a bit more grunt

[achris]

I just take the top nuts off... Nothing wrong with that...

 

[whiskeyRichard]

The motor is ready to come out, just have to remove the 2 nuts from the tops of the mounts at the front of the motor.

Hopefully will get it out this next week. I'll take pictures.

Not sure if I am going to use an engine hoist mounted to my flatbed or the loader bucket on my tractor to get it out. I dont have the patience to build a gantry and I keep all my trees limbed up to high to use.

 

[Rick Stephens]

Just use your loader. Takes me a few minutes that way and I have a lot less clearance than you. You need a second pair of hands is all, to guide you and the motor. No need for a gantry. They just get in the way 99.9% of the rest of your life.

 

[whiskeyRichard]

Earlier in this thread, there is a good recommendation for a cam from comp cams.

If I am running an exhaust where I have to worry less about reversion, can I get more cam? I am going to do the retrofit roller deal. Here is the risers I am going to run:

http://www.diamondperformanceparts.com/product.php?productid=17197&cat=283&page=4


I need to be able to have a low idle and I'd prefer to have it lopey, and I want to keep the working RPM's under 5500 for the safety of all my parts. I assume more cam is going to require some head changes and that is OK.

I am strongly considering the Edelbrock 170 e tec aluminum heads.

 

[Scott Danforth]

unless your full dry exhaust (jacketed and the water exits past the transom), you are limited to 270 degrees of duration. more than that you need full dry exhaust.

 

[whiskeyRichard]

I have read a couple examples of people running the lt4 hotcam even on stock exhaust with no problems and that cam is listed as 279/287

 

[achris]

I have read a couple examples of people running the lt4 hotcam even on stock exhaust with no problems and that cam is listed as 279/287

Citation needed...

 

[whiskeyRichard]

post number 3. there is also a link to his build in there. also check out post #14....the crower cam that guy is talking about is 273/284.

https://www.offshoreonly.com/forums/...-question.html

not by any means trying to argue with you guys....you all know way more than I will ever know, just researching and trying to digest right now. Between researching heads and cams, I think I am getting information overload. I wake up thinking about it in the middle of the night.

wR

 

[Scott Danforth]

if you want it to idle, and you want to keep it below 5500 RPM, exhaust reversion aside, you dont need more than 264 degrees of duration. the wet exhaust limits you to 270 degrees (and marginal idle). more duration than that, idle quality goes to hell, and you start sucking water up the exhaust.

 

[FreeBeeTony]

Interesting thread.......
I am currently modifying my Vortec heads after lessons learned re: cams/lift/coil bind/rocker studs/etc........
See link below :

If I had to do it over again I think I would have gone the E170 Head route.......or something equivalent, and upgraded to a stroker.
I went w/ the CompCams XM270HR cam and had coil bind issues.

Question for the experts: When we speak of max duration, is it the Intake or Exhaust duration we are referring to?

 

[whiskeyRichard]

still doing lots of research on this. I came across a post from Dennis Moore on offshore only where he stated that a cam like the comp cam XM270HR would be good but that it should be made with an LSA of 110 instead of the off the shelf 112 LSA.

Am going to call comp cams today and see what they say on the matter.

 

[aimlow]

Interesting thread.......
I am currently modifying my Vortec heads after lessons learned re: cams/lift/coil bind/rocker studs/etc........
See link below :

If I had to do it over again I think I would have gone the E170 Head route.......or something equivalent, and upgraded to a stroker.
I went w/ the CompCams XM270HR cam and had coil bind issues.

Question for the experts: When we speak of max duration, is it the Intake or Exhaust duration we are referring to?

Both. Many marine cams are split duration, usually with more duration on the exhaust. Lobe center affects overlap.

 

[Scott Danforth]

Interesting thread.......
I am currently modifying my Vortec heads after lessons learned re: cams/lift/coil bind/rocker studs/etc........
See link below :

If I had to do it over again I think I would have gone the E170 Head route.......or something equivalent, and upgraded to a stroker.
I went w/ the CompCams XM270HR cam and had coil bind issues.

