#1  
Old 10-02-2022, 05:39 PM
Phoenix79 Phoenix79 is offline
Junior Member
 
Join Date: Oct 2022
Posts: 13
Default 1976 400 Build for T/A

My daughter is carrying on the Pontiac family legacy with her 79 T/A. We are ditching the monster 301 powerplant for a recently purchased 76 400.

400 engine runs, but 185 hp isn't going to cut it. We have the 557 block and well aware of it's weakness, just looking to pep it up and need some suggestions (other than boat anchor).

1. Pistons can we bump up from 7:1 to like 8.5:1?
2. Cam to work with stock 6X heads and Performer intake?
3. Ram Air exhaust manifolds?
4. Distributor upgrades (module, coil)?

  #2  
Old 10-02-2022, 05:59 PM
25stevem's Avatar
25stevem 25stevem is offline
Ultimate Warrior
 
Join Date: Jan 2022
Posts: 1,744
Default

Is the car a auto or manual trans?
The block that you have is fine to rebuild for a nice fat power increase.

Please first state the budget your looking to invest in this as that will help to get you the most bang for the Buck, and to limit crazy suggestion that sometimes get tossed around here!

What is the casting code on the center exh ports on the heads on that 400, 6X or 6 whatever?

This is where you can find the secondary code which will tell you the chamber size of the heads your working with.
Attached Thumbnails
Click image for larger version

Name:	318104C3-B1D7-4383-B3D1-9F51E1CB1FB7.jpg
Views:	70
Size:	85.0 KB
ID:	599793  

__________________
I do stuff for reasons.

Last edited by 25stevem; 10-02-2022 at 06:09 PM.
The Following User Says Thank You to 25stevem For This Useful Post:
  #3  
Old 10-02-2022, 06:10 PM
Phoenix79 Phoenix79 is offline
Junior Member
 
Join Date: Oct 2022
Posts: 13
Default

She has a freshly built TH350 Auto. We would like to start around a $3,000 budget but there's room to invest more if needed (Dads $$).

Hoping to use refreshed stock crank and rods. I haven't opened the block yet to see how things look, the motor does run. I have good connections at local machine shop and should save some money there.

  #4  
Old 10-02-2022, 06:12 PM
Phoenix79 Phoenix79 is offline
Junior Member
 
Join Date: Oct 2022
Posts: 13
Default

Heads are stamped 6X, I'll have to recheck the secondary code next week when we pick up the motor.

Thanks for your help!

  #5  
Old 10-03-2022, 10:25 AM
78w72 78w72 is online now
Ultimate Warrior
 
Join Date: Nov 2007
Location: iowa
Posts: 4,683
Default

a 76 400 will have the 6x-8 heads if they are original, usually come in around 98-102cc. you can easily bump the compression by milling the heads .030-.040 & while the block is being rebuilt have it decked so the pistons are "in the hole" about .005, dont need to zero deck the block for a mild street cruiser & that leaves some material to clean up for the next rebuild. doing that will allow you to use stock replacement pistons as opposed to custom made. can use forged pistons if you want but cast or hyperutectic pistons will be fine for a 300-350hp engine that likely wont be raced. should be able to get around 8.5-8:75 compression pretty easy. also, if buying new pistons, best to have the block bored .030 for a little added compression & cubic inches.

crank & rods can be reused if they arent damaged, dont need forged rods for this type of build but thats your call based on the budget, if its not raced regularly, stock reconditioned rods are ok.

lots of options on the cam, will let others suggest that but you need to provide more info on the car like gear ratio, stall converter if any and final compression.

ram air manifolds are a good choice but many are on back order so buy now if you want them when the engine is ready but stock manifolds would be ok for this type of build if the rest of the exhaust is 2.5" with good flowing mufflers, not flowmasters! or consider headers, hedman makes some nice fitting headers that are not difficult to install if you follow instructions & they dont leak with good gaskets & re tighten after a few heat cycles, i have a set in use for 12 years now that are leak free using the original cheap fiber gaskets.

stock HEI distributor/module/coil is fine & very reliable, no benefit to using the MSD or pertronix modules & they may leave you stranded if/when they fail. may look into recurving the timing for best performance but on a smaller cam its not needed, car will still run good with a stock HEI.

if theres anything left over in the budget, have the carb (q-jet) rebuilt to the specs of the motor & converted to electric choke, couple guys on here can do it or i have used SMI with great results, or just buy a kit from cliff r & do it yourself or have the machine shop you use do it. final suggestion for better performance is rear gear of 3.08-3.23 if its a stock 2.56 or lower, 3.08-3.23 will still retain good highway manners but will be a big performance improvement on the street.


