# 73 455 Cam choice



## JLuger (Sep 8, 2012)

Looking for a little guidance on a motor Its a a stock 455 with 4X heads with H1 markings I have a 71 factory intake I'm going to use and stock exhaust manifolds. Also had an edelbrock 650 carb on it. I have it torn down for a timing chain replacement thinking of replacing cam as its showing a little wear. Assuming the cams stock what are my options. Motors going in a 66 GTO 4 speed M20 with 3.55 rear the only change I may make in the drivetrain is a taller rear gear down the road 3.08 or 2.93 for longer interstate rides. Also have a set of 6X 4 heads available that I'm thinking about.
thanks


----------



## LATECH (Jul 18, 2018)

OK, I will bite.


4X H1 heads have a 112 CC chamber size and may or may not have screw in rocker studs.
6X 4 heads are 94 CC chambers.

The 6X 4 would put your compression at around 10.3 to 1 . Too high for a cast Iron headed motor.

4X H1 have 112 CC chambers and would put your compression ratio at 8.87 which is decent and could be milled .020 - .030 and that would shrink the chambers 4-6 CCs . 6 CCs would put right at a sweet spot of 9.29 to 1.

For a street motor on pump gas (93 Octane) 9.3 is at the top of the compression range

But you can make lots of power with a 455 on less CR.

OK ...

That being said, The intake valve does not close directly at Bottom dead center. It closes After Bottom Dead Center or ABDC. This is Important , as this event called intake valve close timing is reffered to as an angle , like say 44 Degrees ABDC for instance. That means that the intake valve is closed at 44 degrees after the crankshaft passes Bottm Dead Center.Important because this lessens the amount of compression ( actual Compression Ratio) as the cylinder does not make pressure untill the valve is closed. This is called dynamic compressionratio.
The angle is used to determine the postition of the piston in the cylinder as it is already on the upstroke, so the cylinder "swept" volume is less than the actual full stroke used to determine the cubic inches of the motor.
Stroke , rod length and intake valve closing angle ABDC are all used in calculatiing the Dynamic compression ratio.

This is important to choosing a cam. Too small of a duration can increase excessive cylinder pressure (CR) because of earlier intake closing event and cause detonation. Too long of a duration closes the intake valve late and can result in lower cylinder pressures and cause a low rpm power loss, or dogginess.

Got to find a cam , with the correct intake closing duration to utilize the static CR achieve a good workable Dynamic CR, resulting in the best amount of power the engine can make.

The big question is , how much do you want to change the engine /parameters. Higher compression makes more power, but sometimes that whole theory can be overthought.

Its a balancing act.


So which cam do I run .......is a pretty subjective answer.

You need a cam that will fit the bill, on how you intend to drive the car. Is it a street car running pump gas (recommended) or a strip car running race gas?


----------



## JLuger (Sep 8, 2012)

Thanks, street car pump gas. Wanna keep it simple.


----------



## LATECH (Jul 18, 2018)

You looking to squeeze every ounce of horsepower out of it, or keeping it somewhat simpler and making just a good running 455 on a budget?


----------



## LATECH (Jul 18, 2018)

OK. Looking at some of my math from above , the numbers are wrong. 

To get to 9.3 to 1 static CR you need 97 CC heads. The 6X 4 heads are 94 CCs and would stillbe too small.

The 4X H1 heads are too large to even mill down to 97 CC .


----------



## LATECH (Jul 18, 2018)

A set of 4X 7 heads would be Ideal.They are 98 CCs

Here is a chart


Pontiac V8 Cylinder Heads


----------



## PontiacJim (Dec 29, 2012)

The 1973 4X H1 heads have a big chamber, 112CC's, but you have the big intake valves and screw-in studs. Compression is low at 8.12, but still a good number to work with.

What you want to do is build cylinder pressure (the Dynamic Compression LATECH mentioned) which is sorta like adding more compression. This is where I like the Competition Cams cam having the 110 LSA ( Lobe Separation Angle). These cams build cylinder pressure. Selecting a grind like Competition Cams "XE262" might be a good choice.