Question for the experts: When we speak of max duration, is it the Intake or Exhaust duration we are referring to?

Tony, you had coil bind issues because your machinist was asleep when you told him which cam you were running on the vortec heads.

as far as the overlap, its a mix of LSA, ICL and duration.

basically you need to minimize overlap where the exhaust and intake valves are open because at idle, this draws in a big breath of exhaust with water in it.

a cam is generally advertised off its intake duration. 270 degrees of intake duration can be anywhere between 270 to 280 degrees exhaust duration. the XM270HR ( http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=202&sb=2) is listed by Comp as the largest for I/O (primarily for wet exhaust) it has 276 degrees of duration with a 112 LSA and a 110 ICL

 

[whiskeyRichard]

well, I got a couple beers in me last night and went an ordered a new GM ht383 from Jegs. Hard to go wrong with that engine I think. If I want more power out of it in the future, there is plenty to be had.

I know myself and I am getting ready to drop about 3k on this 350 and next year I am going to want more again and it seems the closer you get to an engines limit, the more the horsepower starts costing.

I've got a good running 260 for sale if anybody is interested. Comes with a nice Edelbrock manifold and 1409 carb.

Thanks,
wR

 

[whiskeyRichard]

It's been a few months since I updated this, so I figured I'd add some info.

Before the ht383 I ordered shipped, I went online and cancelled the order. After doing some research I decided to stick with 350 cubes and build instead of buy.....I needed a winter project to keep me out of trouble anyways.

I started with a new L31 long block from GM. The basic 'vortec' motor.I pulled the heads and sold them for $500 and replaced them with the Edelbrock e-tec 170 aluminum heads. I also added 1.6 full roller rocker arms from comp cams.

Then pulled the cam and had comp cams modify their xr276HR cam to have a lsa of 110 instead of 112 and installed that.

Here are a few other things I have also added or changed from the stock setup.:

8 qt oil pan from Canton Racing products.

Edelbrock Performer Manifold

EMI thunder cast aluminum exhaust manifolds and will be installing a custom made pipe rise from them that will be dry almost until the tail pipe. I'll be running some clamp on silencers on the through hulls because I think it may be pretty loud.

I had purchased an edelbrock 600CFM carb but need to revisit that because I think I can do better. Probably going to go with a little bit larger Holley instead.

Davis unified Ignition HEI setup


I am hoping to be in the range of 400hp at redline but suspect I'll be a little lower. My dad thinks I'll be a little higher.

I still have some things to do and plan on getting the motor to a dyno for break in and tuning in the next week or so. I'll report back on what she makes.

 

[Scott Danforth]

your going to need dry exhaust.

stock Volvo Penta AQ271 motors had 715 CFM holleys on them back in the 80's. primarily for the hole-shot. your 600 CFM will be fine, however you may need to go bigger. read your plugs.

you wont be near 400hp, closer to 370 (dont forget to deduct driveline loss)

the extra 33 cubes would have made a big difference.

 

[whiskeyRichard]

My exhaust puts water in right at the tips. I have first hand account of guys running this much cam with similar exhausts and being fine. For some reason on this site if you are more than 218/224 at .050 and 112 lsa you will never get by but when you go on other more performance related sites, you find a lot of different information.

Only one way to find out for sure. If she sucks water, it's an easy fix.

I'm also running an alpha 1 (I have a spare just in case). Everything I read on here is that at 300hp they grenade, but elsewhere people report running way more power through them for years as longs as your cool till you get up on plane.

Same as above, one way to find out.

I'll bet you a six pack she makes 380hp at 5200.


wR

 

[Rick Stephens]

That's nice. I like the 110º cam mod. That will help the reversion a lot. Good call.

 

[Scott06]

That's nice. I like the 110º cam mod. That will help the reversion a lot. Good call.

I may be confused but doesn't tightening LSA from 112 to 110 increase chance of reversion? Or is that wider LSA not required at these duration or exhaust set up?

 

[whiskeyRichard]

You definately would not want to run stock exhaust with this cam. tightening lsa increases overlap which would increase the likely hood of sucking water back in.