Last edited by 78w72; 10-03-2022 at 10:44 AM.
The Following User Says Thank You to 78w72 For This Useful Post:
  #6  
Old 10-03-2022, 10:31 AM
Skip Fix's Avatar
Skip Fix Skip Fix is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Katy,TX USA
Posts: 20,541
Default

For my kids high school 81 TA the 301 T was a part when I bought it. Built a mild 400 zero deck TRWs 2262 . I pocket cleaned up and port matched some 6X-4s I got at a wrecking yard. Plain Performer-way ighter than a factory iron intake. Tried a Holley 3310 then went back to a Qjet. RA manifolds. Summit 2801 cam. 3.08 rear gears.

My son never got used to a carb/choke in the cold and would stall it. His younger sister it was no problem.

I did have to put cats on it as at idle it would not pass the "sniffer" , old enough now does not need to.

__________________
Skip Fix
1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
The Following User Says Thank You to Skip Fix For This Useful Post:
  #7  
Old 10-03-2022, 07:45 PM
Phoenix79 Phoenix79 is offline
Junior Member
 
Join Date: Oct 2022
Posts: 13
Default

Thank you both for the detailed and good advice.

Last question, would either of you know if the Ram Air manifolds hook up to the stock Y-Pipe?

  #8  
Old 10-08-2022, 09:14 PM
Gnilrits Gnilrits is offline
Junior Member
 
Join Date: Oct 2022
Location: Spokane, WA
Posts: 1
Default 301 engine

I'm looking for a 301t engine/block.
I understand the 301t block can be found in most firebirds, but I haven't verified that.
Is your 301 block a 301t? If so then how far are you from Eastern Washington State? Is there a way to identify members locations? I could save junking up threads with that capability. Thanks!
Gnilrits

  #9  
Old 10-08-2022, 10:36 PM
b-man's Avatar
b-man b-man is offline
Moderator
 
Join Date: Sep 2002
Location: Sunny So Cal
Posts: 16,410
Default

Quote:
Originally Posted by Phoenix79 View Post
Thank you both for the detailed and good advice.

Last question, would either of you know if the Ram Air manifolds hook up to the stock Y-Pipe?
The RA manifolds definitely will not mate up to the stock Y-pipe.

I would run stock log exhaust manifolds if you must keep the Y-pipe, there’s no good reason to use RA manifolds if you’re not running a free flowing 2-1/4” or 2-1/2” dual exhaust.

On a mild low compression 400 the stock log exhaust are more than capable of handling 300 to 350 hp when coupled with a free flowing dual exhaust. The bang for the buck (probably less than 10 hp) just isn’t there with the RA manifolds.

Not saying the RA manifolds aren’t good, just that there’s probably better things to spend 4 to 5 hundred dollars on when trying to stay within a $3K engine building budget.

__________________
1964 Tempest Coupe LS3/4L70E/3.42
1964 Le Mans Convertible 421 HO/TH350/2.56
2002 WS6 Convertible LS1/4L60E/3.23
The Following 2 Users Say Thank You to b-man For This Useful Post:
  #10  
Old 10-09-2022, 06:26 AM
25stevem's Avatar
25stevem 25stevem is offline
Ultimate Warrior
 
Join Date: Jan 2022
Posts: 1,744
Default

Good logical dollar saving advice in the above!

But on top of that, just make sure that the exh manifolds you use after getting the carbon blasted off there insides only have light rust scale left on the runner walls.

I have seen badly scaled up exhaust manifolds eat up a additional 12 to 15 hp over and above what was lost by switching from headers to exh manifolds!

And yes, the jetting was optimized in each case.

__________________
I do stuff for reasons.
  #11  
Old 10-09-2022, 04:08 PM
Phoenix79 Phoenix79 is offline
Junior Member
 
Join Date: Oct 2022
Posts: 13
Default

My daughter is willing to part with the 301, how do we know if it is a 301T? It's in it's original vehicle, a 1979 Trans Am. The engine has less than 5K miles on a new build. We are located in NE Indiana.

  #12  
Old 10-09-2022, 04:12 PM
77 TRASHCAN's Avatar
77 TRASHCAN 77 TRASHCAN is offline
Ultimate Warrior
 
Join Date: Oct 2008
Location: 31May2013 Temporary home to the world's widest (that we know of) tornado. Lord, NO more Please...
Posts: 6,591
Default

The 301 blocks have "301" cast into the side of the block

Turbo blocks have 301T

__________________
1977 Black Trans Am 180 HP Auto, essentially base model T/A.
I'm the original owner, purchased May 7, 1977.

