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Upgrading Heads: 400 pontiac heads or Edelbrock?

  
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Upgrading Heads: 400 pontiac heads or Edelbrock?

 
triumph triumph
New User | Posts: 17 | Joined: 05/08
Posted: 03/13/09
01:35 PM

I just recently bought a 73 trans am.

It has a 74 block, and the stock 73 heads/intake/carb, and the hc01a cam (so I'm told, but have no idea how to verify this).

The engine is a little tired, and isn't performing all that well, and I want to breathe some life back into it.  I could really use some advice, since this is the first muscle car I've ever owned. I had a compression check done on the motor, and the readings vary anywhere from 150-120. I suppose that isn't great, but it's also not that bad. I don't know whether I want to rebuild the motor yet. My application is a very fast, enjoyable car to drive. I'm not very interested in the track.

I've decided to have the carb rebuilt and tuned (by my mechanic) with the kit from cliff ruggles, instead of upgrading to edelbrock performer intake/carb as I was previously going to do.

I'm trying to decide which heads to go with, as I think mine are the low compression heads. Either 400 pontiac heads, or edelbrock performer heads.

Cliff Ruggles told me that the 400 heads can outperform the edelbrock heads, does anyone have any input there?

Is this because the aluminum heads are not as efficient, and require a higher compression ratio to achieve the the same horse power? I can't remember where I read this, but I think it was in some tech article...

Basically, when I read the specs of the 455 SD heads vs the edelbrock heads, they are close, whereas the 400 #96 heads have a lower intake volume. To me, the edelbrock heads sound like they are comprable to a SD head, which is undoubtedly better than the 400, right?

So, the reason why this is so difficult a decision for me, is that the heads ultimately determine what I do with the block, pistons, and cam.

If the 400 heads, then stock pistons, and a minor rebuild. If edelbrock heads, a rebuild becomes more complicated, right?

Sorry to be so long winded, this is my first venture into engine building and I'm already in over my head! Basically, I'm asking 2 things:

1. Which performs better, 400 heads or Edelbrock?
2. Can you comment pistons/cams with that head?  
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I'm here to learn!

Pontiacman8 Pontiacman8
Moderator | Posts: 5779 | Joined: 02/08
Posted: 03/13/09
03:32 PM

Well it all depends on how much power you are looking for it is a 400 block right.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

triumph triumph
New User | Posts: 17 | Joined: 05/08
Posted: 03/13/09
03:35 PM

It's a 455. That is a pretty important piece of information that I forgot to include, sorry!

Well, it's hard to put a cap on how much power I want, because I honestyl don't know when drivability becomes a factor.

Lets say, somewhere around 450hp?

Thanks!  
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I'm here to learn!

Pontiacman8 Pontiacman8
Moderator | Posts: 5779 | Joined: 02/08
Posted: 03/13/09
05:49 PM

What is the casting number on the heads that are on it now.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

triumph triumph
New User | Posts: 17 | Joined: 05/08
Posted: 03/13/09
07:20 PM

They are 4x
Does h1 mean anything? Its at the shop now, and cant run out and check.  
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I'm here to learn!

blackbird72 blackbird72
User | Posts: 186 | Joined: 08/07
Posted: 03/13/09
08:26 PM

If your 4x's came with the 455, they're the big chamber version (114cc) and give you around 8.2:1 CR. If they were from a 400,they would be around 98cc and give you 9.2:1. An earlier 400 head with a 72cc chamber would give you over 11:1, too much for pump gas. Th e-head with an 85cc chamber would give you about 10.3:1, but since aluminum dissipates heat better than iron it would still work w/ pump gas. The e-heads do like more timing (about 38-40 degrees total) than what is normal for iron heads, but will give you the power you're looking for.

A 450-475 hp level can also be had with ported iron heads. The 6x-4's have a 94cc chamber giving about 9.5:1 CR, and with a good port job flow rates will approach 220-240 cfm, not quite what the e-heads flow out-of-the-box but with the right cam 450-475 hp is more than possible.

I'm gathering the parts for a 455 build next month- I already have the 6x-4 heads and am picking up the block and crank next week. I'm going to use KB forged flattops and PPR Tomahawk 4340 I-beam rods- lighter than a TRW/ stock rod combo so it should rev nice. I was planning to port the heads before getting them serviced, but I may just run them uncut to see how much of an improvement the porting makes.

Geno  

Pontiacman8 Pontiacman8
Moderator | Posts: 5779 | Joined: 02/08
Posted: 03/14/09
05:44 AM

The 1h means they are from a 455 so they have 114cc chambers.
To get the power level you are looking for you will need more than the 8:1CR the engine has now you are going to need around 9-9.5:1 cr.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

triumph triumph
New User | Posts: 17 | Joined: 05/08
Posted: 03/14/09
10:23 PM

Hey, thanks!

