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Old 03-30-2009, 06:51 PM
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DynoSim 455 Pontiac

On another forum, a fellow was talking about warming over the 350 Pontiac motor in his newly-aquired '69 Firebird. Here is my response. I thought some of you Pontiac dudes would like to see it....

As far as the motor goes, you're thinking with your emotions rather than your wallet. You'll spend 2 to 3 times the money on the 350 and get the same power that you could by starting with a bigger motor in the first place. Start with a 455 short block. Bore it 0.030 and use Keith Black #KB371 30.5cc step dish pistons. Set piston deck height at 0.000" to 0.010". Zero with a 0.040" head gasket will give you a 0.040" squish (piston crown to underside of cylinder head with piston at top dead center). 0.010" with a 0.040" gasket will give you a 0.050" squish. Anywhere in that range will be your target for squish. Use Edelbrock #60599 heads with their #7382 head gasket set or #7381 head gasket only. You want to use only the head gaskets recommended by the head manufacturer when using aluminum heads. The wrong head gasket can "brinnell" the aluminum and you won't like the results. These heads have 215cc intake runners, 72cc chambers, 2.11" intake valves, 1.66" exhaust valves. These pistons with these heads will result in a 9.50:1 static compression ratio. Use Edelbrock #7156 or #71564 Performer RPM dual-plane, high-rise intake manifold mounting a 650 cfm, vacuum secondaries carb. Doesn't matter whose carb you use. I like Edelbrock, but others prefer Holley or Barry Grant or whatever. You won't need more carb than this because we're going to use a short, rpm-limited cam. Use long-tube, equal-length headers (not those cheezy shortie things), an "X" pipe right after the collectors and 2 1/2" pipe to the rear of the car with mufflers of your choice. This will be a torque motor, plain and simple.

The cam we're going to use will have an intake closing point of 38 degrees ABDC, so it will make a 8.25:1 dynamic compression ratio in the motor. That DCR with aluminum heads and a tight squish will allow detonation-free operation on 87 octane swill, assuming you tailor the ignition curve to work with your combination. Here's the cam card.....
http://www.compcams.com/Cam_Specs/Ca...csid=1203&sb=0

RPM HP TQ
1000 69 362
1500 128 449
2000 188 493
2500 236 495
3000 293 513
3500 354 532
4000 402 528
4500 441 515
5000 460 481
5500 405 387

You can see that the cam makes good power to 5000, then noses over and is all done. This is a street motor, not a drag race motor. Look at the incredible torque that is available right off idle!!! Over 450 ft/lbs is available from 1600 to 5100. Try doing that with a 350 Pontiac.

Couple of ways to go on the drivetrain. If I wanted to keep it cheap, I might use a TH400 with a 2000 stall converter and a 3.00 to 3.20 rear gear. If I was going to spend a little more, I'd have a 700R4 built, 2000 converter and 3.70 to 3.90 rear gear. 5000 rpm's with a 3.00 rear gear and TH400 will result in a speed of 138 mph. 5000 rpm's with a 3.73 gear and 700R4 will result in a speed of 159 mph, so don't get hung up on more cam and running the motor any higher than 5000.

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  #2 (permalink)  
Old 03-31-2009, 03:43 AM
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X2 on the torque down low!

I've previously mentioned a 55 I had in my '81 Camaro. It had ported 6X 400 heads, decent cam, Performer (there was no RPM then) and a 650 DP.

That combo, 10-bolt w/3.08's, ran 12.90. I could not hurt that 8.5" 10-bolt, and Lord knows, I tried!
Same exact combo w/3.23's in a 12 bolt picked up to 12.71.

We always went Wed. test and tune night at Orlando Speed World.

At the line (running treaded dirt track McCreary's) I would mat it on the last yellow from idle! The car routinely would lift the left front tire, especially after big race the previous w/e- traction compound was still effective, a little.

I left the shifter in "D" one time and let it shift by itself (TH400 w/STOCK calibrated governor) and the 12.7 combo went 12.9!

Always wondered what the dyno numbers would have been on it.
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Old 03-31-2009, 09:41 AM
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Cobalt which dirt track tires you use I,m considering hoosier modified tires they are pretty soft will they hook up 450 lb ft tourque and 550 hp you think? They are available cheap around here.
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Old 03-31-2009, 11:45 AM
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Quote:
Originally Posted by barnym17
Cobalt which dirt track tires you use I,m considering hoosier modified tires they are pretty soft will they hook up 450 lb ft tourque and 550 hp you think? They are available cheap around here.
I used the Road Stars (the star wasn't spelled out, just a star). They have a DOT number, but are imprinted with "DIRT", but it is small.

