
Posted: 12/26/12 08:49 PM

Bob,

Thanks for the info and I would like to get your opinion on this future setup, a 350 GM Performance crate engine (290 HP stock), 7004R transmission and 3.08 or 3.34 differential (I read the lower gear ration improves MPG). I want a more HP and torque, but I am not looking to race anytime soon. In the meanwhile, how much additional power and torque will that 2004R trans and 3.50 gear really generate to my stock setup? I was also looking to add a limited slip posi-traction rear axle.


Ernest  

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mrbigA47
I love my Chevy Chevette!
Posts: 10
Joined: 12/12
Posted: 12/26/12 08:56 PM

I have to verify what type of transmission I have. The 2004R was suggested for my current setup. I am thinking of purchasing a 350 (290 hp stock) and maybe add a 7004R and 3.33 gear differential with a posi-traction rear axle. My 305 was slightly tuned and runs a lot better than it did when I first bought it. There are a few more tweeks required to make it purr. I am looking for the rear end now because its going in regardless what engine I go with. Which tranny do you suggest?  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 12/27/12 04:51 AM

Ernest:

IMO you can go to a lower rear gear ratio. even a 3:70-3:90 . That depends on how tall your tires are. My MC has 26" tall tires.

The 2004R is 27.750" long. Its OD final ratio=0.067

The 700R4 and the 4L60E are 30,750" long and both share the same final OD ratio of  0.070

We hear it  too often. Our Gear Heads of the furure will build a nice street engine. With 350HP. Then we hear its a dog. (some engines are professionally built). They have spent a lot of money.
  The first question I ask what rear gear ratio do you have? a large percentage don't know?
  My 2nd question what transmission are you using? Then we have something to work with.

Ernest its the total package that makes it all work...

Our young Gear Heads do 2 things wrong that I was guilty of doing back in the day myself.

1.We over Cam our engines.

2.We over carburate our engine.

If you want to wake your ElCamino up. You can install a lower rear gear ratio.

Then install a 305HO cam in it or something even better. Then while your getting your parts together for your 350. You will already have the lower rear gears in the rear. You will need them later in your build.

Bob  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 12/27/12 05:05 AM

Ernest:

When you get ready for your 290/350 there are things you can do to step up the HP before you install it also. You can get anoter 25-40HP with very much more.

Bob  

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mrbigA47
I love my Chevy Chevette!
Posts: 10
Joined: 12/12
Posted: 12/27/12 10:26 PM

Bob,

I thought higher gears (=) more speed but (-) fuel economy. So upgrading the cam and rear gear differential will wake that 305 up without the new transmission (of course that is after I finish tuning the engine)? Oh yeah, I found (5) 15x7 steel wheels at a salvage yard today that I may end up swapping out the 20s that came with the car. Saturday I will check for a posi-traction rear end. Maybe I should just purchase that new along with the new suspension setup I was looking at. My car's ride is horrible. The 20s look good, but I feel every pebble on the road. By the way, thanks for the info. It has saved me time and money already.

Ernest  

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pepsi1
Big Block power for the win
Posts: 940
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Posted: 12/28/12 04:48 PM

Ernest
  The lower the numerical gear ratio (For Example only 2:80) gas mileage (NO get up an go) the higher the gear ratio. The higher speed given per Max engine RPM.
  The higher the numerical gear ratio (For example only 3:80) gas mileage may suffer a little? (Good pick up and more power) The lower speed given per Max engine RPM.
The shorter the tire (Example only 26" tall) the more revolutions per mile it will turn.
The taller the tire (Example only 32" tall) the less revolutaions per mile it will turn.
  Higher number gear ratio. More RPM engine turns at 60 MPH Engine may turn 3,000RPM
Lower  number gear ratio. Less RPM engines turn at 60 MPH Engine may turn 2,000RPM
  I used 60 MPH as a given for an example. These are NOWHERE near exact....
I hope this helps....
  Measure the tire HEIGHT. (NOT THE CIRCUMFERENCE) Please don't get confused because sometime the lower gear ratio (Higher number) will get better mileage because of an OD Transmission, and the power will get the vehicle rolling with less effort.

Bob  

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mrbigA47
I love my Chevy Chevette!
Posts: 10
Joined: 12/12
Posted: 12/29/12 10:22 PM

Bob,

I am going with the 3.42 gear ratio. That is the same set used in a Grand National and I have witness that car take off from the line and accelerate in traffic. It's nothing to play with and that amount of "ummph" will suffice for the time being. Ultimately, I would like to have the El Camino purring at 75 mph just under 2000 rpm like my truck. I have also decided to go with 17" wheels with a 235/55 17 tire. The diameter was just under 26" (25.736 I think). Meanwhile, I have more pressing concerns with the engine. I started it today, after it sat up two days, and it idled way over 2500 rpm with white smoke spewing from the exhaust. There's a leak somewhere that requires investigation.

