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 cam advice for 455 in full size '74 please?
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Tribal Scout

7 Posts

Posted - 20 Apr 2017 :  07:51:41 AM  Show Profile  Reply with Quote
G'day All,

I've read many of the post here about cams to the point my head is spinning a little (a lot).
I'm hoping to find some up to date info on a cam for my '74 Pontiac Grandville.

My '74 has the HO option (Y code), which I don't think actually means anything different to other 455's of the same year apart from dual exhausts? The engine has been rebuilt 7000miles ago with a mild (very mild) cam that the previous owner fitted for economy...
Static compression sits at just a smidge over 8:1, which is what they were standard? I think its 4x heads on it from memory, but whatever was factory as they werent changed (previous owner rebuilt the engine as he didn't use the right oil and wiped a couple of cam lobes).
I have some bits and pieces i've collected here that havent been fitted as yet, just sitting in the boxes. I have edelbrock performer manifolds, a holley 850cfm 4150 vac sec that i'm thinking is too big now but come as a package with a manifold, a quickfuel 750, a couple of pertronix flamethrower HEI distributors, along with aluminium water pumps and some cosmetic stuff. I'd like to think I might have a set of the RamAir manifolds by the time I get to putting a cam in it to flow thru the dual 2.5" exhausts and fit some of the bits as well.

As you know (or not) the Grandville convertibles are heavy cars. The 74 in question has 2.92 gears with TH400 with a shift kit and stock converter.
Its never going to be a race car of course, but I would like to not only waken it up a bit, but also have it sound like its got some mumbo (read noticeable idle) and pull hard thru to a mind numbing 4500 or so. I guess sound fast with reasonably decent manners is the order of the day. We live outside the city, so most of the cruising is 50-60mph, but we like going to show'n'shines and classic car cruises in town.

I've read so many posts, i'm plain confused as to what cam I should be looking towards to build some dynamic compression and also what is going to be more suited to a very heavy car with stock converter.

I've been offered a Magnum 270H cheap, which reads ok but seems to be yesterdays technology after reading (and reading) and just because its cheap, it won't work out to be a good deal if its just wrong for the car. I'm thinking maybe one of the Lunati Voodoo or Comp Cams XE family grinds, which are a popular recommendation around here, but usually for much lighter cars.
I did have recommended the .041 factory grind cam, but i'm thinking its not going to be stock converter friendly. I have been offered another cam for free along with the Magnm 270H, but the owner isn't sure what it is (engraved on the end is 5667/5676 CC Y3913-12 with an 'A' stamped in it) and nor am I. The guy has got a Butler built engine and thinks it may have been one of the cams he got and didnt use, but isn't sure hence why it is offered free. I'm aware that free is no good either if it means pulling it out if it doesn't suit.

If anyone has a few moments to provide some advice or can even advise on what the cam listed above actually is, that would be most appreciated. As you can imagine, early Pontiac experience is rather thin on the ground down here and if I can get a head start in the right direction from you guys who have probably forgotten more than i'm ever likely to learn (especially starting at my age) about these engines, that would be beaut!

Blued and Painted

3505 Posts

Posted - 20 Apr 2017 :  11:58:03 AM  Show Profile  Reply with Quote
We will need the secondary head number. http://butlerperformance.com/files/images/cylinder_heads/6xheadlocate.jpg ..
850 cfm is not to much for a 455.
Test show the factory intake will make more power than the base model eldebrock performer.
If it is a low compression engine, i would not go over 220 degrees intake duration for drive-ability and tune-ability. This cam will have some attitude and would be as large as i could recommend. https://www.crower.com/camshafts/pontiac-287-455-hot-street-beast-hydraulic-cam-278-h.html
Complementing components might be a 331 rear gear ratio, 2500 stall converter, modified log manifolds or ram air exhaust manifolds with mandrel bent exhaust pipes.

Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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Tribal Scout

7 Posts

Posted - 21 Apr 2017 :  07:38:53 AM  Show Profile  Reply with Quote
I think I got some info of help.
The heads are 4X, are both date coded K193 (Nov 19 1973?) and have screw-in studs (which I checked to be sure). Unfortunately, and im sorry i looked, they are stamped 1H which are btwn 112-114cc?

I'm fortunate that the previous owners brother who put it back together was a mechanic and wrote everything down. I'm sure the previous owner kept every single piece of paper related to the car also and gave the lot to me when I bought it.

The scribble sheet has a chamber CC of 109, which means it probably got milled around .020"? It also says the pistons are between .012" and .015" down the hole at TDC. The gaskets fitted are 8518PT Felpro, which list as .045" compressed thickness?
The only thing i cant be sure of is what volume is consumed by the crap pistons, which are 4 valve relief cast Badger #P591 +.030". I have assumed 6-8cc for valve reliefs, which is all I can find for similar (TRW/SpeedPro etc) but may be way off.

I've plugged the above figures from what I can find into Butlers compression ratio calculator just now.
With bore of 4.181" and stroke of 4.21" and using .015" piston to deck, .045" gasket and 109cc head volume, it gives me 8.43:1 with 5cc valve reliefs and 8.26:1 with 8cc valve reliefs, so if i've done that correctly and it's accurate, i'm somewhere inbetween?

I don't want to fit alloys to gain static compression. I would love to, but the exchange rate, tax and freight makes them very expensive downunder and I would probably rather spend less money on a Pro-Charger or some other under bonnet/hood supercharger and run mild boost than put a set of alloys on unless a head crapped itself. Iron heads aren't plentiful downunder, so buying another set to probably rebuild is in the same basket to be honest.

