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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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Javelin_GT Quote  Post ReplyReply Direct Link To This Post Posted: Jan/20/2022 at 5:32pm
Originally posted by Trader Trader wrote:

Still stuck on the 6500 RPM with the cast crankshaft.


This Javelin ran vintage for years with a stock 290 crank and rods.  It had forged pistons with good oiling but was still running when they swapped it for a Barry Allen built 5 liter.  In fact its currently in a Rambler that is set up for vintage racing.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote klvn8r Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2022 at 1:09pm
Pretty sure that is a 25 y.o. picture...taken at Pueblo with RMVR! Wink  by a great photographer!

That car wasn't "fast" back then, but the driver was having a ball, and ran all weekend.  Find a club, read the rules, and let your wallet/conscience be your guide.  SVRA is MUCH more liberal these days, and really want cars showing up, not bogged down by a rulebook.  RMVR, CVAR, and others stick to a more "era correct" rulebook, but also have some allowances.  If you have never road raced, or vintage raced, I would recommend a K.I.S.S. principle.  Trying to build a competitive 5.0L AMC today against 60 years of innovation to the SBF and SBC is NOT for the "average" AMC guy.  Look at cars from Cobra Automotive etc and you'll understand.  Not saying it is impossible......I'm just saying its gonna be difficult and pricey.




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Post Options Post Options   Thanks (0) Thanks(0)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2022 at 6:01pm
Not sure I agree 100% with that concept that the AMC is gonna be pricey compared to SBC or Ford.

When talking that kind of horsepower and reliability, even Chev and Ford cost big dollars.

It's just not possible to build a SBC or Ford with 500 horsepower plus that will live at 6K or 7K RPM for 30 minutes to an hour several times a weekend for a season on a shoestring budget. Remember, I'm not considering the leftover crap that you can find at swap meets. Normally those parts aren't going to do the job.  New SBC forged 12.5 pistons cost about as much as AMC 12.5 pistons new. $700 plus a set.

I know, I apologize to those of you are will not agree.

I'd like to get Wayne Davis' opinion on this.



70 Javelin SST, second owner, purchased 1972
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Coloradoamx Quote  Post ReplyReply Direct Link To This Post Posted: Jan/21/2022 at 8:24pm
Originally posted by White70JavelinSST White70JavelinSST wrote:

Not sure I agree 100% with that concept that the AMC is gonna be pricey compared to SBC or Ford.

When talking that kind of horsepower and reliability, even Chev and Ford cost big dollars.

It's just not possible to build a SBC or Ford with 500 horsepower plus that will live at 6K or 7K RPM for 30 minutes to an hour several times a weekend for a season on a shoestring budget. Remember, I'm not considering the leftover crap that you can find at swap meets. Normally those parts aren't going to do the job.  New SBC forged 12.5 pistons cost about as much as AMC 12.5 pistons new. $700 plus a set.

I know, I apologize to those of you are will not agree.

I'd like to get Wayne Davis' opinion on this.




My opinion for what it is worth is that it is simply going to cost money no matter what.  How much is it compared to a Chevy... I don't know because I never built a Chevy.  The bore and stroke are set if you are trying to build period correct spec for 70 and up.  The big bore/short stroke is what allows 8,000 RPM, but the head work is the secret sauce that Barry Allen brings into the picture.  Bigger valves, but especially Barry's porting got me in the 300 CFM flow, but Barry does magic with the intake runners too.  He cuts the top off a Torker and reshapes the runners and floor as well as air gapped it.  Then there is the valve train and cam selection.  My engine makes 100+ HP more than the Traco engines of the day due to Barry's head/intake work and cam.  I would have to look again, but Barry's custom cam grind is in the 700 lift range if I recall with a $3,000 T&D shaft rocker system.  Then there is the dry sump system cost to make it live at RPM and live through cornering g's.  Dry sump pump, pan, tank and hoses and drive add cost.  My destroked crank is ground with narrow journals too, so special rods that added cost.   

