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78.Malibu_ 78.Malibu_
New User | Posts: 39 | Joined: 05/13
Posted: 06/11/13
01:28 PM


I have a 72 pontiac 455 in my 78 chevy malibu.

I have access to alot of spare parts, but i come from a mopar family.

i just want to go fast like my other pontiac drivers.

i dont know a lot past the fact that the engine was rebuilt about 30k miles ago with (for the most part) all brand new, oem parts as if it came fresh off the line.

anyways, I want to know where i would see the most significant performance gains when upgrading the engine. there is no reason that my malibu shouldnt be quite a bit faster.

so my question is, What parts would i change to see the largest performance gain on the car(being cost effective) and what is not neccesary to change?

Thank you!
~the newbie  

barneyformula barneyformula
Addict | Posts: 3306 | Joined: 01/07
Posted: 06/11/13
01:57 PM

What cylinder heads, intake, carb and exhaust system are you running now? What trans, converter, rear gears? Posi? Tire sizes? Any idea how quick it runs in the 1/4 mile now? A stock 72 455 should be a bear to drive in a light weight Malibu! The cylinder head number is cast onto the center exhaust port. What distributor and timing settings are you running? What did you use for motor mounts? It matters if you want to run headers. How quick/fast do you want it to be? What rearend is in the car now? If it is the 7.5" 10-bolt, you will not get much life out of it and should keep an eye open for an 8.5" 10-bolt from a Buick Grand National or 80's Olds 442/Hurst Olds, they are considerably stronger and bolt right in without the expense of an aftermarket rearend, no other stock application will bolt in.
A little help... 'cause we don't all have to learn the hard way!

70bird 70bird
Guru | Posts: 1064 | Joined: 02/13
Posted: 06/11/13
03:18 PM


It would help to also know the following

What is your max budget for engine and ex only?

Do you require vacuum for power brakes?

What type of idle, mild moderate, stupid, lol.

Are you willing to sacrafice some high speed fwys for quicker lite to lite acceleration?

Do you want a mild moderate or serious tire burner?rough idle no power brakes

Big improvements = head porting $800.00 or aluminum heads $2400.00, rods $500.00.

Big hp = low fwy speeds, rough idle no power brakes, maybe $6000.00.  

idrivejunk idrivejunk
Addict | Posts: 5162 | Joined: 12/09
Posted: 06/11/13
05:07 PM

Yeah thats a really wide open question. "Largest performance gain" is fairly ambiguous.

To me, the big log jam in that package is exhaust. If you can't fit full length headers to your engine swap, well theres your bottleneck that will limit engine power. I'd begin with a cheapo set of firebird headers and see if I could make them fit.

Luckily however, the Pontiac 455 has torque to spare. And in bone-stock configuration like yours, it will love life with tall gears, iron manifolds, and a smooth idle. But it will stop pulling really hard after about four grand.

If you can fit headers and have thousands to spend, go right for the aluminum cylinder heads to make power with a proper cam and other mods to suit. If you can get more air out, see about getting more in.

If you have only hundreds to spend and it already has dual exhaust, concentrate on gearing for your needs. That means look at transmission and rearend options rather than under the hood. Oh and you'll need traction too, if you want to drag.  

78.Malibu_ 78.Malibu_
New User | Posts: 39 | Joined: 05/13
Posted: 06/12/13
06:08 AM

thanks for the input so far guys!

I will be out back in the garage tonight after work and i will let you know more detail about it, along with details for internals of the engine(if i can find my build sheet)

but quick question regarding headers,

I am running a dual exhaust system and I am running the bigger, stock, cast iron headers on my car, but i do own straight pipe headers. the only problem and reason that i have not installed them is that I think that the installation would put one of the pipes right at the oil filter, I was told there was a conversion kit to move the oil filter out of the way but have had no luck in finding one, do they even exist?

I also was hesitant to put them on before knowing whether or not i was going to keep the heads the same on my car, because i do own a set of 6H heads but have never known whether they would be better than the ones on my car,

More details later tonight/tmro!


70bird 70bird
Guru | Posts: 1064 | Joined: 02/13
Posted: 06/12/13
06:28 AM


If your car does not have fairly noticeably rough idle then the headers won't give you much improvement in hp. The cast iron headers are pretty good.  

78.Malibu_ 78.Malibu_
New User | Posts: 39 | Joined: 05/13
Posted: 06/12/13
12:43 PM

oh, well the car runs like a dream... that is right along with what my uncle had said.

Usually when i talk about wanting to improve performance on my car everybody always says headers as one of their first suggestions, so i picked some up and they've been laying around ever sense  

My71 My71
Guru | Posts: 1261 | Joined: 02/10
Posted: 06/12/13
06:28 PM

Welcome to the forum Malibu..
70bird is right, unless you plan on running in the upper RPM (6K+) range the factory cast iron Ram Air exhaust manifolds will perform superbly. They are built and look different that the standard log type manifolds.
455's are torque motors so getting to crazy on the cam would be as much detrimental as anything else. Think breath.. In and out.. That big motor needs lots of air. There are several manufacturers that understand Pontiac Motors. Edlebrock, Lunati, Crower are three that come to mind. If your on a budget, there's several tricks you can do also. Remember, with factory cast Iron heads, max CR is 9.5:1.
What trans are you running? What rear end gears? How would you normally drive the car? In town or on the road? What's the weight of the car?  

