View Full Version : Pontiac 400??


NYH1
11-26-2010, 02:38:13 AM
I know this is a Camaro site, but the Firebirds and Trans Ams are sister cars to our cars. So here go's.

Can a Pontiac 400 with 6X heads setup properly make around 400 HP with good torque for street use with the right compression, good hydraulic flat tappet cam, RPM type intake and 750/800 cfm carb, full length headers and a 2 1/2" full length dual exhaust system?

Thanks, NYH1! :bowtie:

firebird69racer
11-26-2010, 04:03:18 AM
Yes.

Kamikaze
11-26-2010, 04:40:40 AM
Most definitely!

Where you are at used to be a hotbed of Pontiac performance! You need to research Nunzi Romano. He was the Pontiac genius in the 60's-80's and some of his performance works produced insane Poncho power!

More parts are available today for Pontiacs but good basic hot rodding will yield great torque and horsepower that rivals Big Block Chevy power

z28rod
11-26-2010, 07:05:41 AM
yes if done up correctly.

warped
11-26-2010, 08:19:50 AM
Most definitely!

Where you are at used to be a hotbed of Pontiac performance! You need to research Nunzi Romano. He was the Pontiac genius in the 60's-80's and some of his performance works produced insane Poncho power!

More parts are available today for Pontiacs but good basic hot rodding will yield great torque and horsepower that rivals Big Block Chevy power

Nunzi romano -- I haven't heard that name in 30 years. Check him out here:

www.nunzi-pontiac-expert.com

markw
11-26-2010, 08:50:41 AM
Some Pontiac combos here...http://forums.performanceyears.com/forums/showthread.php?t=520102

455 Formula
11-26-2010, 01:42:47 PM
NYH1,

Pontiacs are my specialty....my 413 CID Pontiac street-motor devloped 433 HP @ 5500 451 lbs/ft of TQ @ 4800 with 6X-4 heads, 9.00:1 compression, custom-ground Ultradyne .491"/.510" - 231°/235° @ .050" - 110.5° LSA hydraulic flat tappet camshaft, Performer RPM Intake, 800 cfm Q-Jet, 1-3/4" headers and full 2-1/2" exhaust. Ultradyne has done all of my custom grinds for years and their work is excellent.

This is a very simple engine to build. I did a lot to this engine that wouldn't be necessary for the average street engine, but that's just how I build things.

This engine is based on a 1970 4-Bolt Main block bored .060" over to a 4.181" finished bore size. The stock 'N' crankshaft was retained as was the stock 3.75" stroke length. The CID works out to be 411.9 and I refer to this motor as my '413' for discussion purposes.

The block is zero-decked (about .017" overall) to bring the piston crowns level with the deck. Speed Pro Hypereutectic Flat Top Pistons are used (L2262F) with Total Seal Gapless Rings. With the 85cc chambers of the 6X-4 head and a .039" gasket, the static compression ratio (SCR) works out to about 9.30:1.

http://i575.photobucket.com/albums/ss196/10851Man/413RightSide.jpg

To begin with, I install screw-in galley plugs up front in place of the stock press-in plugs and polish all of the casting flash out of the oil passages. I also enlarge the tiny 3/8" oil feed in the block out to 5/8" and polish/enlarge the passage all the way from the pump to the filter housing. The oil pump is also matched to the opening in the block.

http://i575.photobucket.com/albums/ss196/10851Man/OilHole.jpg

This is a critical, often overlooked area of mismatch and oil flow restriction in a Pontiac. Shown below is the stock oil hole for comparison.

http://i575.photobucket.com/albums/ss196/10851Man/400OilHoleBefore.jpg

I use a grooved camshaft thrust plate, that is highly polished and is fitted along with a 9-keyway timing set with a bronze thrust washer. This improves oiling and reduces thrust wear on the face of the #1 camshaft journal and camshaft gear.

http://i575.photobucket.com/albums/ss196/10851Man/GroovedThrustPlate.jpg

The 6X-4 heads use the stock diameter 2.110" intake valve and were fitted with the larger 1.770" exhaust valve. The heads were ported and fully poished to 241 cfm intake @ .600" and 212 cfm exhaust @ .600" lift respectively.

http://i575.photobucket.com/albums/ss196/10851Man/SidebySide.jpg

http://i575.photobucket.com/albums/ss196/10851Man/6X-4Heads.jpg

Crower #68405 dual valve springs are a 100% bolt-on and provide about 115 lbs seated @ 1.700" and roughly 285 lbs @ .500" net valve lift. The 6X-4's have screw-in studs and guideplate from the factory, so nothing is needed in this area. The stock pushrods are also hardened, so they can be used as well.