----------



## JLuger (Sep 8, 2012)

Low budjet, just a gd running motor.
It's a project car that I want to get it running for the summer.


----------



## JLuger (Sep 8, 2012)

Jim they are pressed in studs would that matter on that cam your talking about?


----------



## PontiacJim (Dec 29, 2012)

Several things come into play when selecting cam. The lift would be independent of the Lobe Separation Angle. With press-in studs, you want to limit lift to a safe .450", but I have read you can go as high as .470" with both using stock spring pressures which is about 240 pounds at full lift. I looked at the specs for press-in studs and the dual springs show a pressure of 230 pounds at full lift which is .407" for a typical Pontiac cam. The Comp Cams #CCA -988-16 with 240 pounds pressure are most popular for those less than killer HP engines. Using a higher than stock spring pressure can be too much for the press-in type, not only taking a chance of pulling up, but also snapping the stud.


The stock Pontiac heads are said to flow best up to .450" lift and from that point on, you are not really gaining much. But you might ask," so why have a .500" lift cam?" The higher lift cam opens the valve faster in reaching the .450" lift, but does not make the head flow more effective past .450" lift.

So, going back over my earlier post, the XE262 may be too much lift - but maybe not. https://butlerperformance.com/i-244...tappet-cam-and-lifter-kitcca-cl-51-222-4.html The next cam down is the XE256 which has a safer .447" Intake lift and .455" Exhaust lift. Xtreme Energy 212/218 Hydraulic Flat Cam for Pontiac 265-455 Advertised duration is 256 Intake/268 Exhaust. The XE262 duration is 262 Intake/270 Exhaust.

There may be other cams that will work, so you are not limited to Comp Cams brand. I am just pointing in the direction I would go. Press-in studs will limit your cam selection. Screw-in studs open a wider door to cam selections. The low factory compression will be a key part of the equation in selecting a cam. Too big of a cam will produce a "soggy" engine when you want crisp and responsive throttle action. So you have to be honest with what you have for a stock engine and not expect miracles as to the increase in HP & Torque output.

You might want to email any of the cam companies/Pontiac engine builders and get their recommendations. 

I rebuilt a 1972 4-Bbl 400CI which had the 7K3 heads and had screw-in studs. Stock compression and rebuilt with the inexpensive cast pistons with 8-valve reliefs, so I figure compression was somewhere around 8.0. I cleaned up the heads and gasket matched the intake openings. 3-angle valve job and stainless steel valves. Stock cast iron manifolds with dual exhaust. Used Comp Cams XE274 cam and the matching 988-16 valve springs (as I recall). I was really happy with the way the engine performed since it was low compression- peppy and pulled hard up to about 5,600 RPM's. This cam would be too large for press-in studs due to the cam's lift in my opinion, but it was a good cam for my build, and worked.

So a low compression engine can perform, but it won't be a 400HP performer.


----------



## LATECH (Jul 18, 2018)

I agree with P JIM . I would also look at the compcams xe-268. it is just a tad larger duration and a litle more lift. 









PONTIAC COMP Cams 51-223-4 COMP Cams Xtreme Energy Camshafts | Summit Racing


Free Shipping - COMP Cams Xtreme Energy Camshafts with qualifying orders of $99. Shop Camshafts at Summit Racing.




www.summitracing.com





I would recommend getting BB chevy rocker studs installed, and using posi locks for adjustement. I would also shave the heads about .020 to give the static CR a bump.

I would run the XE 262 in a 400 with the same Compression ratio, but airflow rates are better/higher even at low rpm with a 455, so you could bump the diration up a notch and still get better low end.

I wouldnt worry about horsepower. as Much as you think it is important, torque is what gets the tires moving.The 455 is a stump puller torque wise and if you are running a tall gear for highway use, you want torque. 

