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trying to get to 5.0
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10sec.et
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Joined: 29 Mar 2006
Posts: 3433
Location: Houston,Texas
345276.58 points


1969 Oldsmobile Cutlass

PostPosted: Mon Sep 19, 2016 10:50 pm    Post subject: Reply with quote

i hear ya. same reason the Olds sits in the garage.

test & tune is this weekend. however, i wont be there with the car. my daughter turns 13 this week and her party is Saturday. the chassis guys will be there so they can dial in all of that. if i can get someone to download the data logs and email them to me, ill tune from home.

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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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Knarley Darley
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PostPosted: Fri Dec 02, 2016 10:36 am    Post subject: Reply with quote

10sec.et wrote:
on an unrelated topic.... the cylinder walls had fine surface rust on them. i assume that's caused by sitting for a few days after running the alcohol? should we dump in some race gas and run it for a few minutes after the races?

Just open the throttle and spray a generous amount of WD-40 while spinning it with the starter to prevent rust in between races.
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Knarley Darley
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PostPosted: Fri Dec 02, 2016 10:45 am    Post subject: Re: trying to get to 5.0 Reply with quote

10sec.et wrote:
the little Austin needs some more power. it will run 5.30 consistently, regardless of good/bad air. problem is, i need to get it to 5.0. it has run 5.20s and with some careful tuning, can be there. i did look at the plugs and can probably add a couple more degrees timing. that still wont get me to 5.0.
there's no room for turbos or supercharger. nitrous is out of the question. so, im stuck doing this NA.
thought about adding 20% nitro but that seems sketchy. weve looked at different head/cam combos but everything requires a complete rebuild. the short block was just redone so, thats out of the question. custom cam and porting might be an option but who?

engine (to the best of my memory)...
582 BBC
Brodix BB3 heads (out of the box)


cam- 280/308 @050
830/810 lift
114cl
Rons alcohol injection system. sheetmetal intake with two throttle bodies.
14:1 compression

trans is a glide. converter stalls to an actual 6200.

456 gears

car with driver 2500lbs.

oh, and we have 4 weeks until the next race.


We did a lot of cam testing back in the day, and every similar engine to yours liked a bit more intake duration like in the mid 280s and a bit less exhaust duration like 290. remember also that every point of compression is 4% power increase roughly with gasoline, not sure on alcohol, but I would imagine similar. I think with the porting, and head milling you may already be there without any other changes, but if you put a steeper gear in there I think it would run the #
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Knarley Darley
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PostPosted: Fri Dec 02, 2016 10:47 am    Post subject: Reply with quote

Just a thought that the wide LSA helps with piston to valve clearance. I have run as much as 117.5 for this reason with huge cams around 1" of lift at the valve.
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Big Dave
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PostPosted: Fri Dec 02, 2016 11:50 am    Post subject: Reply with quote

Agree with widening the LSA on a smaller displacement BBC but it does increase bottom end torque which could challenge traction. I think a BBC needs more exhaust duration to compensate for the poor exhaust port found on the stock head design. If you are running a 10 or 12 degree head with raised ports then yes I agree with you.

Big Dave
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10sec.et
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Joined: 29 Mar 2006
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Location: Houston,Texas
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1969 Oldsmobile Cutlass

PostPosted: Wed Dec 21, 2016 12:47 am    Post subject: Reply with quote

a quick update on this....

we got the new motor in back in september. it was a brutal battle with tire shake. finally got that sorted out and the first clean pass, it lost two rods. lots of speculation on what happened. IMO, it didnt have enough rod clearance. it had .003. but what do i know, im not a builder.

engine builder blames it on oil contamination. well, it didnt have 5 full passes on that oil. we used to run all weekend before changing oil in the old motor. still waiting to get it back. hopefully get some test and tune before spring.

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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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Big Dave
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PostPosted: Wed Dec 21, 2016 11:05 am    Post subject: Reply with quote

In my opinion 0.003 is too tight. You loose a rod when parts expand and reduce clearance (resulting in loss of lubrication that results in welding parts together from friction); or you over rev the engine (resulting in loss of lubrication that results in welding parts together from friction).

