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Stroke of crank for 1970 Trans Am Motor
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Javelin_GT View Drop Down
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Points: 1068 		Post Options Post Options   Thanks (1) Thanks(1)   Quote Javelin_GT Quote  Post ReplyReply Direct Link To This Post Posted: Jan/16/2022 at 7:22pm
Originally posted by PHAT69AMX PHAT69AMX wrote:

The reason AMC changed what they were doing to come up with a 305 / 5.0 Liter engine is because TransAm CHANGED the RULES for the 1970 Season allowing companies to change the STROKE.
Prior to that TransAm Rules DISALLOWED changing factory stroke, but allow altering the Bore.
Thus AMC was "stuck" with 3.28" stroke as was stock in the 290 & 343,
and HAD TO USE the 3.28" stroke and change bore to achieve the 305 CI Limit.

Once TransAm changed the rules for 1970, AMC changed what they were doing because obviously a 4.00"+ Block Bore flows better than a sub 4" bore...

AMC stuck with the stock 4.08" bore and de-stroke to whatever was needed to result in 305 CI
but AMC never made & sold to the public in production cars a 4.00"+ 304 / 305 CI engine...
UNLIKE both Chevy & Ford which both did...

I always thought it would be cool to do a 1970 Javelin TA street car like the Boss 302 Mustang or DZ/302 Camaro.  Basically a car AMC never made but should I have.
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Points: 6912 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jan/16/2022 at 9:15pm
My girlfriend/wife beat a 302 Camaro all but once off the street lights, 77/78, 1968 Javelin 232 3 spd manual for about 1/8 mile.
I installed the floor shifter, a bigger single barrel carburetor and some nice wheels I found at the wrecker.
That car lost it's wind at 55 MPH, but she drove it bell bent until there. Most every V8 muscle were left in the rear mirror between lights.
The Pinto in town, with a 302, was the car to beat, other then that girl in the AMC.
A 302 Mustang or 302 Camaro were not that special on the street in the day. 
Add modern bolt on pieces and everything changes.




   
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WesternRed View Drop Down
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Points: 5808 		Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Jan/16/2022 at 9:28pm
What series are you actually planning on running?

SVRA does not run Vintage Trans Am as far as I can see but you would probably fit into here somewhere:


Quote Must be standard or optional series, bore and stroke as provided by the manufacturer for make and model Bore may be increased by .060

The actual Historic Trans Am series doesn't allow tributes, only the original cars that raced back in the day:


Whatever series you are considering, the first thing to do is to get across the rule book.
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SVRA has make and model sheets.  Go here and scroll down to the Javelin.
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WesternRed View Drop Down
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Points: 5808 		Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Jan/17/2022 at 12:19am
Looks like different classes depending if you are running an AMX or Javelin, so for the Javelin you could de-stroke a 360, interesting that the 304 and 343 are not listed as base engine applications. I'm not sure what sort of budget we are working for this exercise, but if the budget was limited I'd probably get started with a 290 or a 304 with a 290 crank if that was allowed and upgrade from there over time.

Edit: Since you are allowed 310 cubes, maybe they will let you run a 304, that way you get 1/2" head bolts and dog leg heads to play with..


Edited by WesternRed - Jan/17/2022 at 7:44am
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Points: 6912 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jan/17/2022 at 7:18am
Just because I have the pieces, I'm putting together a 290 with a 3.44 crankshaft that works out to be 304 CI. Standard bore TWR forged pistons at 1.580" CH is 0 deck height.
Not a race motor, just a 9:1 SCR pump gas friendly.
For the race motor you would want the 290/343 crankshaft but need a log rod in a 343 or 360 block. A 4.0l 6.125" rod could be a good experiment. Right offset, bearing/pin sizes and they make good HP. Custom piston required.

I was getting carried away with the 4.0l connecting rod in thinking of what I'm going to do with my own 343 build. You would have to de-stroke the 3.28 crankshaft to get 305 CI.


Edited by Trader - Jan/18/2022 at 9:00am
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Points: 903 		Post Options Post Options   Thanks (0) Thanks(0)   Quote DragRacingSpirit Quote  Post ReplyReply Direct Link To This Post Posted: Jan/17/2022 at 8:24pm
how about a short deck 390 (as short as possible) with std bore, 4.165" with a de-stroked forged 390 crank to around 2.8 inches with some fully ported, iron, dog leg, large valve heads, crossram ? about 10k+ rpm.........

The small bore block limits your head flow and should be avoided but there are endless combinations i can think of.


Edited by DragRacingSpirit - Jan/17/2022 at 8:42pm
Best 1/4 mile 8.99, 1/8 mile 5.71, 60 foot 1.27, no power adders
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Points: 6912 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jan/17/2022 at 10:53pm
Thinking a 343 or 360 with 3.28  crankshaft and 304 heads. It's been posted several times that the 304 head can flow better then 090 or 502.
Putting 304 heads on my 290 with 1.84" and 1.5" valves (cheaper then replacing AMC valves and guides). The 1.94" would shroud the 290 bore, did the math.
A 1.94" or 2.02" would be good on a 4.080" bore and there are builders here posting 304 head numbers that are better then factory 360/401 heads and as good as aftermarket aluminum heads.
Have a complete 343, standard bore 360 block, spare 3.28 crankshaft, camshafts, and several sets of heads, 290, 343, 390, 360-401, stock timing covers, several intakes ...
All it would take is $$$ for machining, longer rods, custom pistons, custom camshaft, that are hard for many in the hobby to come by!
There are many other hoarders out there with the same parts and the same lack of $$$.
Just saying, a build with a 3.28  crankshaft would get you close to proving a build and the pieces to accomplish this are out there.
Personally would build with the 3.28 crankshaft first and go from there to build this type of race motor. More cost effective then having custom everything made and tweaking as you go.
Personal opinion. A 4.165" bore is too large to keep within 305 CI.
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Points: 683 		Post Options Post Options   Thanks (0) Thanks(0)   Quote rsrguy3 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/17/2022 at 11:52pm
It almost seems like it would be easier to go with a 71 chassis. 
javguy
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Points: 5808 		Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Jan/18/2022 at 7:01am
The 3.28" crank with a 4.08" bore (343/360 block) would put him at 343 cubes, way over the 310 cube limit.
I've finally given up drinking for good...........now I only drink for evil.
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