70bird 70bird
Guru | Posts: 1064 | Joined: 02/13
Posted: 06/13/13
01:23 AM

Hello 78 malibu

I've been thinking, do you have the long factory cast iron manifolds that looks like shorty headers or are you referring to the everyday stock looking cast iron manifolds, not "headers"?

If you have a basically stock cam and stock ex manifolds ANY type of headers will increase your hp but it will not suddenly turn it into a fire breathing tire burning monster. You might get another 30 hp out of it. If you install them on a high perf you will get more.  

78.Malibu_ 78.Malibu_
New User | Posts: 39 | Joined: 05/13
Posted: 06/14/13
05:14 AM

Hey Guys! just some more information,

I have a holley 750 dual feed carb with spacer

I have an intake labled as -496140  which is a 1975 Qjet 1x4 gm intake manifold. But i also own a pontiac Torker intake that I have not installed.

I have 5C heads on the car, But i also have some 6H heads somewhere in the barn.

I have a Delco Remy distruibuter(have no idea which model thats off the top of my head) with the timing ever so slightly advanced. again couldnt tell you a number off the top of my head

my transmission I forgot to check, Its a automatic 3 speed with shift kit that has somewhere between an 1800 and 2200 stall converter(rebuilt last year)... It is one of the transmissions that has multiple bolt paterns so that you could have it on oldsmobiles or some other engines(forget what others).. I dont know if you guys can narrow it down from there too much but i can get the actual model to you guys soon

I have a 2.73 highway rear end(7.5) in at the moment because it was a daily driver when i worked closer to my home town. I had a 4.11 posi rear end but got rid of it and planning on going with a 323 or 355 rear end in the near future.

the car is now completely a weekend car now and im no longer at all concerned about milage. but i figured when running the 4.11 I may run out of gear in a quarter.. so i opted to go with something smaller. Any suggestions on the right gear to pull through the traps if i end up at the strip?

I'll try my best to estimate the other things,

the car probably runs mid 14's right now with the highway gear? thats based off of how competitive my car is with my friends impala.. his car may be a bit quicker and runs mid-low 14s.

I honestly dont know the differences in the motor mounts of pontiac/gm vehicles. i could try and do some research but i couldnt tell you...

I am a college student so the budget can be pretty tight at times. but this is where my spare cash goes. I would not want to spend more than 2-3k upgrading an already pretty fast car, but i want to know where i should be taking this and always have a goal for the next thing i want to get for it to boost its performance.

I do require vaccume for my brakes, really not alot of electronic anything on the car.

very mild and smooth idle

I would really like the car to roar and be a real tire burner. i realize that the goal might take a while to accomplish bug i see alot of potential in the car. i just want it to be impressively quick, with not alot of need for fwy speed.

I was told when i bought the engine a few years ago that the internals were built the right way, i dont know how true it holds as ive never completely disassembled it but it should have eagle rods and diamond pistons already if the guy was being honest.

Lastly i would say that the car weighs roughly 2800 pounds? ive never had it actually weighed so thats just a guess.

I have the long factory cast iron ones thaat swoop back and look sort of like shorty headers.

If i missed any of the questions or some things need to be cleared up let me know!

Thank you again!  

70bird 70bird
Guru | Posts: 1064 | Joined: 02/13
Posted: 06/14/13
05:36 AM

Yes, do you know you're cam specs?

You can not have a Major tire burner and good vacuum for power brakes too unless you are willing to install an aftermarket vacuum can. Are you willing to do that?

A tire burner means a moderately rough idle. Are you ok with that?

For a moderate tire burner in your case I would install a

CAM - Comp xe 274h or xe284h or similar lunati hydraulic cam. $350.00 for kit.

HEADS - Buy some 4c heads to boost your compression so you can optimize the performance of these cams. $400.00 plus rbld of $400.00 = $800.00

HEAD PORTING - Pocket port the heads and back cut the valves. $400.00

INTAKE - Sell your torker on Ebay for $130.00 and buy a new Eddelbrock RPM from Summit for $250.00 It's far better than the torker for your app and should produce more hp/tq.

CARB - 750 Holley  FREE!

STALL CONVERTOR - 2200 with the 274 cam and 2600 with the 284. $300.00

GEARS - 373  $350

POSI - $600.00 [if you don't have one.

GASKETS - $100.00

HEADERS - Stay with what you have.

EXHAUST PIPES - Should be 2 5/8" to 3"  with low restriction mufflers like Dynomax.

TOTAL - $2970.00 including posi with your labor.

Computer dyno estimates the following with the eng mods above including xe284h cam. The first setting below will hurl you down the track in a 3200lb car [including driver weight] at a best et of 11.26 @ 119 mph, the second lowers it to 11.0 @ 120 mph. That's pretty fast for a driveable street car IMO.

