Anyone running 11:1 compression on pump gas?

Larry is giving you excellent advice.

Pushing the DCR past 8.0 can be a tuner's nightmare concerning detonation for street use on pump gas.
The engine becomes real sensitive to changes in gas octane, engine temp, air temp, elevation....

Paul

 

Lary,
Here are the final numbers for my cam. Can you please run these numbers through your DCR Calc and let me know.

LSA 115 - ICL 115
BTDC 14 - ABDC 64
BBDC 72.5 - ATDC - 22.5
0* advance

SBB 350 + .030 over
Fully ported and polished heads with 1.92/1.55 valves
TA intake flow balanced and port matched to the heads
MSD Atomic EFI + MSD dist. coil blaster and 6A CDI
TA super comp headers

Thanks

 

I like that video. The car sounds like a top fueler with all the echoing from the building. What engine is in the '68 at this time? Maybe it is the open exhaust but it sounds llike it has a nice lope to it.

I don't think your new roller will have much of a lope but it should really pull strong.

If you want more low end maybe a 4-hole spacer under the TB will help.

 

Do you think that this cam would work if I dropped my comp to 8:5 and twin turbo'ed the engine?

---------- Post added at 01:32 PM ---------- Previous post was at 01:07 PM ----------

It is a Buick 350 I used to race. I retired the engine and tranny to my 70 Skylark. I am hoping that my new roller doesn't have much if any lope to it (sleeper). I just want it to pull like a freight train when I put my foot in it.

 

Nice cam for turbocharging. What are the valve lift specs?

Paul

 

For sure do the turbo!!!!

 

lift .560 int / .560 exh currently... may play with these alittle to see if I can bring them down more.

---------- Post added at 09:03 AM ---------- Previous post was at 09:02 AM ----------

Did you use the Burton Twin Turbo setup?

---------- Post added at 09:11 AM ---------- Previous post was at 09:03 AM ----------

On my cam I looked at running it on a 115 LSA with 115 ICL but went back and looked at 118 LSA with 115 ICL and the volumetric efficency looks alot better. What do you think?

 

Since you have level 3 port work on the heads it is better to keep the lift around .550 to take advantage of the head flow.

The 118 LSA shows a better VE because it benefits the higher rpm range where the port velocity is higher.
With the higher port velocity at higher rpm the later closing intake valve allows for more cylinder fill.
However you will be giving up some low end torque as a result and that is not your goal.
If you decide to add turbos, the later closing intake valve will make spooling more difficult.

For street turbo application, 114 LSA is a good spread to have.

Paul

 

Brings up a good topic..... Would bit be more advantagous given a consistant gasoline octane rating to either increase dynamic compression ratio and control the ignition advance to deter detonation or increase valve overlap to descrease dynamic to allow full ignition advance ? Which is going to make more power ?
Just something I was contemplating...

 

True the bottom would get alittle lazy on 118 LSA. Turbocharging would be really fun but my budget will not support that kind of fun plus MSD's Atomic EFI doesn't support power adders right now. I think a straight up simple clean build will do just fine for a street car that I can road trip in.




---------- Post added at 02:07 PM ---------- Previous post was at 01:34 PM ----------

I do know that the better the VE the better your engine performs as it doesn't work as hard to move air in and out of the engine. Better mileage, power and quicker response from what I understand but at the cost of having to spin an engine in the higher rpms. I was just thinking... I run a KB118 cam in my race motor and it's VE is over 100% from 3000 - 6000 and it pulls like a freight train from 2500 up to 6000. What would happen if you take a the KB118 profile put it into a hydraulic roller cam? I know that hydraulic roller cams bring the torque on alot sooner... I am going to have to run some numbers.

 

OK straight up clean build, street and road trip so I'm assuming gas mileage is important. Basically we want to have it all.

For gas mileage the overlap needs to be as little as possible and still have a cam profile that gives us the performance needed.
Also the higher the static compression, the better the thermal engine efficiency and the higher the fuel mileage.

A roller cam allows for a steeper ramp rate than flat tappet which meens you can have reliable short duration high lift cam profles.
If the heads are ported for high flow and high velocity (As in a level 3 port job), you can use a less aggressive cam to reach the needed power levels. So take a relatively short duration profile to minimize overlap for good fuel mileage while providing good low end power, combine that with high lift which will take advantage of the port work and increase torque throughout the power band and increase the upper end.

One way to allow a higher static compression ratio while maintaining an 8:1 DCR is to spread the LSA but we sacrifice low end in doing so.
A better way is to have the cam ground with a short .050" duration but a longer .006" or advertised duration.
This has the added benefit of setting the valve down on the seat and picking it off the seat easily or softly.
Here is the perfect example where the intake .050" duration is only 215 degrees but the advertised duration is around 270 degrees with a valve lift around .550. The static compression ratio is 10.2

http://www.v8buick.com/showthread.php?252771-New-Buildup!-448ci-STG-2-SE-Hyd-roller-an-MPG-motor

I'm sure you've studied this thread and yes it is a 448 instead of a 350 but it demonstrates this discussion.
Looking at the last 2 dyno sheets on post #19 you will see the power out to 6000 rpm. Pretty incredible for such a short duration cam.

The LSA on this cam is 115. If it were pushed out to 118 degrees, the power band would be moved higher. The problem is the dual plain intake manifold will attenuate any higher power and with the loss of low end, the power band just gets shorter instead.

Paul

 

Yes, Burton has built my whole car from the cro mo roll cage, new sheet metal, custom intake manifold, custom tube headers, custom turbo kit etc. Should be a fun street car and should leave the line violently off the trans brake at 3000 RPm under boost.

 

Nice!

---------- Post added at 09:48 AM ---------- Previous post was at 08:24 AM ----------

But don't we all want it all! Gas Mileage and Power! LOL!
I think that I did fairly good with my cam design. 115 LSA 115 ICL .560 lift 214/230 duration. I achieved the goals I wanted in the cam. Broad flat torque curve from 2000 - 5000 with over 400ft/lbs, good vacuum, smooth as possible idle. of course this is my first hydraulic roller cam so it is a learning curve. Do you think my cam will work really well? I am thinking it will!

 

You did a great job on figuring your cam and it will work well with the head work and manifold you specified.
With -8 degrees overlap the idle will be smooth.
If you can gear the car so your cruising rpm is less than 2000 rpm the gas mileage will be great also.

Can you have the cam ground with a 270 degree advertised (.006" lobe lift spec) intake duration while keeping your 214/230 .050 duration?
The exhaust advertised duration will end up somewhere in the 280 degree region.
This way you can have a 10:1 static compression ratio and be able to advance the cam 4 degrees for even better street performance.

Paul

 

I will have to ask it the cam can be ground that way as I have never heard of doing a cam that way. But I sure am going to see if it can be done.

 

Having short duration cam ground with a long advertised duration is what was done here by Jim Weise.
Here is the paragraph from previous post #34

I'm hoping you can do the same.

Paul

 

I don't know. I can only tell you what I am running in my 11:1 455

520/520 lift + 1.65 rockers 245/245@.50 304 adv 112 lobe seperation stage 2 alum heads

turbo 400 3:08s 2800 stall

runs great on pump gas 93