Hi, just thought I would post this because there are a couple of engines being built here. My goals for my engine were to have a bunch more power than I had with my tired 77 400, to maintain excellent low end torque and driving manners, to have an engine that was reliable and easy to tune, and to work with my 4 speed and 256 rear gears. I am not an expert engine builder and I am not pretending to Know what the experts know. The engine is a standard bore, standard crank 76 455 that I took to a shop and had them measure everything, hone the cylinders, polish the crank, hot tank and install cam bearings and frost plugs and oil gallery plugs. Everything measured up very nicely and the shop supplied me with all of the parts to assemble it. The heads are 6x-8 that had new valves and seats ground when I got them. I read Jim Hands book and ported the heads myself but did not change to 1.77 exhausts. It has an 800 cfm Quadrajet, stock 70 400 intake and long branch exhaust manifolds. I measured deck height, combustion chambers etc and came up with 8.96 -1 compression, so now what cam? I studied everything I could find and I still blew it. I chose a comp cams 275 deh, 275,277 advertised, 219-228 @.050 and 110 lsa . It performs well, It does everything I wanted it to do and has a nice idle. The problem is that with this cam I have a dynamic compression ratio of 7.3 according to the "project Pontiac static and dynamic compression ratio calculator" that I used and with my iron heads this requires a steady diet of 91 octane fuel. Its only a 400 or so hp engine, a different cam choice with a dynamic ratio of 6.7=6.9 would have given me everything I wanted but running on 87 octane instead. The Crower 60916 has specs that would have done this well I think with a 4 degree later intake closing angle and 112 lsa. However all is not lost, not only am I stupid, I am also lazy and I did not take the time to remove my inner springs for cam break in. I have about 700 miles on this combo now and the jury is still out on weather the cam survived or not. I have had to re adjust the rockers and even with 1 full turn of pre-load I still have a couple noisy lifters after warm-up. Anybody with thoughts on this? also the cam called for 106 installation, and mine is at 105 degrees. Can I retard the cam 4 degrees to 109 and hopefully achieve my goals? Hopefully this helps someone else and if anybody can give me feedback on my issues I would really appreciate it. Neill
I've never owned or driven a 455 in anything but I have years of experience with 400s and several different cams and from what I gather talking to other people it sounds like that cam is a bit on the small side for your cubic inches. I currently have the Crower 916 in my 400 and it is a mild cam even for this motor. Just guessing but I'd bet it doesn't run too much better than your 400 did. 400s can be made to run real strong but it takes a bit of work. 455s with a few of the right components, from what I understand, run real strong in an Fbody right out of the box. Personally I think you rear end ratio is killing any chance you have at a decent street car. I had my 3.23s go bad on me and swapped in some 2.97s for about a year and with my 4sp it was all I could do to pull away from a stoplight with out double clutching. It really was not as enjoyable to drive around town.
I'm new to the site, but not exactly a spring chicken.
If I understand your post, you want to lower your dynamic compression enuff to get by with running 87 octane gas. So, it's my understanding that you need more advertised duration. The steep ramp cams work just the opposite. They have much lower advertised duration in relation to their dur at .050 lift. Therefore, they will increase the cylinder pressure, rather than lowering it.
So, with this in mind, the smallest cam I'd recommend for your 455 is a Summit 2802. It looks to have about 20 degrees more advertised dur than the Crower 60916 you mentioned. That should lower your DCR considerably. Will also be a lot cheaper.
Now, for me personally, I would not even consider anything short of a RA4 grind, with Rhoads lifters. But some guys hate the thought of the "old school" RA4 / Rhoads combo and can't stand the "ticking" sound the Rhoads make at low rpm. If you are one of these guys, then the Summit 2802 may be your best bet. IMO If I'm wrong, it won't be the 1st time. I would also consider running 91-93 octane gas. It's not that much higher.
However all is not lost, not only am I stupid, I am also lazy....
I can't help with your question but do appreciate your candor!