They are a lightweight tire, and don't have beans for sidewall strength or tread depth when compared to a regular tire.

The tread wear rating (usually around 180-220 for street tires) was a "000"!

It hooked up my 55 w/maybe three total rotations during launch. My 60' w/them was consistently 1.68- 1.72. Remember, this was w/3.23's.

The size was L-60/15 and was all that would fit. I also had used a Hoosier tire but I liked the McC's better.

I can't say how they'll work for you, but I had a lot of torque. I would say to try them, especially if you can get a deal on them.
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Old 03-31-2009, 12:10 PM
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Did you try playing around with the cam at all? Maybe going to a single pattern or messing with the LSA/ICL? Getting a custom cam is a fairly easy process now a days as long as you use catalog lobe patterns. I bet you could pick up anohter 30 ftlb.
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Old 03-31-2009, 12:28 PM
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Barnym17, I've also used the McCreary with the same success as Cobalt, the L-60/15" and G-60/15 Road Star IMCA dirt compound tire. The IMCA label makes it DOT approved. Upper 1.6's in 60', 11.50'S @ 117 mph with 400 chevy and 4.56 gears at 3600 lbs. Decent, cheap, street/drag tire with a 4-ply sidewall and enough tread to not totally suck in the rain. They go by the name American Racer now in my neck of the woods.

Friends tried a similar Hoosier "Dirt Bozz" tire but it wears a lot faster with no better traction.
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Old 03-31-2009, 12:43 PM
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Quote:
Originally Posted by ericnova72
Friends tried a similar Hoosier "Dirt Bozz" tire but it wears a lot faster with no better traction.
What kind of a burn out did you use?

I found that all I needed to do was back into the water box (driving around it first so my skinny's didn't track water in front of the McC's), pull forward and give it long enough in second gear for smoke to get going pretty good (~4 sec.?), then right up to the line.

Required (for me) no heroic measures to get them ready. Lasts longer that way, too.
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Old 03-31-2009, 01:06 PM
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Cobalt,
On the McCreary's.
Pretty much the same technique, get them too hot with a long John Force burnout and they just get greasy. Basically just a clean-em off burn with a little heat like you said, was lifting both fronts a coupla inches in an all steel '72 Nova, driving it to the track 75 miles one way. 14-16 lbs air best at the track, but drove on the road better at 20-22 lbs. Back of the car tended to sway on the big end at 12 lbs or less, made me nervous.

Never tried the Hoosiers myself.
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Old 03-31-2009, 02:58 PM
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Thanks guys I'm going to give it a try.The tires I can get are amra spec they are a lot softer than IMCA spec but I'll give itn a shot.The other option I'm looking at is Hoosier Street stock tires they apear to be identical to the tires jegs advertises as for street strip P285D, P305D etc. only I can grab them for about $20.00 each after being run one night on dirt.
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Old 03-31-2009, 03:56 PM
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Quote:
I can grab them for about $20.00 each
Heck, for that price you could run em on the street 24/7! I did anyway, but the mileage was the pits, but then again, I ran that car.

How much tread is left?

Quote:
14-16 lbs air best at the track, but drove on the road better at 20-22 lbs.
Ditto on the track pressure- I ran more (28 psi) on the turnpike run to the track from the W side of Orange Co. all the way to the E side where the track was- my round trip was about what your one way was.

Sat. nights would see them back down again so I'd be ready.
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Old 03-31-2009, 06:49 PM
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Barnym17, at $20 apiece you can't get hurt to try them. I've seen guys run the 285D and 305D too.
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Old 04-01-2009, 04:59 AM
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Most of the fast guys swap there ttr tires every night, ussualy no real wear it is just that after one night on the dirt they get just a tick slower witch can cost ya the race.
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Old 04-01-2009, 05:01 AM
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Sorry about the spelling for some reason I can,t back up and correct mistakes when submitting a post. The wrong stuff can,t be deleted?
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Old 04-01-2009, 05:20 AM
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Quote:
Originally Posted by barnym17
Sorry about the spelling for some reason I can,t back up and correct mistakes when submitting a post. The wrong stuff can,t be deleted?
Spell check before submitting, edit feature after it's posted.
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Old 04-01-2009, 06:19 AM
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Tried, I updated to msn 8 and it seems to have messed something up I'll keep working on it.
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