Ad Radar
Popular Hot Rodding
Click here to find out more!

77 pontiac grand prix 400 tuning

  
Popular Hot Rodding
1 |  2 |  Next   | Last 
Item Posts    Sort Order

77 pontiac grand prix 400 tuning

 
bwalker89 bwalker89
New User | Posts: 5 | Joined: 04/13
Posted: 04/29/13
08:16 PM

i have a 77  GP with a 400, at least that's what i was told when i bought it. as far as i know it was a 350 or a 396 that was bored over to a 400 and has a 350 cam in it. it has an edelbrock 650 carb with manual choke. thats about all that is not stock on it, the guy i bough it from bought it from an older lady that said it was her husbands "someday project" and she had no clue what was done to it besides that.

it doesn't seem to matter what i do to tune the carb, it is ALWAYS running rich. and i have black soot coming from the drivers exhaust (dual exhaust with little restriction) it sounds real nice at idle and drops jaws while revving it up, but everyone giggles when i release the gas cuz it sounds like a retarded machine gun when coming down in RPM  it also seems to hesitate during hard acceleration. it has been quite a while since i have done timing and whatnot to these older engines so i'm a bit rusty. but i am looking for some decent/accurate specs to get this thing sounding and running good.

**notes: stock rear end, dual exhaust (no glasspacks or mufflers), have not gotten around to plugs/wires/cap/rotor yet, no a/c (removed), no emissions pump, unsure how to tune/clean/rebuild carb (did it once in college 4 years ago so it never sank in)  

68scott385 68scott385
User | Posts: 51 | Joined: 07/09
Posted: 04/30/13
09:39 AM

Pontiac had their own 350" & 400" motors. A 396 is a Chevy engine. You need to know which one you have. 1977 is about the time GM started mixing engine and body makes to suit their end goal. Trans Ams had Olds 403s for a few years. Some Oldsmobiles had Chevy motors, it was a real disaster for purists.

Posting pictures would be a great help for us to determine what engine family you have. From there, casting numbers will tell the true story. You could look at the 5th & 6th digit of the vin to see what the factory put in it.

5th digit is engine code
6th digit is last number of the model year  
68scott385 68scott385 68scott385

bwalker89 bwalker89
New User | Posts: 5 | Joined: 04/13
Posted: 04/30/13
04:06 PM

i'll get some pics and grab the vin # while i'm there.  

bwalker89 bwalker89
New User | Posts: 5 | Joined: 04/13
Posted: 04/30/13
06:14 PM

here's some pics... and the 5th and 6th vin is 7A

0430131852

0430131852A

0430131852B

0430131853  

68scott385 68scott385
User | Posts: 51 | Joined: 07/09
Posted: 04/30/13
10:14 PM

The 5th digit should be a letter and the 6th should be a number. If what you have is A7, that does not match the picture as an A engine code is a v6 starting in 1978. Allowing for a typo on a qwerty keyboard, S7 would be a Pontiac 400 in a 1977 body.

Either way, what you have in the picture is a Pontiac motor. The 350 & 455 blocks from 1970 and all 400 blocks from 1971 should have the displacement value cast in front of the driver's side motor mount. SA-Design prints a Pontiac performance book that can be found at cartechbooks.com.

The carb in the picture will have a four digit number cast into the foot next to the small vacuum hose. It should be 14xx, you can look at Edelbrock.com for any & all parts needed to rebuild and/or modify it.  
68scott385 68scott385 68scott385

68scott385 68scott385
User | Posts: 51 | Joined: 07/09
Posted: 04/30/13
10:22 PM

http://www.edelbrock.com/automotive_new/mc/carbs_acc/performer.shtml  
68scott385 68scott385 68scott385

bwalker89 bwalker89
New User | Posts: 5 | Joined: 04/13
Posted: 05/02/13
03:04 PM

awesome! thanks a ton. next question. i am thinking about cutting a coil out of each of the front springs but i don't want the front to sit too low... does anybody know how many inches that would drop the front end and would it be ok to put stock shock on after that? i only do street travel, nothing bumpy, but the front end floats like a cloud so i need to do the front shocks anyway.  

