# Head swap out



## par4n1 (Jan 28, 2010)

Soon I will be re installing my base engine 350 cdi im my Tempest. In the months ahead I will be replacing the 350 with a 455 I have. Is there a set of heads that I can put on my 350 now that will work as a performance head for the 455 when its installed? I do want to run pump gas in the 455 when the day comes


----------



## eeyore (Oct 23, 2014)

6x-4


----------



## BearGFR (Aug 25, 2008)

6x-4 is indeed a good choice. Big valves, screw-in rocker studs, 92cc (nominal) chamber. They'll run on a 350 (be sure and check for interference between the valves and the edges of the bore in case you need some relieving there). 92 cc's on a 455 ( or a 400 stroker) will put you in the sweet spot, compression-wise.

Bear


----------



## oldskool (Apr 26, 2015)

The 6x-4 would also be my 1st choice. But, it's not the only choice. I think the 5c-4 heads are almost identical to the 6x-4's. I've also read that the factory hardened valve seats were better on the 6x heads, than the earlier heads which had been treated to the process. Can't confirm. Many have posted that they've run non-hardened seats on the street for many years, with no problems. So, I'm not sure how important the hardened seats are, for street pump gas use.

If you want more performance out of the 350, you can use some of the smaller chamber heads. Then, when you build the 455, use custom pistons, with the correct size dish, for the compression you want.

This has several advantages. The custom pistons are lighter and have thinner rings. Plus, you can have the pin height changed, so that you won't have to cut a lot off the block deck, to achieve near zero deck height.

A compromise might be the #64 455 heads, if you can find some for a reasonable price. They're listed on some sites as having 87cc chambers. Some sites list some '73 and '74 #4x and #46 350 heads, as having 89cc chambers. These heads all switched over to screw-in studs sometime during the spring of '73, according to some online sources. I cannot confirm. Also, if you switch to E-85 fuel, you can run safely with high compression. It's fairly cheap and will make the engine run a bit cooler. There are lot's of guys running it, nowadays. You can Google up lots of info on it, including E-85 carbs and conversion kits.

But, as mentioned, with the 350 block, you'll need the clearance notches, at the top of the cylinders, to clear the bigger valves. I've read that some 350 blocks had one notch and some had 2. I know that the '69 350HO blocks had both, for use with the #48 heads. Not sure about the other years. I'm sure Pinion head can tell us which years had how many notches.


----------



## par4n1 (Jan 28, 2010)

Thank you all. There are so many variables to consider. Maybe I will just install the 350 as is and work on the 455 while its sitting on a stand. Is the 6X -4 still a good head just for the 455, added with a cam and intake manifold can I reach 350hp or so?

What about 455 HO heads or aluminium Edelbrock heads ect?

Sorry I dont know some of the basics and when researching I find there is so much to calculate. From valves to pistons and detonation. Its like a foreign language to me. My 455 is a 73 out of a firebird its a 2 bolt main but I want the radical sound of a cam and roller rockers, ect. Im looking for a strong runner on 93 octaine gas.


----------



## PontiacJim (Dec 29, 2012)

par4n1 said:


> Thank you all. There are so many variables to consider. Maybe I will just install the 350 as is and work on the 455 while its sitting on a stand. Is the 6X -4 still a good head just for the 455, added with a cam and intake manifold can I reach 350hp or so?
> 
> What about 455 HO heads or aluminium Edelbrock heads ect?
> 
> Sorry I dont know some of the basics and when researching I find there is so much to calculate. From valves to pistons and detonation. Its like a foreign language to me. My 455 is a 73 out of a firebird its a 2 bolt main but I want the radical sound of a cam and roller rockers, ect. Im looking for a strong runner on 93 octaine gas.



Take the time to learn so you have some basic knowledge and then you will know what questions to ask because there is so much to learn. Mis-match your parts, and you will have a slug of an engine. Go for big HP you really don't need, and you will have a hefty bill on your hands and then you will need to invest in trans/rear-end upgrades.

My suggestion, because you don't have the knowledge, is to first build a nice mild street 455 that will more than keep you smiling. The 455 gets built for torque at lower RPM's. So match your parts to such. Keep in mind that the "radical cam sound" comes from a cam with a lot of overlap which means it will suck at lower RPM's and will need to be wound up to higher RPM's to take advantage of that type cam. So streetability may suffer some and unless you build the engine to rev, you won't be able to fully utilize it.