Shut it off
Shut it off
Buddy, I just shut your Prius down...
The Following User Says Thank You to 77 TRASHCAN For This Useful Post:
  #13  
Old 10-09-2022, 04:37 PM
Phoenix79 Phoenix79 is offline
Junior Member
 
Join Date: Oct 2022
Posts: 13
Default

Thanks b-man, good advice. We don't need to keep the y pipe, I was just curious if it would fit or even where I would get the mating pipe. We definitely want to junk the single pipe and muffler.

I think she is leaning towards headers, she wants it loud she said when she rolls up (kids these days ). Looking for a good set of headers and duals to the back, she wants the stock T/A tips to still show.

  #14  
Old 10-09-2022, 04:45 PM
F ROCK's Avatar
F ROCK F ROCK is offline
Ultimate Warrior
 
Join Date: Jun 2003
Location: sicklerville nj 08081
Posts: 1,938
Default

You've got a fresh, 5K mile 301, with a fresh 350 trans, and your ditching it for an old 400 w/ $3K for upgrades?
It will have more power for sure but 3K wont get you far in rebuilding; at least not as i have experienced.
Cylinders will likely have taper and need bored. heads will need to be milled and redone, crank trued, rods reconditioned, carb gone through, parts purchased, etc.
My Econobuild 464 cost me 5K$ with stock rods. The two reputable builders here in my area hate the idea of "Freshening up" an old engine.


you've still got the "Y"pipe.
If it were mine, I'd run the 301 for now, and gather other stuff; I'd get a nice stainless exhaust under there, ($400?) i think there's one at jegs or summit for $300; and use the remainder of the money for other stuff, maybe gears and posi.
Just my opinion.

  #15  
Old 10-09-2022, 04:46 PM
b-man's Avatar
b-man b-man is offline
Moderator
 
Join Date: Sep 2002
Location: Sunny So Cal
Posts: 16,410
Default

Headers are more trouble than they’re worth.

They have poor ground clearance in most cases, the second-gen Firebirds are one of the worst cars in this respect.

A set of louder mufflers will get the job done here, I ran the Dynomax 17734 14” case 2-1/2” mufflers on a ‘76 T/A right off of the factory log manifolds and it had a nice muscular sound. I fabricated a 2-1/2”’dual exhaust without a crossover pipe right up to the mufflers and used a pair of 2-1/4” tailpipes I scavenged at a junkyard, it sounded awesome.

Flowmaster mufflers (too loud and annoying in my opinion) would also more than satisfy the need for a muscle car sound without the headache of running headers.

She’ll likely bottom out those headers and flatten the bottom tubes in short order while you’re constantly trying to keep the bolts tight at the heads.

Good luck with the project.

__________________
1964 Tempest Coupe LS3/4L70E/3.42
1964 Le Mans Convertible 421 HO/TH350/2.56
2002 WS6 Convertible LS1/4L60E/3.23
The Following User Says Thank You to b-man For This Useful Post:
  #16  
Old 10-09-2022, 04:59 PM
b-man's Avatar
b-man b-man is offline
Moderator
 
Join Date: Sep 2002
Location: Sunny So Cal
Posts: 16,410
Default

Quote:
Originally Posted by F ROCK View Post
You've got a fresh, 5K mile 301, with a fresh 350 trans, and your ditching it for an old 400 w/ $3K for upgrades?
It will have more power for sure but 3K wont get you far in rebuilding; at least not as i have experienced.
Cylinders will likely have taper and need bored. heads will need to be milled and redone, crank trued, rods reconditioned, carb gone through, parts purchased, etc.
My Econobuild 464 cost me 5K$ with stock rods. The two reputable builders here in my area hate the idea of "Freshening up" an old engine.


you've still got the "Y"pipe.
If it were mine, I'd run the 301 for now, and gather other stuff; I'd get a nice stainless exhaust under there, ($400?) i think there's one at jegs or summit for $300; and use the remainder of the money for other stuff, maybe gears and posi.
Just my opinion.
No matter how you slice it the 301 is a 150 hp turd no matter how much to try to polish it.

Maybe 175 to 200 hp?

Still a turd. There’s not much horsepower to be had with those anemic Siamese port heads that all 301s are saddled with.

