455 Build / Cam Choice...And Other Topics

Well it's almost spring time and I would like to freshen up my 455.  Here are the details; 455 .040 over, Original 350 HO Heads from a 69 Firebird, CC'd to 82 CC's.  Ross Flat Tops, Eagle Rods, RPM intake, Stock Crank, Rock And Roll engineering solid cam.  234/238 duration / with .510 lift, but I have 1.65 Harland sharp rockers. Over the last few years I made a few changes.....none have really helped.  My best 1/4 mile time so far is 11.61 at 114mph. Its a all stock bodied 69 firebird with a 6 point bar in it, weighs 3550.  Anyhow I ran into a problem where the car was turning into a slug, running 11:80s, we thought it was the converter, it had a tight 10" ati converter and 4.10 gears.....so I put a loose TCI 10" in the car...didn't really make a difference. long story short my unilite distributor's limiter broke off so my timing was going up to 50 degrees.....and you ask if I can use a timing light, yes I can, I used a dial back light and it didn't catch the problem...the timing was fine up to 4000, it was above that it went through the roof.....So anyhow more changes.  I put a different cam in, it was huge, 252/263 at .050 hydraulic, with 108 lobe centers.  Took it to the track, and my tires got blown away...so we re-geared the car with 3.55's and new 29x9 slicks, and it ran well again...7.42 in the 8th mile, 11.70's in the 1/4 (96 degree day)...so the car is street driven...the cam was awful, made my car loud and run way hotter...so I went back to the solid 234/238.  Back the the 8th mile, its running 7.70 now....so Im thinking if I put the 4.10 gears back in I may get back to square one, but im also thinking the converter is loose, the throttle response is great with this car, but it seems like its not getting to the ground.  Im thinking its the converter..the ATI is in my other 64 GTO and it goes great..another street car with E heads, 250/258 solid cam with .600 lift and 112 lobe angle, Torker 2 intake.   It dynoe'd at 543 horsepower and I think the torque was close to 575.  I want to freshen up the firebird, the 16's are ported already and seem to be good to go, the compression is high...I just have a lot of runs on it an street time and I want to take it apart and inspect it all, oh and do a leakdown/compression check before hand. At the same time I want to change the cam..im thinking a Crower 60311...Solid, what do you guys think?? I chased my tail for a bit with this car, I think the biggest problem was the broken tab on the distributer advance, and maybe a bad set of slicks.  But I know I don't want to ever run that big hydraulic cam again, but may put the 4.10's back in. Let me know what you guys think.  

Read more: http://forums.highperformancepontiac.com/70/9459345/drivetrain-restoration/another-455-build-cam-selection-question/#ixzz2NXc3krpU  

Rockin,
As for cam choice, What's the red line of your motor? That Crower kicks in @ 3000 and goes to 6500. If you're only pulling to between 5-6K RPM, there's probably a better match cam out there for you. Has your Performer RPM been port matched? Has it been ported out and the heads also?  
Jim,

Hello

I’m not sure if I personally can offer you any suggestions at this point if ever simply because first off I unfortunately don’t understand your specific question or the end goal you are wanting to achieve because your question was so long I got a bit lost in it. Also you already have the first hand experience with your various set ups etc so again I don’t see how I personally can be of much help but I’m happy to try if you can explain your question and goal in a much simpler way for my simpler mind.

Are you asking for suggestions for the firebird set only?

Are you taking the 69 350 ho heads [which should be 48’s] off the firebird set up and installing the no 16 409/428 RA/HO heads back onto the firebird or are the heads you are referring to one in the same?

If the heads are not one in the same then why are you changing them?

If they are in fact different then what is the difference in flow and other mods between the two?

What is your specific purpose for NOT wanting to reuse the rock and roll 234/238 cam other than the fact that is hydraulic as opposed to a solid?

Are you trying to either match or improve your previous et’s with the firebird?

Quote - "I want to change the cam..im thinking a Crower 60311...Solid, what do you guys think??"

Think about what exactly?

Do want someone to tell you if they think you will get more hp out of this cam over the 234/238?

Why don't you just install the 250/258 cam you have in your gto since you seem to be happy with it?

Again I'm only asking these questions so I and others can have better idea of your goals so either I or others can better answer your questions.

REGARDING THE SLUG SYNDROME – Unless some other mechanical aspect changed to cause the increase of your et’s it makes sense that it was caused by the unidentified broken advance stop problem as you mentioned.

234/238 CAM – Even though this cam may look fine if you ever want to use it again then I would at least measure all the lobe heights with a simple set of veneer calipers to make sure they are not worn.  