I would build a strong stout shortblock, forged rods/pistons, ARP main studs, etc. and go with a nice set of iron heads, torque pulling hydraulic cam (maybe the factory "041" cam), and the factory Q-jet intake & carb, RA exhaust manifolds and 2.5" duals. Enjoy this for a while and get used to the power. If you want more later, you have built a solid shortblock that you can now add aluminum heads, bigger cam, aftermarket intake/carb, etc.. :thumbsup:


----------



## par4n1 (Jan 28, 2010)

Thanks PontiacJim. I did read all evening about pontiac head selection and can say that I learned quite abit (having known little to none prior). I will be going with a cast iron OEM, maybe keeping the one thats on the motor. I actually have one of the 3 or 4 recommended by hotrod mag. and other engine builders.


----------



## oldskool (Apr 26, 2015)

*350hp ?*

"...Is the 6X -4 still a good head just for the 455, added with a cam and intake manifold can I reach 350hp or so?..."


I figure you can probably make that 350hp number, with your '73 heads. If they have screw-in rocker arm studs, I'd consider using them. They'll make fairly low compression, but with some thinner Cometic head gaskets and a Lunati Voodoo cam, it'll make plenty of power and LOTS of torque.

But, if the heads don't have screw-in studs, I'd choose some of the others that have been mentioned. For the 455, my #1 choice would be the 6x-8's. They will give the 455 plenty of comp for pump gas, and they are probably the cheapest decent heads you'll find.

After the 6x heads, my next choice would be the 350 or 400 5c heads, followed by the mid '73-'74 #46 heads with screw-in studs.

There are a lot of sites with Pontiac info. Some is correct. Some is not. But here are the links to a few sites with Pontiac head info. If you need more precise info, ask for Pinion head. He seems to have worked with more Pontiac engines than anybody I've run across. 

Technical Information: Pontiac Cylinder Head ID Numbers

Ron's Pontiac Page: Stock Pontiac Head Specs

Alamo Area Chapter of the Pontiac-Oakland Club International (AACPOCI)

Pontiac V8 Casting Numbers

Wallace Racing's Pontiac Engine Search


"...What about 455 HO heads or aluminium Edelbrock heads ect?..."


Both heads are good. But they share one thing in common. They are expensive ! Some Edlebrock D-ports will probably cost at least $2500 complete. And the 455HO heads will probably cost even more. The alum heads are a much better value, unless you need the HO's for a numbers matching build. The alum heads will also take some weight off the front of your car.

The KRE 85cc D-ports are slightly cheaper than the Edelbrocks. And I've read that the valves and other parts are of better quality than out of the box Edelbrocks. For that reason, places like Butler and SD Performance offer the E-heads with better valves and CNC porting. But that pushes the price up to around $3000 or more. 

Kauffman Racing Equipment

http://www.jbp-pontiac.com/products/cylinder_heads/edelbrock_aluminumD_Port.htm

http://www.sdperformance.com/viewProduct.php?productID=1823

http://www.sandovalperformance.com/#!cylinder-heads/c1ojh

You can have a set of iron D-ports, built right, with stainless valves, for under $1000. I've seen 6x heads, ready to bolt on for around $600 or so, plus shipping. And, on a good 455 shortblock, these will make around 400hp with around 500ft lbs of torque, easy. Ebay usually has LOTS of Pontiac heads for sale.

pontiac cylinder heads in eBay Motors | eBay


----------



## BearGFR (Aug 25, 2008)

A few things to keep in mind:

* The intake and exhaust ports on practically all Pontiac D-port heads are close enough to being 'the same' that you can treat them as if they are.

