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1979 Pontiac Firebird 400 build

3K views 18 replies 4 participants last post by  Saldazzo 
#1 · (Edited)
Back when my brother was 16 (2006), he bought himself a 1979 Firebird with the 301 engine. For years I wanted to build a Pontiac classic car with a 400 engine and so right then I began scouting for a 400 block.

The list below shows the work I did to the car which concluded a decent running car that I never had dyno'd or tuned. The list is as followed:

1975 400 block bored .030"
stock style pistons and rods

1968 #16 heads 10:1 compression chamber
3 angle valve job

Wolverine WG1014 (041 grind) camshaft

Harlem Sharp 1.65 roller rockers

Edelbrock Performer RPM intake

Holley 770 Street Advenger carb (never tuned)

Full tube Hedman Headers and true dual 40 series flow master mufflers

Console fit B&M quick silver ratchet shifter

Shawn Cassidy built performance level 2004R transmission

Carter mechanical fuel pump

Stock HEI with no vacuum advance. Base timing is 14 degrees and the advance curve kit is stock.

PTC 2000 stall converter with B&M lock up kit

3.73 gears

Aluminum Radiator with electric fan



I took the car to lebanon valley dragway when it had the TH350 and experienced no traction in first gear (60ft was 2.7 on street tires) and the car still completed a 100 mph pass.

I never went back to experience the 2004R tranny but for now I am trying to get some opinions about this build. I have a feeling having no vacuum advance was a bad idea and at the time, the local performance shop "locked" my distributor. I don't even know what the full advance is yet.

Now that I am getting back into it after all these years I would like to educate myself on some dos and don'ts. For now, what do you guys think about this build so far?

Thank you!
 
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#3 ·
I find that I get 7" of vacuum.Throttle plates are not opened and the primary and secondary metering screws are adjusted for max vacuum.The car runs good and doesn't stall or bog.

My questions are:

If I wanted to improve low end without changing the cam should I reinstall an aftermarket vacuum advance cannister and advance the camshaft position using a keyway slotted gear set from Comp Cam? Anyone have any experience on 2, 4, or 6 degree advances without interference?

The car will be going to Janetty Racing for a tune and I want to prepare the car for him as best as I can. The charge is $180.00 an hour to tune. Any information would be appreciated.
 
#5 ·
100 mph through the gate is pretty decent.
Sounds like what you need are Tyres.
Drag slicks for draggin .
I assume you have an LSD rear?
Vacuum advance is good for when you are cruising on the highway.
Not much use for it at the track.
Decide where you want to drive the car, then set the distributor up for one or the other, or for the street, and live with whatever you get at the track.
The 041 cam isn't a real street friendly cam is it? I would think vacuum would be low at low RPM too and would be a constant source of tuning tinkering. Just my .02
 
#7 ·
Not really that bad




I do have LSD rear yes

I agree that I do need tires. I was impressed with the trap speed after my tail end swung to my left at the launch, ( i recovered nicely) :)

I also agree that the 041 isnt a really street cam. The car was never intended to be a daily driver but more of a weekend/strip type. To reduce the amount of tinkering the tuner will have to do as far as fuel jetting and timing, I would like make it easy on my wallet since the price is $180 an hour. :rolleyes:

Putting a vacuum can would be benfiical for idle quality but at 7" vacuum I bought myself a vacuum cannister VC1825 that advances at 3-5". If I go this route then the tuner could work on the advance curve too.
OR,
Should I invest $120 on a keyway timing kit to advance the cam 4 degrees and bring up the combustion pressure/vacuum?
 
#8 ·
Advancing the cam timing will not be the way to go IMHO.
It will increase the chance of detonation as dynamic CR will rise a bit.
At 10 to 1 Static compression , that overgrown cam is probably the only thing keeping you from detonation now anyhow.
You are going to need to change a bunch of stuff, including the cam to get a more manageable street motor from that 400.
Are you looking to make a street car/ driver out of it?
Or are you still planning on competition at the track?
 
#9 ·
Thanks for the reply.

I definitely do not want this to be a daily driver only a weekend car, (street/strip).

Ok so advancing the cam even two degrees will raise the compression too high? That's pretty much what I wanted to know. I am trying to find an easier way of increasing the manifold vacuum a bit without changing the cam. 7 in Hg is low even though it idles decent with a lope. I do have an auxiliary booster can for the brakes which works pretty well.
 
#11 ·
You could go back to stock ratio rockers if you want more vacuum. If it were mine I'd get a 3500-4000 stall converter, better tires and tune for the highest mph. Then go see the tuner if you want a piece of paper with numbers on it but the mph on your timeslip will tell you what you need.
 
#13 ·
I think I still have the stock rockers too, need to check the garage. How much of an increase do you think they will make? 1-2"?

I guess I should go and see what the car does with better tires before doing anything, this way I have a base reference to compare. I never ran it with the 2004R.
 
#15 ·
For the time being I found out that the 770 Holley Street Avenger carb I have came stock with 72 primaries, 76 secondaries, and a 6.5" power valve.

I am going to take a shot at ordering 2.5" and 3.5" power valves as well as #80 and #84 secondaries, and a vacuum secondary spring kit.

Right now my vacuum is 7" in park and drops to 5" in drive so according to the Holley instructions the power valve should be half the vacuum in drive. Easy change for what it's worth. As tresi stated if I tune for highest mph then I minds well spend the 30 bucks and try to get there.
 
#17 ·
I wouldn't race with that engine unless money were no object. It's going to self destruct and since you have already run it, it may happen soon. Your best bet would be to find another 400 block (any other than the "557"), have it machined and use the internals from that engine as long as it has forged pistons. Consider yourself for warned!
Bill
 
#18 ·
Oh boy. Thank you for the warning. Money is an issue. I am getting married in May and we're trying to plan for a kid next Fall, as well as a house. I live in Hartford Conn and do not want to raise my kids here.

I even put my 89 IROC 406 project on hold for this but that's for another post subject.

In the mean time thank you and I will keep the warning in mind. It's been a good weekend car the last 5 years, especially with the 2004r and lock up converter so I will enjoy it till it goes.
 
#19 · (Edited)
Noticeable difference

Update

The other day I ordered the 2.5" Hg power valve from Holley, the #82 and #84 jets for the secondaries, and the vacuum secondary spring kit and I got them today.

I installed the 2.5" power valve and saw a 1" vacuum increase in drive (brother assisted) after opening the metering screws one full turn. The idle itself sounds different (lower tone as oppose to hollow) and smoother. The exhaust even smells different.

Attached in this thread is a link of what the car sounds like with the 6.5" PV. Monday I will post the sound of the car idling and will do the jet and spring tuning another time. Not bad for 13 bucks.
 
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