An engine has to make power(torque) at all rpms on a street motor , not just at say 5800 rpms where the peak power is at. The xe 262 or xe 268 is a good base set of numbers to look for in your cam choice. Also a narrow LSA makes more power, but at a narrower RPM range , where as the same grind with a wider LSA (higher number) makes power across a wider rpm range. 
My ( 389) 400 runs a CRANE cam with .454 in .480 ex lift 112 LSA (216in 228ex @.050). Its a 9.3 to one engine.
It pulls hard right off idle to above 5500 rpm (forged rods of course)


----------



## PontiacJim (Dec 29, 2012)

LATECH - Yep, I liked the XE 268 myself, BUT, in post #9 it is stated that the heads had *press-in *studs. So my concern was pulling them out with a higher lift cam and so my suggestion was to go with something more on the lines of a stock-ish lift. Now if there is a cam with a 110LSA .450" lift and around 270 duration, that would be perfect for press-in studs in my opinion. Otherwise, as you wrote, swap in those Big Block studs, poly locks, better valve springs, and go with more lift but still keep duration 270 or less to keep the throttle response crisp. Now lift may also be limited as the valve length on the 455 head is actually shorter in length than the 400 heads. Do not know why, but this might need to be taken into consideration when selecting a higher lift cam for this application.

I'd go with the XE262 and take my chances, but that is me. If I pulled a stud, then I'd consider different heads with screw-in rocker studs or have them installed on these heads IF I was happy with the performance of the 455 as is. As an added plus, the factory rocker arms were not generally 1.5, and often came in at 1.48. So that would really make the lift of the XE262 lower and come in more like .455" Int/.463" Ex.


----------



## JLuger (Sep 8, 2012)

Thanks guys I called butler they recommended the melling SP-7 that is a copy of the factory 068 cam one up from the on that came in the motor I called melling and they said they don't list that cam for my motor.
Very frustrating. At this point I'm all over the place. Jim if I'm understanding your post right I can try the XE 262 without changing springs pushrod rockers just lifters?
Thanks John


----------



## LATECH (Jul 18, 2018)

Summit has the melling . It has .407 .408 lift so the stock springs will be OK and bottleneck studs will be OK too.








PONTIAC Melling SPC-7 Melling M-Select Class 1 Camshafts | Summit Racing


Free Shipping - Melling M-Select Class 1 Camshafts with qualifying orders of $99. Shop Camshafts at Summit Racing.




www.summitracing.com




It should wake up your 455 nicely.


----------



## PontiacJim (Dec 29, 2012)

OK, here goes. I pulled out all the literature I have on Pontiac engine builds and not a one really had much to say about the limits for press-in studs with regards to spring pressures or lift. Of course the 1967 and up performance heads with screw-in studs were covered. About the only thing I did find was a 389CI build with the factory "77" heads and press-in studs. The cam used in the build was an Elgin flat tappet cam with duration of 264 In/274 Ex, lift .444" In/.466" Ex, 112LSA.

So, with that, the XE 262 would seem to fall within that lift range using the highest lift of .466" from above. Again, there is always a chance of pulling a press-in stud and have known of a stock 2 Bbl 350 engine that had this happen. The stud pulled out enough to start the rocker arm clicking, and the cure was to smack it back down into place with a hammer - no more problems were had after that.

The main concern in my mind is making sure you do not have any coil bind or interference problems with the spring retainer hitting the valve guide at full lift. The installed height of the 1971 455 head is slightly less than most 400CI engines. So there may be absolutely no issues, but it would still need to be checked. I think a quick way to check might be to measure from the bottom of the oil shield that goes over the valve spring to the head surface. This will at least tell you if you can go the .470" lift with the shorter spring heights and not bottom out on the oil shields. I am going to contact an engine builder and ask a few questions and maybe this will help figure this out.

Next, I am not sure why Butler recommended the "068" cam. The cam has more duration, late intake valve closing, and overlap which in my understandings will bleed off cylinder compression as well as put the engine's power curve higher up into the RPM range - "Long duration cams delay the closing of the intake valve and substantially reduce the running compression ratio of an engine." So I got out my Dyno 2000 engine program and played around a bit inserting different cam specs.

