cam thoughts

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scampy

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Looking for what to expect from the new cam.Old cam was http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=671&sb=2 244 int/252exh [email protected] .520 int .540exh lift 110 lsa 106 intake center line.New cam http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=672&sb=2 252int/262exh duration @ .050 .542int .555exh lift 106 lsa and 106 intake centerline.Cams seem kinda similar.
Car will be drag race only
360 cid 10.3 compression,eddy rpm performance heads,m1 intake 750 holley,tti headers,904 trans and 9.5 converter 3.91 rear gear.28"tall tire in a 72 scamp
1st should we advance this new cam to like 102 or keep it "straight up".
What kind of power increase would you think this new cam may do over the old,more torque more hp.Old cam ran a best of 11.70 at 114 with a 727 trans and 10" converter,hoping to see 11.20's,think we have a shot??
 
Dont think you are going to pick up half second with cam change...

if it is a race only car...get a race converter....8 inch flashing to 4800-5000 rpm...and 4.56 gears...In fact you will see a bigger improvement with a converter then the cam...
 
I agree - lose the street convertor and go two steps up to a set of 4.30s.

A quick reality check - calculate the slippage in that convertor:
What rpm does your engine cross the stripe at? Divide that by what mathematically you should be crossing at (0% slippage).
 
Switching to the 904 trans is probably worth 1-3 tenths alone. The cam change might be worth a tenth...might run the same....hard to say, if you already have it, try it and see. With more gear the new cam would probably be happy (because you will probably give up some low end torque with the increase in duration). Stock stroke small blocks like a little gear, like the others said, 4.30-4.56 gear sounds good...and a good 8" converter......but now that we suggested rebuilding your whole car, what do you think? Just kidding:D, good luck with the car, and let us know how it goes.
 
Just some general questions: What is the 9.5" converter's stall rating? If this is a race car, then why on 3.91? 3.91 with a 28" tire is like a 3.55 with a 26" tall tire.

If you plan to run the cam with the 3.91s and the 28" tall tires, then I would advance the cam 4 degrees, IF you have enough piston to valve clearance.

If it was me I would swap the converter and transmission first to see where you are. The converter and trans swap may improve your MPH at the finish line and affect rear gear selection.

The longer cam duration won't affect max torque, just move it up in the power band. With only 8 degrees additional duration the power should migrate roughly 400 RPM higher. Make sure your valve springs are up to the additional RPM shift points. The tighter lobe separation angle should help it build more peak HP and torque.

The real trick is will the new converter stall let you take advantage of the additional torque higher in the curve.
 
To Moper
I used one of those converter slip calculators and was coming up with like 17% slip seems high to me,114mph at 6400rpm with the turbo action 10" street s-800 converter,this new unit 9.5 for the 904 is supposed to be built based on the new cam and other car info they took so hopfully is better.
 
flyfish said:
Switching to the 904 trans is probably worth 1-3 tenths alone. The cam change might be worth a tenth...might run the same....hard to say, if you already have it, try it and see. With more gear the new cam would probably be happy (because you will probably give up some low end torque with the increase in duration). Stock stroke small blocks like a little gear, like the others said, 4.30-4.56 gear sounds good...and a good 8" converter......but now that we suggested rebuilding your whole car, what do you think? Just kidding:D, good luck with the car, and let us know how it goes.
Click to expand...

THanks,we have been a bit concerned about getting the car to stick off the line,we can only get a 10.5 tire under the car right now,we wanted to minitub/narrow and then go to like a 4:30 but money says maybe next year for that project.THe 904 switch is partly why we are switching,the 727 was tired/slipping on 3rd gear shift so making the move to the 904 now with a low 1st gear set,and the 9.5 converter is what they speced for the car so hopfully works good/better than the turbo action off the shelf unit:burnout:
 
sledger46 said:
Just some general questions: What is the 9.5" converter's stall rating? If this is a race car, then why on 3.91? 3.91 with a 28" tire is like a 3.55 with a 26" tall tire.

