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I ran twin TP 174s (from memory) years ago before going to the HOT roller cam and fast burn heads. Close to Artics suggestion....typically described as an "RV cam" in the books.. .457 lift int & exh, .269/.269 /112
Used stock exhaust and corvette Al heads with 1.94 valves. peak 357 HP at 5500, 341 ftlbs...according to GM (crate motor)... Lane |
Question?
Originally Posted by pipes
(Post 3480915)
I am in the process of replacing the 350/260 engine in my scorpion 230. The engine I am replacing it with was built by a local machine shop, I was told it would have a conservative 350+ hp.(@ 5000RPM) I was just wondering on your take on it. The engine has 9:1 compression 4 bolt stock bottom, (heads) 2.02/1.60 valves with 3 angle blended bowls unshrouded valves and a 30 deg. backcut on valves, cleaned up runners, gasket matched and pinned studs. Weiend stealth air gap intake ( has roughed up runners for better fuel atomization) gasket matched with 2 inch spacer and a holley 600 spread bore carb with stub stack. The cam specs are 262/272 adv duration, 204/214 @ .050, lift 420/442 and a lobe seperation of 112. Stock omc exhaust (for now) with warmed over and smoothed runners and thru hulls. I am concerned with cam. Is it enough to get me to the 350+ hp mark and with a ls of 112 will this give me probs. with water reversion. A lot of the cams I read about are at 114. Any input would be greatly appreciated. Thanks
112 ls should be fine with that cam and exhaust but it may be good to increase the idle speed just a bit to insure against reversion I would recommend a Comp Cams XM270HR paired with the vortices which would put you around that HP. |
Originally Posted by TEXASRPM
(Post 3482045)
What type of cyl heads are do you have? Vortecs 12558060 - SD8060A would be the way to go.
112 ls should be fine with that cam and exhaust but it may be good to increase the idle speed just a bit to insure against reversion I would recommend a Comp Cams XM270HR paired with the vortices which would put you around that HP. |
Heres what Comp Cams says about their Extreme Marine Cams.....
Comp Cams 'Xtreme Marine' Hydraulic Flat Tappet Camshafts A Unique Cam for Marine Applications If you're heading to the great outdoors, Comp Cams offers camshafts designed specifically for marine applications where low idle speeds are necessary and where restrictive exhausts require special cams that work well against wet exhaust system back pressure. These unique camshafts generate an extremely wide powerband, offering the low-end torque needed to jerk skiers up quickly and the high-end power needed for maximum performance. Also, Comp's larger camshafts are engineered for engines with less restrictive exhausts and drives that will tolerate higher idle speeds. An excellent choice for jet boats or power boats. |
heres the list.....from the Jeg's catalouge
Chevy 262-400ci Small Block 1955-98 249-12-232-3 Xtreme Marine™ Hydraulic Flat Tappet Camshaft Lift .447/.462 Duration 256/262 RPM Range 1000-5000 More info on Comp Cams 12-232-3 $129.99 Ships in 6 days 249-12-236-3 Xtreme Marine XM262H Hydraulic Flat Tappet Camshaft Only Lift: .462''/.477'' Duration: 262°/268° RPM Range: 1300-5500 More info on Comp Cams 12-236-3 $129.99 Ships in 6 days 249-12-240-4 Xtreme Marine™ Hydraulic Flat Tappet Camshaft Lift .480"/.489" Duration 270/286 RPM Range 1600-5800 More info on Comp Cams 12-240-4 $139.99 Ships in 6 days 249-12-244-4 Xtreme Marine™ Hydraulic Flat Tappet Camshaft Lift .498"/.500" Duration 278/292 RPM Range 2000-6200 More info on Comp Cams 12-244-4 $139.99 Ships in 6 days 249-12-248-4 Xtreme Marine™ Hydraulic Flat Tappet Camshaft Lift .516"/.522" Duration 290/306 RPM Range 2500-6500 More info on Comp Cams 12-248-4 $139.99 Ships in 6 days 249-12-318-4 COMP Cams Xtreme Marine Hydraulic Flat Camshaft Lift .464"/.464" Duration 268/276 RPM Range 2400-5400 More info on Comp Cams 12-318-4 $139.99 Ships in 6 days 249-12-324-4 COMP Cams Xtreme Marine Hydraulic Flat Camshaft Lift .483"/.483" Duration 280/280 RPM Range 2600-5700 More info on Comp Cams 12-324-4 $139.99 Ships in 6 days 249-CL12-232-3 Xtreme Marine XM256H Hydraulic Flat Tappet Camshaft & Lifter Kit Lift: .447''/.462'' Duration: 256°/262° RPM Range: 1000-5000 More info on Comp Cams CL12-232-3 $199.99 Ships Today 249-CL12-236-3 Xtreme Marine XM262H Hydraulic Flat Tappet Camshaft & Lifter Kit Lift: .462''/.477'' Duration: 262°/268° RPM Range: 1300-5500 More info