tips for a 400

Hey I was wondering if anyone could help me I am just about to put a 400 in to my car now and im wondering what are some cheap tips to boost horsepower?

any help with greatly be appreciated

Is it a Pontiac 400 or chevy 400?

Its a pontiac 400 from 1977

The amount of parts available for american V8's are endless. The best thing to do would be to slap on a exhaust system and maybe even some headers. If you want to get advanced you can port and polish the heads add a cam or even throw ssome nitrous on that beast. Good Luck

Originally posted by m3mark
The amount of parts available for american V8's are endless.

Not really, what parts you can get for Pontiac mills are limited and expensive. As far as performance goes: Don't over carb it, all you need is a 750 cfm. A cam, and a good oil pump. Do you know which heads are on the motor?

as far as i know the heads are stock 77 400 heads and I'm pretty sure that means that they have an either 96cc or 101cc combustion chamber.
I wasnt planing on puttin a big carb on anyway i was thinking of a 650 vacum secondary for now untill I put a bit more work into it.

Good choice, it's very easy to over carb Pontiacs. You could have the block decked to gain some compression. That could get expensive though.

other then decking the block what could I do to gain some power

here is what i plan to do soon:
cam and lifters
headers and 2.5 inch dual exhaust
650cfm vac secondary

You could port it fairly cheap. Lets see..Balanced & Blue Printed, you could look else where on the car too ie better radiator, aluminum drive shaft, ect. You also could look at different heads but again that can cost some money. Umm.. I think 6Xs would gain compression. The reason I keep telling you to up the compression is that in the mid 70s they ran around 7.5:1. I think it would produce better results if you went up to 8.5:1 to 9:1.

6x heads you say?

I was offered a set of 6x heads for 100 bucks canadian

do you know other information about them because this is what I know about the heads the have oval exhaust ports there is a D above the left most exhaust port and 6X right above the 2 middle exhaust ports

and overcomming this lack of compression is high on my list of things to do

Yeah that engine has 7.6:1 compression. Instead of decking the block you could have the heads milled, or both is porbably neccessary to get 9:1 compression. But get a long duration, short lift cam. Pontiac big blocks soak up duration like nothing I've ever seen. The headers and exhaust will help A LOT, the cam is a good idea cuz the stock one is a nothing cam. And also get the Edelbrock Performer RPM intake manifold.

you have read my mind, I was thinking of doing the exact things you juts said to do but all i need now is money

and could you give me any ideas on cams? like comp or crane?

and what duration? and lift?

Comp cams, Extreme Energy series - XE262H. It has 218/224 [email protected]'', and .462/.470 lift.
My friend has a 77 T/A with a 400 in it, but he has a rebuilt 455 waiting to go in it. He put the XE268H in it, with 224/230 [email protected] and .477/.480 lift. But a 400 doesn't need as much cam as a 455, so the one I recommended is one step down.

all right thanks

How much power was your friends 400 making? and could you give me the specs of his engine too please if its making around 300 hp or over

400cu. Flat top pistons
No. 13 heads
288/296 Ultradyne Cam
roller tip rockers
Torker II Intake
650-750 carb.
HEI dist. with aftermarket coil
Headers
3000 converter if its auto
3.42-3.55 gear
26.5 inch tall tires

This setup pushed my buddies 78 t/a to low 12's in the quarter

Originally posted by TorinoGT69
400cu. Flat top pistons
No. 13 heads
288/296 Ultradyne Cam
roller tip rockers
Torker II Intake
650-750 carb.
HEI dist. with aftermarket coil
Headers
3000 converter if its auto
3.42-3.55 gear
26.5 inch tall tires

This setup pushed my buddies 78 t/a to low 12's in the quarter
Pontiac Big blocks never like to rev really high, a single plane intake really hurts the low end power. I would suggest a dual plane, and maybe 2500 stall. Torque is what pontiac is all about.
What was the [email protected] on that ultradyne cam? Advertised duration doesn't mean crap.

The torker II pontiac version is a real low rise single plane and it works real well on pontiac motors. It was the perferred intake to use until the performer rpm came out.

also I was just giving the advertised duration to let him know which cam. but since you wanted to know it is 231/239 @ .050 and has 110 degree centerline. and a 2500 converter is not enough with this cam.

5200-5500 was the shift point on that car power drops off after that. Pontiacs definately do not rev.

Originally posted by TorinoGT69
also I was just giving the advertised duration to let him know which cam. but since you wanted to know it is 231/239 @ .050 and has 110 degree centerline. and a 2500 converter is not enough with this cam.
Yeah I meant 2500 with the cam I recommended.

alright thanks alot for all of the info, I was thinkin of using a preformer RPM air gap maifold if i had enough cash but I will at least get the RPM

and what size primery tube headers were on the 400?

low 12's is awsome, is all on all motor or dose he have it on the bottle too, because i was thinkin of puttin a 150 shot through my 400 once i have it all built up so that should drop it to mid 11's

and i was also thinking of puttin a higher gear ratio in such as 3.7's but no higher then that because it is a day to day car...