Pontiacman8: So 9.5:1 with iron casts. What chamber size is sweet spot? Somewhere around mid 90's? Which heads are good? #96?
10.5:1 with aluminum heads, right?

Which is better performance? Will it be similar? If so, i want to stay all pontiac..

The other option my mechanic recommends is if i rebuild the engine, bore .40 over, keep these heads and change the pistons to achieve higher cr.  What i need to know, is, if i rebuild the engine and bore over, can i still run 400 heads, or will my cr be too high?

Ahh too many questions!!!

Blackbird72: that sounds like what i want to do, i just got to get my mechanic to understand it. Right now he doesnt really think its a good idea.

Thanks for the help, i really appreciate it.  
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I'm here to learn!

barneyformula barneyformula
Addict | Posts: 3306 | Joined: 01/07
Posted: 03/15/09
05:18 AM

After reading this thread all the way thru, a few points/questions come to mind. First off, triumph has stated that this is his first engine build. That makes me wonder what his expectations really are, does he have any performance benchmark to measure his car by? A friend's stock 5L Mustang LX 5spd for example.
He says he wants a very fast, enjoyable street car that won't see the track. OK what gears and trans does he have? Does he really want to drive it on the highway for any distance, because honestly most people can't stand listening to a V8 spin over 3000rpm for an hour straight and any gear deeper than 3.08 will do that!
Next is his mechanic, if he doesn't understand Pontiacs any better than this, Triumph needs to find an engine builder familiar with Pontiacs! I assume from the statement about putting in higher compression pistons, that this guy thinks he's dealing with a dish piston Chevy or that it's still 1970 and pop-ups are the way to go.
I'm not big on aluminum heads unless they are proven to be necessary. Don't get me wrong they are a great performance piece and well worth the $2500 price tag, IF they are needed. But I see so many aluminum headed 455's in HPP shootouts that are turning in low 14's and 13 second time slips that I don't see why the owner thought he needed them. A good builder should be able to put a mild iron head 455 into the 13's with no more than a 3.42 gear and stock th400 auto. Trust me if Triumph hasn't driven a car with mid 13 potential and Pontiac torque before, he will think the world has sudenly started turning the other direction!
the reason I say all this is that many years ago, a guy I know went to a local machinist with a 1981 Cutlass and a SBC 350 wanting to beat all the stock 5.0's running around. The guy built him a 9:1 355 with ported 882 heads, 280/.480 cam, Torker2 manifold, 650DP Holley, 3000 stall converter and 3.73's. Did it beat 5.0's? You bet! By a full second or more in the 1/4 mile, except he couldn't drive more than 55mph on the 2hour trip to the track and he needed slicks to hook it up. It was way overkill and although he enjoyed it for what it was, he couldn't drive it outside the city limits. With a 455 Pontiac, Triumph doesn't need a bigger stick to get where he wants to go, he needs a better combo that works right. I think we can give it to him without spending $2500 or more just on heads.
Steve  
A little help... 'cause we don't all have to learn the hard way!

blackbird72 blackbird72
User | Posts: 186 | Joined: 08/07
Posted: 03/15/09
07:54 AM

I agree- a 455 with around 9:1 CR, iron heads, and the right cam should make enough power to push most 3800 lb. cars with 3.08 into the mid to low 12's. And with the right trans/converter, carb/ignition tuning, chassis setup, it should be able to get into the 11's. My '72 'Bird with a healthy 406, ported no.48's, built TH-350, mild converter and 3.08 posi runs 13.0x's, and with the same setup and a 455 with ported no.64's I built some 13 years ago the car would run 12.0x's (street trim, suspension set up for road race). Some drag racing buds help me set the car up for drag and with drag shocks, pizza cutters and slicks the car ran a 11.85.

I also agree about finding a new mechanic- if he doesn't know Pontiacs he won't know how to get the most power out of them, let alone built it right. A well built 455 also doesn't need alot of gear to go fast- a popular drive train combo with the 455 is a TH-400 and 3.08 posi. This combo keeps the revs low on the highway but will still have enough torque multiplication (like you even need that with a 455) to lauch hard.

