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Discussion Starter · #1 ·
Hai guys,would like to hear yr opinions..

Say money wasnt an issue and i intend to go with an alpha12 package,would the Jun 4.2l block be an added advantage say on the 1mile races?

Will there be a reliability issue in terms of block thickness and also,will the rpm limit be a little lesser?

Sorry for my bad english,hope i can get some usefull info.. Cheers
 

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some had bad experiences with the jun block however jun covered them well. i'd just stick to ams for more proven power. if you are strictly wanting a stroked 4.2 engine i'd go with the boostlogic which costs less than Jun.
 

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Go with JUN, they have the new design engine which can now hold the power and they give warranty too.

its not JUST JUN engines that had issues, other vendors on here have also experienced the same as JUN.

but JUN will cover you if the fault is theirs.

thanks
 

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Discussion Starter · #6 ·
Go with JUN, they have the new design engine which can now hold the power and they give warranty too.

its not JUST JUN engines that had issues, other vendors on here have also experienced the same as JUN.

but JUN will cover you if the fault is theirs.

thanks
Apart frm warranty issues which i doubt i will hv problems with as ive seen them make good of their words on their products,id like to know of the rpm limit and also apart frm their brand new, does the xtra .2l hv a significant advantage over the 4.0l race blocks?
 

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There is nothing fundamentally unique about the Jun 4.2L and as mentoined before, the important thing is to choose a shop that stands behind their work, and has a reputable for reliable power and good customer support. When running a large turbo, I would always prefer higher revs over long stroke. Remember that intertial loads are parobalic, not linear with respect to RPM. So a small increase in RPM results in a disproportionate increase in intertials loads on those rods. Given that your desire is a larger turbo such as the Alpha 12, I would stick to a 3.8 or 4.0L stock stroke engine, coupled with good camshafts and cylinder heads.

Another option to so do a 4.0L stoker rather than an overbore. This will give you better spool and more trq than a 4.0L overbore while keeping piston speeds somewhat more manageable. Our engine program has all of these options available in house. Many images and details here: http://www.forgedperformance.com/store/product.php?productid=17395&cat=512&page=1
 

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The reason we went with our 4.0 over a larger motor is not only strength but RPM capabilities. Our 4.0 race engine with our special reinforcement service is capable of withstanding 8200-8300rpm safely this is primarily due to our quality components and by retaining the stock stroke. When running a big turbo having a long legged motor paired with a larger displacement one not only improves spool time but widens your entire power band creating not only a fun car to drive but a blindingly quick one at that.

Eric
 

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I think if money is not the problem why not use all the AMS component or Switzer. When you use Jun block then some AMS and then some others like Switzer part to work with Jun block, now if the problems occurs it's hard to say it's because the AMS or Switzer component dont match or don't work good with other parts. Go AMS all the way if your from the USA the support will be easier..
 
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