Whats in it now is an Aussie brand "Crow Cams" HFT #90631.
Duration is 200/208 @ .050" and advertised 260/266. Lift is .4017/.4154 with 1.5 rockers (.2678/.2769 at the lobe) on a 112LSA with 2degrees advance ground on the cam and installed straight up. Valve timing is -10deg BTDC inlet/+38deg BBDC exhaust @.050" or 20deg BTDC inlet/67deg BBDC exhaust advertised. It also says inlet lobe lift at TDC on overlap is .033".
It sounds pretty much stock to my old ears.
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Tribal Scout

7 Posts

Posted - 21 Apr 2017 :  07:42:44 AM  Show Profile  Reply with Quote
ps: i don't want to fit a high stall or change gears, but will fit RamAirs to run into the twin 2.5" system and also run an H/X pipe which will probably help.

Edited by - BigBazz on 27 Apr 2017 10:05:13 AM
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Tribal Scout

7 Posts

Posted - 27 Apr 2017 :  10:11:11 AM  Show Profile  Reply with Quote
went to a large cruise on Tuesday, had some cams suggested to me that may be appropriate for my setup. i had a look at them in the respective catalogues, most of them have suitability listed as daily driver, stock converter with ac/ps/pb and these are the ones below (i removed some that seemed too much).


Lunati StreetMaster 10510312
Lunati VooDoo 60901 or 60902
Lunati High Efficiency 10510211
Comp Cams XE256H or XE262H
Comp Cams Hi Energy 268H
Comp Cams - Dual Energy 265DEH or 275DEH
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Sitting Bull

139 Posts

Posted - 27 Apr 2017 :  11:08:31 AM  Show Profile  Reply with Quote
Sounds stock all right.

4X-1, so you at least have the 2.11 intake valves. And they will flow enough below 4500 rpm, maybe.

Are you planning to totally rebuild this thing?
or just leave as much intact and just very carefully slide the cam out the front and put in a new one, with new lifters, same pushrods, same rockers, and same springs?

I second CortComp's recommendation to stay below 220 degrees.

Be careful about the total lift. If you know the spring numbers then pick the lift to at least make use of your available lift and improve things a bit. The unported 4X heads won't benefit from anything more than .450 likely anyway. You could select the cam for .450 with a 1.5:1 rocker. Then you can get 1.65 rockers and try those. If there is no improvement then go back to 1.5. All that can be done without any major engine work, in your garage - assuming the springs can handle .500 lift.

71 LeMans Sport Convertible with 340,000 miles driven year round since 1994.
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Tribal Scout

7 Posts

Posted - 03 May 2017 :  11:21:41 AM  Show Profile  Reply with Quote
the motor is only 7000kms or so old, not really wanting to do anything apart from cam and lifters, perhaps timing gear (so i can advance it a few degrees if needed) and maybe springs if needed.

i've taken the liberty of listing duration/lift below to make life easier for anyone to comment?

lunati streetmaster has 221/230 w/ 454/454 lift <- says stock valvetrain

Lunati VooDoo 60901 has 213/219 w/ 455/468 lift <- says a/c p/b and stock converter

Lunati VooDoo 60902 has 219/227 w/ 468/489 lift <- says daily driver

Lunati Hi Efficiency has 207/217 w/ 432/454 <-says stock parts and access

Comp Cams XE256H has 212/218 w/ 447/454

Comp Cams XE262H has 218/224 w/ 462/470 <-says stock converter

Comp Cams Hi Energy 268H has 218/218 w/ 454/454

Comp Cams - Dual Energy 265DEH has 211/221 w/ 442/465 <- says good everyday w/stock exhaust

Comp Cams - Dual Energy 275DEH has 219/228 w/ 462/480 <- says hi perf street w/ stock converter
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Bill Boyle
Horse Feathers (Charter Member)

5126 Posts

Posted - 03 May 2017 :  2:45:11 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
I ran the 270H in my 400 with low compression heads. I wasn't unhappy with the performance. The lift is .470" which is just slightly above the max for stock Pontiac springs. Better springs with a slightly taller installed height are called for IMO.

Yesterday's technology? The 068, 067. 066 Pontiac grinds as well as the 041 were old when Comp came up with the 270H. So, true it's not new, whereas Pontiac grinds are ancient by today's standards.

The 268H is slightly milder than the 270H. You could probably get by with it, using stock springs, but I don't think you'd be too excited about the performance in your 455. Either cam requires an adjustable valve train and definitely new hydraulic lifters.

If you can get that 270H for dirt cheap, spend the money on new lifters and a set of aftermarket springs and you won't be disappointed running between traffic lights or cruising down the road.

"Dedicated to keeping the classic Pontiac engine alive."

400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Tribal Scout

7 Posts

Posted - 17 May 2017 :  08:37:13 AM  Show Profile  Reply with Quote
hey bill, thanks for the input. unfortunately the cam that was to be a 270h actually wasn't when measured and subsequently run on a cam machine. it worked out at 440/440 with 216/216 and the engine builder said take it back, too small for me, so back it went. if it had been the 270h i would have kept it. at the behest of the same builder who said dont compromise on a factory grind that isnt a match for what i have, ive since made a call to an aussie cam grinder and awaiting for some info back to what may suit. the guy with the cams has a nice set of comp cams valve springs cheap, so it worked out ok in the end (and he wants to buy one of my neons, so even better).
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Steve C.

1953 Posts

Posted - 17 May 2017 :  10:29:39 AM  Show Profile  Reply with Quote
Play it safe and upgrade the valve springs.
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