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Old 09-27-2005, 19:45   #1 (permalink)
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what bore size would you recommend for DART block?

I am looking into building a Dart short block up using the 8.7" deck height block (I don't want to cut bonnet so 9.2" or 9.5" block will not fit) looking at 360

If I go with the Dart 8.7" block that comes in 4.125 bore but can be taken out to 4.185 safely, what should I take the bore out to considering it is my street car, or is it not worth taking bore past 4.125?

Also Dart states that max bore and stroke recommended is 4.185 x 3.5, is it worth going straight to this or should I go 3.4 stroke and less bore?

I am looking at using Scat 4340 forged internals, what do you think of this brand?

What brand and port size heads do you recommend that I use?

I was looking into using Edelbrock RPM2 intake, will this be a good choice for flow capacity and usable rev range, if not what others may be better?
Thanks guys
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Old 09-27-2005, 20:51   #2 (permalink)
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Re: what bore size would you recommend for DART block?

I think you should go more bore and less stroke- it'll leave the bottom end stronger to have shorter rods/crank throws, in my opinion.

The RPM set-up would be a good run. Are you EFI? They make a great cam/lifter kit, hardened pushrods, heads, intakes, etc that are all designed to work together, which leads to another point:

Keep your parts matched up. Edelbrock didn't put over six decades of research and development into their packages for you to go and mix up their heads and intakes and cams and whatnot- they're designed to work together and they do one Hell of a job. Go with the 2.02" intake valve design on your heads and be sure to get pistons that are notched to clear those ungodly valves.

As far as the bottom end goes, unless you're blowing it, boosting it, or juicing it, you really don't need a completely forged bottom end. If you're going to do it, though, do it right. It's a long argument between Scat and Eagle, but do what makes you happy- I don't feel like starting a fight.

Most importantly, though: KEEP US UPDATED ON YOUR PROGRESS!! We'd like to know how your build is going and we definitely want to see some dyno charts when it's done! Good luck.

Oh- Edelbrock also sells a great double-roller timing assembly for only $60. I'd greatly recommend that.
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Old 09-27-2005, 21:03   #3 (permalink)
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Re: what bore size would you recommend for DART block?

There is nothing to be gained in a street car in going beyond 4.125. Infact 4.125 is already pretty much the ultimate. It also leaves more meat in it for future rebuilds
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Old 09-27-2005, 21:04   #4 (permalink)
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Re: what bore size would you recommend for DART block?

I just re-read your post. I hope you are not talking about a naturally aspirated car here??
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Old 09-27-2005, 21:13   #5 (permalink)
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Question Re: what bore size would you recommend for DART block?

If I use the 4.125 bore with a 3.4 stroke in the 8.7" deckheight block and use 5.7" rods then I get a 364 ci motor, by increasing the bore up to 4.185 then i get a 374ci motor. The 8.7" deckheight allows the use of longer rods so the rod ratio is much better making for better durability I believe.
With the heads what port size are recommended for street use, 185 or 205? Also would I still go with the 2.02 intake valve size?
I am thinking of going NA to start with but may look at blowing it later if wanted, enough is never enough from what others have said!
Any comments or suggestions appreaciated.
Thanks for replies
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Old 09-28-2005, 05:09   #6 (permalink)
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Re: what bore size would you recommend for DART block?

I kept mine at 4" bore as I'm turbo induction..With 3.25 stroke/ 5.4" rods as used by most 347's..To get compression low enough I had to use custom C.P pistons with 27cc dish..Something you are going to have to make your mind up what you want to do? If forced induction 8.5 for blow and lower with turbo to make untold torque & power..All up my chamber size is 90cc....Yes low comp...But SAFE!!! Carefull with notching piston too close to bore as any detonation will blow through where there is any weakness..Using bigger bore puts you deffinately in custom piston field!! Have you checked the $$$ of them ?...Bloody expensive!!!
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Old 09-28-2005, 08:31   #7 (permalink)
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Re: what bore size would you recommend for DART block?

A few notes:

Racer- there is no problem going 4.185 with the block if that's what he wants to do. Dart doesn't charge $2500 for weak blocks. I do understand what you mean about leaving more meat, but I also know that high RPMs hurt long rods and that Dart blocks are damn near bulletproof.

Blown- if you want to start N/A, start that way and if you want to add a turbo later, just switch to the 27cc dished pistons as mentioned. I've seen STOCK (130,000 miles) 302s with STOCK intakes, heads, pistons, crank, rods, etc. (okay- they did add a main girdle) running sub-11s and over 500hp.

EBXR- piston companies know how to notch pistons to clear the valves. If he's running high compression with boost, then he needs to be shot, but that's probably the only time the notch could possibly be seen as a weakness. Also, it's not expensive to order pistons as high as 4.185" bore. Forged aluminum pistons with 4.185" bore is another story- maybe that's what you're thinking about.

Blown, back to you- I don't know how rich you are, but from the parts you've listed, you're looking at investing $7,000 in this motor, minimum, if you assemble and install it yourself. If you're going to do that, go ahead and run Edelbrock's Victor or Victor Jr power package and turbo it with the dished pistons mentioned above. That's my opinion. It makes absolutely no sense to waste a Dart block and forged rotating assembly on a N/A motor that isn't running on alcohol. That's my opinion. Again, keep us updated and keep asking questions- good debate going here.
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Old 09-28-2005, 08:32   #8 (permalink)
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Re: what bore size would you recommend for DART block?

Oh- and listen to EBXR when considering turbo equipment- he seems to know his stuff and has first-hand experience- good combination.
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Old 09-28-2005, 22:54   #9 (permalink)
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Re: what bore size would you recommend for DART block?

I must correct a few things.that are applicable to Aussie....Custom pistons cost around $1800 Au for a set, rings included....For top quality ...
In my combo with Twisted Wedge heads attention was paid to inlet valve notch NOT going too close to edge of piston as some off the shelf are...Obviously if you need clearance you must!!!
Plus we had the top ring alittle lower than a N/A piston...To keep it away from heat as much as possible..
On a 8.7 deck block there would be way more room in this area..
The reason we used the Oliver rods was they have oil feed to pin, which we used as a piston cooler to squart oil under piston...As these rods are designed to work on dry sump engines where the vacuum they produce pulls oil from this area so they adapt an oil feed...Sounds very Jap but in this case Yank...

Bore size???
I'd go the bigger bore..But keep in mind in turbo situations a long stroke engine and SMALL bore will tolerate more boost before detonation in most cases..The flame has to travel further, plus scavanging exhaust from cylinder is better with smaller bore.. Generally ....
A bigger bore will unshroud valves also.But forced induction this isn't an issue....
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Old 09-29-2005, 02:23   #10 (permalink)
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Re: what bore size would you recommend for DART block?

Quote:
Originally Posted by Freshmeat
A few notes:

Racer- there is no problem going 4.185 with the block if that's what he wants to do. Dart doesn't charge $2500 for weak blocks. I do understand what you mean about leaving more meat, but I also know that high RPMs hurt long rods and that Dart blocks are damn near bulletproof.
I actually meant leave more meat in it, so that it has something left for a future routine rebuild, or a piston failure that scuffed the bore.
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