That was all motor. As far as gearing the 3.42 he had was almost perfect it went through the traps at almost 5000 rpms anything more would really hurt performance, it would just top out. Pontiacs do not need a lot of gear. It had hooker super comp headers I do not remember the primary size.

o man he ponyed up for super comps eh... thats nuts...

but if it went throught the traps at 5000 and yah pontiacs dont rev to high i guess ill throw a set of 3.4's in my car and i bet if they were super comps the primery must have been 1 3/4 ill probly go 1 5/8

do you know how much power his car was putting out? If not do you know what mph he ran and what the cars weight was because i can get the power from that.

and the 288/296 is the duration in degrees of the cam for int/exh right?

and finally one more question did your friend use his car as a daily driver or just drag car?

It was both daily driver and racer but terrible gas mileage. The mph was very low i believe it was 109. The weight was around 3450 if I remember right. The front bumper under the bumper cover was removed along with all the a/c equipment.

oh yeah and yes that is the advertised duration on the cam.

We found the headers used.

alright thanks with that info ill find out what hp the motor had so I can just have it as knowledge I build mine thats good the he found the headers used because they are to damn expensive

you want me to post the aprox hp?

One thing to remember with pontiacs is that its the low end torque not the hp that makes them fast.

yah thats true and torque is what wins races

What did your formula say about the hp?

and the no. 13 heads were from what earlyer year of firebird and do you knwo the cc?

because i was thinking of gettin a pair of edelbrock heads

They are early model. I think they are 72cc if memory serves me right.

The edelbrocks are nice but expensive.

those are the exact same cc edelbrocks i was thinkin of getting

the formula puts the rear wheels horse power at 345.4 approx.

the formula is HP=(0.00426 x MPH) to the power of 3 x weight

those heads were probly some type of ram air heads im guessing

and yah if i get the edelbrocks they will be about 1600 bucks american or more and then more if i get them machined at all

and did your friend have any machine work done to his engine (block decking, head milling, boring??)

also did you know the compression it was running at?

around 10:1

alright thanks

but did he have any block or head work done to it?

no head work just a valve job and new springs. rotating assembly had arp rod bolts and was balanced thats it.

alright thanks for all of the information this has been alot of help and takes alot of guess work out of my engine building and has saved me some cash too

so thanks alot

no problem glad I could help out.

yah thanks


how dose your torino run?

unfortunately its apart right now. I am just building a mild 302 for it right now. no money for performance right now.

gotcha

Originally posted by TorinoGT69
One thing to remember with pontiacs is that its the low end torque not the hp that makes them fast.

Exactly, that is why you need a dual plane manifold and mild gears. No more than 3.55, and radical cams only steal low end power.

I did not argue with you about the dual plane manifold. The performer rpm is a great manifold thats what I would recommend but at the time the car was built I was describing that manifold did not exist and the performer was exactly like a stock intake. Look at the ram air IV cam pontiacs react well to long duration. if you run a cam with a short duration you just increase the already abundant low end torque of the engine and do nothing to help the mid range power. Then you end up with a car that will not hook up and when it does it is already past its powerband.

yah so I will run the same came as your friend exept I will use a preformer RPM cam


which should only increase torque

You mean performer INTAKE right? edelbrock cams suck, thats the only thing i've ever seen that they suck at. Otherwise, edelbrock is good.

yeah intake not cam I was typing fast.

o crap I ment the intake too their cams do suck

edelbrocks carbs arent the greatest either and their headers kinda suck as well other then that they are a good company

which do you think is better a preformer RPM air gap intake or just the regular preformer RPM

is it worth the price difference?

I don't think they make the air-gap for pontiacs do they?
If they do then get it, providing that it can fit underneath your hood! I don't think it will, I've seen one on a small block chevy and it was very tall. It probably won't work on a car.

well I am planning on putting a 4 inch cowl or so on my car so im guessing that the air gap will fit underneath the hood even with a tall air cleaner

I don't think there is an air gap for pontiac. there would be no point pontiacs have a seperate valley pan so there is already a gap under the intake.

yah I have looked and I havent found an air gap manifold for pontiac but o well im sure the preformer RPM will do just fine

it should fit no problem if you have a 4inch cowl .

yah I think I will have lots of clearance under a 4 inch cowl but I will still wanna try and fit everything underneath the stock hood because the cowl will be one of the last things I buy

do you have a shaker hood or flat or formula type?

with a built up 400 do you think I will need to run an after market distrubuter?

or could i get away with running a msd ingnition pack whch has a coil, the 6A box and a couple other things