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400CI Overhaul and upgrade help needed.

  
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400CI Overhaul and upgrade help needed.

 
gunnarig gunnarig
New User | Posts: 5 | Joined: 12/13
Posted: 12/07/13
07:47 AM

Hello. I have a 400ci 74 engine out of a grand prix i beleve. i havent checked the engine codes yet as the car is in storage so i am not exacly sure. but considering  i am correct and this is the original engine i removed from the donor car.

I am planning on getting a 461 stroker kit for the engine along with a full restoraion gasket set.

what do i need to do to the top end to make the kit work.

the pistons in the set are -6cc flat top i beleve

what i think i need to do.

Camshaft and valve train kit
i am going to put in roller rockers but do those fit the original heads?
i am going to put in harder valve springs
i will be putting in a new performer manifold
i do think i need to bore the engine out to fit the new pistons in as i beleve they are 0.035 overzize

But i need a resident gearhead to help me out here. as funds are kind of limited i cannot afford a set of heads so i will be using the original steel heads until i can afford a new nice set of heads.

now what i need. What camshaft do i need with this ? i want an idle speed close to normal but dont mind a few rpm more. i need to know wich camshaft has enough opening time to use all the sucktion and compression of the stroker crankshaft. i have also heard i need a better oil pump to accomandate the stroker kit. is there anything i am missing? is it a terreble idea to use this motor since its 74? should  i have the original steel heads planed?

Anyways thanks for any insight you can help me out with. I am a mechanic so i do know all the work involved i just want to know if its worth it.  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 290 | Joined: 11/13
Posted: 12/07/13
08:50 AM

hello new guy and welcome.


Hello. I have a 400ci 74 engine out of a grand prix I am planning on getting a 461 stroker kit.

what do i need to do to the top end to make the kit work?

i cannot afford a set of heads so i will be using the original steel heads until i can afford a new nice set of heads.

he pistons in the set are -6cc flat top i beleve



It would be helpful to know all the codes on the heads, there is one on top of the center ex port and a tiny one close to the valve cover. there is a code under the head also.

the biggest thing you need is air flow hopefully your heads have 2.11 and 1.66 valves

stock flow on most 4c and 4x heads is purportedly around 170 intake and 110 ex, unfortunately you really need 200 - 240 intake and 140 - 170 ex to optimize your displacement especially if you use a cam that is bigger than stock.

PORTING - You can get some porting done but i'm not sure how much you can make those heads flow.

pocket porting is the biggest bang for the buck at around 400.00

back cut the intake valves.

you need screw in rocker studs installed if tour heads do not have them

you might have around 750.00 in your heads ported and finished with new valves, new eddy heads are around 2000.00

maybe just leave them stock and put the money towards a new set.


COMPRESSION - You want to go between 9.0 and 9.5. if you deck the block to .005 [almost 0] you need 94 cc chambers. if yours are 98 then mill them .025" from stock. this will give you 9.6 comp.

if your block is stock and you do not mill it 94 cc will give you around 9.26.

98 will give you around 8.98


xxxxx


what i think i need to do.

Camshaft and valve train kit

i am going to put in roller rockers but do those fit the original heads?


yes, i suggest scorpions, if you use eddy aluminum yiu might need to grind the pushrod slot for clearance for the push rods.


xxxxx


i am going to put in harder valve springs


the cam will come with the proper springs


xxxxx


i will be putting in a new performer manifold


that is good for strong bottom end buy an rpm if you want big hp, but it won't help you until you get more air flow thru the heads.


xxxxx


i do think i need to bore the engine out to fit the new pistons in as i beleve they are 0.035 overzize


no such thing a .035 unless they are custom, std is .030, .040. .060.

.060 is too big, your engine might run hot.

get the cylinders sonic checked for thickness.


xxxxx


now what i need. What camshaft do i need with this ? i want an idle speed close to normal but dont mind a few rpm more. i need to know wich camshaft has enough opening time to use all the sucktion and compression of the stroker crankshaft.


your cam must be matched to head flow, intake, gear ratio, compression and driving style.

do you want:

mild, moderate or rough idle?

need vacuum for power brakes?

fwy, street or inbetween driving?

tire burner or tire warmer?


without more info i think a comp xe262h is best suited for your heads.

an xe268h or lunati 60903 is better with ported heads sand at least 3.00 gears, 331 is better.

an xe274h is fairly stout but needs a ton of air so you might need the aluminum heads with this cam and 3.32 - 355 gears.


