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Old 12-11-2009, 12:37 PM   #1
mr curious
 
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Default 4.9 Bore Spacing

Hi,
I am curious to build a 4.7 Bore and 4.250 Stroke on a Dart Block with 11.1 inch deck height! so my question is: I not see any where listed cranks and heads for
4.9 B.S ? Can i use just regular crank and heads for 4.84 B.S ?

Also is there anyone out here that have tried 11.1 Deck height with 4.250 stroke
with very long rods for good rod to stroke ratio ? Any benefits compare to the
conventional set ups?

Thanks,
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Old 12-11-2009, 01:42 PM   #2
jerry clayton
 
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Front end weight is greater so if you can get it to lift you'll transfer more weight====

I used to build and race the 4.0 stroke 7.0 rod in 10.2 blocks--can't see advantage of greater rod /stroke ratio than around there---if you really want long rod ratio with big bore, use shorter stroke and 9.8 deck(or less) and turn it higher
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Old 12-12-2009, 01:28 AM   #3
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If you're going to use the 11.1 deckheight block you might as well run the 4.750 stroke crank, with a 7.450 long rod and a piston with 1.027" pin height. This will net you a 1.568 rod stroke ratio. Myself I like anything thats above the 1.53 ratio. So you'd be doing pretty good. With the 4.7 bore and the 4.75 stroke.you'd be building a 659ci engine.

But if you went with the billit block and wanted to go to an even wider bore sepperation you could build bigger.

After considering all that. What heads, intake and distributor are you going to run?

Don

1.568 rod stroke ration
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Old 12-13-2009, 06:47 AM   #4
mr curious
 
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Default 4.9 Bore Spacing

Hi,

Thanks for all quick replys!
I am currently running a 632 with 4.75 stroke and 6.700 Rod with 10.2 D.H Big M
Block.
Also have Big chief heads and a single Dominator and turning it to around 7500-7600 rpm maximum.

I was just thinking to build a similar or little smaller cu.in short block and take advantage of the raised cam,large cam core,Big Bore and the deck height and turning it higher.

Do i Think in the wrong Direction ????

And for the crank and heads use regular stuff or special order for 4.9 B.S ?????

Thanks,
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Old 12-13-2009, 01:22 PM   #5
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Some of the best HPing engines I've been around had a rod/stroke ratio on or real close to 1.53. Sporting a nice broad power band. Thats why I try to stick around it when I have creative input on a new build. I've seen engines twist well above 8-8.5 kRPMs using it and have a very good life to them. With a good maintanence program that is.

I don't really think there is a "thinking in the wrong direction" actually. You are the end user and are wanting this engine for your use. So as long as it achieves what your end goal is then thats all that really matters.

But here is why I had suggested the bigger CI when using this block of choice. Keep in mind that these are just my opinions. I'm sure I'll be hounded for some of them.

: Everything you mentioned about the 11.1 block was designed around the longer stroke.
: Being able to fit the propper rod length in the assembly to support the longer stroke.
: Being able to fit the above in there and still fit a cam in there that will be able to get the job done.

What heads and intake combination are you wanting to run on this block? The same ones may not get you to your goal of a higher rpm without more work to them. We would need to know some more information on them. Bigger inch would more then likely need a better head cam combination to get more of everything includi9ng rpm. You will also run into some issues with the intake. Possibly the distributor also if you intend to use the stock location for it. But there are easy sollutions to these things.

Are you wanting to still be able to use your 632 as a spare and build a whole new 11.1 build? Would help us if we knew what all you are wanting to do for the whole build.

Everything I've said in this posts revolves around the 11.1 block build. I'll make a different post with my thoughts on a 4.25 stroke build.

Don
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Old 12-13-2009, 02:06 PM   #6
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If you were to come to me and ask for a totally new build wrapped around 4.25" stroke crank using the 4.9" bore spacing block this would be my suggestion.

