opinions please

[red brew]

Ok guys.  I bought the above TA almost 2 years ago.  i have only put 100 miles on it.  Its an all original 180 horse 400 with  turbo 350 and 2.56 posi.  I have added a dual gate shifter and grant wheel.  Right now in my possesion I have a new Performer intake and proform distributer.   I will eventually put in a 455 but for now I just want to add some bolt ons for moderate performance.  My question is mainly camshaft.  Is there enough room to do a cam swap in the car?   If so........then I am really trying to figure out what cam to use.  I have heard great things about the Crower 60918 with Rhoads lifters.  I dont hear very good things about Comp cams as it seems they are just not holding up.  Im not averse to installing headers but if I did.......what brand fits the best with the least amount of hassle?   I am kinds leaning towards the Ram Air IV manifolds and going true dual back.  Any recommendations for exhaust kits?  My car still has the original cat on it but its now smog exempt so to the scrap yard with that.  Im having problems locating a valley pan and front cover.  Any help with that would be greatly appreciated.  i do have pesos saved away for aluminum heads if you think this may be the route to go with such an anemic engine.  Im sure the compression is only 7.7 or so.  This car has the 500577 block and I just dont think its worth the effort to tear apart and build up in the future.  My goal is a healthiy 455 with over 575 torque and will never see anything over 5000 rpm but thats a few years down the line.  Let me know your recommendations.  Thannks for your time.............Red

[5th T/A]

The 500577 is OK for mild rebuilds, but if you are planning building for higher power, better to find a better block.

The cam can be replaced without pulling the engine, but radiator and AC condenser would have to be removed. the type of cam would depend on if you are going Edelbrock heads or not as they will raise the compression and tolerate a larger cam. The problem is you would use different heads on a 455 block with larger combustion chambers, so better to buy the correct heads for a 455. Final rear end gearing might also determine what cam you want to use.

Timing cover and valley cover can be purchased new from Butler Performance. Not cheap but a used timing cover might be junk from a 45-50 year old engine due to corrosion .

I personally am not a big fan of headers on a street car and prefer Ram Air exhaust manifolds. With your D port heads you need Ram Air III exhaust manifolds not Ram Air IV. Ram Air exhaust manifolds are available from Ram Air Restorations, also not cheap. Last I heard they were on back order.

If you are seriously considering a high performance engine build buy the book "How to Build High Performance Pontiac V-8's" by Rocky Rotella ISBN 978-1-61325-474-5. Take your time and do your research. Make sure you get an experienced Pontiac builder.

Short term if you just want a little more performance install true dual exhaust, maybe a mild cam. Consider changing your rear axel ratio.

[b_hill_86]

5th hit all of the points I would make plus some. The only thing I’ll add is I’ve READ, because I haven’t personally tested, that a stock intake actually flows more than an edelbrock. EB is obviously a little lighter but it may be something to look into. Then again, you already have it so it may be a toss up.

I did do a cam swap in my car with the engine in years ago so I can confirm that.

[81Blackbird]

I would leave it alone if you're planning to pull the engine in a couple of years on a car you only drive a few hundred miles a year on, if that.  Save the time and money and put it into the heavy breather you're planning.  Do it once, yeah right, and go to the next phase of the project.   

[rkellerjr]

I too agree with 5th. I have a 400 with the 500577 block. I went a bit more than you are talking about but initially I started out with a cam and an edelbrock intake. It pepped it up a little and it sounded mean. Then a crank bearing went and I did a full blown build. Bored it .040, nice street cam, roller tip rockers, forged pistons, ram air iv manifolds from RARE amongst other things. That woke the motor up but, having said that, your now in the 455 build territory. I'm not sure adding a few adders to the 400 is going to do much in the realm of smiles for miles but only you can decide that. I kinda lean with blackbirds assessment for the very same reasons he gave.

[Jeremy]

I'll echo the others.  I think you would be money ahead putting money into one motor instead of a little now into the 400 and more into the 455 down the road.

I run Pypes Mandrel bent exhaust on my 455 and am very pleased with it.  Good ground clearance and bolts nicely to factory or ram air III manifolds.  I took the time to clean up my factory logs and open them up as much as I could.  While I'm sure I'm giving up some HP to RA III's, the motor does everything I want it to on the street.

I'd recommend a roller cam as I just had to rebuild my motor due to a flat cam.  Previously I had the tried and true RAIV cam and Rhodes lifters and the roller is night and day difference.  I've made no changes to the basic tune of the FITECH between cams and can't believe how much better the roller cam runs.  Smoother idle, better vacuum and rips through the RPM's.

Do it right once and cry once (hopefully).

[DynoLee]

Do things NOW, to your existing motor, which will transfer to a more powerful motor down the road.

Several years ago, I stumbled upon a great deal on a 455.  It had "66" casting heads and beveled-edge pistons, resulting in just 7.8:1 compression.

I designed my own low-lift camshaft (0.443/0.435").  A Q-jet on a Performer intake, stock HEI, and the factory log manifolds.  On a DynoJet chassis dyno, it put 225hp to the wheels - better than I expected.