If you plan to run the cam with the 3.91s and the 28" tall tires, then I would advance the cam 4 degrees, IF you have enough piston to valve clearance.

If it was me I would swap the converter and transmission first to see where you are. The converter and trans swap may improve your MPH at the finish line and affect rear gear selection.

The longer cam duration won't affect max torque, just move it up in the power band. With only 8 degrees additional duration the power should migrate roughly 400 RPM higher. Make sure your valve springs are up to the additional RPM shift points. The tighter lobe separation angle should help it build more peak HP and torque.

The real trick is will the new converter stall let you take advantage of the additional torque higher in the curve.
Click to expand...

Thanks,the 9.5 converter was specced for the cam,at least he took the cam info along with other info,he is thinking apprx 3800-4000 stal has yet to be run,the new 904 also has a low 1st gear set.THe 3.91 is in there now and are concered with hook on ss springs and 10.5 tire,we are on the look out for 4:30's and wil be moving up when we can minitube/narrow for some more tire but maybe we are over cautious,with old cam and 727 we had 1.66 60' times.We installed the cam at 103 and funny you mention IF on the Pto V cleareance brings up my next question how much do I need,Looks like we have about .080 on the intake and we have to redo the exhaust our check spring was too long and binding:burnout:
 
You should not have a problem getting it to hook on a 10.5 tire. My car is on 10.5 Hoosier quick time pro's...hooks just fine with a stroked small block and runs 6.8's in the 1/8 (10.7's 1/4). The car currently has Caltracs, but it ran the exact same number on stock springs (not super stock) with a snubber and a set of drag shocks....no joke.
 

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scampy said:
750 holley
Click to expand...

with the new cam you might want to bolt something a bit bigger on if this is all-out race

750 holley covers a very wide spectrum though. if you had the right one that was jetted/tuned/etc it would get the job done. if you have an out-of-the box 750 you would probably do better with something a bit larger.

if you do the holley interactive carb thingy with your specs it seems to suggest a 800-850cfm with mech secondaries / manual choke.

http://www.holley.com/applications/CarburetorSelector/CarbSelection.asp
 
17%?!! That's the "10 inch" convertor. They're just not that efficient when yo ureally spin them. You should be less than 1/3 of that at the stripe. that's wasted horsepower and lost MPH.
Looking closely at both those cams - you're really only looking at another 10° or so between .050 and .200. It's almost no change. I wouldn't expect a dramatic improvement in power. I also don't think it's going to move up the rpm range much at all. They are very, very with the exception of the shape of the middle of the lobe. I'd suggest you change the trans and go witha real convertor, then tune it and see what it might want. Better doing one change at a time and optimizing it, then make another change.
 
moper said:
17%?!! That's the "10 inch" convertor. They're just not that efficient when yo ureally spin them. You should be less than 1/3 of that at the stripe. that's wasted horsepower and lost MPH.
Looking closely at both those cams - you're really only looking at another 10° or so between .050 and .200. It's almost no change. I wouldn't expect a dramatic improvement in power. I also don't think it's going to move up the rpm range much at all. They are very, very with the exception of the shape of the middle of the lobe. I'd suggest you change the trans and go witha real convertor, then tune it and see what it might want. Better doing one change at a time and optimizing it, then make another change.
Click to expand...

Yea was hoping for better from this converter being "made for the combo" time will tell,and one change at a time for tuning sounds just like my dad,thats always been our motto:cheers:
 
Ok the cam is in and we advanced it to 102 seems like that was the concensus and we have .079 p to v on the intake and .116 on the exhaust,was a little concerned on the intake but from what i've read should be good??
 
Did you check the pressures of the springs? I think you're ok if they are still strong. I like .100/.100 but I think you're ok.
 
springs are brand new matched for cam from comp,those numbers are with checking springs and 0 lash on rockers,so should be a bit more when actual set up is used i'm guessing
 
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