78 Grand Prix project

[Bonnewagon]

It has been determined that the best all-around manifold is the stock factory 4 barrel. They got it right and stuck with it. It's got just a shade less flow than the exotic RamAir series, you'll never tell the difference on the street, and much more common. The Edelbrock Performer is an aluminum exact copy of the factory unit, so there's an idea.

 

[G-Body_Vet]

I came across two reasonable priced, running engines. Ones a '76 455. The other is a '72 400. I'm awaiting a response on the details. All I know so far is the '72 is from a Catalina with 90K. Any suggestions? I like more cubes but I know the '76's weren't the most stellar performers of the time.

 

[Bonnewagon]

I have two 72' 400's and both were from Cat's, both were 2 barrel motors, small valve low compression heads. Not screamers but strong. A 4 barrel would have a better cam and much better heads but be aware of the missing end exhaust bolt holes . I also have a 76' 455 out of a Bonneville, (relativly) large valve heads, gobs of torque. Niether of these are considered high performance, but what the hey at the time they were all we had. Because of the long stroke a 455 makes it's torque peak at around 2800 rpm and the 400 peaks at around 3600 rpm. A 455 is great for a big fat *ss car but I think a 400 is perfect for our G-bodies as it can be safely revved to what we consider "fun" around 5500-6000 rpm. If you had a strong overdrive automatic or a T-400 with decent gears the 455 would make a stump pulling cruiser, but I prefer the 400 on a stick. Right now I have the 455 in a 68' Firebird with ST-10 and I can't believe the torque. It's not registered but I'd be shocked if it got better than 10 mpg. Here is a good chart for heads. http://www.wallaceracing.com/head1.htm

 

[G-Body_Vet]

An improved 200-4r will be a must with whatever I run. I'd like to be able to drive this car on the highway without the engine screaming. Hopefully the guy that has them gets back to me. I can probably get both of them together for $650 or $700 with a little haggling. We will see though.

 

[tdvick]

My thoughts are, do it once, do it right and don't leave room for second guessing. Go with the extra cubes right off the bat. Either start with a 455 or buy a 400 and rebuild it with the stroker crank. If you're looking to change heads and cam anyway, that '76 455 will be just fine. The '75 and'76 blocks were supposedly a little weaker casting, but I really doubt you would ever push it far enough to care unless you were building an all out drag car. Also, a 455 is going to be more driveable than a 400 with the same head/cam setup. The extra cubes help swallow up the extra lope from a larger cam. You'll also have more torque and throttle response which you'll want for a street driven car.

Just my 2 cents,
Troy

 

[jcbannis]

man that is a damn good looking grand prix it really makes me miss my 78 i used 2 have

 

[G-Body_Vet]

man that is a damn good looking grand prix it really makes me miss my 78 i used 2 have

Thanks. I hope to have it on the street by the summer. I've been gathering parts but haven't made it out to the garage yet. I have a Pontiac 455 standing by for pick-up and a ton of suspension parts to install. If I can find a buyer for my 305 I'll pull it and get started on coating the frame too.

 

[jcbannis]

keep me updated ive had 2 78s and 2 79s and an 80 but the 1 i miss the most was the 78 i had for years but it had the 301 in it when i got it with a bad head gasket and i ended up putting a 403 in it

 

[G-Body_Vet]

keep me updated ive had 2 78s and 2 79s and an 80 but the 1 i miss the most was the 78 i had for years but it had the 301 in it when i got it with a bad head gasket and i ended up putting a 403 in it

The ironic thing is I've had 3 SS's, including one Aerocoupe. I had a '85 Cutlass years ago with a 403 in it. The rings got so bad that it started blowing oil out of the driver's side tail pipe. It would still fry the tires at will though!

 

[G-Body_Vet]

I came across some more ebay scores today! Got a new set of Moog 5664 springs for $40 on the way. Also found a 36MM GTA sway bar for $70 shipped. My ebay Riviera steering wheel and GP emblem came too. This was the end product.