Ken’s lists both the 16’s and 48’s as 400/428 ra [Except ra 4] and ho all with 72cc, Tuffnuff’s list shows the 48’s as 350 325 hp. Tuffnuff’s list does mention that it is incomplete and it’s hard to tell the accuracy of the applications of Ken’s list however I have found ken’s cc ratings to be fairly consistent.

428 375 HP 16/ 216 2.11/1.77 72 cc
428 390 HP 16/ 216 2.11/1.77 72 cc
1969 350 265 HP 47 1.96/1.66 8.6 cr
350 325 HP 48 2.11/1.77 10.5 cr.

Thanks  

i had a 74 firebird with a 10.3 to 1, 468 with 6.8 rods , solid 248/248 cam ,victor intake, 3800 stall,th350, 3.50 gears and 28 x 11 slicks. the car weighed  about the same. ran a best of 11.46 at 119. most of the time 11.50's

i think the 4.10's  would be better with 29" tires. 3.73 work the best with 28" tires on the 455's  i shifted mine at 5500!

it could be your transmision gettin week! what happened to your trap speed? where did it fall off at 60', 330,or top end?  
76 455/4spd TRANS AM
69 GRAND PRIX 406/5SPD

rockin646769

If the cam isn't pulling to it's potential, there maybe other limiting factors.
I'll list some not in any order of importance.

1.Carb too big or too small, secondaries?, bogg lean or rich?

2.Distributor mechanical advance stuck or not curved correctley for your engine

3.Valve springs worn out, or not the correct valve springs or maybe not shimmed correctley

4.Too much rear gear and your running out of RPM on the high end.

5.Cam timing chain stretched, "engine retards timing"

6.Cam could be worn out, or mismatched CAMponents

7.Carb running out of fuel, etc, etc.....

8.Wrong heat range spark plugs, or improper gap. Close the gap to .025 to .028

These are just a few things to start on.

Check the timing, set the base at 12* with the vacuum source disconnected, and plugged so the engine won't idle rough.
Then (Not knowing cam specs) set the total advance to 32* all in at 2,500 RPM.

Just go back to some basic settings, and see what happens.

Bob  aka-pepsi1  

Sorry, you are correct, the heads are ported 48's, they were the stock heads on my 69 firebird.  They were ported, Combustion chamber opened up to 82cc's, the intake was port matched as well, but both were opened up to the larger ram air IV intake gasket size.  The carb is an 830 holley.  My basic question is if when I freshen up my motor, I am thinking about a little larger cam, I shifted the car at 6000 when I had the large hydraulic cam in it, and about 5400 with the 234/238 cam.  I like the 60311 crower cam, and I know you mentioned to use the same cam I have In my other motor, I may do that, but why not try something different?!?!  The motor in my 64 has Butler / Edelbrock heads, so its not a direct comparison. So my goal here is to freshen up my 455 and gain a little more power at the same time.  

Hi,

I have eagle h-beam rods, so i'm not limited any particular rpm.  But even the last Pontiac motor I built with the E-Heads and 250/258 solid cam was done at 5700, even though we still pulled it to 6400.  Im thinking I need to do a compression test, then if that is all good look into getting the tight ten inch back in the car, and the 4.10 gears as well, since I mostly race 1/8 mile.  The heads and intake were both opened up to the RAIV gasket size so that should help.  I mean don't get me wrong going 11.63 with my setup is respectable but, I think I can do better, I have a stout bottom end and gobs of compression, so I think maybe a little more cam would be beneficial, and thought someone on the forum would be able to give me an good cam choice.  Thanks  

Hey Bob,

The car actually feels like it runs great..It just seems like its slowing down.  I have a 830 carb with 82 jets (Square)  I run 16 degrees of mechanical advance and 14 degrees of initial giving me 30 total, which it likes.  I have a good electric fuel pump and regulator set at 7 psi, 3.55 gears.  I'm only off a tenth or so since it was a new build, but I made some changes, thinking I had other problems (when after all the distributor was broke).  One thing I do know the big hydraulic cam I had in the motor ran 7.42 in the 8th, now with the smaller cam its running 7.70's, with no other changes.  So bigger was better...Initially when I ran the small cam I had 4.10 gears and the tight ATI converter. So I know that was a great combo, except the motor screamed in the 1/4 mile, so I do like the 3.55s way better for that reason.  So I want to leave those for now. After I do a compression test I will make a whether or not I freshen the motor.....Im thinking the loose tci converter is where i'm losing my time.  Thanks

Rockin  

Good point Rowsley,

I think it all went downhill when I put the loose converter in the car..when I had the ATI 10" it felt tight like a stock converter, but it was used when I ran my best times.  