* For a street engine on pump gas, your primary concern should be static compression ratio if you want it to be safe and reliable. The RIGHT way to manage CR is via chamber volume in the heads first, followed by piston dish volume (and you want D-shaped dishes, not full round dishes). You can get additional volume in other ways, such as 'thick' head gaskets and increased piston deck clearance, but those approaches also will "kill" your quench pad area and that's bad, It can actually promote detonation, so don't go that route unless there's absolutely no other way to hit your target CR. (I have a spreadsheet you can use to calculate CR that's already primed with common Pontiac measurements. I've posted it on this forum before, or holler if you want a fresh copy.) In general the "rule of thumb" is to shoot for the octane rating of the fuel you plan to use / 10. For example, 9.3:1 for 93 octane. Yes, it's possible to "push that" some in some situations but my personal opinion is that the risk isn't worth the potential benefit. Educate yourself and then make your own choices.

* Jim Hand's book has a good section on porting your own heads. Even if you choose not to take that on yourself, I recommend reading it for familiarization (and also protecting yourself from 'chevy' engine builders who think they know what they're doing, but don't.)

* Even small valve heads with pressed in rocker studs can be upgraded to the large valves and screw-in studs. It just costs more money to do that so it's better to start with 'good' heads, but if you can't find any it's not the end of the world.

* Speaking of rocker studs (and rocker arms). The factory arrangement with the bottleneck studs and their fixed, non-adjustable rocker balls and nuts are really only adequate for a bone stock engine. Even then I recommend switching to the fatter 7/16 all the way studs and fully adjustable rocker nuts (poly locks). Factory studs are one of the weak points and have been known to break at the neck, especially when running a rowdier than stock cam and associated higher spring pressures, and you really "want" the positive adjustability anyway.

* If you're considering running the higher ratio 1.65:1 rockers at some point, take the time to elongate the pushrod passages in the heads before you install them, then make sure they're nice and clean afterwards. This is not a job you want to attempt with the heads on the motor.

* Speaking of chamber volumes in the heads. ALWAYS measure them yourself. Pontiac heads can vary quite a bit from the nominal factory values, plus you never really know whether a set of used heads have been milled at some point. Even 3-5 cc's of volume makes a significant difference in compression ratio.

* There is a dividing line on heads having to do with the intake manifold bolt pattern (and sometimes coolant passages): 64 and earlier, and 65 and up. (Actually there are more divisions on the early side than just "pre-64" but I'm guessing that won't matter to you.)

* Exhaust valve seats. Prior to the introduction of unleaded fuel in 72-74 the lead in the fuel also served to lubricate exhaust valve seats and cushion them from the hammering effects of the very hot exhaust valve. After the lead was gone from the fuel, factories had to start induction hardening the seats to keep them from "receding" into the head from the hammering. There are two schools of thought on this one. Some say that as long as you're not pulling a trailer or putting a heavy load on the engine very often, that you'll be ok with non-hardened seats on unleaded. Some say you always need them no matter what. Replacing the seats involves a machining operation where the old seats are cut out and new ones (hardened inserts) are installed. Some say this has an effect on heat transfer due to the fact that the seat is now no longer one continuous piece of metal with the head. I'm not sure I have an opinion either way. Just be aware of the concern, and make up your own mind.


Bear


----------



## par4n1 (Jan 28, 2010)

I am always amazed at the time and detail the forum's members take to answer questions only to assist others. Oldskool thank you AND everyone else for their help. I realize the importance of research before asking questions and to try and learn on ones own before bringing up the subject. While my questions can be the most basic to most please know that I do research until ive exhaused my options or just get exhausted before posting my questions.

Today I removed the tranny, exhaust manifolds, alt, compressor ect from my motor. Tomorrow I will remove heads (mine are x4) to look at the rockers, push rods and springs and valves. I hope to look at the cylinder walls and cam for wear. Im excited to see the internal working of my motor. It will give me greater satisfaction once its put back together rather then just paying someone to do all the work. 
Until then


----------



## par4n1 (Jan 28, 2010)

Thank you Bear. Great reading.


----------



## BearGFR (Aug 25, 2008)

par4n1 said:


> Thank you Bear. Great reading.


You are most welcome. 

I just noticed "Virginia" under your name. I don't know how 'serious' you want to get, but you might check with Dave Wilcox via Central Virginia Machine in Burkeville (Jim Lehart's place). Dave did the E-heads for my car and they are works of art.

Bear


----------



## par4n1 (Jan 28, 2010)

Hmm interesting to hear. Im about 45 mins from burkeville and hit the wineries up there often. I will give them a call.


----------

