Cam Change/ will post dyno results

Hi all, glad to see a new board up and running, can allways use new info, I'm running a T/A built 494 stroker motor with stg.2 heads flowing 300+ at .050 , 12.2 to 1 comp. 2' headers with full 3" exhuast, sp1 intake port matched, pro-systems 1088 dominator carb. current cam is a lunati 258'258 single pattern cam 110 l.c. Iam going to install a T/A 308s solid cam, 108 l.c. any thoughts in this install, where to degree the cam? will it be a benifit? anyone using a computer dyno? when I make the change I will run the eng as is on the dyno, 4yrs old motor never apart, then make the cam change and note all changes, then possibly clean up the intake and post again, thanks for any input.

 

Bruce
I always ran my 308 "straight-up"never tried anything else 'cause it ran so good,glad to see ya' making that change,should see some solid 10 sec. passes!

 

Hi Guys,

Bruce.......what do the exhaust ports flow? I like to determine my camshaft duration split I/E by the percentages of flow I to E. The better the exhaust is, the less duration the exhaust needs and vice-versa. You probably know that.....others may not?

I'll look forward to seeing your results!

 

Kerry, here are the head flow #s on my stage 2 T/A aluminum heads.
Intake : @ .500 =293
exhuast : @ .500 =232

Intake .600=300
exhuast: @.600=248

What are your thoughts on these #s? and what cam would others recomend? this car is ocassionally street driven (short dist.) It has run a best of 11.18 @ 121mph Foot brake car ,th400,4500 ati convt. 4:10 gears, 29.5x10 inch tires. gotta get a rollbar soon!
also, 1:65 rockers, cam in motor now is hyd. @.614 lift.
thanks for any input guys!

 

Hi Guys,

Bruce............Those are flow numbers for two different heads or a further clean-up of the same set that was increased?

The:

I.....293@.500
E....232@.500...........gives an excellent 79.2%

I.....300@.500
E....248@.500...........gives an even better 82.7%

Those are excellent percentages for a supercharged engine. Your's being naturally aspirated allows you to drop back on exhaust duration and "lessen" the spred (overlap) between the two. As efficient as your exhaust is having to much spred will over evacuate the cylinder and pull to much fresh charge out with it so you will have some lost power potential. The 308 has a 6* more exhaust than intake with 268*I and 274*E at .050 and 65* of overlap. It also has slightly less lift on the exhaust side. I'll tell you that I've never personally ran one of these grinds but I will say I think this is going to be a perfect canidate for your dyno test. Improvements over your current hydraulic I believe are a "for sure" thing.

10's look out cause here comes Bruce!

Keep us posted!

 

Kerry, maybe just a typo? the second set of flow #'s should have read, .600 are the percentages still correct? thanks Bruce

 

Hi Bruce,

Sorry, I misread..........yep the percentages still remain the same.

 

Bruce, Gary Paine has desktop dyno at his office, He likes to run diff. combinations, give him a jingle. The 308 cam is awesome, his son put one in his "street" engine and ran 10.80's on 9'' slicks last year! Randy ( still got to get that bumper from you)lol

 

Hi Guys,

Bruce......I have DD2000 myself so if you can send me or post a complete build up, especially the spec's from your cam card and the complete flow numbers from .100 to where ever you quit flowing them, I'll be glad to see what we can come up with. It will be interesting to see how close the real dyno compares!

 

Here is what I think about the cam. Now this is just my opinion and that is all. I don't have a buick but my brother and I race Caddy 500 engines and this board is a lot better then the caddy board for race and engine info. So here is what I think. I believe that you have a little to much exhuast flow for what you are doing. Here is my bases. We built a Caddy 500 with 4.375 bore and 4.4 stoke. The Compression is 12.9 to 1. The intake valve is 2.125 and the exhaust is a 1.84 valve. The heads flowed with the carb and manifold on it at .600 lift 276@28 and the exhaust flowed 233 at .600 also. That is 84% intake to exhaust ratio. We put a cam in that was 262 and 268 at .050" The lift was .634 and .654" We ran this in a 73 Nova and the car would not pull past 3800rpms. We screwed around with this combo for 2 years and finally took it apart and installed a new cam for Elgin Cams. These guys know what they are talking about. So we gave them all the info on the combo and this is what we got back. First they wanted us to get the exhaust to intake ratio down to around 75%. So what they did is built the cam backwards for what we normally know. The cam is now 268 and 264 @ .050" and the lift is .650" on the intake and .623" on the exhaust. The intake centerlines at 109 and the lobe center is on a 112. We dyno'd this engine and it made 649hp @5600 and 660ftlbs @ 4400rpms. The engine now has a top end to it were the other cam had none. Also the engine idles at 1000 rpms out of gear and 800 in gear. So if you guys are looking for another cam some day I would highly recommend Elgin Cams. I will not get any other cam again. So I guess what I am saying is I think that you could use a little less duration on the exhaust but this is just my opinion. Good luck and post the numbers.

