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Old 04-26-2017, 12:39 PM
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68 firebird 400 performance

Hi. New to the forum and seeking some advice. Recently purchased a firebird with rebuilt 400. Edelbrock intake, not sure how to tell which model. Awesome car, but I really thought it would have more get up. I'm looking to smoke the tires, awesome take off,much faster acceleration (car is an automatic). I'm not looking to go to a racetrack. I want to do this in phases. Can someone provide some recommendations of what changes I can make. Sorry for the limited tech data. I'm not sure how to extrapolate this from a car I bought and didn't out together. Thanks

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Old 04-26-2017, 05:20 PM
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Remove the original 400 CI engine and slip in a complete 455 CI Pontiac engine. Don't use the 400 heads if you do not want to use race gas. The only major problem with that conversion is finding a good rebuilt or rebuildable 455 CI engine. All the Pontiac owners have grabbed the 455 CI engines. Now the 400 CI engines are being bored and stroked to 455 CI. That is expensive.

I learned the following geometry lesson many years ago:
"The only substitute for cubic inches is rectangular money"
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Old 04-26-2017, 06:16 PM
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THIS ^^^^^^^^^^^^^^^^^

Or , yank your 400, get a butler stroker kit to make a 462.Done

There are still a few 455s around.I know where there is one, but I dont need it.Nor do I want to go get it.
Guy I was talking to the other day has one, as a spare, but he isnt selling.

Point is , there are still a few around.Just gotta be patient and keep watch.

Personally ,I would build the 400 you have ,unless it is a 557 block
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Old 04-27-2017, 06:40 AM
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Thanks for the great ideas. I'm trying to stick with the current engine and perform mods to it. Going to look into the butler
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Old 04-27-2017, 08:11 AM
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In 1971, my 1969 Firebird 400 4-speed was equipped with a 4.33:1 Saf-T-Track under the Pontiac 50k mile drive line warranty after I broke the original 3.36:1 rear gears. I installed a Crane ZIP510 solid lifter camshaft to go with the 4.33 gears and 28" tall GoodYear 11" wrinkle wall slicks. My Firebird was a mid 12 second combination with closed exhaust and without sub frame connectors. I traded the original Q-jet on my 1969 Firebird 400 for a Tri-power from a friend's 1966 GTO ........ and lost 0.4 second.

The only problem I had with my Firebird 400 and 4.33 gears was overheating when I made an attempt to go anywhere at highway speed or more than sustained 60 MPH. The stock radiator in the Firebird did not have the cooling capacity for the 4.33 gears at highway speeds.
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Old 04-27-2017, 10:34 AM
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Quote:
Originally Posted by hcompton View Post
...Tall tires can also require more gear to run right.
HC, Do you proof read your posts or is this something you somehow believe?

Ridiculous statement, bad/inaccurate information...again.
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Old 04-27-2017, 12:50 PM
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OK...I took that sentence to mean turning right, as in left and right, wording is confusing. Matter of fact tire size can be a useful tool for varying conditions, not necessarily adversely affecting performance.
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Old 04-27-2017, 04:30 PM
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Quote:
Originally Posted by 68NovaSS View Post
HC, Do you proof read your posts or is this something you somehow believe?

Ridiculous statement, bad/inaccurate information...again.

That would be true a tall tire reduces the effective gear ratio compared to a shorter tire because the taller the tire or think of it as a larger diameter also presents a larger perimeter or circumference which means the tire goes further per revolution thus the engine would turn slower for a given road speed which puts the engine lower down in its power band thus the vehicle accelerates slower.


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Old 04-27-2017, 05:11 PM
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Quote:
Originally Posted by hcompton View Post

I would pull the motor set it aside and put in a chevy big block or small block stroker either can make easy hp that will be a lot cheaper than any pontiac options.
You really believe This ?

How much is a stroker kit to get a SBC to 383 cubes?

Then add in all the machine shop work, clearancing the block etc

I Mean ...come on man really? Cheaper?

How about put together a SBC projected build, every part needed to stoke a SBC to get a 3.75 stroke ( which a poncho 400 already has BTW) and all the goodies to bolt it in and then convert ,replace /adapt the trans to run the said SBC . Then put all the parts, prices and your sources so we can verify it.

Then I will post a same list for a pontiac 400, and if you like , I will also price it out as a stroker to bring the cubes up to 462.

THEN I will also mention there will be no need for any exhaust conversion, motor mounts, wiring changes,transmission change yada yada yada, And I will then be able to prove my point.

