1999 Longhorn Nautique Restoration Thread |
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ultrarunner
Platinum Member Joined: October-02-2005 Location: Ridgefield, Ct. Status: Offline Points: 1809 |
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Ok, the following pics clearly show that crazy Texan's will paint that damn cow on anything, and that Dominic is out prowling Texas airports. This a few minutes ago in IAH.
Enjoy Dom.... |
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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Not a whole lot to update but initial dyno pulls on the gt40 converted 408 look good. Still have some tuning to do but pretty happy considering we are using the stock intake. Should pull nicely. Wish the horsepower was higher but it’s not a race boat.
HP 375.5 @ 4800 rpm TQ 484 @ 3000 rpm TQ 488 @ 3300 rpm TQ 487 @ 3500 rpm TQ 481 @ 3700 rpm |
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Treybizttu
Gold Member Joined: October-02-2014 Location: Grapevine, TX Status: Offline Points: 534 |
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Nice numbers....
I know there are some High HP boats running around this site. I don't know many have dyno-d their motor but it would be fun to see who is up there. Looking forward to seeing progress on the boat and re-assembly! |
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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Thank you! PCM advertises the gt40 at 310 hp and 375 ft lbs. So on the torque front, it’s a nice jump. I do like the consistency between 3000 and 4000. It’s 470-480 throughout that entire rpm range. |
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beretta5spd
Senior Member Joined: February-16-2013 Location: Gladstone, MB Status: Offline Points: 255 |
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these are great numbers. all motor with great tq numbers like that will be money |
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1996,1997 Sport Nautique 1986,1992 Ski Nautique - Sold
1995 Sport Nautique - Current |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21109 |
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That intake may be hurting you more than I thought. With big cubes and big heads, the power fell off a lot sooner than I would have expected. Post the curve if you can.
One nice benefit of building a lefty... not too many dyno’s can be run backwards. |
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JoeinNY
Grand Poobah Joined: October-19-2005 Location: United States Status: Offline Points: 5693 |
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If still possible I would try throwing some higher ratio rocker arms at it looking for another 500 usable RPM. A bunch of torque between 3 and 4 k rpm is less useful than one might think in this application. Can't really prop for it without lugging the engine up high, can't really use it for much. Built a similar 408w with 402hp at 4900 hp and can confirm more RPM is betterer...
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21109 |
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Info was spread out throughout the thread... consolidated. Need more details on the exhaust manifolds, it’s not possible to “make them 4” if referring to the original PCM’s. What brand are being used? Presumably the dyno run was using dyno headers anyways... 375hp @ 4800rpm doesn’t compute to me... something isn’t right. Hopefully they stopped the dyno before peak hp was achieved? I’d like to see the curve. |
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rosconole
Gold Member Joined: May-10-2008 Location: United States Status: Offline Points: 758 |
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The cam is similar to X303 which needs 6200-6500 RPM to really work. It probably had not peaked yet.
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1989 ski nautique ,1991 barefoot nautique, 1993 Mustang Cobra 1998 5.0 Magazine shootout invitee
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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Here’s what the builder sent me.
https://i.imgur.com/f6kRy2p.jpg https://i.imgur.com/zLLYjAn.jpg |
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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The 4” exhaust manifolds were used during the run. GLM is the manufacturer. https://www.cpperformance.com/p-30077-complete-exhaust-manifold-set-ford-v8-fits-4-hose.aspx
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21109 |
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Peak rpm quoted by the cam manufacturer can be wildly different based on the engine it’s installed in... certainly if it’s spec’d out nominally for a 302 and then installed in a 408. |
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21109 |
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Looks like it is only picking up 25hp from 4000rpm to 5000rpm. Seems like it’s choking on something.
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JoeinNY
Grand Poobah Joined: October-19-2005 Location: United States Status: Offline Points: 5693 |
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Mine runs better than that on 7 cylinders - which begs the question is it down a cylinder. I would expect the builder l/dyno operator would know that immediately but the AFR doesn't seem to be reporting correctly as it is way rich and not changing, so it seems the engine is perhaps not fully sensored up. My similarish longblock has a bit more lift and duration to the cam .568/.565, 220/230... and was designed for 5400 rpm peak hp and 6000 max cruise rpm with a 408w. Certainly the cam here is not too big without more data we dont know that you aren't just running out of injector or fuel pump or have a different tuning issue or if you just cant suck through the straw fast enough. Dynos are all different so the hp number doesn't scream disappointment but the curve does...
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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I expected more but I have faith it will get better. Gonna try a different intake. AFR wasn’t hooked to the dyno. Dominator was controlling.
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rosconole
Gold Member Joined: May-10-2008 Location: United States Status: Offline Points: 758 |
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I was going to say many that is waaay rich , a/f should be 11.5-14 neighborhood. May be starting off light on the timing as well.