Ernest  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 12/29/12 11:02 PM

Ernest
  Thats a real good choice. If you keep the Cam Specs to operate in that RPM range, you will have a nice little package with an OD trans, and a 26" tall tire.. Idle to 5,000-5,200 is respectable for a 305. 2000 RPM at 75MPH is very doable. I don't remember what the MC I have was at 70MPH it would only be a guess.
  What they did with the Monte Carlo they play with the HP specs. Thats why some have 3:42:1 and others have a 3:73:1 rear gear ratio.
  I had some info from years back on the Monte Carlo SS. Only the SS (G Code) was really played with. I will have to find it. Then I'll post it. Its interesting.
  Don't try to compare it to the GN. "The GN was an animal of its own". With the series (2) 3.8. My kid brother had one. He bought it off the lot. It had T-Tops in it. He said the T-Tops leaked after about 9 months. The torque from the 3.8 was twisting the Body, that the roof was buckling. GM did nothing for them either. He still has it in Moth Balls. Like My SS.

Bob  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 12/30/12 12:06 AM

Ernest
The (LG-4) versus the (L-69)

1.Both use the same head casting #601 thats as far as it goes.
The (L-69) has 1.84/1.50 valves 58cc Combustion Chamber
The (LG-4) has 1.76/1.46 valves 64-68cc? Combustion Chamber
2.Compression Ratio (L-69) 9:5:1
 Compression Ratio (LG-4) 8:6:1
3.(L-69) uses a special (L-81) from Corvette
4.(L-69) has a performance calibrated (E-Prom)
5.(L-69) torque convertor Stall Speed is 1900RPM
 (LG-4) torque convertor Stall Speed is 1200-1500RPM depending on year
6.(L-69) uses a fuel pump from a Z-28
7.(L-69) produces 30+ horsepower more than the (LG-4)

I have more info on the Monte Carlo SS (L-69) when I find it I'll post it.

Bob  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 12/30/12 05:00 PM

Ernest

Just a little more info for you on. The Monte Carlo SS
I know I posted the Trans Lengths but not the bell housing to Trans pad mounting
holes.

Trans              Length            Bell housing to Mounting Pad holes

TH-350-C           27.750"                    20.5/8"

TH-700-R4          30.750"                  22.50" to 27.750"

TH-400             28.00"                     27.00"

TH-200-4R          27.7/8"                    27.00"

Bob  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 12/30/12 05:19 PM

Ernest

These numbers are for the rear gear ratios. Just if your in a bone yard looking for rears that have been removed from the Monte Carlo SS. All this information is only for the MC-SS....

1983 to 1984 was only a 3:42:1 Ratio Rear.
1985 to 1988 was only a 3:73:1 Ratio Rear.
There were no other Combinations......

Now on the SPID Sticker its located on the trunk lid.

  G80 indicates a limited slip rear.
   
On the axle housing sometime you have to scrape the grease off the upper part of the axle tube to find this. (so if in a bone yard bring carb or brake clean with you). I sometime use paper White out to emphasize the letters and numbers.

AXLE CODE for 1983 to 1984? a 3:73:1 open rear is "2TF" on the SPID Sticker if the rear housing is still in the car.

AXLE CODE for a 1985 to 1988 a 3:73:1 limited slip rear is "2TH" on the SPID Sticker if the rear end housing is still in the car.

Bob  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 12/30/12 05:44 PM

Ernest

These numbers are for the engine and trans only for the Monte Carlo SS.

1983 and some early (1984 rare) the 1983 had the TH-350-C 3 speed automatic transmission. At 65 MPH the engine was @ 3,000 RPM.

1985 to 1988 The TH-200-4R was a 4 speed automatic transmission.At 65 MPH the engine was @ 2,400 RPM.

1983 (L-69) 175 HP @ 4,800 RPM and 230 Ft/Lbs torque @ 3,200 RPM Measured at the Flywheel.

1984 to 1988 the (L-69) 180 HP @ 4,800 RPM 225 Ft/Lbs torque @ 3,200 RPM measured at the Flywheel.

The eighth digit of the Vin. for the (L-69) is (G). Now you may run into people that will say their 1983s came with 350s. No it never happened. If so it was a dealer installed opition. I can't begin to imagine the paperwork they had to to do for the DMV...

I have a 1979 Z28 and a 1981 Z28. The 81 has the TH350C trans in it. That is really the first lock-ups that were starting to come into play from GM. They shifted all the time. Motor Trend referred to them as GMs bucking broncos.
  I got company cars. In 1978 I had this beautifull Caprice Classic S/W. I took it on its first long run. I was going up this steep hill in eastern PA. That trans was shifting up/down-up/down. You get the picture. I called the service manager. He told me what to dissconnect. I ran that car until the body rotted off the frame. It had 274,000 on it. I did 2 timing chains, and pulled my race car and our boat. I could not kill that 350 engine.  

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