68 350 - anything else to do to optimize? - Performance Modifications - Firebird Nation

Jump to content


FirebirdNation.com is the premier Pontiac Firebird forum on the internet. Supporting Members do not see the above ads.
Photo
- - - - -

68 350 - anything else to do to optimize?


  • Please log in to reply
3 replies to this topic

#1 kdubya

kdubya

    Firebird Newbie

  • New Member
  • Pip
  • 2 posts
  • Gender:Male
  • First Name:Kevin
  • City:Chesterfield
  • State or Province:VA
  • Country:USA
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 350
  • Transmission: TKO 600

Posted 6 days ago

I've found a ton of useful info here, some really knowledgeable folks. Appreciate what I've learned so far. Time to post though, have questions that are probably most easily addressed by just asking.

I have a new to me '68 coupe with numbers matching 350 and TKO 600 trans. Liberty 3.73 gear with eaton posi. Detroit Speed suspension, real fun driver. Super clean, originally California car.

Questions are with the engine and seeing if there is much else I can reasonably do as it is, or by rebuilding, to really optimize it for a driver. Zero intent to be a drag car. It's heading down the corner carver route. I like that it's got the Pontiac motor, no real intent to change any time soon, or later for that matter.

The info I have is from a previous owner who was gracious enough to spend a lot of time telling me what he did. He did or oversaw all the work.

 

Engine was fully rebuilt in '09. Bored 30 over, balanced, heads remanufactured but I don't have definitive answers if it had a proper valve job or screw in rocker studs done. It was decked, also not sure of details on how much or what gaskets were used. I have details from the balancing job. Notes show SPC stuff, hard to read the chicken scratch - I think timing set, main bearings, rear seal. ARP rod bolts. Has 17 heads, Melling 26204 cam which is basically identical to the Summit 2801 and roller tip 1.5:1 rockers. Performer intake, edelbrock 1406 4-barrel, stock iron manifolds, MDS ready to run distributor with 6AL analog box..

The bottom end was rebuilt again in '13 due to an oiling issue, oil press light would come on during hard cornering (think fast, fun highway on and off ramps) and had a rod bearing noise. Ended up with a spun rod bearing that they caught real early. Had all new bearings done, bigger oil pan (though I wonder if they added baffling rather than increased size since capacity seems to still be 5 qt) and he said the engine guy did some things with oil galleys, not sure what was done.

Since then it's got probably 20-25k miles on it. In the last 4 years, just 3k miles. I have no idea what horsepower would be at this point. On a Mustang dyno, before the 26204 cam so no idea what cam that would have been, it made just 208 hp @ 4500 rpm and 267 ft-lb @ 3350rpm. This may have been the original stock cam, I'm really not sure. I would really like to know what it makes now, but don't really have plans for dyno it, unless I go forward with EFI and tune it and even then, might not have to tune it formally, like at a shop.

I'd like to switch to EFI, probably Sniper system. Beyond that, without another rebuild, so as it sits, is there anything else could I reasonably do to optimize things further? I feel like it's probably pretty close to as good as it gets, I can't imagine a different cam being all around better at this point. Maybe long branch manifolds.

If I were to at some point pull it and tear it down, what would you suggest to get the most out of a 350 block for a driver? While trying to maintain drivability, what's the max HP/TQ that could be expected from a 350 intended to be a fun driver? Maximizing power while maintaining maners would be the primary concern, that's the balance I'm after. I know 350s can be made to make a lot of power if someone is willing to commit to it, but it sounds like you take a hit on street manners when you really push it.

If I were to bore and stroke it, to a 383 for example, would I be looking at a different cam, heads or intake at that point? From what I've seen, seems like the 17 heads are a pretty good deal here, and anything more in the cam might hurt it for what I want but I don't know if there would be a better options if the displacement is increased.

I don't want to max out HP just for the sake of more HP at the expense of everything else. Torque in a driver ends up being what you really feel anyway. For the intent of the car, I could see it being a real blast in the 400-450hp range. Can that be done with a 350 while maintaining good manners for regular driving? 

Sorry that was long, I wanted to lay it all out. Thanks for any good insights!

Attached Files



#2 tjs

tjs

    Firebird Mechanic

  • Full Member
  • PipPipPipPipPipPip
  • 594 posts
  • Gender:Male
  • First Name:tom
  • City:long beach
  • State or Province:CA
  • Country:USA
  • Interests:pontiacs,shooting and fishing
  • Year: 1969
  • Make: pontiac
  • Model: firebird
  • Engine: 428 RA V
  • Transmission: TKO 5 speed

Posted 4 days ago

IMO,the carb and exhaust manifolds are no help.A proper QJ and RA long branch exhaust would be a big help.A RPM intake would help also.2801 cam is a great cam for a 350.EFI wont get much more HP.I would not mess with the 350 block if you really want more.If you could find a good 400 block everything but the pistons could be transplanted in the 400 block.Good luck with your project.Tom



#3 kdubya

kdubya

    Firebird Newbie

  • New Member
  • Pip
  • 2 posts
  • Gender:Male
  • First Name:Kevin
  • City:Chesterfield
  • State or Province:VA
  • Country:USA
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 350
  • Transmission: TKO 600

Posted 3 days ago

IMO,the carb and exhaust manifolds are no help.A proper QJ and RA long branch exhaust would be a big help.A RPM intake would help also.2801 cam is a great cam for a 350.EFI wont get much more HP.I would not mess with the 350 block if you really want more.If you could find a good 400 block everything but the pistons could be transplanted in the 400 block.Good luck with your project.Tom

 Thank you Tom. In place of a QJ I may go EFI and long branch - two things turn me off from the prospect of headers, just being headers and headaches from that, and fitment. That's a good thought about things swapping onto a 400 block. You think staying with the small valve heads on a 400 would still be ok?



#4 tjs

tjs

    Firebird Mechanic

  • Full Member
  • PipPipPipPipPipPip
  • 594 posts
  • Gender:Male
  • First Name:tom
  • City:long beach
  • State or Province:CA
  • Country:USA
  • Interests:pontiacs,shooting and fishing
  • Year: 1969
  • Make: pontiac
  • Model: firebird
  • Engine: 428 RA V
  • Transmission: TKO 5 speed

Posted 3 days ago

You want a good street car,they will be fine.Just be aware of your CR,keep it in the 9.5 range with what ever piston you order to do it.I like Autotec.Tom






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users