So first off, I input numbers into the program to get my best match to the factory specs for the 1971 455. Factory with the "067" cam called for 325 HP @ 4,400 RPM and 455TQ @ 3,200 RPM. I got the HP - 325 @ 4,400 RPM, but could not hit the TQ number - 418 @ 3,000. But, it gave me a base line to work with in inserting the cams.

*"068" *Cam - 313HP @4,500. 382TQ @ 3,000. Best TQ 389 @ 3,500. Cam all done by 5,000 RPM with 314HP.

*XE256* - 298HP @ 4,500. 453TQ @3,000. Best TQ 453 @ 3,000. Cam all done by 4,500 RPM with 298HP.

*XE262* - 308HP @ 4,500. 450TQ @ 3,000. Best TQ 450 @ 3,000. Cam all done by 4,500 with 308HP.

As you can see, the "068" cam really suffers in the TQ numbers and only has marginal gains in HP, but goes an extra 500 RPM's into the power band which is expected with more duration.

The XE256 shows a slight loss in HP, slightly better TQ, and out of steam at 4,500.

The XE262 shows a slight gain in HP over the 256, a slight loss of TQ over the 256, and is also out of steam at 4,500.

So it appears that the "068" may not be a good choice even though it has a little more HP and will RPM higher. The choice then becomes the XE256 or XE262. The differences are so slight that the XE256 might be the better choice in that it has the lower and safer lift limits .447"/.455" - as long as you don't find you have coil bind. The XE cams build additional cylinder pressure while the "068" cam will lessen it (I did plug in the numbers) which is opposite in the direction you want to go with an 8.0 compression engine. Remember, TQ is what moves the car and I want TQ over HP which is what Pontiac engines offer.

That all said, are my dyno numbers right? I can't guarantee it as it is not a real sophisticated program. But I think it can be used to be close to reality and used for a comparison as shown.

As you can see, cam selection is not always cut and dry. 


'













'


----------



## JLuger (Sep 8, 2012)

You got that right!! Thanks again


----------



## bigD (Jul 21, 2016)

With the new format here, I am just now seeing this. My take may be different than those who have previously posted. 

To me, the press-in studs are the limiting factor. there have been studs pulled out even with stock cams. 

So, I'd say the Pontiac clone cams with just barely over .400 lift would be safest. The 1971 & '72 455HO engines all used the 068 cam. Those engines were low CR. So, that cam recommendation from Butler was not that bad, with all this considered.

The '73-'74 SD455 engines were also low CR. They had a cam with the 744 lobe specs. It has the same lift as an 068, but more duration. However both these 455 engines were vastly undercammed, from a performance standpoint. 

Between those to cams, I'd choose the 744, which today would be a Melling SPC-3. But, if you will hardly ever rev your engine past 4000 rpm, the 068(Melling SPC-7) should be all you need. The best prices for these Melling cams are most always either from an Ebay store, or Auto Zone. But, when you find the best price, Summit will probably match it, if you prefer to buy from them. 









Melling Camshaft SPC-7


Shop for Melling Camshaft SPC-7 with confidence at AutoZone.com. Parts are just part of what we do. Get yours online today and pick up in store.



www.autozone.com













Engine Camshaft-Stock Melling SPC-3 for sale online | eBay


Find many great new & used options and get the best deals for Engine Camshaft-Stock Melling SPC-3 at the best online prices at eBay! Free shipping for many products!



www.ebay.com





With the press-in studs, I would not consider the steep ramp cams, such as the CC XE series cams mentioned, or the Voodoo cams. Engine builder Paul Carter loves the Voodoo cams. BUT, he also recommends stronger valve springs than with normal profile cams. So, I think any XE or Voodoo MIGHT be more likely to pull a stud than either of the Melling cams mentioned. 

IF you choose to try to get by with more lift. The first cam I'd recommend is the Lunati 10510312. It has .454 lift, but not as steep a ramp as the XE & Voodoo cams. 









