[daduck]

thanks for all the suggestions and info. I have some more reading to do.

Dave

[daduck]

and the post count of everyone that responded is amazing!!!!

[b-man]

A friend of mine had a +.030 455 with stock 6X-8 400 heads (8.6:1 compression), 3-tube headers/full 2-1/2" exhaust, and ran the Performer intake with a Q-jet carb. He used the HO Racing HC-01A cam (224/230 @ .050,.465/.492 lift w/1.5 rockers).

In a street '64 Lemans it ran 12.90s all day with 10X28 slicks, a TH350 trans and 3.08 rear gear.

[Cliff R]

We've actually done about half a dozen 455's with lower compression that well over 400hp without any head porting and they were all fine to drive on the street.

I didn't include them because one used some home-ported 6X-8 heads and the others were either Super Duty or 455 HO builds.

Every single one of them used cams with at least 230 @ .050" and all but one made 1hp/CID and that was the one mentioned earlier that used stock 1974 350 heads with the larger 2.11/1.77 valves in them. It still cranked out 440hp and over 500ft lbs torque thru most of the loaded RPM range making peak power at 5400rpms. The only thing I don't know about the build was the exact compression ratio because I didn't CC the heads. Most of those are dubbed to be around 96cc so it wouldn't have been over 9.5 to 1 compression.

I used Rhoad's lifters on every one that had a flat cam in it to improve vacuum at idle and street manners, plus we ran high ratio rocker arms on them. One of those engines has logged over 60,000 miles since we did it in a full size car with a TH400 and 2.50 something rear gears. We added a low gear set to the TH400 and Continental 13" converter. The owner says that it has great street manners.

I use and prefer custom ground HR cams for the "low" compression builds and never anything less than 230 @ .050 and tighter than 112LSA. Matter of fact the ones we've done on 114LSA have made more power and more user friendly on the street. What folks fail to consider here is that a 455 engine sees a 230 @ .050" cam about like a 350 sees a 214 @ .050", as far as idle quality, throttle response, street manners, etc. Not to mention the 455 is a HUGE engine and you are not going to take full advantage of it's potential using tiny cams in them, especially if they are on tight LSA's.......FWIW.......Cliff

[GTOLou]

Originally Posted by daduck

and the post count of everyone that responded is amazing!!!!

Yeah - that is worth repeating. I have an old Porsche 968 - and the help you get from a pontiac forum compared to that (a porsche forum) is, well, not comparable...lol.

And the expertise in the help here. Just in this thread alone. You've got some guys who really know their ****.

Anyway! Back to your build - good luck!

[1967Tempest]

I love the TQ that my 468 has. the fun pedal is hard to stay off of.

That said, my weakest link up until early this year was the 50+ year old 3.23 10 bolt open rear. Now have the Quick Performance ford 9". I have only driven it a few times as I am still troubleshooting brake issues, but damn!

I have said this on another thread, but the Eaton Trutrac is amazing. Seriously consider the rearend upgrade.

Even with as heavy as the 67 Tempest is, at 50 MPH, downshift from 5th to 3rd, it will annihilate the tires and pull like a freight train. The car gets sideways with a blip of the throttle. Most fun you can have... (Insert pun here).


Also do you have a trans upgrade? What trans?

[1967Tempest]

Originally Posted by Lee

Not without making a motor that is miserable to drive around.

Oh, yeah. this is a true statement. With the bigger cams, the car does not like to just put put through town.... It really likes to be above 1500 rpms. Might be different in an automatic, but the stick is bad in traffic. On Power Tour, I really had a chance to open this up and the sweet spot for her is 60 to 100.

Keep that in mind when browsing through the 1.5 million cam selection threads.

[Lee]

As a reminder, attached are the chassis dyno results from when I tested log manifolds vs. Tribal Tubes Tri-Y headers on my very-low compression stock headed 455.

Notice how the HP curve goes effectively flat at 3800rpm, with the logs. Hogged out and with a bigger head pipe, you may raise that point SOMEWHAT, but I doubt it will be more than a few hundred rpm higher.

[steve25]

Just keep in mind that the lower your compression ratio is the more low lift Exh flow the head should have so it not have to work at pumping out the spent Exh gasses which chokes it off and caps off the power band.
Also keep in mind that at whatever rpm any given motor makes it peak torque at it is saying that the combination of Intake system flow and Cam opening time are done , fully done passing air!
Horsepower will keep on increasing however as rpm goes up until the amount of fiction the motor makes over comes the HP level the motor is producing.

[meangene]

I agree with pastry chef Voodoo 703 cam and don't go past 9.5 to 1 we have crappy gasoline around here, I notice it liked 32 degree of timing in my last build.

[SD455DJ]

daduck, Here is my dyno sheet to see that you can really close to your 400 hp goal with a variety of combinations. It looks like it uploaded as a pdf file, not a picture, so I'm trying it again. Hopefully this works...

Mine was with a stock 1970 Bonneville YH 455 with it's small valve #15 heads (non-ported), the exhaust logs and the only nod to performance was the addition of the Summit 2802 cam. I also just pinned the pressed-in rocker studs just like they did in the good old days and used the crimp nuts to zero lash the lifters.

Keep us informed on your progress. Dennis

[SD455DJ]

...I should have mentioned we didn't ring every horsepower out of it and felt confident we could break the 400 (+) hp and 520 lbft torque with more dyno time, but were happy to dial-in the carb jetting and overall tune. With RA manifolds or headers it would have done it for sure. I will also say that with an actual STR of 10 to 1, it needs a sharp tune to run well on 93 octane fuel with the 2802 cam. It could use a RAIV cam with that compression to reduce cylinder pressure. The 2802 is very mild in that motor.

Dennis

["QUICK-SILVER"]

Originally Posted by daduck

I have considered going with a 3.08 Limited Slip once the 455 is done.

Need to do more than consider on this.

For a street car, not wannabe drag car, the whole package needs looked at to determine engine build and cam choice.

71~72 big car 455's were rated 325 HP with 8.2 compression and 067 cam.
With factory log manifolds, quiet exhaust, TH400 and 2.41 rear gears...Those big old cars ran strong for their size and weight. They'ld pretty much smoke the right rear, on take off, as far as you wanted. Absolute hoot on the interstate and got pretty decent gas milage. Monster torque right off idle and didn't need a 3,000+ stall converter to get the cars moving.

Leaving the short block pretty much stock, 067 cam and all, you could bolt on a set of 6X-8's for a bump up in compression and add stamped 1.65 rocker arms for a bit more valve lift. With just those mods, HP and TQ numbers went up a bunch from idle to WOT.

Pump gas friendly, does not need a big stall converter, still get good gas mileage, more power than your back tires can handle taking off....Kind of hard to go wrong for a true strong running street car.

And donate the HEI recurve package to someone you don't like. For a strong running street, you want the advance curve to climb with RPM's like factory.

IMO
Clay

[1967Tempest]

Originally Posted by meangene

I agree with pastry chef Voodoo 703 cam and don't go past 9.5 to 1 we have crappy gasoline around here, I notice it liked 32 degree of timing in my last build.

I have the 704. I was gonna go with the 705. Glad I didn't. it would be terrible on the street. I bought the 704 after GTOFREEK recommended it. Absolute blast!!! other than traffic.....

https://www.lunatipower.com/Product....d=1777&gid=287