451 stroker chally up and running!!! • The Dodge Challenger Message Board

by **73challengerguy** » 31 Jul 2008 16:30

well guys the beast is running.......thanks to eddie and advice from dave to send my dizzy to don at fbo!!!.......got it right.....revs like prostock drag car....unreall........havent flogged it yet....doing some plug checks and fine tuning on the carb now that i have the timing down......very happy so far....car pulls sick hard and i havent even reved it real hard yet.....cant wait for that...........any sugestions on the jetting boys?.....runnin 74's unpfront and 82's in the rear......changed the power valve from a 4.5 to a 3.5 cuase of the low vacuum my cam is making........like i said gonna do some plugs check and see what its doing.........by the way running a 850 quickfuel techs.....vacumm secondaries..........lots of arguements about this size of carb on this motor ...some say too much....need a 750..,.some say just right with a lil tuning.....wadda ya think....thanks

by **dave-r** » 31 Jul 2008 16:44

Glad you got that sorted. :s017:

The problem with carbs these days is that different people are rating their carbs in different ways.

They are flowed at different pressures and some are "wet" flowed. Two barrel carbs are rated different to 4bbl carbs etc.

So a 750 demon carb for example flows about the same as a 850 holley. A 1350cfm six pack flows about the same as a 950 4bbl.

I would say that if your carb flows better than a 850 Holley 4bbl then it is probably too big. However if it has vacuum seconday opening then it may be OK.

If the primaries are smaller than the secondaries then that will help too.

by **73challengerguy** » 31 Jul 2008 17:02

thanks dave!........well the choice i have to make is tough.....cause im sure if i take the 850 back to summit and say hey......trade for a 750 they would......ive spent alot of money there lately........lol
but how am i gonna know to do that really?......should just swap to a 750 or tweak the 850 .......????.....ya know...how iwlll i know whats best for me......

by **Eddie** » 31 Jul 2008 17:20

I would say with the setup he has the along with the Carb/Single Plane intake, Cam and compression) is perfect for that combo. Leave it alone and put a hundred or so miles on it . Power wise it wont mean that much of a difference between a 750/850 it's more about drivability on a street machine. Then pull a plug to just establish a baseline. With his Jetting and vac sec. operation it should be close to perfect. :thumbsup:

If you do make a change Jeff please make one change at a time. That way if it doesnt run according to your expectations it will be easy to figure out what went wrong. Making numerous changes at once leads to aggravation. Trust me on this!!!! :lol:

by **73challengerguy** » 31 Jul 2008 17:45

oh yes eddie.....im listening buddy.......drive it a while...keeping an eye on the plugs........u know one thing i did notice though......i dontknow if i got my email or not about putting a light on it???....but i didnt....i just dropped it in and it was living at 21 intial........but it does crank a lil bit before it starts now....were before it fired very quickly....its not struggling or nothin....just spinns longer......any ideas on why? and the should i put a light on it to double check dons work>?

by **Eddie** » 31 Jul 2008 18:08

You can put a light on it and double check his work, if you placed the dizzy back in the same spot you might be right on the money. I wouldnt worry to much about it as long as it starts OK and revs quick. Take it for a spin and see how the mid range and top end feel, without crashing of course. :lol:

It should have 34 degrees at 2800- 3200 RPM's end of story! :thumbsup:

If it does all that, close the hood, time to enjoy instead of fiddling around and worrying about it too much Jeff. You have deserved this for a while. Relax :s002:

Hope i didnt step on daves toes. he can tune a 440 better than anyone I know. :thumbsup:

by **73challengerguy** » 31 Jul 2008 18:24

yeah im gonna leave it........unless it dentonates on the high end or something........drive and keep and eye on the pluggos! :mrgreen:

It is at low speeds that you will find out if the carb is too big or not. Poor throttle response is one sign the carb is too big.

by **dave-r** » 31 Jul 2008 20:15

I meant to ask if it was a single or dual plane manifold.

Being a single plane manifold helps a lot with a bigger carb as Eddie says.

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by **73challengerguy** » 31 Jul 2008 20:24

it is a single plane dave........being a novice...i really dont understand....how carbs and there circuits works.......as far as the powere valve vs the front and rear main jets....ect.......i would think a 451 cube motor could handle or run bad ass on 850....but what do i know... :s008:

like u and eddie say the single plane helps me then.....
thanks for the leads on the front end stuff,......... :wink:

by **dave-r** » 31 Jul 2008 20:41

I was going to explain a bit more but decided to stick while we are ahead. :wink:

by **73challengerguy** » 31 Jul 2008 21:41

okay.....dont understand that one...but thats cool.......