square bore holly on spread bore intake?
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06-13-2003, 07:42 AM
#3
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Could be. Yes they make an adapter, which I am assuming you are using to mount the 830 carb to that manifold. You may be chasing things that you will never be able to fix. This morning I reread your complete other thread to see if there was something I was missing & I have never had a motor where just the back 4 cylinders were so way over rich. I had just assumed (I know) that your manifold was set up for a square bore carb. Might be time to buy 2 new manifolds before you spend anymore time chasing jetting.
06-13-2003, 08:32 AM
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It's been a long time since I've tinkered with a Holley. There are two things that come to mind. If it is a double pumper it should have a powervalve on both the primary and the secondary side. Is it possible one or both is blown-out, or the wrong size/rating for your vacuum needs? Or, and I'm sure you've already done this, have you looked at the float bowl settings? Also, those holley metering blocks are far from perfect(being that they are cast) they should be made from billet aluminum.
I just read your other thread as well.....HMMM, both engines huh?
Have you changed power valves? Do you have the anti blow-out Holleys? Holley sells a kit for this if not. How radical is the cam timing in these motors? I would think that you would heve to have some very big cams for the spread bore intakes to become an issue.
GOOD LUCK
Brian
I just read your other thread as well.....HMMM, both engines huh?
Have you changed power valves? Do you have the anti blow-out Holleys? Holley sells a kit for this if not. How radical is the cam timing in these motors? I would think that you would heve to have some very big cams for the spread bore intakes to become an issue.
GOOD LUCK
Brian
06-13-2003, 12:11 PM
#5
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just ordered two world products dual plane intakes for 4150 carbs at $215 each (more receipts to piss off the wife with). A couple "experts" I spoke to said they are quite sure thats my problem. Possibility of a vacuum leak is pretty good, but said theres no way the"venturi" effect thats so important in carb applications would not be all screwed up with using those carbs on the the quadrajet manifolds. I've tried everything else, including new power valves and float adjustments...this has gotta be the problem. I'' be outa town next though, so wont have it running for 2 weeks now with having to paint the manifolds first when I get back.
06-13-2003, 03:42 PM
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If you cannot use a holley or qjet with these merc 502 manifolds why would merc put the dual bolt pattern in? That baffles me, which is not hard to do. I hope the new intakes fix your ellusive problem, but am curious as to how a vacuum leak would cause a rich condition. Should go lean with the extra unmetered air. 
Certainly does sound like a rigging problem of some sort with both engines affected. Let us know how you make out.
BT
Certainly does sound like a rigging problem of some sort with both engines affected. Let us know how you make out.BT
06-13-2003, 06:04 PM
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Thats why I never gave it a thought....it fit the bolt pattern. Additionally, I used a summit linkage plate under it that had a square bore pattern....and I forgot all about the larger holes being below them cause you could'nt see them! The fronts were LEAN...and the rears black. Lucky I only had about 15 minutes of running on it with #86 jets all around. I have a feeling this will cure all the puddling of gas on the manifold floor problem too. And I know that was'nt from the floats being too high....in fact they were too low to get me over 4000 rpm. Theres lots of "dead area" on the sides of the intake throat when you put a square bore over the hole....I"m keepin my fingers crossed...but have a pretty good feeling about this
06-13-2003, 06:15 PM
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If you used an open adaptor, you just burned $430.00. If this fixes the problem, you either used a poor adaptor or you fixed the problem some other way. I commonly run square bore carbs on dual bolt pattern intakes with just a plate adaptor and have had NO problems. Please let us know when you find the problem.
06-14-2003, 12:36 AM
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I did'nt know there was an adapter. I had a summit square bore sized plate under the carb to use as a linkage adapter, and it hid the extra size of the spread bore flange from my view....I forgot all about the size difference from when I originally installed it and have switched carbs since. It looked like lots of dead air space below the gasket compared to the sportsman II made for a 4150 from Merlin.....and when I found the adapters it looked like about $50 or $60 per engine with longer studs, additional gaskets, and shipping. Additionally...after finding out about the adapters I got both pro and con reports from guys about using them...so I figured I would not blow the bucks on the adapters, and hope to offset the costs of the new manifolds by selling the stock marine intakes for whatever I can get for them. I just wanna get all these plugs burning some kind of even color before I put a hole thru a piston...and the summers are so short here in Michigan I'd rather get these things squared away sooner than later. I'm not gonna be able to post the results for two weeks due to shipping time, painting on delivery, and a vacation I can't get out of...but I'll post the results cause I'm gonna start out with the carbs set the same as they are now....so it will definitely show if there is a difference...I'm not even gonna change the floats for the first run on new plugs....thanks for the input...it all helps....Glenn