It is NOT cheaper to put a SBC or BBC for that matter, in a car that had, was designed and deserves a PONTIAC engine in it.

We have been over this in the past. It IS NOT CHEAPER , (or better for that matter) to build ANY chevy motor and replace the OE Pontiac engine that has all the parts for a Pontiac engine.

If the OP wants a CHEVY motor, then he maybe would buy a CAMARO.

I am waiting for you to post your parts/price list.
Dont forget all the nickel and dime BS
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Old 04-27-2017, 06:00 PM
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Quote:
Originally Posted by Bird-man View Post
Hi. New to the forum and seeking some advice. Recently purchased a firebird with rebuilt 400. Edelbrock intake, not sure how to tell which model. Awesome car, but I really thought it would have more get up. I'm looking to smoke the tires, awesome take off,much faster acceleration (car is an automatic). I'm not looking to go to a racetrack. I want to do this in phases. Can someone provide some recommendations of what changes I can make. Sorry for the limited tech data. I'm not sure how to extrapolate this from a car I bought and didn't out together. Thanks

If this really is a 400 than it isn't exactly a slouch, it did or does suffer from GM's constant fiddling with power to weight ratios around 1 hp per 10 pounds of vehicle weight.


Given that the times have changed quite a bit since 1968 it's really due for a set of aluminum aftermarket heads, a modern intake and cam. Today's fuels really can't support the original compression ratio with an iron head nor will the exhaust valves last with unleaded fuels, and a modern fast lifting cam with shorter ramps and more .050 to .050 action is more suited if not required to get if not exceed its 1968 performance.


If this hasn't had a timing set replacement it is undoubtedly due. The plastic gear teeth never held up well but the Pontiac and Buick were hard users of those things often deserving replacement with something made of steel pretty early in their lives.


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Old 04-27-2017, 06:51 PM
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OP wants to build the pontiac engine he has.Wants to make changes to get HP up.
Not put a chevy in it.

Crate motors are cheap.
A 500 horse poncho wont cost 15K

Did you not feel like posting a build/price sheet?

The turbo 400 is a BOP pattern as none were a multi pattern, so it would need changed $$$
Motor mounts and stand would need sourced and changed $$$

Exhaust would need changed $$$

Wiring would need to be re configured $$$

Radiator would need changed, as hose inlets and outlets arent the same $$$

Accessory drive brackets would need to be sourced$$$

on and on and on

Sure the motor may be cheaper, but wont have the torque a pontiac is capable of.

Its the cost over run of converting everything to fit an SBC that makes it not "Cheaper" to do.

FWIW I built my 389 into a 400 for about 3200 bucks. That included machinework,Polishing and balancing the crank, all internal parts, new intake.Heads are 80 CC 7H1 ponchos, ported.
No parts from butler ,except 5140 rods
I rebuilt the quadrajet.
Curved my own dizzy.

Runs excellent. I am in for way less than 5k

I estimate my Tq/HP to be an easy 375/420 lbs
Cheaper to put in a chevy, yeah,OK

Cheaper to get all the junk to hook it up.....not so much
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Old 04-27-2017, 06:56 PM
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455 Pontiac High Performance balanced crate engine with cast heads | eBay

More money, more CI.

Not to keen on buying an engine from an E Bay vendor

http://www.ebay.com/itm/Turn-key-exc...FZARFq&vxp=mtr

Been a Auto tech for too many years.
Besides I have a killer machine shop here in the rust belt

Plenty of less expensive pontiac options available
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Old 04-27-2017, 07:00 PM
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car engine Pontiac Tin Indian performance 455 -- 640HP | eBay

Whats 11 K for 640 HP

How much is a crate 572 ?
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Old 04-27-2017, 07:05 PM
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OOPS Its only 621 HP for 14 K (actually almost 15K)

ZZ572/620 Deluxe Crate Motor 621HP 19331583 Chevrolet Performance

Not cheaper.19 Less HP
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Old 04-27-2017, 07:17 PM
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Sad thing is, the OP hasnt been seen for a while.

The thread took the same old "put a SBC in it" turn as many do.

The whole thing was ruined by posts that people posted that were geared more toward what They would do, instead of answering the OPs questions and helping him with advice and tips to get his current setup putting more power to the ground.

Posts need to be relevant to the OPs questions and needs. Not eluding to sales pitches or vendors and a cheaper product because it suits you.

Instead of closing this thread because it has gone so far off the track, why dont we try and give the OP an answer.

How about help him re configure his current engine,like he wanted to do.
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