Slipping a Summit 2800 cam and plopping a set of 6X-4 heads onto that running 400 bottom end would yield 275 to 300 hp. A new Melling M54D 60 psi oil pump with a new Melling driveshaft and a top quality timing chains set and a recurved HEI would round off the build. That way you’re removing the oil pan, cleaning it and resealing it.

If the lower end is still functioning and in decent shape leave it be. Getting the compression bumped up to a little over 8:1 by replacing the 6X-8 heads with 6X-4 heads won’t over stress the short block.

300 horses good.

200 or less won’t put a smile on anyone’s face.

__________________
1964 Tempest Coupe LS3/4L70E/3.42
1964 Le Mans Convertible 421 HO/TH350/2.56
2002 WS6 Convertible LS1/4L60E/3.23
The Following User Says Thank You to b-man For This Useful Post:
  #17  
Old 10-09-2022, 05:06 PM
Phoenix79 Phoenix79 is offline
Junior Member
 
Join Date: Oct 2022
Posts: 13
Default

The car has been in the family most of it's life, I rebuilt the engine 15 years ago and my in law parked it and never drove it. Also painted it and new interior, well the storage was sub-par and ruined the paint and interior. Motor is good, but my daughter likes her power. She loved my 73 formula with a 400, but it had a bit more invested in the engine than what she can afford. Her other ride is an SRT8 Grand Cherokee.

The 301 can barely get out of it's way and there really isn't much you can do with them that I'm aware of. I'll probably help invest to get her a little more HP. I'll also be in the paint booth again to freshen it up soon.

Appreciate everyone's help!

  #18  
Old 10-09-2022, 05:14 PM
Phoenix79 Phoenix79 is offline
Junior Member
 
Join Date: Oct 2022
Posts: 13
Default

Quote:
Originally Posted by b-man View Post
No matter how you slice it the 301 is a 150 hp turd no matter how much to try to polish it.

Maybe 175 to 200 hp?

Still a turd. There’s not much horsepower to be had with those anemic Siamese port heads that all 301s are saddled with.

Slipping a Summit 2800 cam and plopping a set of 6X-4 heads onto that running 400 bottom end would yield 275 to 300 hp. A new Melling M54D 60 psi oil pump with a new Melling driveshaft and a top quality timing chains set and a recurved HEI would round off the build. That way you’re removing the oil pan, cleaning it and resealing it.

If the lower end is still functioning and in decent shape leave it be. Getting the compression bumped up to a little over 8:1 by replacing the 6X-8 heads with 6X-4 heads won’t over stress the short block.

300 horses good.

200 or less won’t put a smile on anyone’s face.
b-man you nailed the project right on the nose. 300 HP would suit her perfect. We just got the motor home and I do believe the bottom end may be solid, we'll know shortly. The engine was running before it was swapped. Compression test was good. Still will check cylinders for scaring or scratches and a look at the bearings. She just wants something nice to roll around in to shows and stuff. She's a 21 year old kid, she'll have fun in this.

  #19  
Old 10-09-2022, 05:51 PM
25stevem's Avatar
25stevem 25stevem is offline
Ultimate Warrior
 
Join Date: Jan 2022
Posts: 1,744
Default

Please inform her of safety concerns even with just 225 Hp out of a motor on wet roads if the car has a posi rear!

A down shift along with full throttle can send her fish tailing out of control.

You know how young adults Boys and even girls like to show off .

__________________
I do stuff for reasons.
The Following User Says Thank You to 25stevem For This Useful Post:
  #20  
Old 10-09-2022, 06:05 PM
b-man's Avatar
b-man b-man is offline
Moderator
 
Join Date: Sep 2002
Location: Sunny So Cal
Posts: 16,410
Default

A couple examples of freshened up Pontiac V8s.

This one is a 455 with a completely untouched factory lower end. I removed the number one main cap and inspected the bearing, it looked so good I didn’t bother checking any more bearings:

https://forums.maxperformanceinc.com...5&postcount=19

A low compression 400 that did see a set of rings and bearings in the lower end but nothing more in the short block:

https://forums.maxperformanceinc.com...1&postcount=22

You can do a lot of improvements and have a good runner without having to do a complete machining job if your lower end is still in decent shape.

Been there, done that and had fun doing it.

__________________
1964 Tempest Coupe LS3/4L70E/3.42
1964 Le Mans Convertible 421 HO/TH350/2.56
2002 WS6 Convertible LS1/4L60E/3.23
The Following User Says Thank You to b-man For This Useful Post:
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 11:01 AM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017