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help with a build?

 
jackdunn67 jackdunn67
New User | Posts: 1 | Joined: 02/14
Posted: 02/13/14
12:38 PM

i have a 67 firebird convertible with a turbo 350 trans and a low compression 400 motor in it i fried the piston rings so im going to pull the motor out and when its all done i plan on putting my muncie rock crusher in it so i was wondering what kind of mods i can do to the motor to get 450+ hp out of it i was looking at getting 670 heads its already got a gto intake with a 4bbl carb on it so im curious as to what kind of work i can do to the heads what cam? a different crank? anything really  

69GTOby 69GTOby
Guru | Posts: 1113 | Joined: 02/09
Posted: 02/13/14
02:06 PM

Hello.  450+ hp for a 400 is a tall order, that's not to say it can't be done; however, the same power can be attained much more cost effectively and easily with a 455.  What is your budget on this build and your overall goals for the car?  
****
1969 GTO resto in progress. '76 350+.060, #13 heads, 9.2:1 CR, Lunati cam, Edelbrock Performer, 750 Holley, HEI, Ram Air manifolds, 2 1/2" exhaust. TH400 trans w/shift kit and 2400 stall.  235/60/15 front, 275/60/15 rear on Rally II 15X7s.  GM 12 bolt posi with 3.73's.

tempest1964 tempest1964
User | Posts: 66 | Joined: 11/11
Posted: 02/13/14
04:53 PM

Or you could look at a stroker kit like Butler sells to achieve more cubes and horsepower,  

69GTOby 69GTOby
Guru | Posts: 1113 | Joined: 02/09
Posted: 02/13/14
05:50 PM

Yes, the stroker kits are an option, but again, not as cost effective as just building a 455.  Generally, it costs about the same to rebuild any Pontiac engine.  But, the stroker kits are a little costly and require some modifications.  Basically, the cheapest way to reach 450+ hp with a Pontiac is with a 455...

I'm all for the 400's, don't get me wrong.  But, if I were building an engine for that much power on a budget, which most of us are, I'd build a 455.  Actually, what I would do is build the 400 and settle for near 400 hp, maybe 385 or so.  If the rest of the combo is in harmony and set up properly, the trans, the rear, the suspension, the car itself and so on, it should be plenty fast.  
****
1969 GTO resto in progress. '76 350+.060, #13 heads, 9.2:1 CR, Lunati cam, Edelbrock Performer, 750 Holley, HEI, Ram Air manifolds, 2 1/2" exhaust. TH400 trans w/shift kit and 2400 stall.  235/60/15 front, 275/60/15 rear on Rally II 15X7s.  GM 12 bolt posi with 3.73's.

ROWSLEY ROWSLEY
Guru | Posts: 1015 | Joined: 07/11
Posted: 02/14/14
12:09 AM

+2 69 GTO. don't forget about nos, turbo or a pro charger. a little boost can go a long way and still be street friendly.  
76 455/4spd TRANS AM
69 GRAND PRIX 455/5SPD

barneyformula barneyformula
Addict | Posts: 3306 | Joined: 01/07
Posted: 02/14/14
04:49 AM

The debate over 400 vs 455 has been thoroughly rehashed in my own thread from a few years back. Here's the link: http://forums.highperformancepontiac.com/70/8747136/the-general-discussion/dawnas-406-433-build-a-tribute-heaven-can-wait/
It takes a bunch of reading but there are dyno simulation charts and tons of other good info in that thread. Well worth the read. FYI, I did build the 400 and have run it on the test stand but I'm waiting for the car to get finished so I can get some real world performance numbers from the track and maybe a chassis dyno. We expect 470+hp and 500+ ft.lbs from "only" 406 cubic inches. It's all about volumetric efficiency! Wink
Steve  
A little help... 'cause we don't all have to learn the hard way!

Pontiacman8 Pontiacman8
Moderator | Posts: 5775 | Joined: 02/08
Posted: 02/14/14
07:56 AM

More cubes needs more air so better heads will be needed to feed the larger engine.
I would also look for better heads then the 670 as these are closed chamber heads and can restrict flow.
I recommend some edelbrock aluminum heads for your build.
450Hp should not be a problem with these heads and the proper cam,intake,carb and some decent headers.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 02/14/14
08:36 AM

+1 Steve.,. VE is something that is often overlooked in an engine build and the closer it approaches 100%, the more efficient the engine is.
For a crude example, let's take a 300 cube engine and give it a 2" intake and 1.6" exhaust valve.,. this would give it an easier time to achieve high VE.,. by upping cubes by 50%, we simply can't increase valve size to 3" and 2.4" respectively.,. because there is simply not enough room to park these valves side by side in a head.
Admittedly, this is a crude example, because flow curtain area enters the picture as well.,. but that is quite another long winded story.

Flowcurtainarea


Dawna's 406 Build

Dawnasdreambuild406

Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

thinman56 thinman56
User | Posts: 110 | Joined: 04/13
Posted: 02/14/14
10:37 AM

Hey, Tuffnuff, can you post the dyno test results from that build sheet?  I went through a couple weeks when I first got the software when I was obsessed with building engines on paper...  

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 02/14/14
10:58 AM

Sure thing.

Shawnas406build 1
Shawnas406build 2
Shawnas406build 3
Shawnas406build 4
Shawnas406build 5
Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 02/14/14
11:07 AM

My 400 Output

My400pontiacspecs
My400pontiacoutput
Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

thinman56 thinman56
User | Posts: 110 | Joined: 04/13
Posted: 02/14/14
03:13 PM

Thanks, Tuff, impressive results on both engines.  Are you running your 400 now?  If so, do you think the dyno sim is pretty close?  

tuffnuff tuffnuff
Moderator | Posts: 2567 | Joined: 12/09
Posted: 02/14/14
03:43 PM

The 400 is on the engine stand for another rebuild, with consideration for reg gas.
Sims are based on ideal builds and could be out as much as 5% either way.,. the end result depends entirely on rounding up ponies,,,,, IF, you know how.

Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

thinman56 thinman56
User | Posts: 110 | Joined: 04/13
Posted: 02/15/14
06:11 AM

Both of these look like good models for what jackdunn wanted to get done.  I thought the horsepower numbers seemed high for the cam you ran on your 400, but I also see you got some trick heads, so I can see now where the power comes from.  

I ran some dyno sims on the VirtualEngine2000 of other published motor builds that actually made it to the dyno, a couple from Rocky Rotella and the 350 HO posted on this forum and elsewhere, and the results were more optimistic than actual tests.  Still a great tool for running comparisons and looking at the impact of various mods, but wise not to take it too literally.  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 450 | Joined: 11/13
Posted: 02/15/14
06:36 PM

hello

it would be more helpful to you if you post this question as a new topic.

go to the home page and there is a small gray box on the left. click that to post a new thread.topic.


if you don't stroke it, one option is to buy some eddy heads, get your static comp up to arpund 10.5, built the bottom end with good parts, insatall a victor jr intake, 650 cab and massive cam.  

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