Street Master Hydraulic Flat Tappet Cam - Pontiac V8 276/286


Hydraulic Flat Tappet Cam. Excellent for street performance with 455 c.i. motors. Works with stock valvetrain and all power accessories. Fair idle. ; Advertised Duration (Int/Exh): 276/286 ; Duration @ .050 (Int/Exh): 221/230 ; Gross Valve Lift (Int/




www.lunatipower.com





Then there is the Summit 2801, which is a higher lift version of the 068, with .466 exhaust lift. Don't know how much cam your press-in studs will stand. The Summit is definitely the cheapest of all the choices. 









Summit Racing SUM-2801 Summit Racing™ Classic Camshafts | Summit Racing


Free Shipping - Summit Racing™ Classic Camshafts with qualifying orders of $99. Shop Camshafts at Summit Racing.




www.summitracing.com


----------



## Richard Hooper (11 mo ago)

JLuger said:


> Looking for a little guidance on a motor Its a a stock 455 with 4X heads with H1 markings I have a 71 factory intake I'm going to use and stock exhaust manifolds. Also had an edelbrock 650 carb on it. I have it torn down for a timing chain replacement thinking of replacing cam as its showing a little wear. Assuming the cams stock what are my options. Motors going in a 66 GTO 4 speed M20 with 3.55 rear the only change I may make in the drivetrain is a taller rear gear down the road 3.08 or 2.93 for longer interstate rides. Also have a set of 6X 4 heads available that I'm thinking about.
> thanks





JLuger said:


> Looking for a little guidance on a motor Its a a stock 455 with 4X heads with H1 markings I have a 71 factory intake I'm going to use and stock exhaust manifolds. Also had an edelbrock 650 carb on it. I have it torn down for a timing chain replacement thinking of replacing cam as its showing a little wear. Assuming the cams stock what are my options. Motors going in a 66 GTO 4 speed M20 with 3.55 rear the only change I may make in the drivetrain is a taller rear gear down the road 3.08 or 2.93 for longer interstate rides. Also have a set of 6X 4 heads available that I'm thinking about.
> thanks





JLuger said:


> Looking for a little guidance on a motor Its a a stock 455 with 4X heads with H1 markings I have a 71 factory intake I'm going to use and stock exhaust manifolds. Also had an edelbrock 650 carb on it. I have it torn down for a timing chain replacement thinking of replacing cam as its showing a little wear. Assuming the cams stock what are my options. Motors going in a 66 GTO 4 speed M20 with 3.55 rear the only change I may make in the drivetrain is a taller rear gear down the road 3.08 or 2.93 for longer interstate rides. Also have a set of 6X 4 heads available that I'm thinking about.
> thanks


With the


----------



## Richard XE 268 (11 mo ago)

JLuger said:


> Looking for a little guidance on a motor Its a a stock 455 with 4X heads with H1 markings I have a 71 factory intake I'm going to use and stock exhaust manifolds. Also had an edelbrock 650 carb on it. I have it torn down for a timing chain replacement thinking of replacing cam as its showing a little wear. Assuming the cams stock what are my options. Motors going in a 66 GTO 4 speed M20 with 3.55 rear the only change I may make in the drivetrain is a taller rear gear down the road 3.08 or 2.93 for longer interstate rides. Also have a set of 6X 4 heads available that I'm thinking about.
> thanks





JLuger said:


> Looking for a little guidance on a motor Its a a stock 455 with 4X heads with H1 markings I have a 71 factory intake I'm going to use and stock exhaust manifolds. Also had an edelbrock 650 carb on it. I have it torn down for a timing chain replacement thinking of replacing cam as its showing a little wear. Assuming the cams stock what are my options. Motors going in a 66 GTO 4 speed M20 with 3.55 rear the only change I may make in the drivetrain is a taller rear gear down the road 3.08 or 2.93 for longer interstate rides. Also have a set of 6X 4 heads available that I'm thinking about.
> thanks


I would consider the comp cam xe268 but with a head change to Kauffman Racing Equipment aluminum heads 85 cc it would be the best 25 hundred bucks you ever spent. With your 4 speed and a 308 you would be looking at great highway rpms and you could pass a semi like its standing still. My Best Richard Hooper


----------

