What camshaft should I put in my Chevy 305 while it's apart?

[rs2k]

I have an 18 foot 2800 lbs (with engine) tri hull with a Chevy 305 and OMC stringer out drive. What kind of camshaft should I put in this engine while I have the engine apart to replace the bad cylinder heads? I have a feeling this engine has an automotive camshaft in it now.

 

[HT32BSX115]

Re: What camshaft should I put in my Chevy 305 while it's apart?

You know,

It might be worth considering going to a wrecking yard and finding a truck 350 to put in place of the 305....

 

[rs2k]

Re: What camshaft should I put in my Chevy 305 while it's apart?

My plan is to eventually put a 350 in it. I don't currently have the funds to do that right now though. I'm figuring $500 in repairs and upgrade to this 305 VS $1000 to do a 350. I should have the money to build a very nice 350 by late winter. Until then I'll use this 305. It had around 150 PSI compression even with cracked heads and blown gaskets. The block appears to be in good shape.

 

[Mkos1980]

Re: What camshaft should I put in my Chevy 305 while it's apart?

True with the adbove 350 swap, but if you have to keep what you have. I see the boats a trihull, so I assume its an older motor. If not, I would run the RamJet/Mercruiser roller cam with the roller lifters and other stuff needed but if not and you have to stay flat tappet, the stock one is good. Dont go with the cam recommended above. Thats wayyyyyyy too big. The lift on the cam would require machine work on the heads which is not cheap, new springs, screw in studs and a good exhaust. Duration is very high.

 

[captmello]

Re: What camshaft should I put in my Chevy 305 while it's apart?

If your block is in good shape and you're doing the heads, why touch the cam if your building a 350 this winter? I love my 350.

 

[wca_tim]

Re: What camshaft should I put in my Chevy 305 while it's apart?

consider that what's healthy for a 350 is probably too much for a 350 is a little milder for a 383 and so on...

That being said and in the context of risking too much cam, losing a bunch of bottom end torque where you need it, having reversion problems and trashing the engine you have, etc... i might put thje money you would spend on a new cam now in the cookie jar to help with your 350 build...

I wouldn't bother with a roller cam if you've got a non roller engine now. The upgrade is pricey, and the money is much better put into the heads in the long run.

That being said, if you're anything like I am.... I would probably go with the milder comp cams xtreme marine grinds... xm250 if you're dead set on upgrading the cam... it won't be enough for your 350, but much more would be too much for your 305...

imho

ps. Holy Crap Bubba, are you sure you linked the right page? thats similar lift and more duration (overlap) as the cam in my stroker engine... and lists a 3000 - 6500 rpm operating range...

 

[John_S]

Re: What camshaft should I put in my Chevy 305 while it's apart?

Check the part numbers on the cam. If it is an auto cam you will probably want to replace it. If marine, stay with it. Select a cam with stock marine cam specs or just slightly more.

Also read up on the stringer drive. While I don't read many of those posts, my impression is it is not a "robust" drive, which adding a built 350 to, won't last long.

 

[MikDee]

Re: What camshaft should I put in my Chevy 305 while it's apart?

IMO one of these would be your best choice for a camshaft, these are factory hi=perf designs, they work well without having to worry about changing springs, or anything else, nor do they need any machine work because of too much lift, they fit right in, and a lot of the replacement engine builders use these on a regular basis in their hi-perf engines, I've used the L79 myself in a 262 Chevy V8 (otherwise stock) which achieved 7k rpm with a 2bbl carb, & dual exhaust!, it has plenty of power for what you need, it was used in the 327/325hp & 327/350hp motors. Anything more is overkill, unless you like having engine work done, raising compression, & putting a large 4bbl on:

03863151 L-79 350HP, 327 Hydraulic Flat Tappet
This hydraulic flat tappet is used on the 65-67 Corvette and Chevy II L-79. It has excellent power and torque (ID# 3863152). The duration at lash point in degrees (intake/exhaust) is 320/320; duration at .050? tappet lift (intake/exhaust) is 221/221 and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 447/447. Valve lash is zero/zero and lobe centerline is 114 degrees. --

03896962 L-82 330HP, 350 Hydraulic Flat Tappet
This hydraulic flat tappet is used on the 68-81 L-46 and L-82 Corvette. The duration at lash point in degrees (intake/exhaust) is 312/312; duration at .050? tappet lift (intake/exhaust) is 222/222 and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 450/460. Valve lash is zero/zero and lobe centerline is 114 degrees.

http://www.sallee-chevrolet.com/Camshafts/index.cfm

 

[rs2k]

Re: What camshaft should I put in my Chevy 305 while it's apart?

If you go to the link and then click on the "Application" Tab and then scroll down you will see this cam is specifically recommended for a 305 (Gen 1) chevy marine application upgrade. (Over the stock cam he has.) As I said, I have used this cam before and been very happy with the results. It gives the 305 a mountain of low end torgue.

Perhaps I misunderstood what the poster was saying as I thought he wanted to upgrade from his current cam. By all means if he wants a stock marine cam he should stay with what he has.