 

Talk to the administrator and see if they can make a special forum just for the CAD V8 boys.

I worked part time at a Buick/Cadillac dealership as a mechanics helper when I was going to trade school. So I got to work on both types of engines.

 

Jim I my have not said it right but the cam that we had would run to 5500 rpms with no problem but it would not pull hard past 3800rpms. The car would die at half track. We changed the cam and we gain 3 tenth just with the cam change. We now have a tranny problem because the engine is making more power. We should have the car in the 10.9 by the end of this year. What cam company do you like to use Jim?

 

I have had really good results with Lunati, comp cams, TA perf. and straight line performance.
What tranny are you running and what problems are you having.
Your input on your cam is good, people's experiences are a big part of what a board like this is all about. Jim Burek

 

Wouldn't pull past 3800??? What was it a diesel???

 

Talking about intake to exhaust splits on the camshaft here is a general rule of thumb.
If the intake and exhaust has a 80% ratio in head flow, then you want the same duration on the intake as the exhaust, or a single pattern camshaft. As the exhaust flow decreases as compared to the intake flow in %, then you want to add more exhaust duration, to simulate a better flowing exhaust port. For every % point below that 80% ideal you want to add two degrees of duration on the exhaust. This is a general guideline and you can fool around with the %'s a little, just don't get too far out of wack. And don't just look at maximum flow numbers when comparing cyl. heads. You'll want to look at all the lifts, the low numbers are very important. My Stage 3 heads are currently flowing 340 on the intake and 261 on the exhaust (281 exh. with a 12" test pipe). That's a ratio of 77% or about a max. of 6 degrees more exh. duration. There's still room for improvement with these heads, so hoping to improve a bit at both the low to mid #'s and max. I can post overall flow #'s in .100" increments if anyone's interested.

 

This thread is some good info. I am getting my motor back together with stage2 street eliminator heads. Mike Philips valves 11/32 guides some minor port work. I already have a 308s. This is the cam I was running with the stage1 heads. My cam is a older vintage with 266/276 duration 601/592 lift.

Maybe I should have the intakes worked to about 320 or so.

You guys think I should run this old 308s?

 

Jim the tranny was a TH350 with all the goodies in it but it just could not hold anymore. We did pick up 3 tenths with just the cam change. We did nothing else to the car except that. The Nova weighs in at 3700lbs fully loaded with 30x13 Mickey Street ETs and 3.90 gears. The converter is a 10" ATI with a 3000stall in it. All we could get was 11.76@115 at Bandimere. We changed the cam in it went 11.41@ 118. Talking to Alan Lockhead he said that we should go with a 4500-5000 stall and yes we are switching to a TH400 tranny. So with doing that we hope that will work better for us. Do you build none switch pitch TH400 Jim? Anything that we should look out for? We used Elgin Cams for our cam and they was a great help to us. Here is there website www.elgincams.com They was not anymore expensive than getting a cam from Crane but they was really helpful. Also on flowing the heads most of you now already but for those who don't you should really flow the manifold and carb with the cylinder heads. Nobody told us this when we started building the caddy's. It sure would have been nice if they did. Lets just put it this way if your head flow 350cfm without the manifold and your manifold will only flow 300cfm then your total cfm getting into your engine will be 300cfm or less. I think it is hard to compare numbers without the manifold and carb on it. Sorry if it sounds lame but nobody in those stupid magazines ever talk about doing this. If anybody wants more info on the engine I would be happy to share it with you guys. There is no secrets here.

 

Yes , we also build non s-p trannies. You are right about flowing a head with the intake and carb, the closer you are to what the engine will be, the better. On my stg-3 heads, I am getting 370 cfm at .650 lift on the head, with the manifold and carb, it's flowing 358 cfm.
Still, improving the head flow will improve performance. Jim Burek

 

Hey everyone, motor is just about out of the eng. bay and hope to drop off at EARICK Racing Engs. this week. have the 308s cam to test but will also be looking at other options as well, Looking closer at my info. I see that the heads should flow 300 cfm @ .500intake and 248@.500 exh. not at .600 as I orig. posted.
will try to keep you updated on the out come of this eng. combo, I will run it "as is " then do some changes and try to post as much as possible, looking forward to learning more with the Dyno. Later, Bruce P.S. this eng. was a t/a perf built motor and has not been touched what so ever in four years, other than swap from sp1 holley to sp1 dominator, eng has not been apart whatsoever in over four years. should have some interesting info.