443  hp  5500, 491  tq  4000  with torker intake

463  hp  4000, 509  tq  4000  with Eddy RPM intake  

78.Malibu_ 78.Malibu_
New User | Posts: 39 | Joined: 05/13
Posted: 06/14/13
07:26 AM

thanks 70bird! thats perfectly specific haha. would you go about having these parts installed in that order? or do some things have to happen at the same time to see major performance gains?

a moderately rough idle is completely fine with me as long as i dont have to be adjusting any solid cams and it is still a dependable running car.

I am surprised that youd call an 11 second car a moderate tire burner! haha. thats all the moderate i would ever need and more!

I dont know my cams specs, but it has very smooth and has little range, i was told that it was just a super mild cam and never told the details. my car probably shifts at or below 4k rpm full throttle.

And ive never installed a vaccume can so im not sure what that is or is involved with that, but if i can get sub 12 seconds with vaccume brakes that is pleanty enough for me  

70bird 70bird
Guru | Posts: 1064 | Joined: 02/13
Posted: 06/14/13
07:49 AM


If you do not change your heads you can use the ones you have on there if they measure 96 cc's. It looks like they made a set that was 101 cc also.

MILL YOUR EXISTING HEADS - .025" from  stock which will give you close to 92 cc this will raise your estimated compression from 9.0 to 9.3. This is small but significant.

CAM - XE 274H is the largest you should use with this compression and probably will not require an xtra vacuum can.

XE 268H Is the smallest I would use otherwise it might be too mild for your taste. You will definitely not need an xtra vacuum can with this cam.

VACUUM CAN - They start at $35.00 and require 30 minutes of easy installation.

Using the suggested specs above including your existing heads with no pocket porting and XE274H cam. ET 12.4 @ 108 mph

345  hp  4500, 429  tq  3500

PORTING VS COMPRESSION - Porting will give you substantially greater gains than increasing compression by .75 - 1.0

ORDER OF MODIFICATION - If you leave your existing heads untouched just do the cam and intake at the same time.  

barneyformula barneyformula
Addict | Posts: 3306 | Joined: 01/07
Posted: 06/14/13
12:02 PM

Here's a couple of points to consider. First you say you think your malibu weighs 2800 lbs, I highly doubt it unless it is a stripped out shell. My 81 Lemans, virtually identical car, with a small block Chevy, no a/c and only power steering and brakes weighed about 3500 lbs with 1/2 tank of fuel on the local refuse station certifed scales without me in it. Use that as a benchmark for reference.
You may not need a vacuum canister at those cam levels, I'm running a Lunati 00071 Bracket Master2 in my 455 and it's just about at the point where I will need a canister. Here's the specs on my cam:

The reason I say this is because the larger displacement and long stroke of the 455 makes it much less sensitive to what we generally consider to be a "big cam".
My 79 Formula weighs 3650 lbs with 1/2 tank, I have a .020" over 455 with stock rods, "rebuilder" flat-top pistons, 5C-8 heads (101cc, 2.11"/1.66" valves), has 8.75:1 CR. The cam I mentioned above with COMP 1.5 Magnum roller tip rockers and 7/16" studs, Edelbrock standard Performer and 750 Performer carb, HEI, Hedman 3-tube hedders and flowmaster 2.5" duals. The B&M 2400 stall converter/TH400 and 3.08 posi make it easy to get sideways from a 20mph roll in first gear on 235/60R15 Goodyears (that's with both my Dad and I, almost 600 extra pounds on board!), I think that qualifies as a tire-smoker! I haven't made it to the track yet due to crappy weather but I'd bet the farm it'll turn mid 13's thru the mufflers on street tires.
Interestingly enough, my Dyno Pro 2000 sim gives almost the same numbers that 70 bird listed with the XE274H cam and unported heads.
A little help... 'cause we don't all have to learn the hard way!

78.Malibu_ 78.Malibu_
New User | Posts: 39 | Joined: 05/13
Posted: 06/15/13
02:44 PM

hey guys!

My first step with my budget will be to run the xe274 cam kit, along with replacing the rear end with the 373 posi. I will be using the torker intake until i can afford to upgrade to the RPM/sell the torker. My plan is to do a vacuum canister(although not positively necessary i might as well)and run all of the other components the same.

however, that leaves the heads untouched completely until I get my hands on some 4C heads, I would get them milled but that is probably going to be 200 dollars or so(says a family friend) and if i plan on replacing them in the future i dont think that it would be necessary...  unless it is completely necessary in order to run that cam.

How do you think the malibu would do under those specs? i know it wont be complete, but if that will be significant and cut my time on the strip by a bit it would satisfy me until i can finally afford the heads and intake upgrade

also, how to check cc of heads? ive never heard of them having different cc heads under the same model name until you mentioned it and i looked it up..

barneyformula-- you could be completely right, i mean alot of the parts are stripped on the car and it is run with buckets instead of benches but i could have been shooting way low at 2800 pounds, it was a complete guess  

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