The block and heads are drilled between the center cylinders, as was the early 421's, to provide additional cooling into the center exhaust port section of the heads. This is very easy to do, as most Pontiac head gaskets all have this hole.

http://i575.photobucket.com/albums/ss196/10851Man/421CoolantHolein400Block.jpg

Since Pontiacs use oil, draining back out of the right rear orner of the RH cylinder head to lubricate the distributor gear, I drill a .030" hole in the galley plug right in front of the gear. This gives the gear pressurized oiling.

The engine that the local Chevy guys really hate is my 9.50:1 Pontiac 350, cleverly disguised as the original 455 that came in my 1975 Formula.

http://i575.photobucket.com/albums/ss196/10851Man/AlmostDone-1.jpg

This is a basically stock, 1975 350 short-block with factory flat-top pistons. The heads are 1966 421 (092 castings) with 1.920” intakes and 1.660” exhaust valves. The heads have been fitted with ½” screw-in studs, replaceable valve guides and the spring pockets were cut to accept Crower 68405 dual springs @ 1.700” installed height.

http://i575.photobucket.com/albums/ss196/10851Man/092HeadsReadytoRun.jpg

The camshaft is another one of my creations and features .466”/.467” (actual) – 220°/226° @ .050” on a 111.5° LSA.

http://i575.photobucket.com/albums/ss196/10851Man/CamshaftDataCard.jpg

The intake is a simple Edlebrock Performer, the only aluminum intake that will fit under the Ram Air Hood, with a 800cfm Q-jet featuring .070” air bleeds, .039” idle tube restrictions, .056” idle channel restrictions, a 7 in/Hg power piston spring. .074” main jets with .045” metering rods. The secondary side features .029” metering rods and a ‘G’ hanger.

The ignition is handled by a stock GM HEI with a zero-resistance carbon button between the coil and rotor, which replaces the stock carbon button, which has a whopping 9kΩ. This is one of the big limitations in the HEI unit as far as ignition output goes and a source of elevated coil temperatures. You just don't need that kind of resistance, especially with resistor wires and plugs!

The timing specification is 20° BTDC at 800 rpm with 16° of mechanical advance and a Crane adjustable vacuum advance set to provide 8° of advance for 44° total advance.

Headers are 1-3/4” primary Heddmans with full length, 2.50” mandrel-bent Flowmaster exhaust with a 42585 crossflow muffler.

Corrected HP and TQ output was 373 HP @ 5650 rpm and 397 lbs/ft of TQ @ 4200 rpm.

For dyno testing, 92 octane pump gas was used with #2 heat range Autolite AR72 Racing Plugs gapped at .045" respectively and open exhaust. When the AC R46SZ plugs, gapped at .080" were used, HP and TQ levels remained unchanged, but the engine starts faster, had better throttle response and a smoother idle with reduced exhaust emissions.

I hope this information is helpful...

455 Formula
11-26-2010, 03:52:02 PM
One of the weak areas of any Pontiac V8 is the cast connecting rods. Shown below is a stock (cast) Pontiac rod on the left and a 5140 forging on the right.

http://i575.photobucket.com/albums/ss196/10851Man/StockRodVs5140.jpg

It is important to note that I always use a 5140 I-Beam Rod (at a minimum)in all Pontiacs to replace the factory cast steel rods.

http://i575.photobucket.com/albums/ss196/10851Man/5140RodSideProfile.jpg

These feature 7/16" ARP Wave-Loc Bolts and torque to 75 lbs/ft. They are good insurance at less than $250.00 a set.