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1989 ski nautique ,1991 barefoot nautique, 1993 Mustang Cobra 1998 5.0 Magazine shootout invitee
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zwoobah
Senior Member Joined: September-13-2018 Location: Providence RI Status: Offline Points: 308 |
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Wideband sensor must not have been hooked up. It's not possible for the AFR to remain static across the RPM range.
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1968 Mustang 16 - 351W powered
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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So after some more tuning, it appears the engine is running out of air. As much as I wanted to maintain the iconic GT40 intake, it’s just not going to flow like I need. I have ordered the Holley Hi-Ram EFI intake with a 95 mm throttle body. We will see how it goes from here!
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rosconole
Gold Member Joined: May-10-2008 Location: United States Status: Offline Points: 758 |
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Bummer on the GT40 , hold on to that thing they continue to increase in value pretty steady lately. Hopefully cam can make up for low end,, alot of volume in that plenum it really likes above 5000 rpm., small base circle distributor too I see. , Systemax I think would really match up good with the combo and keep a good hole shot.
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1989 ski nautique ,1991 barefoot nautique, 1993 Mustang Cobra 1998 5.0 Magazine shootout invitee
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21109 |
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No intake you put on that combo is going to hurt the holeshot in any measurable way with 408ci and those heads.
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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Couple updates:
1. Fiberglass work is moving along nicely. Once all of the deck repairs are complete and newly laid fiberglass is cured, the deck will be removed from the hull once more, then re-sprayed inside and out so that even when you lay under the dash or observer seat, no raw fiberglass will be seen. Everything will be finished out. For the floors, short strand fiberglass filler is being used to flatten everything out. Then a layer of glass will be laid down to seal everything in. There are 10 ribs that run vertically up the sides of the bow. Once the deck is removed again, those will be cut out and replaced. The rear ribs were reinforced and re-glassed. 2. The engine was run a couple more hours on the dyno. A little more timing and some tuning brought the horsepower up but the more data that was logged, the more it became apparent that engine was starving for air. My goal with the rebuild of this engine was to maintain the GT40 intake so that anyone who looked under the engine cover would know what PCM engine this boat shipped with. I didn't think the stock intake would be such a bottle neck but the ecm and dyno don't lie. When I thought about the money spent thus far on the engine, I could no longer put form over function. I decided to make the swap to a Holley High-Ram EFI intake. Throttle body size is moving from a 70mm to 92mm. New fuel rails and shorter distributor are part of the package. Hopefully the engine will be up and running next week. 3. I've started talking with Ron Tanis from Ski Boat Parts Online about him doing the engine and trans installation. I am still deciding if I am going to a 1 1/8" prop shaft. If so, he will also be replacing the strut. After watching his video's online, he's the man for the job. |
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13510 |
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Ron Tanis is the man
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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Agreed, he has been beyond helpful in determining what transmission I am going to need. |
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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Pylon came in yesterday also! I wasn't crazy about the extra height but then I realized that I may have to rise the engine cover a little bit for the taller intake. Either way, it should work out just fine.
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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Don't know how I missed this! Very funny, thanks for sharing! |
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ultrarunner
Platinum Member Joined: October-02-2005 Location: Ridgefield, Ct. Status: Offline Points: 1809 |
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Hey Dom, have you considered putting in a non-skid molded fiberglass floor with a snap-in/snap-out carpet, like modern boats? I believe someone actually did one here several years ago, and there is a thread. Eons ago I had a Bryant with the same. Loved it. Just seems the way to go with all this other work, rather than just gluing down carpet again.
Ultra... ps. can I swing by and see the project? I'm flying folks down to SXSW. |
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13510 |
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Go back and read the very first post. He mentions the flooring plans.
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rosconole
Gold Member Joined: May-10-2008 Location: United States Status: Offline Points: 758 |
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That intake is that much taller than GT40...I would think you should have plenty of clearance.
I think the transmission should be good for 100hp over stock from what I have heard..atleast thats where it seems where they differentiated between a 71c and 72c . |
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1989 ski nautique ,1991 barefoot nautique, 1993 Mustang Cobra 1998 5.0 Magazine shootout invitee
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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Absolutely! Shoot me a text with a little heads up. I am spraying gelcoat throughout the entire inside of the boat and then polishing the floor to install seadek. The same seadek on the trailer is being used inside the boat. Color combo is: Beach Sand base Terra Brown top |
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DHMcFadin
Senior Member Joined: May-27-2019 Location: Austin, Texas Status: Offline Points: 312 |
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You are probably right about the height. Measurement from distributor hole to top of intake: GT40 intake: 13" Holley intake: 16.75" Here's my concern with the trans, it's not the horsepower I am worried about, its the torque. This engine with the gt40 intake made 488 ft lbs. That seems like a lot of torque for a PCM 40 series trans. |
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