Next I installed a set of headers.  I used a set of tri-Y headers, which I am afraid are no longer available.  But I would expect similar results with a set of quality 4 into 1 headers, like Doug's.  I gained 45rwhp, and extended the power band much further.

Next I replaced the entire exhaust system with 3" pipes, 3" Borla ProXS mufflers, and an H-pipe.  Now, all the "experts" SWEAR that was "too much" exhaust for such a mild motor.  Yet, I gained over 15 more rwhp. 

[scarebird]

concur. 

save your time and money for a new mill.  I went LS3 in the TA, L84 in the Lemans

[Wallington]

Maybe it was too much exhaust and slightly smaller would have gained 20hp. If you're happy with it, done.

[roadking77]

For starters I know zilch about motor building, but will add. What 5th ta and Rich stated is about how my car (77 ta 400 auto) is set up. Its also a 557 block which is frowned upon. My car has a mild build and it will move down the road just fine. Has more than enough power. I am having a 400 4 sp built right now and did a very small amount of research. From what I found the stock iron intake is just as good as a Ebrock performer, however you will be saving a small amount of weight. That is important if you plan on drag racing but for an occasional use car I doubt the 10lbs is worth it. But use it if you got it. My original was cracked so I ended up going with Ebrock as well, only because it was easier to find.

Motors need to breath, freeing up the exhaust will easily add up a few hp's. I would not scrap the cat, someone doing a correct resto may want it.

IF you are dead set on the 455, then save the time and money and have it rebuilt leaving the original motor alone. Personally I think the 400 will do the job just fine.

[Bluebandit]

Years back I started on my TA by first removing the converter and replacing it with a straight pipe. Made it louder and did improve the performance some. Those old cats killed exhaust flow. Later I ran pipes from the manifolds to the mufflers for a dual setup and again gained some performance. Next I replaced the manifolds with headers and added an exhaust crossover, that was what really woke it up.
 
The performer will flow about what the stock intake will but it isn't a good choice for your 455 build. The runners are a little smaller than the factory intake to promote velocity at lower rpms. If you have it it'll save you a little weight, just don't expect a big power boost from it.

Put a good free flowing exhaust system on it and replace the 2.56s with a 3.23 gear set. That'll put a smile on your face.

[rkellerjr]

Put a good free flowing exhaust system on it and replace the 2.56s with a 3.23 gear set. That'll put a smile on your face.

Good point, you want to add pep you have to think about the entire drive train, not just the motor.

[gstrandfarm9420]

I would add a re-curved distributor to the above suggestions. The factory mechanical and vacuum advance was more for emissions than performance. along with the other improvements it will wake that stock 400 up a bit more.

[silver78]

I would leave it alone if you're planning to pull the engine in a couple of years on a car you only drive a few hundred miles a year on, if that.  Save the time and money and put it into the heavy breather you're planning.  Do it once, yeah right, and go to the next phase of the project.

I agree with 81Blackbird. Why spend money on the 400 when your plan is for a high HP high torque 455. Sometimes building a car from the rear forward is the logical approach.  These areas will need upgraded or addressed for the 455 anyway. Rear gears, upgraded transmission, brakes and probably subframe connectors. There's an old saying "You have a 200 MPH engine in a 100 MPH car." Just some things to think about.

[ryeguy2006a]

I like the idea of building the drivetrain from the rear forward. I might add a suggestion that if you plan to do it this way, go with a 200r4 trans and rather than going with a 3.23 rear, look at a 3.55/3.73 gear. You'd be surprised how much changing a rear gear ratio will change how a car will perform. That performance change will really be felt in the seat of your pants.

[737driver]

Excellent suggestion on 200r4 with 3.55/ 3.73 gears. Excellent choice for overdrive transmission.
Jim

[ryeguy2006a]

Here's an interesting Article from Motortrend. https://www.motortrend.com/how-to/148-0208-gear-ratio-calculating/

From it they state:

An automobile uses gear ratios in both the transmission and the drive axle to multiply power. The two ratios multiplied together equal the final drive ratio. ...For most street performance applications, a 10:1 final First gear ratio is usually considered optimal.

So in your case with the current setup, from what I can find the first gear for a TH350 is 2.52 and with your 2.56 rear gear ratio, you'd be at 6.45 ratio. That is far below the optimal ratio of 10.

If you were to go with a 200r4 with the 2.74 first gear and a 3.73, you'd end up with a 10.22 drive ratio. Or with a 3.55 it's 9.72.

Then with the .67 OD at 70 mph and a 27" tire, you'd be at 2100 rpm with the 3.55 and 2200 rpm with 3.73.

https://www.tremec.com/calculadora.php

[5th T/A]

Ryan,

Thanks for posting these two great links. This is very helpful for figuring out gear ratio for the differential. I am still running my original 2.41 axel and kind of on the fence as what ratio to use. I would prefer to keep my turbo 350 transmission with a 1-1 final drive. As it stands now, I typically don't do any expressway driving, just back roads 55 - 60 MPH. I am really happy with my cars acceleration, but I am going 70 MPH when shifting from 1st to 2nd gear!

My apologies for the thread hijack!