http://i575.photobucket.com/albums/ss196/10851Man/RodBoltDetail.jpg

Very good rods...

http://i575.photobucket.com/albums/ss196/10851Man/5140Rods.jpg

NYH1
11-26-2010, 04:05:22 PM
Thanks guys. My friend swapped out a 400 Pontiac and installed a GMPP 454 HO Crate Motor for one of his customers GTO's. The 400 wasn't original so the guy didn't want to rebuild it. He wanted a bolt in crate motor instead. My friend has the 400 Pontiac and it's just sitting in his shop. I figured if he's not going to do anything with it and wanted to get rid of it, I might be interested in hanging on to it for a future build.

I like Firebird's and Trans Am's even GTO's, Lemans, Tempest, and Ventura's. Not that I'd do anything with it anytime soon. But if it'll make around 400 HP with good street torque on pump gas, that's got me written all over it.

How does the 400 compare to the 455? Can the 400 be stroked? Or is it better to stay with the stock stroke in a 400?

Thanks again guys! ;)

455 Formula
11-26-2010, 04:16:30 PM
Stick with the 400.

Yes, you can use a 421 crank (4.00" stroke) in a 400 and make a 440 or a 455 crank (4.210" stroke) and make a 462, but the 400 is hard to beat and is a very stout performer.

A 440 or a 455 will make more torque, but requires clearancing the oil pan rails with a die grinder and custom pistons.

Here is something to chew on....

I recently took a bone stock, USED junkyard 400 with unported 6X-4 heads with the stock (1.660") exhaust valves and installed one of my Ultradyne 231/235 @ .050" - 110.5 LSA hydraulic camshafts in it. That's only about an 8.50:1 compression motor. With a tuned Q-Jet and headers it made 380 HP through the mufflers.

That's 380HP from a nothing junkyard motor with used rings, guides, bearings and unported heads....

NYH1
11-26-2010, 04:19:46 PM
Cool, thanks for the info!

455 Formula
11-26-2010, 04:34:20 PM
The 6X-4 is a good flowing head. It will support your 400 HP goal without porting. You can mill them and zero deck the block and get the SCR up around 9.00:1 very easily. The L2262F Speed-pro pistons are good.

AVOID the Federal Mogul 411NP piston.It is a cast 'rebuilder' piston with 8 valve reliefs and it sits a whopping .050" down in the hole at TDC.

http://i575.photobucket.com/albums/ss196/10851Man/411NPPiston.jpg

STOCK Pontiac dual valve springs will work with up to .466" lift. You can buy them for about $45.00 a set from www.sivalves.com

The Isky 256/262 Megacam is a great stock-replacement Pontiac camshaft.

For higher lift and rpm, Crower #68404 dual springs will pop right onto the 6X-4 heads, which already have screw-in studs and guideplates from the factory. You can even retain the stock, hardened 5/16" pushrods and save money. The stock retainers are super-strong and can be reused too.

The stock cast rods are fine under 5500 rpm in a 3.75 stroke motor and you can avoid spending money on re-balancing the engine. The stock balance on a Pontiac is second only to the 472-500 Cadillacs. they are very smooth running engines.

The stock oiling system is fine and will require no modifications. If you are using headers in an F-Body with a Pontiac engine, you will need the small case PF-61 oil filter for adequate clearance.

Heddman #28150 1-3/4" headers will fit a 1970-1981 F-Body without any modifcations.

There are a number of good camshafts available, but I am partial to my own custom grinds, which I developed after lots of trial-and-error testing.

My Hurricane F-220 grind features .466.467" lift - 220°/226° @ .050" on a 111.5° LSA.

There are several Crower grinds that are close to this camshaft in specifications.

The MOST important thing on a Pontiac is getting the right lifters. Chevy and Pontiac lifters are the same diameter, but the oil groove is in a different location. Many Pontiac lifters on the market are really Chevy lifters. This can cause drastic oil pressure loss if you get the wrong lifters.