Hi 70Bird,

The original 234/238 cam is a solid cam as well as the cam I want to replace it with, I wasn't sure you understood that.  Its kinda on the small side for a car that is mostly at the track, I think I can push It a little bit more.  It is comparable to that 224/234 hydraulic cam that summit racing sells, except theirs is a 114 lobe center, mine is 110. Thanks
Brian  

Rockin,
For your use, that Crower cam is a good choice (IMHO). I'm running a crower roller just a tad bit bigger than the 60311 and I think it fills the bill. I think you'd like it..  
Jim,

rockin646769:
Hey Bob,

The car actually feels like it runs great..It just seems like its slowing down.  I have a 830 carb with 82 jets (Square)  I run 16 degrees of mechanical advance and 14 degrees of initial giving me 30 total, which it likes.  I have a good electric fuel pump and regulator set at 7 psi, 3.55 gears.  I'm only off a tenth or so since it was a new build, but I made some changes, thinking I had other problems (when after all the distributor was broke).  One thing I do know the big hydraulic cam I had in the motor ran 7.42 in the 8th, now with the smaller cam its running 7.70's, with no other changes.  So bigger was better...Initially when I ran the small cam I had 4.10 gears and the tight ATI converter. So I know that was a great combo, except the motor screamed in the 1/4 mile, so I do like the 3.55s way better for that reason.  So I want to leave those for now. After I do a compression test I will make a whether or not I freshen the motor.....Im thinking the loose tci converter is where i'm losing my time.  Thanks

Rockin

Rockin
  If it feels like it lays over I would check the valve spring pressure first. It either your valve springs or as you said you cam is too small.
  Check the color of your spark plugs, if they are dark, and sooty the plugs may need to be changed for a different heat range.
  How Tall are your rear tires? You only have a 3:55 rear gear. It shouldn't be running out gear.

I would check the valve spring pressure. Even a brand new set of valve springs when you run 10 or 12 runs recheck the pressure. I'll bet they are down on spring pressure. When I set up new valve spring a add some shim, but working with them for along time I kind of know what they need....

Bob  

Hello

I'm pretty sure I have solved a major part of your hydraulic cam problem at least. When you installed the big hyd cam even though you ran quicker you had lowered your cranking compression to a level where it did not have as much hp/tq as it could have. The compression you had with the 252 cam also prevented it from revving with power up top. You went from around 170 cranking compression with the 234 cam to 140 cranking compression with the 252 cam. 140 is way too low!


The comp computer dyno says there is aporox a 7% difference in hp and 5% difference in tq from 140 crank comp to 170 using your 252 hyd [comp 305h] the way you did. If you simply use the 252 hyd cam with static compression increased to 12.5 [equaling same cranking comp of 232 can with 10.5 compression then I can't guarantee you it will lower your et from last time but I'm pretty sure it will at least spin your tires more, lol.

You will notice the sym said you actually lost hp/tq by installing the larger cam. I ran all tests using comps medium flow dual plane I will reconfirm difference using max flow intake. Post numbers later.

Dual plane medium flow intake

282s   451 hp  5000, 539 tq 2500  10.5 your current static comp

305h  430 hp  5500,  455 tq 2500  10.5 your current static comp

305h  439 hp  5500,  462 tq 2500  11.0  7.48 dyn 145 crank milked heads to 79cc not 78

305h  454 hp  5500,  474 tq 2500  12.0  8.13 dyn, 162.33

305h  461 hp  5500,  480 tq 2500  12.5  8.46 dyn, 170.90 crank



Dual plane max flow intake

282s  485  5000  552  4000  10.5

305h  495  5500  499  4500  10.5

305h  502  5500  507  4500  11.0

305h  520  5500  522  4500  12.0

305h  527  5500  529  5000  12.5

305h  539  5500  539  5000  13.3 =  98.98 dyn comp, 184.52 cranking comp needs 115 octane


Currently crunchin numbers back in a few!.


What octane gas are you using?

Are you opposed to a roller cam? Roller solid = max hp/tq!

I know you said you had “gobs” of compression but failed to supply an actual number that one could use so when I tried to enter the term “gobs” into the space reserved for the static compression in the dynamic compression calculator it simply sat there and did nothing when I pushed the “calculate” button [lol], so instead I decided to calculate it with other known criteria. Calcs listed below.

An estimate of optimal crank comp vs detonation risk on 93 pump gas is 160.0, 170.0 max per Jim Hand. Optimal crank comp vs deto risk using 115 octane race gas is unknown to me but I’m guessing a safe estimate would be 185.0

Your 234 hyd cam has approx 8.42 dyn, 169.85 crank comp in a 10.7 static comp motor with your stroke and rod length.