What is the idle like with the cam you mentioned?

 

[dan t.]

Re: What camshaft should I put in my Chevy 305 while it's apart?

dont use any of those old chevy performance cams. they are usless below 3000 rpm and totaly unsutable for a boat. check out comp cams website,they have some good marine cams

 

[MikDee]

Re: What camshaft should I put in my Chevy 305 while it's apart?

dont use any of those old chevy performance cams. they are usless below 3000 rpm and totaly unsutable for a boat. check out comp cams website,they have some good marine cams

Oh Really? That's not what I found! If Jasper uses these cams, and Rapido uses these cams, I'd think they'd be good for anyone wanting a mild upgrade from stock, rather then do a lot of engine work, or spend a lot of money! Check this out, it appears to be the same specs as the L82 cam:

http://www.jasperengines.com/pdf/Chev-350-Marine-325-05.pdf

Rapido doesn't publish it, but I believe he uses either this, or the L79 cam, in his 290hp engines, as has been proven by a few members here with that engine.

 

[dan t.]

Re: What camshaft should I put in my Chevy 305 while it's apart?

I speak from experience using the 151 cam in a chevy 350 4x4 motor ,it didnt take long before i pulled it out and put in a comp cams 252h, far better bottom end power and fuel milage. used the 962 in an oval track car,worked good from 3000 to 6500 below 3000 rpm it was a gutless wonder.a far better cam for a 305 is merc #431-5943 or 431-811658. as for what jasper uses i realy dont care.the most common mistake with engine building is over camming and over carburating

 

[MikDee]

Re: What camshaft should I put in my Chevy 305 while it's apart?

I speak from experience using the 151 cam in a chevy 350 4x4 motor ,it didnt take long before i pulled it out and put in a comp cams 252h, far better bottom end power and fuel milage. used the 962 in an oval track car,worked good from 3000 to 6500 below 3000 rpm it was a gutless wonder.a far better cam for a 305 is merc #431-5943 or 431-811658. as for what jasper uses i realy dont care.the most common mistake with engine building is over camming and over carburating

The 151 cam is the wrong cam for 350 4X4, unless you've got the right gearing, and, or 10X1 compression! You then put in a 252h comp cam with less duration, & lift, I'm sure it ran better with that. Even a 260h Comp cam would. Yes, I'm sure that either of those comp cams would be fine for the orig. poster, but they are more expensive to begin with. Stock chevy hi-perf cams are designed around duration, not so much lift (at the time they were designed, low gearing, & high compression was the norm) so they worked as intended, but lift is too much on some of these comp cams, .500 or more, requiring machining of the heads, with dedicated valve springs, & lifters, sure you'll have mucho torque! but at what price? Yes, there are better cams out there, I'm not familiar with the Merc cams you mentioned? but it would be nice if you provided the specs, with those numbers, so people could decide for themselves! Apparently these engine builders found out that these stock chevy hi-perf cams work well as designed, at a reasonable cost factor, without any issues, that's why they use them.

If you want a smooth running engine with good torque, & milage, you can always get the # 050 1962- 327/300hp hyd cam, with only 10X1 comp. at the time it was listed as having more torque then the 327/340, or 327/360hp, 11x1 comp, 097 solid lifter Duntov 2 cammed motor. I know, because I had that 327/300hp motor in a 62' Impala SS, that eventually snapped the cam, then I put the 097 soild lifter cam in it, (a big mistake) no real hp increase, just more maintenance hey, I was young, & dumb, back then in 62'

By the way, the 62' 327/300hp, 340hp, & 360hp engines all had 61' corvette (double hump) 283" fuelie heads, and this #050 cam is a hydraulic version of the original famous 283hp/283cu.in. power pack motor cam, and was used from that point on throughout the GM line as Chevys main "plain vanilla" stock cam, ever since!

Another fact, Chevy took that same exact 327/300hp motor that I had, and put the L79 (151) cam in it, then put it in a Chevy 11, rated at 325hp! 25hp, Quite a boost!, so you see, I had the right engine, but the wrong cam (#097) at the time

 

[John_S]

Re: What camshaft should I put in my Chevy 305 while it's apart?

Single pattern performance cams are not good matches to stock or near stock marine engines. A dual pattern cam with longer duration and lift on the exhaust vs intake compensates for the restrictive exhaust system. Both the stock flat and roller cams are of such design.

I also agree with wca_tim that the summit cam suggested has too much lift and duration. The lift is too much for vortec heads (which poster probably doesn't have), and probably standard 305 heads. While the application guide does say "marine", it also says "Supercharged", "Street/Strip", "Turbocharged", and "Nitrous oxide" recommendations for V8 305's. I would be very sceptical of claims by any cam that is good across all those applications. Also, the specs provided are not close to any provided by recognized subject matter experts, like Dennis Moore. That goes for the single pattern cams, too.

 

[MikDee]

Re: What camshaft should I put in my Chevy 305 while it's apart?