on Comp Cams CL12-236-3 $199.99 Ships Today 249-CL12-240-4 Xtreme Marine XM270H Hydraulic Flat Tappet Camshaft & Lifter Kit Lift: .480''/.489'' Duration: 270°/286° RPM Range: 1600-5800 More info on Comp Cams CL12-240-4 $205.99 Ships in 6 days 249-CL12-244-4 Xtreme Marine XM278H Hydraulic Flat Tappet Camshaft & Lifter Kit Lift: .498''/.500'' Duration: 278°/292° RPM Range: 2000-6200 More info on Comp Cams CL12-244-4 $205.99 Ships in 6 days 249-SK12-232-3 Xtreme Marine™ 256H Hydraulic Flat Tappet Camshaft Small Kit Lift: .447/.462 Duration: 256/262 RPM Range: 1000-5000 More info on Comp Cams SK12-232-3 $225.99 Ships in 6 days 249-SK12-236-3 Xtreme Marine XM262H Hydraulic Flat Tappet Small Kit Lift: .462''/.477'' Duration: 262°/268° RPM Range: 1300-5500 More info on Comp Cams SK12-236-3 $225.99 Ships in 6 days 249-SK12-240-4 Xtreme Marine XM270H Hydraulic Flat Tappet Camshaft Small Kit Lift: .480''/.489'' Duration: 270°/286° RPM Range: 1600-5800 More info on Comp Cams SK12-240-4 $229.99 Ships in 6 days 249-SK12-244-4 Xtreme Marine XM278H Hydraulic Flat Tappet Camshaft Small Kit Lift: .498''/.500'' Duration: 278°/292° RPM Range: 2000-6200 More info on Comp Cams SK12-244-4 $229.99 Ships in 6 days 249-SK12-248-4 Xtreme Marine™ XM290H Hydraulic Flat Tappet Camshaft Small Kit Lift: .516"/.522" Duration: 290/306 RPM Range: 2500-6500 More info on Comp Cams SK12-248-4 $232.99 |
Originally Posted by pipes
(Post 3480915)
I was told it would have a conservative 350+ hp.(@ 5000RPM)
As DMoore suggested 218/224 at .050" with 112LSA , and another person on the HotCam (218,228) , will get you close or just over depending on the heads used. These (Comp Cams + GM Hot Cam) have been run in tons of marine small blocks and believe it or not they stop pulling at 5200rpm on 5.7's. Fact, not theory. As mentioned, Bob Madera is a great resource + cam supplier to help you get to your goals. |
So over the weekend I was looking for a set of vortec heads and came across a vortec long block which I ended up purchasing from a friend. I am just going to shelve the other motor. It is a fresh motor with flat tops and it is suppose to be 9.2:1 compression eith the stock roller cam setup. So now my question is, I would like to obtain between 350- 400 hp. Is it possible and what cam, intake and exhaust to run. I would like to keep the roller setup and have plans to upgrade the exhaust. I appreciate all the responses and am learning a lot about .
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Best thing you can do is find a copy of Dennis Moore's book "Small-Block Chevy Marine Performance". It'll answer a lot of your questions.
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Suggestion
Originally Posted by pipes
(Post 3484965)
So over the weekend I was looking for a set of vortec heads and came across a vortec long block which I ended up purchasing from a friend. I am just going to shelve the other motor. It is a fresh motor with flat tops and it is suppose to be 9.2:1 compression eith the stock roller cam setup. So now my question is, I would like to obtain between 350- 400 hp. Is it possible and what cam, intake and exhaust to run. I would like to keep the roller setup and have plans to upgrade the exhaust. I appreciate all the responses and am learning a lot about .
Intake. edelbrock RPM Air Gap Camshaft Comp Cams XM270 HR Exhaust. Dana, Stainless Marine or if on budget GLM Aluminium. Make sure at minimum that good rod bolts (ARP) are used for higher RPMs. Yes this combo should put HP approx 350HP but not much more. If mor power is needed you may want to go with 383 rotating assembly. Just my opinion THX |
350 horsepower is doable (on pump gas) but you will need to twist the engine at least to 5200-5500 rpm. 400 horsepower is doable (on pump gas) but you will need to twist the engine to 5700-5900 rpm.
You will need a camshaft that works at high rpm but will give up a little torque at low rpm. Are you prepared for the increased noise of your engine at the higher rpm? The reduction of torque at low engine speeds? How about the extra noise of thru-the-transom exhaust? Most people have an unrealistic idea about a pump gas 350making 400 horsepower at 4800 rpm. The only way that happens is with a supercharger and premium fuel. By all means modify the engine for more performance but set your goals a little lower. 325 horsepower @ 5000 rpm is very doable with a 350 on pump gas. Dennis Moore |
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