Your 252 hyd cam has approx 7.29 dyn, 140.83 cranking comp in a 10.7 static comp motor with your stroke and rod length.

Both your 250 solid cam and the 247 solid crower 112 60311 have approx 7.98 dyn, 158.46 cranking comp in a 10.7 static comp motor with your stroke and rod length.

The dyn/cranking numbers posted above suggest that based upon a [your current max possible] static compression ratio of 10.7 that at the very LEAST, you need to increase your static compression to a level that will raise your cranking compression level to the “ideal” levels mentioned above to extract the optimum amount of performance from each particular cam. The cam also should not exceed the amount of max flow the intake/heads can flow. Since you have not provided those numbers I personally can only give you a “guestimate” of which cam that might be. Ideally the head flow, cranking comp and cam should all be “best” matched for overall optimum performance etc. but it sounds like you may know that anyway.

CRANKING COMPRESSION – crank comp levels reduce by approx 5 lbs for every 1000 ft in elevation.

The following intake closing times are estimates, it is impossible to know exactly what yours actually are however they are a very useful reference in this case because comp does not use “long advertised duration vs duration at .050 ratio. Therefore the numbers generated below should actually be a best case scenario and your actual cranking compression numbers are much more likely to be similar or less than those below but not likely to be more. In other words your crank comp with each actual cam you might very well be even less than those below.

“234/238 solid fulper cam” A similar non roller solid comp 282s has an intake closing time of 67 degrees abdc.

“252/263 hyd 108” A similar non roller hyd Comp cam 305h has intake closing time of 82 degrees abdc.

“250/258 solid 110” A similar non roller solid Comp cam 294s has an intake closing time of 73 degrees abdc.

“247/252 soild 112 crower 60311” A similar non roller solid Com cam 294s [same as above] has an intake closing time of 73 degrees.

The most static comp you can get from your motor according to the calculator is 11.22. This is done using a 0 deck block and a 73 cc head. If you remove 5 cc from your head they will be 73cc. The problem is that once your heads have been surfaced beyond.025 from stock it becomes likely you will have to mill the intake to properly fit the heads. Your head guy can measure this distance for you.  

11.22 static compression generates the cranking compression numbers below.

Cam with 82 degrees abdc = 7.93 dyn 157.17 crank comp. Good for 93 pump gas.

Cam with 70 degrees abdc = 8.94 dyn, 183.47 crank comp. Estimate for 115 race gas.


I might run one of these below and adjust compression for octane level used.

Below is a list of a few cams for consideration out of these I would probably run the 290b-6 comp but I would have them grind it out of a roller blank with the lobes designed for a roller lifter. Then I would adjust my static comp however I had to, to get the crank comp to a point where it required around 12-115 octane race gas. You could also run it on 93 if you lower your static comp slightly with a thicker cometic brand head gasket available from Butler perf. Or run with existing compression and add a little race gas with the 93 octane pump gas.

288r solid roller             288/288 244/244 5.50/5.50 110/106 2200-6500 rpm in close 70 deg abdc

308r solid roller             308/308 262/262 5.75/5.75 110/106 3000-6700 rpm in close 80 deg abdc

290b-6 solid non roller   290/304 255/266 5.40/5.40 106/106 3500-6500 rpm in close 71 deg abdc

300b-6 solid non roller   300/314 265/276 5.62/5.56 106/106 4300-6500 rpm in close 76 deg abdc

Crower 60311              292/302 247/252 5.05/5.17 112 3000-6500/7000 rpm in close aproxx 73 deg abdc


Hope this info helps  

Rockin,
For your use, that Crower cam is a good choice (IMHO). I'm running a crower roller just a tad bit bigger than the 60311 and I think it fills the bill. I think you'd like it..  


I chose that cam because of its lower lift may be easier on valve train parts.  I have fearra valves which are the .100 long length, and good springs and all that, but I need to keep it under .600 lift.  Most other cams have a higher lift.  Thanks

Brian  

Hey Bob,

The car never lays over and dies...it's just coming up way short when compared to my 64 gto.  11.70's aren't bad times, but on the street I floor it, the revs come up fast, it will pull way past 6 grand, but what's the use in that..I think I need the bigger cam to spread out the torque and rpm range.   I think the loose converter is the problem I am thinking. 3.55 gears are great for the street and track.  And like you suggested, the springs may be tired.  I am going to do a compression check off that bat.  And a few guys suggest the 60311 crower would be a good fit.  Thanks

Brian