Good morning, I am presently running a 77 400 with what I believe to be a 067 cam. I will be replacing it with a 76 455 with all the same bolt ons with the exception of ported 6x=8 heads and a ram air 3 (744) camshaft. My question is how much will the cam change affect my off idle performance, will I lose a lot of power below 1500 rpm or will the extra displacement of the 455 make up for it? I am asking because I presently have 256 gears and 2.64 first gear. It performs well now but driveability depends on the low end torque. The carb is 800 cfm Q-jet, stock 71 Gto cast iron intake and ram air 3 exhaust manifolds with 2.5 exhaust with X=pipe. Thanks in advance.
I can't comment on your cam but don't you think you should consider 3.xx gears for your car?
My coupe had a 850 cfm themoquad, Crane Thunderball cam, 3.42 rear end and low 1st gear in my SuperT-10 4sp. I could open that puppy out right from 0 (/w no spring to limit secondary opening) and no bogging in the carb. Huge diff over my 2.73 rear end.
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A 4.55 with 101 cc heads allbeit ported with 2.56 gears is not a good combo. Running such a cam with the lift and overlap may kill your compression even more than the 8.7 I calculated.
First of all, you'd be better off with a set of #64 heads with 87 cc. Could you make those heads you have work? Sure, but you'd have to mill quite a bit off the deck and intake side to raise compression. Milling that much off will likely cost you ballpark $300.
The other issue is the camshaft. I had a 400 with 5C heads (94cc) with a comparable RAIII grind. My problem was vacuum, idle quality and streetability with an auto. In essence, with that 744 grind and no compression, you will no doubt have issues.
All things being equal, with a 455 and 2.56 gears and a manual..you are so so. I would bring the rear gear ratio with a 455 and a manual to 3.08 plus or minus. Also, you must increase the compression with that 455 before you even consider such an aggressive cam. Otherwise, you will fall flat on your face...engine will not idle, idle quality will be poor, engine will load up, vacuum signal will be scarce.
I see you are in BC. Finding proper heads to start with is #1. I would call Super Duty Firebirds in Washington and see what he has. For all intents and purposes, it may be more economical to have your heads milled down at least 70 thou on the block side and 40-45 on the intake side for proper geometry.
Thanks for the responses. I was hoping to hear from someone with first hand experience with this cam. I would like to stay with the 2.56 rears because I do quite a bit of highway driving and the limit here is 120 kph ( a little over 75 mph I think) and like I said earlier the combo with the stock 400 works well but is worn out. I will get the cr of the 455 up to 9.0 to 1 or maybe a little higher and go for a different cam with less duration. to keep the dynamic ratio up. The summit 2801 or Pontiac 068 look ok. Any suggestions ?
I have had a ra3 cam in a 350 and three 400's you really need a higher stall converter and at least 3.55 gears with an automatic. No experience with the 2801 cam but I did install the 2800 in a 400 with #16 heads which is a nice cam if you have a stock converter and 2 series gears. Smooth idle and great for an everyday driver.
I believe he is running a 4 speed with 2.64 first gear...unless I missed something. With a 400, yes, with the bore/stroke and 3.55 gears and a RAIII cam, definitely if you have the compression. By the way, what transmission are you running?
However, 55 more cubes, more low end torque, 3.55 is too steep a gear for a 455 with an M20.
If you are daily driving...personally, a 3.08 with a 400 and #62 heads (78-80cc)
Here is my thinking...If you use 2.56 rear gear with a 455 and a daily driver and those heads, you will be sucking fuel down so bad...because the setup is mismatched and inefficient. If your concern is daily driving, why the 455? why such a radical cam? Why a mismatched rear for a torque monster? You will not be close to getting the full potential out of that 455, those heads, that cam and rear..you are probably looking at 8-10 mpg, crappy low end, idle issues..and no performance at all. I say you would be in the 180-200 HP range to be honest. a 455 came with 067 grind and similar cc heads and was pushing only 200 hp. Now you are going to increase cam size by leaps...
An excerpt...from 1975..regarding the 455.
"Rear axle selections were becoming increasingly limited. Automatic/400 equipped Trans Ams had a 2.56:1 rear axle ratio . A 3.08 gear was included when the 4-speed was specified. Included as part of the "Performance Package" in which the 455 V8 was the major element, the ratio was a more satisfying 3.23:1
And what makes the setup even worse so to speak...the heads have "X" amount of porting. Do you have the flow numbers?....more flow, less restriction. That fact adds to the "fall flat on your face" effect.
You need 9 to 9.7 to 1 You need a smaller 067 grind. (IMO an 068 may be too harsh for a "daily driver") You need gearing in the 3.08 (preferred) to 3.23 arena to bring the potential of the 455 inline.
Based on bore/stroke differential between the 400 and 455 and where the power bands are at...the 400 will wind up faster than the 455.
Honestly, I would confer with Butler on this...
HP CI TR BC CR CAM HC Carb My notes...