xxxxx


i have also heard i need a better oil pump to accomandate the stroker kit.


most people use a melling, some use the high pressure one, butler performance also sells a blueprinted melling.


xxxxx


is there anything i am missing?


money.


xxxxx


is it a terreble idea to use this motor since its 74? should


i don't think so, others might know better.


xxxxx


i have the original steel heads planed?


what does this mean exactly?


xxxxx


CARB - Holley street avenger 750 cfm vacuum secondary annular boost venturi type.


xxxxx


push rods - buy high perf ones like manley's etc.


xxxxx


get eng balanced


xxxxx


damper - buy an ati from summit.  

idrivejunk idrivejunk
Addict | Posts: 5000 | Joined: 12/09
Posted: 12/08/13
12:57 PM

Hello and welcome.

The 73-4 400s are a fine choice for a Pontiac V8 build. They have compression ratios suitable for currently available gas. You've given zero information about how you plan to use the engine and without that, nobody can help much. I am more of a bodyman myself, but one thing I have learned is that those stroker kits are not always the best route to go as fas as bang for the buck, especially if using iron heads. Kinda depends on the condition your existing parts are in, like do you already need a crank. Proper cam and valvespring selection can only happen after everything is apart and measured, the usage purpose and vehicle are chosen, math is done, and all the other replacement engine parts have been selected.  
idrivejunk

gunnarig gunnarig
New User | Posts: 5 | Joined: 12/13
Posted: 12/08/13
04:17 PM

The engine was allways to be rebuilt. and the stroker kit was just an idea since it increases displacement without actunaly gettig a 455. but i havent made any final decicion i just know i need to rebuild the engine as the car has been restored and painted and all thats left is to fix the mechanical aspect. i wanted the stroker kit as it comes with a hardened crankshaft and pushrod and new pistons. i dont know the original specs of the pistons and how much abuse they can take if i decide to do the top end and skip the rotating assembly. but i came here for advice so if you got any ill gladly take it. i am looking to spend around 2500-4000$ and i want 400ish maybe 500 hp in return i want a car that has an ok idle speed where i dont need to change the stall or change the AT every 400mi i have a 400TH and A 12bolt rear end with a lock. but the biggest problem is is as this is a cold ass country with snow the car goes to a storage location i can ongly acsess every other sunday so i cant get the engine codes. this post was just to throw in ideas and get some professional advice. anyways cheerz  

gunnarig gunnarig
New User | Posts: 5 | Joined: 12/13
Posted: 12/08/13
04:17 PM

.  

gunnarig gunnarig
New User | Posts: 5 | Joined: 12/13
Posted: 12/08/13
04:17 PM

.  

idrivejunk idrivejunk
Addict | Posts: 5000 | Joined: 12/09
Posted: 12/08/13
04:57 PM

Well, maybe read back through fuh3's post there. Making around 500 TQ is fairly easy, 500HP gets serious with iron smog era heads. Type 406 in the forum search box, theres a popular thread under the general discussion that you may want to read through. The forum search is separate and just looks in the forums but I'm sure you can find some helpful build articles searching the magazine's "tech" part of the site also. I guess I missed what kind of a car you'll be installing it in.  
idrivejunk

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 290 | Joined: 11/13
Posted: 12/08/13
05:46 PM

ok

cold where you live and yoiu said cheers

are you a kiwi, an aussie living on the top of mount kilimanjaro or an englander?


i have little to add to my previous post.

ADD HP TO ORIG UNREBUILT BOTTOM END - Not a good idea imo.

STROKER KIT - Good idea imo.

STOCK TRANS - 400 plus hp might cause it to prematurely fail, if so just rebuild it with a shift kit and high parts.

$4000.00- You will need eveery penny of that for a full high perf build and it does not include headers or ex pipes etc.

GEARING - If you don't drive often at 65 or above you might consider perf gears like 331 - 350.  

gunnarig gunnarig
New User | Posts: 5 | Joined: 12/13
Posted: 12/09/13
07:00 AM

I am icelandic. The car is a 73 Le mans.  owned it since i was 15 and im 30 now. it already has headers. and it compresses around 9.5 but the engine is out of a 74 grand prix and i dont know exacly what was done to it before i got it. but the pan on the AT has cooler pipes running throgh it wich i have heard are not original.  i guess it will be an intresting expirience to tear it apart to see whats inside.