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09-09-2012, 04:59 PM #1
88 looper 120hp big block to 140..........
Guys I know this has been beaten to death but quite honestly I did a search and still don't have everything. What I do know is I'd need the intake manifold and 6 petal reed blocks. Now I'm no expert but I would think I'd need to upsize the jets as well? Does anyone have old carb specs on these? And what else if any would complete the package?
Also if anyone knows any other cheap bolt on type mods I'd be interested....and what if any gains will I see with Carson sport reeds on either my 5 petal or the 140 6 petals? What do intake stuffers do?
This thing has 150lbs comp. in each corner and VRO still works fine. Still have QL77JC4's and see no reason to go with QL78s unless someone wants to chime in on that deal too... Sorry about all the questions in one thread lol.
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09-10-2012, 03:52 PM #2
Everyone forgot about the old dinosaurs? lol.
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09-11-2012, 06:40 PM #36000 RPM
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You are correct on the manifold/reed block swap. The jetting is richer on all three, I don't have my parts manuals with me but you can look this up on Iboats or Evinrude.com. If you have already increased compression you are reaching the end of the line for simple bolt-ons for that motor. You could remove ("gut") the inner liner of the airbox and make sure you have enough air coming in the cowl, but these will definitely require rejetting. The 6-petal blocks can be machined for more flow, and custom composite reeds will then be mandatory. To really wake up that engine it needs a lot of port work, preferably including fingerporting. Don't get me wrong, great engine, I just sold my '89 and loved it. By the way, if you needs any hard parts for that motor send me a note.
MattLast edited by MattGreen; 09-11-2012 at 06:41 PM. Reason: can't type worth a damn
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09-11-2012, 07:03 PM #4
awesome thanks for the help Matt.
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09-15-2012, 07:14 AM #5
I can buy the intake/reeds/carb set and gasket kit for a 140 big block looper for around $300 on ebay. Does anyone think this is worth the time and effort for a supposed 20hp?
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09-15-2012, 02:50 PM #6
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09-17-2012, 12:01 PM #7
Rob,
It seems you may already have some things done to your motor if your compression guage is accurate.. 150psi is not stock for a looper v4 regardless of horsepower.
Before you go much further into the modification world, investigate deeper to find out what you currently have. Get the casting numbers off the heads and carb bodies. Pull the main jets to determine there size. Confirm which reed cages you currently have in your motor and if you have the foam and baffles in the air box. Also take a photo of your gear case and post it here.
You will gain the most right now buy installing a jack plate and moving everything you can to the rear of the boat.. Or simply taking the weight out of the boat. (removed weight is free power)
Try the Raker again while adjusting engine height for the best combination of handing, top speed and low speed acceleration. Be sure to keep a log of the changes you make and the performance gains or losses. Dont forget to note the weather conditions.2006 Action Marine Comp
1980 Ventrua 2
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09-17-2012, 02:28 PM #8
Thanks for chiming in Laker. Good idea. Going to write down what i have first before I jump the gun. The most I will do internally is the intake/reeds and jetting but quite honestly i'm scared to mess with it cause it runs so smooth now lol.
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09-29-2012, 07:53 PM #9
Ok well my dealer was right. It is a 93 powerhead (with 339154 heads 1993) and 1988 120hp intake/carbs-432902 and reeds. Not sure why I have that high of compression. Could just be my gauge. Anyway time to find some jets and the rest of the goodies!