360 455 M WA 10.25 68 64 4 70 (068 grind 64 87 cc heads) 370 455 M WG 10.25 68 64 4 70 (same as above) 370 455 A XF 10.25 67 64 4 70 (smaller cam) 360 455 A YA 10.25 67 64 4 70 (smaller cam) 360 455 A YC 10.25 67 64 4 70 (smaller cam) 360 455 A YH 10 67 15 4 70 (small valve heads (1.96/1.66) 335 455 M WC 8.4 68 197 4 71 (Round port heads 335 455 M WC 8.4 68 197 4 71 (round port heads) 280 455 M WG 8.1 66 98 4 71 (smaller cam, small valve 1.96/1.66 114 cc heads) 325 455 M WJ 8.1 67 66 4 71 (same cam as above, large valve same 114 cc heads) 335 455 M WL 8.4 68 197 4 71 (round port, RAIII cam) 335 455 M WL 8.4 68 197 4 71 (same as above) 325 455 A YC 8.1 67 66 4 71 325 455 A YC 8.1 67 66 4 71 325 455 A YC 8.1 67 66 4 71 325 455 A YC 8.1 67 66 4 71 335 455 A YE 8.4 68 197 4 71 335 455 A YE 8.4 68 197 4 71 280 455 A YG, YA 8.1 66 98 4 71 300 455 M WD 8.4 68 7F6 4 72 (round port 111 CC) 300 455 M WM 8.4 68 7F6 4 72 250 455 A YA 8.1 67 7M5 4 72 300 455 A YB 8.4 68 7F6 4 72 250 455 A YC 8.1 67 7M5 4 72 300 455 A YE 8.4 68 7F6 4 72 200 455 A YH 8.1 66 7L4 2 72 250 455 A ZH 8.1 67 7M5 4 72 250 455 M WT 8 67 4X 4 73 250 455 M WW 8 67 4X 4 73 250 455 A YA,XL 8 67 4X 4 73 250 455 A YC,XE 8 67 4X 4 73 250 455 A YD,XM 8 67 4X 4 73 250 455 A YK,X7 8 67 4X 4 73 250 455 A ZC,ZA 8 67 4X 4 73 250 455 A A4 8 67 4X 4 74 250 455 A AU 8 67 4X 4 74 250 455 A UX 8 67 4X 4 74 290 455(SD) M W8 8.4 323 16 4 74 250 455 A Y4 8 67 4X 4 74 250 455 A Y6 8 67 4X 4 74 290 455(SD) A Y8 8.4 323 16 4 74 250 455 A Y9 8 67 4X 4 74 250 455 A YR 8 67 4X 4 74 250 455 A YU 8 67 4X 4 74 250 455 A YW 8 67 4X 4 74 250 455 A YY 8 67 4X 4 74 250 455 A Z4 8 67 4X 4 74 250 455 A Z6 8 67 4X 4 74 250 455 A ZU 8 67 4X 4 74 250 455 A ZW 8 67 4X 4 74 250 455 A ZX 8 67 4X 4 74 200 455 M WX 7.6 67 6H 4 75 200 455 A YU 7.6 67 5I 4 75 200 455 A YW 7.6 67 5I 4 75 200 455 A ZU 7.6 67 6S 4 75 200 455 A ZW 7.6 67 6S 4 75 200 455 M WX 7.6 67 6H 4 76 200 455 A Y3 7.6 67 6H 4 76 200 455 A Y4 7.6 67 6H 4 76 200 455 A Y8 7.6 67 6H 4 76 200 455 A Z3 7.6 67 6S 4 76 200 455 A Z4 7.6 67 6S 4 76 200 455 A ZB 7.6 67 6S 4 76
Well, you get the hint....
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1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
Thank you for the involved response and I will try to show my rational in this. Trans is super T10, 2.64 first, 1.75 second. Like I said the present engine is a 77 400 rated at 180 hp (sae net). Internally the only change was to upgrade to the 067 cam. The stock cam for these engines was a #549431 with only .364 lift and 264 (Wallace Racing) advertised duration. The 455 is near new and appears to have the same cam (the lift measures the same.) I was hoping to duplicate the low rpm power of the existing 400. Even with the 256 gears it pulls away acceptably on hills and will light up the tires in first without use of the clutch and you can use 4th gear in town. The 400 has 7.6 compression, the same 6x-8 heads (unported). What it doesn't have is a lot of power past that. I have a set of ac delco rebuilt 6x- 8 heads that I am mostly done the Jim Hand style port job on. I felt that the 455 with the ported heads (15% more displacement and maybe 15% more flow) with the added benefit of a little higher compression mated with the right cam should give me all the bottom end power I have with the 400 plus a bunch more above that. I only suggested the 744 cam because I already have it from another pile of stuff I bought. I guess I'm looking at it from the perspective of maintaining and improving what I have and you are looking at it as what could be. I would like to add that unless I'm reading your specs wrong it lists the wrong cams in the 76-77 engines (067 not used in mine at least) and the hp ratings beginning 1972 are at the back of the trans with all accessorys functioning. (alt, water pump, a/c , trans) so all the ratings dropped 50-70 hp. That makes the 180 and 200 hp ratings of these two engines even more obscene than they really are. My 400 definitely makes more power than a 1965 195 hp 283 and the 74 455sd motor made more than 290 hp At any rate I'm stretching my knowledge to the limit to get to this point and I'm very likely wrong about my assumptions about what will work. If need be I will change the rear end, it will just come after the engine swap . I will do more research before I set this one in stone and thanks for your help. Neill Oh, and the other question, why. I have it, its there, I have to use it just to say I did. And the 400 has developed a very audible Knock above 2000 rpm
You can go BACKWARDS in HP by over camming and over porting. Engine building is not a one way is up street. Not that within the chart above, nowhere after the 7F6 round port heads did Pontiac use a cam larger than an 068 in a 455. 2 reasons. Compression and smaller valves.
