Compression & Ignition Question

Thanks for the Help. My fear was, that the cc are to small for a 10:1 CR and the heads are crap for a 455 engine. Puhhh now im happy!

 

That is a pretty small cam for the static compression ratio you will have as stated. You will have a dcr of 8.63 if installed on a 108 C/L (4*adv.). 8.5 dcr if installed on a 110 C/L(2*adv.).
A good cooling system and proper timing curve is must not to spark knock when hot due to the cylinder pressure you will have will be sky high. I would choose a larger cam (it wouldn't neccessarily idle rougher depending on the L/S. Perhaps someone will chime in on their experience with this cam and a fairly high comp. ratio, where to install the cam, timing ect. or call TA. Detonation destroys an engine. What octane gas is available where you live?
Ray

 

We have here ROZ 98 thas yours MOZ 91 but im not sure...

Hmm thats sound not good. Wich Cam from TA can you recommend me? remember the idle quality and i drive with a stock stall converter .

Wich Sparkplugs is the righ for this 450hp application? NGK Iridium or Platinum, but with temperatur level?

thanks

Robert

 

Robert I must ask you why you think you have 61cc chamber heads and intake flow of 320cfm? TA lists them as having 64-66cc chambers and to get an se intake port to flow 320 would need chamber work making the chambers even bigger.
Ray

 

Because of the datasheets

 

They may have simply milled the heads to bring chamber volume back down. My TA Stage 1 SE's flow 328 cfm on the intake with 58cc chambers after milling.

Devon

 

Those are some great flowing heads. So they milled the heads approx .007"/cc. Didn't you ask TA if that small cam would work with 10.5/1?
Ray

 

Devon how was the alignment of the ports/fitment of the intake? I read on Greg's site he raises the intake ports when milling alot of the joint face.
Ray

 

I'd already messed with the intake manifold ports a bit for the work I'd done on my iron heads, and was happy to see that the roof and sides matched when I installed the new heads.

I have a mismatch on the port floor of about 0.020" because I enlarged the TA intake to match my iron heads back in the day. If I knew then what I do now, I would have never tried to enlarge/deepen the floor of the intake port.

Devon

 

Yes, I recall your old big ports heads were angle milled also. The old TA sp1 intake had smaller ports than the heads you were using. I was in the same scenario back in the early 90's (w/1989 casting sp1) but used the Performer instead as it had about the same size ports. The center dividers were thin like the big ports too.
Ray

 

While that mismatch on the port floor bugs me, I am in no position to complain about anything. Even at 4575 lbs the car is already too much for the radial tire street driving that I do right now. Dragstrip fun has to wait.

Devon

 

TA is very busy and they not answered my question about the compression rate. But why is CR on 10.5:1 a issue, i guess the stock CR was 10.25:1 and the cam was also smal. I know the problem with the detonation and i want not a engine that produces explosion when she is hot. How much do this cam reduce the detontion risk?

Wich opportunities can i reduce the CR to a secure level. And how much HP will it produces... My Goal is 450Hp i hoe i can reach that.

regards

Robert

Edit: Fuel is BP Ultimate 98 thats MOZ 88 :/

 

The factory rated 10.25/1 455 engines were actually around 9.5/1. There is research on the board. Here is one of the posts.

I can't recommend a cam for a 10.5/1 comp., alum headed engine/stock ex. and induction and have it idle like stock as there are to many variables. I would call Jim Wiese or Scott Brown. A custom cam may be recommended. They have done alot of dyno testing and alot of people recommend these guys. Keep in mind the mufflers you use will affect the sound at idle as well.
I did a search on the ROZ/MOZ ratings. Basically your ROZ 98 in Switzerland is equivilant to the 93 octane available here. R+M/2.
Ray

 

I've run the TA 212 cam with a true compression ratio approaching 10.4:1 with Gessler ported steel heads and full timing. No problems with knocking. I run a 160 thermostat, aluminum radiator and I make sure I don't put myself into positions that will cause knocking. That means no full throttle blasts if the car is hot or I have the AC on or up steep hills and I always manually downshift to a lower gear if I want to accelerate hard. I don't wait for the automatic downshift to kickdown.

DCR doesn't take into account the better heat rejection of the aluminum heads. To get a .020" deck with those pistons you'll probably have to mill the deck nearly .030". I'd just do a .010" cleanup of the deck and that will lower your compression closer to 10:1 and the aluminum heads will take care of the rest. The stock forged replacement pistons have very little true quench area on them anyway. Not that a minimal quence doesn't hurt but I think in your case it will be fine.

Somebody should see what the DCR is on a stock factory 455 cam with 9.25-9.5 compression ratio. GM controlled detonation with highly restrictive timing events in their distributers. Set yours up for maximum timing 32-34 and if you get any knock try using the heavier advance springs or pull a degree or two out of it. Use the 8 vacuum advance cannister too.

A lighter car, steeper gears, and looser converter can all help stave off knock/ping. I did it with the car at 4250 lbs with me in it on 93 octane so you should be able to do it too.

You won't believe the torque with that cam and good heads. The big flow of the heads extends the power band of that cam way out. I would shift at 5700 for best times with my '76 Century.

This is in another thread somewhere but it is good reading for the engine you want to build, especially part 2:

http://www.carcraft.com/techarticles/ccrp_0906_buick_455_engine_bolt_ons/index.html

http://www.carcraft.com/techarticles/ccrp_0907_buick_455_cylinder_heads/index.html

 

If i mill only .010" than i have a big quench from .080 . Is that not to big?

 

I think the legindary old C118 cam will give you a near stock idle and low dynamic compression that will get you by on 92 octane and produce lots of torque and HP.
Read about the "sneaky" cam that Jim Weise built with only 6.5 dcr, 90 lbs cranking compression, and 500 HP.

 

I have read the sneaky thread from Jim. The issues are:

1. Keep the dynamic compression rate down <8
2. Keep a good idle
3. Create power and torque in low mid rpms
4. Stock or little higher stall converter
5. Pistons only notching if is absolutely necessary

A engine builder recommend me a custom cam like this:
284/306 adv, 220/235 at .050 on a 114, lift would be .488, but ground with at least 6 degrees advance


I don't know if the cam passes all 5 issues. I wonder why produce this cam less top end power than the TA212 in the Dyno2003 Software?:Comp:

thanks

 

Adding torque on the low and mid range can make ET improve a bunch. Adding a few HP on the top may have less effect on ET but will bump up MPH.

High torque motors are awsome with the right cam. Compare TQ number averages on these cams, like 3500 to 5500, or 3200-5200.

Jim's "sneaky" cam has awsome torque spread for 90 lbs compression, yeah!!!!

Love this sneaky, torque monster, low rpm stuff.
Want to see more tests of combos like this.

 

In this link you can hear my car idling. I use Kenne Bell C118 Camshaft.
http://www.youtube.com/watch?v=zQ-JpUFSp8o