The block would be the 10.2" deck height Dart Block with 4.7" bore. Stoke would be the 4.25" you're wanting. Using a 6.800" long rod. This would build you a 590 ci engine with a rod stroke ratio of 1.6 . This short block ought to be more rpm friendly then your current combination. If this were my personal engine, built around this short block combination, I wouldn't be afraid of 8500 rpms at all. How much higher rpm are you wanting to go with this build?

The good thing about this build is the head, intake, & distributor deal would be alot more common. I'm not sure that you can get to where you want to go on just one carb though.

From this short block you could have a head, intake & cam tailored for your needs of the higher RPM goal.


Don

Where are you from?
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Old 12-13-2009, 02:40 PM   #7
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One other combination you might consider is the same 10.2" DH on 4.9 BSing with the 4.7" bore block with the 4.375" stroke. This would build you a 607 ci engine.

You could still stay with the 1.27" pin height on the piston , use a 6.740 rod length and still have a 1.54 rod/stroke ratio.

OR...

If your ok with the 1.125" pin height on the pistons in your 632" engine you could build a 625" engine in the above block by running a 4.5 stroke and a 6.825 long rod and still have a R/S ratio of 1.517.

This post was just to promote some thought.

I do have a 540 out there running the 9.8 deck height block 4.25" crank and 6.400" rods thats making good power @ 8kRPMs. It's r/s ratio is 1.506. He had the block already when he came to me though, or it would have been a different engine.

Don
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Old 12-14-2009, 10:51 AM   #8
mr curious
 
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Default 4.9 Bore Spacing

Hi Don,

Thanks for all information !
I did'nt know there was a 10.2 D.H Block with the
raised cam location!!! Yes i have thought about all these combos and now when there is the 10.2 block it gives this thread a new dimension.

I have run a 10.2 540 cu in with 4.250 stroke and 6.800 rod and i liked it very much!
Yes i was thinking of use the big chief heads and maybe run it with the new ram box manifold.

Yes my plan was that to build a new shortblock specially made for a lot of nitrous
and use my existing top end with some work to fit the new combo!

Good to hear that you run it so high rpms successfully with your combos!

(i just read in magazines when talk about rod lenghts that use the longest rod
you can for good rod to stroke ratio so i have always looked for a rod ratio between 1.70-1.75. Very good to read your inputs and get a new thinking about
Rod Ratio.

Sorry,but no answer regarding crank and heads for 4.9 B.S compared for 4.84 B.S or do i have missed something?

Thanks
Lo, Sweden.
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Old 12-14-2009, 11:25 PM   #9
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Sorry Mr curious,

I have no experience with conterting from 4.84 to 4.9 bore spacing. Anytime I've built a 4.9 bs block, it was from the get go and all the parts were ordered accordingly.

I haven't addressed the issue cause I thought the Dart guys or Awesome Bill would hit it subject for you. Bill usually posts on the weekends. For some reason he didn't this past one.
You'll get an answer when he visits.

I did get my shinny new Dart catalog today, and in it they have the version of block that you're talking about in a 10.6 Deck Height version. Using it though would take just a lil' adapting of your intake and distributor.

Back to Bill,....I don't know who your supplier is over on your side of the world. But I would recomend Bill at Awesome Engines. Look him up on the Dart Board and you can get his contact information. Bill can spec the block to your needs and I'm pretty sure that he has offered to ship over seas. He is one of the members on this board, that I think offers this service, that I would trust.

If you need any other help, PM me and I'll send you some contact information. I'd be more then happy to help out as best I can.

Don
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Old 12-27-2009, 02:53 PM   #10
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you use the 4.840 crank in the 4.840 block they just put the 4.9" bore centers and bolt hole for them The larger 4.7" bolt will be good but your heads are most likely 4.840, they will not work. You can get 4.9 bore center heads, get a block done and your back in business with new intake and heads. I like the short stroke big bore but your going to go a long way to make just a few more hp. A rod that long with a 11.10 block is useless. You just don't need it.
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