There are plenty of piston choices now for the 455- most of them are lightwieght race pistons, but unless you know you're going to be racing full-time the extra expense isn't necessary. Forged Sealed Power/TRW ($360) or KB ($400) flattops are strong enough, but the forged KB's are lighter. You could also run PPR forged 5140 I-beams ($240), which are a good upgrade from the cast rods. The 4340 I-beams ($400) I chose were lighter than the H-beams and as strong, so I went with those. The 455 also has so much torque at lower rpms you can get away with running a single plane manifold like a torquer II or Tomahawk, but if you know you're going to be doing mostly street driving I'd stick with the factory manifold or an RPM.

Geno  

Pontiacman8 Pontiacman8
Moderator | Posts: 5779 | Joined: 02/08
Posted: 03/15/09
10:41 AM

Triumph: the 94cc 6x 350 heads with head gasket P#z1016 from felpro a .040 over bore and flat top pistons will give you a 9.2:1CR.The 98CC 400 4x heads yield a 9:1CR so either should get you close to your goal.
Along with a lunati cam kit P#LUN-00072LK, a dual plane intake and a rebuild if needed.
For head work I would recomend getting a 3angle valve job as well.
This should make for a torqey combo.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

Pontiacman8 Pontiacman8
Moderator | Posts: 5779 | Joined: 02/08
Posted: 03/15/09
11:08 AM

I also agree with Barney you need to find a engine builder that is familiar with pontiac engines because you can't build a pontiac engine as you would build a chevy and exspect it to perform good.
Also the edelbrock heads are not nessesary for the power level you are wanting.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

triumph triumph
New User | Posts: 17 | Joined: 05/08
Posted: 03/15/09
04:36 PM

Ok, this is really great info!

I have a turbo400

How do i figure out what gearing?

I drove this car down the 101 from san francisco to la directly after purchasing it. It was a great trip, and had no problems. i will spend most of my time cruising around, probably drivig it to work 1 or 2 days a week (8 miles, no traffic), and generally having fun with it, but i DEFINITELY want to still be able to take it on the highway. Maybe drive to san diego or vegas from la. A drive over 30 mins on the freeway wouldnt happen all that often, but i dont want it to be a problem, and constantly have anxiety if i do.

If i change heads to iron pontiac 400 or 350heads, it will still be a streetable drivable car, right? I also dont think the block has any significant problems,though not in tip top shape.  is it risky to not rebuild, and stick with the existing pistons, just upgrading the heads and cam?  
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I'm here to learn!

Pontiacman8 Pontiacman8
Moderator | Posts: 5779 | Joined: 02/08
Posted: 03/15/09
06:05 PM

If it still has the factory rear gears they should be 3.08 gears.

The head change to get the 9:1 Cr will require 93 octane gas but will still be streetable.
There is always a risk when you don't really know the true condition of the bottom end of the engine.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

blackbird72 blackbird72
User | Posts: 186 | Joined: 08/07
Posted: 03/16/09
09:37 AM

triumph,
The simplest way to figure out your rear end gearing is to jack up and support the rear end, put a chalk mark on the driveshaft and tire, and count the number of rotations it takes for the tire to turn for one rotation of the driveshaft. You can also tell if your rear end is a posi or not- if the opposing tire turns in the opposite direction your rear end is open, if it turns in the same direction as the tire you're spinning it's a posi.

I've had a 3.08 posi ('79 WS6 disc brake rear end) in my 'Bird for about 16 years- it has delivered power from 350s to 455s and has been proven performer from the ET's alone- the 'butt dyno' likes it too. As I mentioned earlier, the 455/TH400/3.08 combo is probably one of the best overall drivetrain setups for any Poncho- good for the street and not too hard on the revs on the freeway.

There are a number of 96-98cc heads that will give you a more desireable 9.1-9.5:1 CR with factory pistons. Since SoCal is saddled with crappy 91 octane carb/igntion tune will able need to be dialed-in to run at peak performance.  

Putting fresh heads on a used shortblock with some mileage isn't that uncommon, but it may reveal how tired your shortblock is (blowby from worn rings). It also depends on how many miles your motor had and how hard it was run. From the description of your your compression test I would suggest it's time to rebuild the whole motor, since your compression numbers have more than a 10% variance. You would see an improvement from just a set of fresh heads and cam, but in the long run you would begin to notice poor idle and mediocre performance from having strong and weak cylinders. A 455 makes this harder to notice due to the engines ample torque while driving, but a leakdown test will reveal the worn cylinders.

The rebuild question is more a choice of what you want out of your motor- if you want solid reliability, the knowledge that you know what exactly is in your motor and what kind of power it makes, then you should rebuild it. But if your budget is limited and you just want to keep it running for another 10k-20k mi, that can be done as well. Pontiacs from the factory last a long time if maintained, but with the potential to almost double the factory power output and the availability of reasonably priced performance parts a rebuild makes good sense to me.

Geno  

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