[cutrone]

i just bought a bone stock original 69 grand prix 428 h.o. auto (60,ooo)miles.i want to build a wicked street car!im lookng for some motor & drivetrain build up advice. i have about $10 grand to spend.i want to leave the 3:23 posi alone for now.keepin the D ports too.what kind of performance can i expect??? i was hoping for high 12's???did i say street car?

[cutrone]

i just bought a bone stock original 69 grand prix 428 h.o. auto (60,ooo)miles.i want to build a wicked street car!im lookng for some motor & drivetrain build up advice. i have about $10 grand to spend.i want to leave the 3:23 posi alone for now.keepin the D ports too.what kind of performance can i expect??? i was hoping for high 12's???did i say street car?

[Keith Vrabec]

Let me say first, before you modify it too much, considering it's an original HO car, you might want to do it to something else....

But that being said, you have an excellent platform for a STOCK appearing 12 sec car....Proof in that pudding is the 65 GP of Doc Shutello, built by Ed gartner to run 12.99, and also hit gold restored at POCI nationals....Neat car.

If you have a true HO car, you have the long branch factory exhaust manifolds and D port 62 or16 heads. Good setup. A good porting job and then perhaps a flowmaster exhaust is all you need there. Not going to gain much except weight over stock intake. Perhaps HEI or Petronix ignition should do too. Going to have to mix gas or use race fuel though with 10.5 compression.

You might need more gear to go that fast though, since you have a lot of weight. Probably at least 3.90, maybe more. My buddy Brian has a nice one, all stock, 3.23 gears, runs 13.9's on street tires. I can't recall if he has headers and what exhaust he has, but his engine is the 370 hp version of the 428. (I'll have to just go to the garage and look...I'm holding it here for the winter until his garage is finished....Perhaps he'll forget it's here....)

Of course you'll have to tune the hell out of it and run slicks but it can be done.

Also you could go with the Edelbrock heads and headers, that will get you there sooner.

Just don't butcher an original HO with tubs and such.....Sell it to one of us crazy restoration guys first and we'll find a Model J 400 car to get to you...

K

[cutrone]

thanks for the reply keith.i am going to keep it stock appearing,keeping all the original parts i take off.i have a great engine builder who will be doing all the machine work.long brach man.vs.headers i am struggling with,since i have not found anyone who sells them for this appl.im guessing that first gen. firebird set up will work?like you said my ported #62's will keep the stock look going.(dish piston for lower compr.)how about a cam & converter suggestion?

[engineer]

If you cut compression, you will not get into the 12s with that 3.23. You will have both HP and gearing working against you.

[cutrone]

what compression should i be looking for? just did a 406 (same #62 heads)dished piston for 9.6:1

[Motornoggin]

9.6:1 is a good compromise on compression. If done right, you can cetainly get into the 12's. I had a 75 T/A that weighed 3900#, with an 8.4:1, hydraulic cammed 462 that ran a best of 12.8. That was with an M-21 and 3.07 gears.

Prevert? I'm way past that! I'm a Postvert!
http://community.webshots.com/user/motornoggin

[David Holmberg]

http://pontiacgroup.com/

Alex has the info you need for a 69 GP! [img]/infopop/emoticons/icon_biggrin.gif[/img]

[10second70GP]

here's my street grand prix that i street race, full steel except bumper, full interior, should be in the tens on motor 10.1 compression who says you can't build a fast grand prix. 3800 with me it.let me know if you need help.