You said Wallace Racing was your reference for the 549431 cam...Well, Wallace Racing shows me that for ALL 455's with 6X heads 067 grind was used for all 4X, 5C, 6X, 6S 6H heads. 455 Just type in 455
Pre 72, HP ratings were gross HP, after that, they were rated net HP.
Here are the different 6X/H and S heads built between 75 and 79
You have a difference here...a high revving 400 that loves to get to the power band quick, versus the grunt of a 455 that likes to make it's power down low. You have a different bore/stroke ratio on both engines. You also have different rear end requirements for both as to the optimal bang for buck benefit.
I have a 455 rated in my 68 Firebird with 3.36 gears. I also have a 400 with 3.36 gears that has the same transmission. IMO, and my Pontiac buddies opinion, the 455 would be better suited with a lower gear 2.93 or 3.08 as there is way too much torque for the steep gearing and streetability. Fun with a 3.36? YOU BETCHYA! As a daily driver? NO way!
I would close with calling Butler and asking...I have a 455 with 6X-8 heads that flow "X" amount and have 2.11/1.66 valves. (most guys who port 6X-8 heads for 455 also install larger 1.77 valves) I also have a 2.56 rear and using a ST-10 trans with a 2.64 first. What camshaft would you recommend? In the same breath, I would fish for answers from Butler as to the feasibility of building the 455 for daily driver use as you intend versus building the 400. I am stuck on daily driver...You have a 400 and a 455. The 455 is streetable sure, as a daily driver?....Why spend an extra 20% on fuel with a 455 if you really will not be utilizing the added benefit of your build?
A guy came to me years ago wanting to build an engine for his vette. He wanted to spend the money all on the engine to get 550 hp. Mind you, this was in the early 2000's and it was a daily driver. He wanted ported heads and a cam..that's it. nothing else. In essence, it's not as easy as a head and cam swap and nothing else. What about beefing up the trans? Axle shafts? suspension? free flowing exhaust? upgrading throttle body...
All I am saying is that an engine build just isn't cam and heads...it's everything that needs to be considered.
If I were you, based on your daily driver desire...I would build the 400, install 3.23 gears with that T-10 and go with a 067 or o68 grind and a set of 80 cc heads. You will have plenty of grunt, torque and smiles.
What you could do is find any set of large or small valve heads that are ready to go and bolt them on...such as 1970 #15 or #16, 1968 #46. The 1970 #15 were small valve but are gross rated at 360 HP on a 455 with an 067 grind. I just want you to try a higher compression head first on that 400 if still in the car. Find ANY head from 67-73 that has an advertised combustion chamber size of 80-85 and bolt them on. You will be surprised at the difference compression has.
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1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
And sorry for the rant...I get a little long winded, sidetracked and too much passion when it comes to my past learning curve. There will be many different opinions on this...and by NO means am I right or 100% correct...comments and advice is based on personal experience.
I was where you were once long ago on a build..5C heads..400, and no power. Wanted bigger...wanted more.
The key for me was the hours of toil, the gobs of cash...when all I had to do was switch out heads that I had in my garage and voila!
The compression increase from 8.0 to 9.4 solved 90% of my issues. No loading up, no idle issues, had some carb issues with running a 3.55 gear and a Th400. Solved that by swapping out a Holley for a Q jet.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
If he did that..he would like to be in the 3.90 to 4.11 gearing depending on the trans gearset.
The salient fact regarding compression and cam remains. You can have an OD trans and steep gears..but without a properly configured engine...the OD transmission is moot.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
yes I could but 5 speeds that hold up to the way I push them don't come cheap. I'm just trying to work with what I've got and a few good decisions go a long way towards a happy combination. It won't kill me to change rear ends later, I probably should go to an 8.5 just for safety's sake. Thanks again Banshee
Just adding to what's already been said.....and my .02 cents.... the lobe separation angle LSA on the cam will have an impact on your trapped compression. Some cams like Comp cams 268XE has a 106 deg. LSA which will trap more compression that a 744 in the 114 deg. range.
Advancing the cam will also have an effect when building the engine. Lot's of things to consider but all good info.
FWIW I did have this cam in a 400 with maybe 7:1 compression. Ran great with a 4 speed and 3.73 gears and the cheapest gas you can find. Sold the engine and it now is in a 68 with an automatic and 3.73 gears that's running around the country somewhere. Tuning is the key.