1968 400 Coupe, verdoro green, black vinyl top, auto 1969 GTO Judge coupe, Carousel Red, manual 1971 Trans Am, cameo white, auto 1970 Buick Skylark Custom Convertible 350-4(driver), Fire Red, white top, auto 1972 Buick GS Stage 1, Royal Blue, black vinyl top, auto
I recommend an intake duration of at least 230 @ .050 on a 114 lobe separation. Wider lobe sep has wider power band and works better with low gears. 110 lobe sep has a narrower power band. Better for high gearing and keeping engine inside power range during shifts. Prefer 3.23-3.55(3.73 with big/tall tires) for street. 3.73-4.11 for drag racing.
I recommend an intake duration of at least 230 @ .050 on a 114 lobe separation. .
Yep, and unless you have a cam custom ground, the RA4 grind is about as close to that as you'll find. Several cam grinders offer their version of the RA4 cam. The Melling SPC-8 from Ebay is always the cheapest--about $100 shipped.
And, if you're not gonna use Rhoads lifters, the Howard's 410051 or the Crower 60243 might be a better choice. They'll probably have a smoother idle than a RA4 grind without Rhoads lifters, because of slightly less advertised duration. The reason I prefer the Rhoads / RA4 combo is because it widens the power range, gives a smoother idle, more vac, and more bottom end torque. And the "ticking" sound doesn't bother me a bit--just part of the "High Performance" sound. Now I'm not posting links to the Summit site because they have the best price on all these cams, but because they have all the specs right there, easy to read.
Now for those who would like to get a cam custom ground to their own specs, Bullet Cams has a list of MANY possible lobes. They'll grind 'em like you want 'em.
thanks all of you for all the responses and the links. I have to admit one of my concerns in all of this was over camming this setup. Now that I know what 219 @ .050 is like, 231 is much less bothersome and my next cam will be bigger.I did have some people try to discourage me from going more than 220. Any thoughts on which cams are the most dependable? Do you guys remove your inner springs for cam break in? I have Crower 68404 springs if that matters. Thanks again. Neill
I'm thinkin that for a little more, you can switch to a mild street roller set-up and have the advantage of more power, without having to worry about cam break-in, lobe failure, or running special, high priced oil. It seems to me that the whole idea of using a flat tappet cam is the price. But when just the cam costs $250-$300, why not spend a little more and go roller ?
But again, that's just my opinion. And as we know, opinions differ.
I have a roller, the reason being I didn't want to pull the engine and start over if a flat tappet cam failed. I know flat tappets are dependable and very few fail, but I wanted the piece of mind. I can relate to your cam woes, everyone wanted me to buy their wild cams even though I told everyone and their dog I wanted a street/road engine not a race engine. This all boils down to cylinder pressure. More pressure, more power. More pressure, more potential for detonation. All the talk about static compression ratio means little to me, as a low static C/R engine can make more pressure, depending on valve train, than a higher static C/R engine. All your engine parameters are locked in, now that your finished building, but the valve train can be changed without a rebuild. Determine what pressure you, and your fuel, can live with and select a cam that will give you that pressure and still have the manners and performance you want. Not an easy thing and I'm sorry I can't recommend a specific camshaft grind. I also wanted low end torque which is why I chose the 230/236, if I'd paid a little more attention to pressure I would have gotten one just a little larger, and may change out to a 236/245/112. That cam seems to be a favorite with the 455 owners over on the lower mainland.
Then there's the gasoline. What's it like finding high test up in Campbell River Niell? I would like to be able to run on regular gas as well, not only is it $130.50 cheaper per gallon than the high test, it also gets used out of the tanks quicker. I'm the only one I know of that buys high test on this island and I've never seen anyone at the premium pump in Sidney. The last time I bought premium on Pender Island my car would hardly run, the gas was so old. No one else buys it so it just sits in the tank. I've taken to buying mid grade boat gas, over on the big island, that pump is always getting used and the gas is fresh. Better to have fresh mid grade than old high test. Sorry to get off topic.
Just filled up, $1.32 per litre for 91, $1.18 for 87 @ Chevron, so only about 50-55 cents a gallon difference here today. last week was $1.37 per litre. Chevron has 94 here as well but I bet its a pretty slow mover this time of year. Once the car was tuned pretty well it stopped pinging except for just off idle in higher gears and I tried some 89 octane, I had to put 91 in two times after for it to stop pinging. again.