Adam got me the service black and crank, but the cost or rarity of those pieces is something to consider.  

The engine is just the beginning.  The fuel system, suspension, brakes, exhaust...geez, I have over $1,000 in -an fittings and braided hose alone.  The most complex issue I had to deal with was the exhaust system.  No headers worked, so I had to have a custom system built for clearance and tunneled it into the floor.  Im embarrassed to mention that cost.

But I never regret a dime spent from the time I fired it up.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2022 at 7:49am
Don't know what the plan or rules your looking at, outside the box, if you went Jerry Grant's way with a flat plane forged crankshaft, which are cheaper to make, lighter, RPM loving. 
You could do a 2.79" stroke in a 4,165" bore 390/401 or a 2.91" in a 343/360 4.080 bore.
Indy heads would bolt on, Victor Jr intake, 1-7/8" ARH Headers ...
Rods and pistons required, nice to get rods in there for a durable 1.3" CH piston.
Would be higher HP then the Trans Am motors with quite a few bolt on parts.
Still, a lot of money and you would need an engine builder.
Not minimalizing the build, but a flat plane forged/billet crankshaft, if allowed, would be something to consider.



Edited by Trader - Jan/22/2022 at 8:27am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Coloradoamx Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2022 at 9:32am
Must be iron heads if you are thinking of SVRA vintage classes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Coloradoamx Quote  Post ReplyReply Direct Link To This Post Posted: Jan/22/2022 at 10:23am
Originally posted by Javelin_GT Javelin_GT wrote:

Originally posted by Trader Trader wrote:

Still stuck on the 6500 RPM with the cast crankshaft.


This Javelin ran vintage for years with a stock 290 crank and rods.  It had forged pistons with good oiling but was still running when they swapped it for a Barry Allen built 5 liter.  In fact its currently in a Rambler that is set up for vintage racing.



This link will take you to that same car 6 months ago at High Plains Raceway with the Barry Allen engine.  It is very competitive, winning its class at RMVR a couple years in a row


Edited by Coloradoamx - Jan/22/2022 at 10:25am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Jan/23/2022 at 2:08pm




[/QUOTE]
My opinion for what it is worth is that it is simply going to cost money no matter what.  How much is it compared to a Chevy... I don't know because I never built a Chevy.  The bore and stroke are set if you are trying to build period correct spec for 70 and up.  The big bore/short stroke is what allows 8,000 RPM, but the head work is the secret sauce that Barry Allen brings into the picture.  Bigger valves, but especially Barry's porting got me in the 300 CFM flow, but Barry does magic with the intake runners too.  He cuts the top off a Torker and reshapes the runners and floor as well as air gapped it.  Then there is the valve train and cam selection.  My engine makes 100+ HP more than the Traco engines of the day due to Barry's head/intake work and cam.  I would have to look again, but Barry's custom cam grind is in the 700 lift range if I recall with a $3,000 T&D shaft rocker system.  Then there is the dry sump system cost to make it live at RPM and live through cornering g's.  Dry sump pump, pan, tank and hoses and drive add cost.  My destroked crank is ground with narrow journals too, so special rods that added cost.   

Adam got me the service black and crank, but the cost or rarity of those pieces is something to consider.  

The engine is just the beginning.  The fuel system, suspension, brakes, exhaust...geez, I have over $1,000 in -an fittings and braided hose alone.  The most complex issue I had to deal with was the exhaust system.  No headers worked, so I had to have a custom system built for clearance and tunneled it into the floor.  Im embarrassed to mention that cost.

But I never regret a dime spent from the time I fired it up.
[/QUOTE]

Thanks for responding, your input and opinions are well respected here.
70 Javelin SST, second owner, purchased 1972
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BBO UK Quote  Post ReplyReply Direct Link To This Post Posted: Jan/24/2022 at 5:55am
Worth building the car just for the sound it makes...  Clap

But clearly something that requires the budget of a small race team to acheive.  LOL

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