The 2 hydraulic cams I'm talking about are in the middle here, (the rest are solid lifter cams) they are Crane blueprinted versions of the popular old school musclecar cams, the 327/300hp cam is torquey, but it's smooth like a stock engine, usually good for about 5500k rpm, The 327/350hp cam will give you a smooth but "rhythmic cammy idle", and pull strongly up to at least 6k, you just need to prop up, to drop the rpm's into range, and take advantage of the power!

http://www.jegs.com/p/Crane/746644/10002/-1/10707

The Comp cams that dan t. mentioned are fine also, they are in between these two, and will give you more torque then the 327/350hp, and more power then the 327/300hp. I don't know about the Merc cams he mentioned, because I have no specs on them?

I see Comp cams has some marine specific cams that are pretty hot, on this page as well, it all depends on what you're loooking to do,,, But, all of the cams that apply, on this Jeggs page are very reasonable IMO

In any case, I believe the Max lift you can use on most stock Chevy heads is .480, then you have to cut down the valve guide area.

 

[wca_tim]

Re: What camshaft should I put in my Chevy 305 while it's apart?

I buy a lot of stuff from summit (probably way too much...), and when they list applications, it is like every possible potential application - not necessarily meaning it is going to work for your application.

In building te last couple of engines I have and in particular for the recent one, I've read a pile of posts, literature, etc.. on cams for marine use, etc... I've also talked to an experienced marine builder who had run many of the combinations of heads, intake, cam, carb, exhaust, etc... on the dyno in careful, side by side trials for a performance boat manufacturer. Lots of people do overcam and often there is significant horsepower to be gained by going with components that are selected to work together adressing the goal you have for the engine. too much cam for example and sure it'll make more horsepower, but with less it may have made even more hjorsepower and still mnaged to pull like a train on the bottom end. Most of that kind of thing is well understood and talked about above. A couple of pieces of information:

Stock hydraulic marine cam in merc 305:

200 / 212 intake / exhaust duration @ 0.05" lift

.4 / .41 intake / exhaust lift with 1.50:1 rockers

Dennis Moore recommendation for performance gain in slightly modified 305 or a stock 350:

206 - 208 / 208 - 216 intake / exhaust duration @ 0.050"

.41 - .43 / .420 - .460 intake / exhaust lift w/1.5 : rockers

I was told not to believe everything that I read... but that most of the build specs are pretty accurate.

the current comp cams extreme marine cam xm-256-H

is 212 / 218 @ 0.05

0.447 / 0.462

He recommends an xe-250 grind rather than xe-256 (more agressive), but the xm-256 is ground with a 112 degree lobe separation angle rather than 110 for the xe-256 and would be fine - probably making the most power of the two and retaining a gentle lope at idle...

there are a number of cams from crane and others that fit in the same range. I like the comp xm series because they're ground with a steeper ramp than many of the older grinds and allow you to get away with a little more lift and duration without as much overlap, but to each his own on brands. I'll bet any of them would riun great in your 305. The bottom line is that it won't take much more cam before the heads are the limiting factor anyhow.

imho

 

[MikDee]

Re: What camshaft should I put in my Chevy 305 while it's apart?

I buy a lot of stuff from summit (probably way too much...), and when they list applications, it is like every possible potential application - not necessarily meaning it is going to work for your application.

In building te last couple of engines I have and in particular for the recent one, I've read a pile of posts, literature, etc.. on cams for marine use, etc... I've also talked to an experienced marine builder who had run many of the combinations of heads, intake, cam, carb, exhaust, etc... on the dyno in careful, side by side trials for a performance boat manufacturer. Lots of people do overcam and often there is significant horsepower to be gained by going with components that are selected to work together adressing the goal you have for the engine. too much cam for example and sure it'll make more horsepower, but with less it may have made even more hjorsepower and still mnaged to pull like a train on the bottom end. Most of that kind of thing is well understood and talked about above. A couple of pieces of information:

Stock hydraulic marine cam in merc 305:

200 / 212 intake / exhaust duration @ 0.05" lift

.4 / .41 intake / exhaust lift with 1.50:1 rockers

Dennis Moore recommendation for performance gain in slightly modified 305 or a stock 350:

206 - 208 / 208 - 216 intake / exhaust duration @ 0.050"

.41 - .43 / .420 - .460 intake / exhaust lift w/1.5 : rockers

I was told not to believe everything that I read... but that most of the build specs are pretty accurate.

the current comp cams extreme marine cam xm-256-H

is 212 / 218 @ 0.05

0.447 / 0.462

He recommends an xe-250 grind rather than xe-256 (more agressive), but the xm-256 is ground with a 112 degree lobe separation angle rather than 110 for the xe-256 and would be fine - probably making the most power of the two and retaining a gentle lope at idle...

there are a number of cams from crane and others that fit in the same range. I like the comp xm series because they're ground with a steeper ramp than many of the older grinds and allow you to get away with a little more lift and duration without as much overlap, but to each his own on brands. I'll bet any of them would riun great in your 305. The bottom line is that it won't take much more cam before the heads are the limiting factor anyhow.

imho

It took awhile to get to this point, but to sum it up then, the xm-256 having a dual pattern, sounds perfect! IMO