68scott385 68scott385
User | Posts: 51 | Joined: 07/09
Posted: 05/03/13
07:35 AM

My best advice on cutting springs is to measure the spring from one coil to the next while the weight of the car is on it. This will tell you how much cutting one coil will lower the ride height. When you cut the spring, don't use a torch, use a bandsaw, sawzall, or hack saw, what you're trying to avoid is excess heat that will adversely affect the spring material. Many people advise against cutting springs while others say it's fine. I say it's up to the individual but keep in mind that there is no going back without purchasing new springs.

I also suggest replacing the suspension bushings while you have the springs out, if your budget can handle it. My point is that it is a good deal of work to remove the springs and only two more bolts for the lower control arm and two nuts for the upper control arm, why not improve the ride and handling while you've got it apart.

I may have a liking for suspension work and curvy roads that skews my opinions.

If you are interested in pro-touring, a fun car for curves, or just replacing worn bushings, I can post links that will be very helpful in finding parts for your forgotten G3. I have a 75 Monte Carlo and have spent years digging to find parts suppliers while Camaro & Chevelle guys can buy parts at Walgreens.  
68scott385 68scott385 68scott385

bwalker89 bwalker89
New User | Posts: 5 | Joined: 04/13
Posted: 05/04/13
07:16 PM

sweet, that might help. the drivers side is a little rough, fender wells are rusted, and the trunk pan is getting thin... so a good site to visit wouldn't be all that bad. i was gonna say "you have no idea the kind of troubles i have had finding parts for this" but it seems like you know exactly where i'm coming from. and another crappy thing about looking for parts is i'm not "trained" in what can cross over from other cars. ex: i look for 77 Grand Prix parts and i get 10,000 sites that are for GTO's, Trans-Am, Firebird, etc. the only car that i have been told can be used as parts for mine (but its close)is the ole moonshine runners... the pontiac lemans. is there a site or book i can get my hands on that will let me know that kid of stuff, or am i gonna just have to gather that wisdom with my age and troubled experinces? Smile  

68scott385 68scott385
User | Posts: 51 | Joined: 07/09
Posted: 05/05/13
12:00 PM

I'm goin got post these links one at a time because the forum won't allow some but allows others. I don't intend to post any links to companies that do not offer parts for you car. When looking for suspension parts you may have to use the LeMans application to find the parts, that's okay, all 1973-1977 GM A-bodies used the same suspension parts, i.e.; upper & lower control arms, upper & lower trailing arms, control & trailing arm bushings, ball joints, shocks, inner & outer tie-rod ends, drag link, and idler arms.

Here's a wiki link for further knowledge expansion. Unfortunately there is no book that I know of that breaks this stuff down, it's all gained, at least mine is, from extensive reading, research, and experience.

http://en.wikipedia.org/wiki/GM_A_platform_(RWD)

Detroit Speed has tubular control & trailing arms for the best of corner burneers.

http://www.detroitspeed.com/  
68scott385 68scott385 68scott385

68scott385 68scott385
User | Posts: 51 | Joined: 07/09
Posted: 05/05/13
12:01 PM

http://www.energysuspension.com/

Energy Suspension has suspension and body bushings. You nay have to download their catalog and browse through that to get the part numbers you need.  
68scott385 68scott385 68scott385

68scott385 68scott385
User | Posts: 51 | Joined: 07/09
Posted: 05/05/13
12:08 PM

http://www.hotchkis.net/index.html

Hotchkis has control & trailing arms too. For optimum performance pick one company to buy suspension hard parts from. Unless you plan on doing serious autocross you probably don't need the tubular arms but if your factory pieces are on their last legs, these are the option to scouring junkyards to find equally old but less worn pieces.

You will notice that the prices of these vary some across manufacturers. The quality should be nearly equall as all the ones I consider for my use are known companies with good reputations for parts and business dealings, not some backyard engineering outfit.  
68scott385 68scott385 68scott385

68scott385 68scott385
User | Posts: 51 | Joined: 07/09
Posted: 05/05/13
12:09 PM

http://www.metcomotorsports.com/categories.asp  
68scott385 68scott385 68scott385

68scott385 68scott385
User | Posts: 51 | Joined: 07/09
Posted: 05/05/13
12:09 PM

http://www.p-s-t.com/  
68scott385 68scott385 68scott385

68scott385 68scott385
User | Posts: 51 | Joined: 07/09
Posted: 05/05/13
12:10 PM

http://www.globalwest.net/  
68scott385 68scott385 68scott385

1 |  2 |  Next   | Last