Anyone running 11:1 compression on pump gas?

Hello all,
I am gettin gready to start a new project in November and am trying to finalize my build details and was wondering if anyone was running 11:1 compression on pump gas? I am currently looking at running 10:1 compression right now but if I can get awy with 11:1 then I may just go for it. Here are some of my build details. SBB350 +0.30 over, Gessler stage 3 heads + TA intake port matched by Gessler. MSD Atomic EFI and MSD complete ignition setup. Custom ground hydraulic roller cam 256/273 LCA110 Overlap 44.5 with TA 1.6 roller rockers.

I am building this engine for the street and will be running a TH350 with 2000 stall and 2.93 posi.

Any input would be appreciated.

 

What about mixing some E85 in with pump gas?

 

Even with Aluminum heads that is a lot for the street. I agree with Larry (read both of his posts again.) As far as mixing E85. You will need to make sure you mix it the same every time since your tune up will be set for a specific mix. Good luck and run less comp until someone makes Alum. heads for a 350".

 

I hate to be harsh but this one needs nipping in the bud. I have to ask. Who recommended that cam for any kind of street use? With that driveline? Big is big and that thing is huge! You would need 170lb on the seat valve springs to rev it up at all. Generally speaking a roller will respond at slower speeds like a 10* smaller hydraulic. It will still be a pig at the low end with that compression. 3000 stall Larry? You're being too conservative. Try 4500 stall and maybe a set of 4.30's out back. 12 or even 13:1 would be more appropriate with that baby. Forget the pump gas although out your way E85 would be great.

Figure on trying out shift points starting at 6500 rpm and going up to optimize. Also I can't believe the old custom single plane hasn't been brought up because just when that cam gets rolling, so to speak, the intake you have will be choking it off.

A roller cam like Larry's latest would be good and would still rev to 6500 at least and you could run the 10:1. Of course your gears and converter are still too low unless you plan on running the Sandhills Open Challenge in Nebraska.

Like I said I hate to be harsh especially to a guy trying to make his way in Buick land but this sounds like the typical speed shop story where the guy goes in and says he needs a cam, looks at the catalog, takes his finger and just goes right to bottom of the page and says "Give me the biggest one you have!"

http://www.taperformance.com/proddetail.asp?prod=TA_510-350

http://www.taperformance.com/proddetail.asp?prod=TA_608-350

Notice they said "good stuff" on the second one. 3500-7000 power band and that doesn't mean it will make good power at 3500 rpm. Plus that 10.5:1 minimum is a joke. Maybe if you are worried about running 87 octane.

 

Oh my.

I'm afraid I'm in agreement with the others; this sounds like a badly mismatched combination.

To answer your question, I don't think you'll be happy running 11:1 with that cam with iron heads on 93 octane or less. I did the same with two big block Buicks, 10.8:1 with an even more aggressive cam. I ran highly polished chambers, pistons and other tricks - I still fought detonation, especially in hot weather. That went away when I replaced the iron heads with aluminum.

But more importantly, with the cam profile you've chosen, you're fighting the same battle the rest of the small block folks have to. The intake and heads simply cannot support flow at the higher rpms that such an aggressive cam is begging for. As has been said already, the low end torque will be dismal because of the cam profile, but by the time the cam can do its thing at higher rpm, the intake and heads will be restrictive. You could lose on both ends of the spectrum because of this.

Devon

 

Like the others are saying for that big cam you would want a 4000+ stall converter, a single plane intake, and a 850 CFM Holley. For a street car it would not be very fun!

I would switch to something like this cam I ordered. I sold it and it will be used in a race car. In fact Who knows the guy I sold the cam to might want to trade you for yours as his car is track only. I know it is still new in the box and would be a way better match for your car.

 

I run at 11-1 with no detonation, of course as the others say alot of it has to do with the camshaft as well as the combination to avoid it. Where is that cam measured at for duration ? What are the other specs ? With those short gears and low stall detonation will only be invited even more.
I run the 11-1 with a solid lifter 267/273 duration cam , single plane intake but with a 3200 stall and 3.92 gears and alot of other parts on pump gas .