The bell housing pattern is different between Pontiac and Chevrolet. Sppedway Motors offers a couple of bellhousings:

http://www.speedwaymotors.com/Explosion-Proof-GM-Bellhousing,5213.html

http://www.speedwaymotors.com/Quick-Time-Olds-Pontiac-V8-Steel-Bellhousing,8356.html?brandName=QUICK TIME&page=1

You can also find used STOCK bell housings for not too much money.

If you are using a stock balance engine with a stick-shift, you MUST use a stock flywheel. The aftermarket Hays flywheels are neutral balanced and the stock Pontiac stick flywheels have a slight imbalance.

If you want and automatic, there are TH350's and TH2004R's with both the Chevrolet and BOP (Buick Olds Pontiac) bell housing patterns, which allows you to swap back and forth between a BOP or a Chevrolet engine without changing the tranny.

If you want a TH400, look no further than 1970-1979 Cadillacs.

So, to sum it all up, you won't need much more than pistons, rings, gaskets, cam, lifters and springs to arrive at your 400 HP goal....

NYH1
11-26-2010, 04:51:06 PM
Thanks again! :bowtie:

NYH1
12-01-2010, 06:06:20 PM
455 Formula, I sent you a PM. Let me know if you didn't get it. Thanks.

onebad71
12-01-2010, 06:42:19 PM
yes and pretty easily. wish i had more pics of my old trans am, jim butler pontiac is a very good source as is performance pontiac, tin indian, and there is another i cant think of.. ill pm you when i remember its killin me not knowing it..lol

NYH1
12-02-2010, 12:23:53 AM
yes and pretty easily. wish i had more pics of my old trans am, jim butler pontiac is a very good source as is performance pontiac, tin indian, and there is another i cant think of.. ill pm you when i remember its killin me not knowing it..lol
Thanks for the info! ;)

NYH1
12-02-2010, 01:44:46 PM
My friend with the Pontiac 400 wants to keep it now. There are a bunch of them out there. I'll take my time and a good deal will come along. I'm pretty sure my next project is going to be a Pontiac of some sort.

455 Formula
12-02-2010, 02:17:54 PM
My friend with the Pontiac 400 wants to keep it now. There are a bunch of them out there. I'll take my time and a good deal will come along. I'm pretty sure my next project is going to be a Pontiac of some sort.


Find you an old 455 from a junkyard station wagon. Any of the Pontiac 350 heads (like the 5C-4 and 6X-4) will give you around 9.25:1 to 9.50:1 in 100% bolt-on condition.

This why the 455 is a better value than a 400 when it comes to making compression if you are wanting to get the most bang for your buck. The point here is that the 5C-4 and 6X-4 heads generally have about 95cc combustion chambers.

On a Pontiac 400, with the Speed Pro L2262F flat-top, 4-valve relief piston at zero-deck, a 95cc head will give you about 8.67:1 compression. You will need to mill them at least .030" to get them down to 89cc's, which will give only yield about 9.08:1 compression.

However, in a 455, the 95cc head will give you mid 9.00:1 compression ratios with no milling. A mild cam is all you need from there.

My .466"/.467" - 220°/226° @ .050" - 111.5° LSA (108° intake centerline) hydraulic flat tappet is a great street camshaft in Pontiac 350's and 455's. This has been my most popular custom grind and it works in a very wide range of applications!

I am using this cam in my 9.25:1 compression Pontiac 350. It idles at 725 rpm with 17-18 in/Hg of vacuum and has a very fast rumpity-rump idle. No one can believe my vacuum readings when they first hear the idle.

The key is not so much the duration, but where the duration takes place along the lobe profile. This camshaft has 0° of overlap @ .050" lift, which gives it very high vacuum and great throttle response for a cam of its size. Most camshafts in a Pontiac 350/389 with 220° intake duration will have very low vacuum, poor idle characteristics and high exhaust emissions. This camshaft puts out exhaust emissions that are very close to what the stock 1975 Pontiac 350 was putting out!!!!

Many thanks to Tim Goolsby of Bullet/Ultradyne Cams for his help in the design of this camshaft....

NYH1
12-03-2010, 12:41:24 AM
455 Formula, thanks again! ;)