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general performance questions

  
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general performance questions

 
67400fb_vert_auto 67400fb_vert_auto
New User | Posts: 1 | Joined: 09/09
Posted: 09/23/09
03:45 PM

My firebird runs well for the most part, it starts easily but needs to warm up a little bit even when it's warm outside. It runs strong but shifts out of 1st gear to quickly even at full throttle, I don't have a tach so I'm not sure what the RPMs are when it shifts.

The initial timing is about 15 degrees advanced. The dist. is curved to 36 degrees @3000 RPM.

The cam is pontiac model 9779068:
Duration             hp/rpm     torque   overlap LSA Intake Centerline
288/302 212/225 360/5100 445/3600 63      116        113

Quadrajet is rebuilt stock
Turbo 400 is rebuilt stock
Rear is limited slip 3.08

The car doesn't launch as hard as I expect it to, barely chirps the tires from a dead stop. It's still faster than my 2000 GT and the tires spin pretty easy if I'm backing up. I checked the gear ratios of the turbo 400: Turbo 400, 2.48, 1.48, 1.00, 2.08 Reverse. So I don't think the gear ratio is an issue. From my limited knowledge reading manuals it seems that that reverse gets a higher fluid pressure than 1, 2, or 3rd. Is it possible that I'm not getting quite enough fluid pressure in drive for some reason?

I have a 160 thermostat, in the summer the car runs 160-190 for the most part but if I cruise 75-80 on the highway it creeps up slowly, then backs down if I slow down or leave the highway. Our speed limits are 70 mph here.

Could I be seeing some extra heat from lower than the correct fluid pressure? Can this be regulated by the governor?

Occasionally it will chirp from the 2nd to third gear shift if I am going up a mild hill.

Just trying to get some ideas before I talk to a couple of local shops and see what they think. Maybe it's something simple I can adjust.

Anyone have any experience with this type of setup?

thanks  

 
Pontiacman Pontiacman
Guru | Posts: 1037 | Joined: 11/07
Posted: 09/23/09
05:16 PM

With only 3.08 gears and the stock 068 cam you are not going to get that seat of the paints feel.

What is the casting numbers on the heads which can be found on the center exhaust port.  
Professional hi-performance engine builder

Horsepower sells Engines and torque wins races.

 
69nova355.1 69nova355.1
User | Posts: 144 | Joined: 08/09
Posted: 09/24/09
04:37 AM

you need to get a tach. you want to know what rpms your shifting at. go with 3.73 or some 4.10s. depending on the heads they may not flow as well as you thought.  

 
wdl4 wdl4
User | Posts: 104 | Joined: 07/08
Posted: 09/24/09
09:17 AM

i agree get a tach. how tall are  the rear tires ?  this will directly affect your take-offs. 3.73 with a 27 in tall tire and maybe a looser converter, you will notice a differance.
the trans is not slipping or you would notice the rpm`s flair up.  

 
400_fb_670 400_fb_670
New User | Posts: 3 | Joined: 09/09
Posted: 09/24/09
04:27 PM

My account got disabled somehow so I am posting with a new username. I'll try to find out what happened after I post.

The heads are the original 670 castings, but they have been rebuilt with new parts and hardened valve seats so that if I use only unleaded gas isn't a problem.

I'm thinking about buying a set of gears and a tach. I looked at Auburn units so far. I'll probably try to find a relatively small inexpensive tach just to see what is going on. Hood tachs rock but no cash for that right now. The rear tires are 25 1/2" tall.

As soon as I get a nice afternoon I plan to try adding 5-10 gallons of CAM 2 and see what that does.  

 
Pontiacman Pontiacman
Guru | Posts: 1037 | Joined: 11/07
Posted: 09/24/09
05:17 PM

Well higher octane will help because 670 heads on a 400 gives you around a 10:1CR and that is a little to high for pump gas on a Pontiac engine with iron heads.  
Professional hi-performance engine builder

Horsepower sells Engines and torque wins races.

 
Pontiacman Pontiacman
Guru | Posts: 1037 | Joined: 11/07
Posted: 09/24/09
05:23 PM

Also a cam change and some lower gears like 3.42's would help.  
Professional hi-performance engine builder

Horsepower sells Engines and torque wins races.

 
400_fb_670 400_fb_670
New User | Posts: 3 | Joined: 09/09
Posted: 09/24/09
05:55 PM

The gears sound like a good compromise. Which cam do you think would perform the best?  

 
Pontiacman Pontiacman
Guru | Posts: 1037 | Joined: 11/07
Posted: 09/24/09
05:59 PM

If the heads have not been ported then I would go with the lunati P#LUN-00072LK.  
Professional hi-performance engine builder

Horsepower sells Engines and torque wins races.

 
400_fb_670 400_fb_670
New User | Posts: 3 | Joined: 09/09
Posted: 09/24/09
06:06 PM

Right, I didn't get any porting. Thanks  

 
Pontiacman Pontiacman
Guru | Posts: 1037 | Joined: 11/07
Posted: 09/25/09
03:08 AM

No problem.
Any time.  
Professional hi-performance engine builder

Horsepower sells Engines and torque wins races.

 

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