498 Dyno, RR270 ovals and Straub cam - Page 3 - Chevelle Tech
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post #31 of 42 (permalink) Old Jan 15th, 19, 11:42 PM Thread Starter
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Re: 498 Dyno, RR270 ovals and Straub cam

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Originally Posted by bracketchev1221 View Post
I'm curious how much vacuum were you able to pull on this setup?
I really don't know Ray, just didn't get that far yet.


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post #32 of 42 (permalink) Old Jan 16th, 19, 8:51 AM
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Re: 498 Dyno, RR270 ovals and Straub cam

Ok thanks. I thought maybe they tuned it on the dyno.
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post #33 of 42 (permalink) Old Jan 16th, 19, 10:45 AM
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Re: 498 Dyno, RR270 ovals and Straub cam

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I really don't know Ray, just didn't get that far yet.
I think I read 107 lsa, there is no way you are running a vacuum booster to this setup right?
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post #34 of 42 (permalink) Old Jan 16th, 19, 11:42 AM
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Re: 498 Dyno, RR270 ovals and Straub cam

At 248/254at .050 on 107, the numbers are not conducive to vacuum much more than 12 inches at idle.

How much vacuum an engine actually has is exaggerated as much as HP and fuel mileage.

A Hydraboost will fix that as far as brakes are concerned.
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post #35 of 42 (permalink) Old Jan 17th, 19, 6:23 AM
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Re: 498 Dyno, RR270 ovals and Straub cam

I had a Comp Magnum 245/252, .650/.650 on 110LSA that I tried with an automatic and a 10" 3000 converter in a 469", rpm drop from neutral to drive was severe, IIRC 8-9" vacuum at 950-1000 rpm in neutral, it was close to 7" vacuum at about 800 rpm. Vince tried it also (his car had a stick) it was just too radical at lower rpm. We both agreed it ran great at WOT and from 4000 rpm up but the idle characteristics just weren't worth it.
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post #36 of 42 (permalink) Old Jan 17th, 19, 11:36 AM
 
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Re: 498 Dyno, RR270 ovals and Straub cam

I cammed a BBF last year, cam is on a 107LSA. 15" at 750 idle rpm. 521CID build.

Chris Straub
Mfg Performance Parts

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Why is it we never have time or money to do it the right way in the beginning but we always have time and money to do it over again?
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post #37 of 42 (permalink) Old Jan 17th, 19, 8:25 PM
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Re: 498 Dyno, RR270 ovals and Straub cam

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I cammed a BBF last year, cam is on a 107LSA. 15" at 750 idle rpm. 521CID build.

Doesn't really tell much without rest of the specs. Guess the real answer is for the owner of the motor in this thread to post the idle speed and vacuum. I'd have thought the dyno operator would've noted that if for nothing else but to baseline the carb.

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post #38 of 42 (permalink) Old Jan 17th, 19, 9:41 PM
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Re: 498 Dyno, RR270 ovals and Straub cam

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Originally Posted by cstraub View Post
I cammed a BBF last year, cam is on a 107LSA. 15" at 750 idle rpm. 521CID build.
With those duration numbers at .050.

'67 Chevelle Malibu, Catalina Blue, 540 inch Rat, Air Flow Reasearch 290 CNC Heads heads, Custom Hyd Roller, .675 lift, 234, 244 at .050, Lemons Headers, Holley Multiport Fuel Injection, TCI 6X 6Speed Automatic, 12 bolt Posi Eaton TruTrac, 3:31 Richmond Gears, front and rear power disc brakes, Global West Suspension, etc.

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post #39 of 42 (permalink) Old Jan 17th, 19, 10:10 PM
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Re: 498 Dyno, RR270 ovals and Straub cam

242/248 646/653 110lsa 8" at 850 rpm. Turbo 400 3000 stall. Great idle. No big rpm drop when putting in gear. Power brakes work fine. Just dont pump them at idle
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post #40 of 42 (permalink) Old Jan 18th, 19, 1:01 AM Thread Starter
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Re: 498 Dyno, RR270 ovals and Straub cam

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Originally Posted by GRN69CHV View Post
I had a Comp Magnum 245/252, .650/.650 on 110LSA that I tried with an automatic and a 10" 3000 converter in a 469", rpm drop from neutral to drive was severe, IIRC 8-9" vacuum at 950-1000 rpm in neutral, it was close to 7" vacuum at about 800 rpm. Vince tried it also (his car had a stick) it was just too radical at lower rpm. We both agreed it ran great at WOT and from 4000 rpm up but the idle characteristics just weren't worth it.
What we each find radical really boils just down to our personal opinion. You make a good case for why we shouldn't buy off the shelf torque converters. I've ran bigger cams just fine, with better converters. I had an ati converter built for this combination and I expect it will be "just fine". This cam delivered everything I asked for, I didn't ask for idle vacuum because honestly it was not high on my list but making power where it did was. It seems anybody can make 650 hp at 6500 rpm, but I'm not smart enough to keep the mile long a/c belt on at 6500!

Quote:
Originally Posted by GRN69CHV View Post
Guess the real answer is for the owner of the motor in this thread to post the idle speed and vacuum. I'd have thought the dyno operator would've noted that if for nothing else but to baseline the carb.
1st post. It was broken in on the dyno, with out the air hat thingy when this run was recorded. went to lunch to let it cool, changed the plugs, put the air thingy on, and broke (self inflicted) early on what was supposed to be our base line pull. It had run a total of 1/2 hour or so, maybe 40 minutes at varying rpm against a light dyno load, checked a plug a few times to ensure we were safe on jet and timing, at those few shut downs were the only times we brought the rpm down to idle territory. We were not recording vacuum.


It idled at 1000-1100 and fairly rough, didn't try lowering the rpm below that, i don't recall either of us touching the mixture screws. I noticed when I removed the carb that the rear blades were closed as when I bumped the pump arm, the gas pooled in the venturi so I'm sure the primary transfer slot was exposed. With some more timing down low and actually tuning the idle circuit it will improve significantly. btw, it is surprisingly responsive down low. I planned to get vacuum readings, get the best idle, and a compression test, along with some lower rpm data, but none of that obviously happened. I'll post up the vacuum when it's running in my car. I'm confident enough to say now it will idle in gear with the ac on.


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post #41 of 42 (permalink) Old Jan 18th, 19, 1:53 AM Thread Starter
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Re: 498 Dyno, RR270 ovals and Straub cam

To be fair, In hind sight, my "fairly rough" idle may have been pretty (very) optimistic, it was bad.... And it's easy and way to early to say if it will work as I have a completely torn apart car. We all know everything is a compromise. When it gets closer, so will my panic level. If it comes up short, I'll post that up too..

Thank you all for the great discussion!


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post #42 of 42 (permalink) Old Jan 18th, 19, 2:27 AM
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Run the timing locked out, move the IFR to the lower position in the metering blocks if they aren’t there already, and a standard v173 pcv valve if you are running one and t will be fine.
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