Big Dave
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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Wed Dec 21, 2016 1:50 pm    Post subject: Reply with quote

especially with those big journals. this thing shifts at 7800. running on alcohol doesnt help either.

the data log showed it letting go at about 6200.

i would be happy with .0045 - .005

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af2
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1933 Willys Coupe

PostPosted: Thu Dec 22, 2016 1:12 pm    Post subject: Reply with quote

We run the Blown alcohol Willys at no less than .009. It does spin to 9500 though.
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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Sat Apr 15, 2017 1:01 am    Post subject: Reply with quote

still havent got the motor back but its making progress. had some issues on the dyno but nothing major. expect to get it back in the next week. still dont have the clearance i want and the builder is dictating how it should be tuned (gonna be interesting at T&T) but its either going to run the number or hes got some splaining to do!!
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Paul P
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Location: Townsend, Mass.
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1971 Chevrolet Chevelle

PostPosted: Thu Apr 27, 2017 12:45 pm    Post subject: Reply with quote

.009 has to be a bearing clearance. Piston the valve would go Boom at .009.

Gearing might get you there depending on how tight it is in the lights. If you have RPM to spare gear the Wee out of it and see what happens.

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2001 Focus 2.0 Zetec
15.63@87 MPH 1/4mi
1971 - Chevelle 408 SBC N.A.
6.95@98.6 MPH 1/8mi
10.97@121 MPH 1/4mi
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Big Dave
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PostPosted: Thu Apr 27, 2017 4:03 pm    Post subject: Reply with quote

10sec.et wrote:
af2 wrote:

You could easily use a .041 gasket IF the clearance is .005.


clearance where? depending on what the machinist says, im planning on using a .030 or .040 gasket.

i think it has 4.56 gears now. go to 4.88 or steeper than that?


Adam says he uses a 0.009" bearing clearance in the rods.

Minimum piston to valve clearance is 0.080 on the intake and 0.100 on the exhaust valves with steel rod; add 0.030" to these numbers for aluminum rods as they stretch like taffy at high RPM.

If your pistons have deep pockets it is better to go thinner on the head gasket as there isn't a lot of flat piston top to worry about quench. That and the smaller the chamber the better the fuel air can be mixed.

I used to run 5.13 or 5.38 with a four inch stroke BBC at the strip. I had 4.56 gears in my old Impala (that I drove on the street with a 4.375" inch stroke).

Big Dave
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Paul P
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1971 Chevrolet Chevelle

PostPosted: Thu Apr 27, 2017 4:50 pm    Post subject: Reply with quote

Big Dave wrote:


I used to run 5.13 or 5.38 with a four inch stroke BBC at the strip. I had 4.56 gears in my old Impala (that I drove on the street with a 4.375" inch stroke).

Big Dave


What size tire were you running on the Impala with those gears? With that much gear and a BBC it must have spun them pretty easily.

_________________
2001 Focus 2.0 Zetec
15.63@87 MPH 1/4mi
1971 - Chevelle 408 SBC N.A.
6.95@98.6 MPH 1/8mi
10.97@121 MPH 1/4mi
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Big Dave
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PostPosted: Thu Apr 27, 2017 7:19 pm    Post subject: Reply with quote

Paul P wrote:
Big Dave wrote:


I used to run 5.13 or 5.38 with a four inch stroke BBC at the strip. I had 4.56 gears in my old Impala (that I drove on the street with a 4.375" inch stroke).

Big Dave


What size tire were you running on the Impala with those gears? With that much gear and a BBC it must have spun them pretty easily.


Could burn through a set of tires in minutes with the aide of a line lock. I used a 4L80e to knock the gear down: but yes that was far too much gear for the amount of torque I was making. It was in the car from a previous 370 horse 350 I had in it before the first big block went in. But i used to run 4.56 gears on the street a lot in my younger days Back when an L-88 427 was the hot ticket in a Camaro.
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Paul P
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1971 Chevrolet Chevelle

PostPosted: Fri Apr 28, 2017 8:31 am    Post subject: Reply with quote

Big Dave wrote:
Paul P wrote:
Big Dave wrote:


I used to run 5.13 or 5.38 with a four inch stroke BBC at the strip. I had 4.56 gears in my old Impala (that I drove on the street with a 4.375" inch stroke).

Big Dave


What size tire were you running on the Impala with those gears? With that much gear and a BBC it must have spun them pretty easily.


Could burn through a set of tires in minutes with the aide of a line lock. I used a 4L80e to knock the gear down: but yes that was far too much gear for the amount of torque I was making. It was in the car from a previous 370 horse 350 I had in it before the first big block went in. But i used to run 4.56 gears on the street a lot in my younger days Back when an L-88 427 was the hot ticket in a Camaro.


All cool stuff. Didn't see the tire size in there Dave.... Cheers

_________________
2001 Focus 2.0 Zetec
15.63@87 MPH 1/4mi
1971 - Chevelle 408 SBC N.A.
6.95@98.6 MPH 1/8mi
10.97@121 MPH 1/4mi
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