 

OK, another 2cents worth. I have a factory 1970 Hi performance motor in one of my Apollos. It pings on 91 octane even if I back off the timing to 30 degrees on a hot day. When I run 100 octane I can put as much timing as I want, but at $6-7 a gallon is not something I want to recommend. If you haven't put the motor together and just want to go fast. Sell off the 350 parts and build a 455 with aluminum heads. I love Buicks but not a 350 fan. I had my fill of V6's all my years at Kenne-Bell and wish I never sold my Stage1's. Now I'm onto Nitro methane. I don't recommend that in your case. I think Bobb Makley has experience with E85 at Finishline motorsports. Jim at Tri Shield may have experience with alternative fuels also. A call to both will probably get that cam put on your desk for a .... you guessed it, paperweight. Sorry! You really need to talk to TA or one of these engine builders for tech support. Sometimes I wish these posts were just set ups. If not at least you came to the right place for a spoon full of sugar!

 

ken......i thought we were friends. your not playing very nice picking on the 350's. :laugh:

 

I am sorry I have to apologize to everyone about some confusion with the cam specs. My cam is a little smaller than a TA 212 cam. 258/273 would be the advertised duration not the actual duration.The actual duration is 214/224. This is a very high torque low rpm cam that will pull like a freight train to 5000 rpms. The cam was designed specifically for the 2.93 gears, and 10:1 compression. I was wondering if anyone was running 11:1 and having any issues or doing it successfully as my cam will support up to 11:1 compression. Again I am sorry to all for the confusion.





---------- Post added at 11:32 AM ---------- Previous post was at 11:09 AM ----------

A dual core aluminum radiator and flowkooler water pump will help alot.

 

Now that is more with the program. It would still be a roller correct? Anyway that will be a fine street/strip cam with your setup.

What is the reason you want to run 11:1? With that cam your cylinder pressure would be way high.

When you say 10:1 are you running .030" over stock type 10:1 pistons which will require some decking and possible head milling to get 10:1 or are you saying custom pistons for either 10 or 11:1 which may require less machine work to get that compression because the dish could be smaller? Make sure you check piston to valve clearance because that cam probably has some nice lift and you may need valve notches.

Anyway if it is a true street car stick with the 10:1, possibly less, unless you plan on running better gas most of the time. In my experience with the 350 when running cams like the TA212 (flat tappet type) getting close to 10:1 compression, if you try to run the correct agressive ignition timing, say 35* by 3000rpm, you can get some ping out of it at times. I believe it has to do with that open chamber cylinder head. If you have to mill/deck anything to get the compression up mill the head first to make the chamber smaller.

Keeping it cool is important when pushing the compression ratio up there. Make sure the exhaust passages to the intake are blocked to keep it cooler. One thing you have to remember. It is better to have a good ignition curve with maximum advance with a lower compression ratio than it to have a compression ratio that makes you pull timing out of it.

 

Yes the cam is a hydraulic roller cam.

I am interested in 11:1 so that I could increase my torque output. Currently with the setup I should be putting down 400+lbs/torque between 1800 - 4800. Yes it is a very flat torque curve but it is right were the engine spins on the street. I still don't understand why anyone would want to spin a 350 over 5000 rpms. The Buick engineers were really smart and designed the 350 as a low rpm - high torque street engine.


I also did address the issue of "keeping it cool" as I did have some issues when I retired my NHRA Super Stocker 350 to the street last year here in southern Oklahoma were it is normally 105+.

 

Actually the 350 is a stronger block than the 455. I still have the Red 74 Apollo with 70 GS350 motor. After we get the 455 billet heads done we will consider a 350 billet head with water jackets so everyone can run them. How is that for 350" love?? ps. I am glad this guy has a more street worthy cam!

 

"I still don't understand why anyone would want to spin a 350 over 5000 rpms."

because its so easy to do with minimal work. we do it all the time.:grin:

ken,
put me first on your list for the 350 heads. i wish i had a bigger machine in my garage so i could build my
own aluminum block.

 

Larry is correct, the static comp ratio is almost just a bunch of garage talk....you need to know the dynamic ratios to really know what is working for you. The camshaft you want will determine the rpm range you make your best numbers and that camshaft will also determine which ratios you need to stay within.

 

I do understand the difference between static and dynamic compression and my cam is designed to run at 10:1 with no issues.

Thank you all for all the input.