small block question heads/cam combo
 

I just did heads and cam on my boat,I have mixed feelings about the results,you guys seem like you know about small blocks,I would love to get opinions here.
For now I reused my short block,280 hrs,very well kept and clean,I have dart sportsmanII heads with 64 cc chambers,cam is crane 114 lca 212/[email protected] with.446/.459 lift with an edelbrock rpm dual plane and 650 holley DP,timing and jetting seem close.
I have a 88 chris craft 245 limited last season with stock engine with only intake and carb mods I got 50 gps with 21 mirage at 41-4200 rpm,46 with a 19 P mirage at 4400 rpm,now I get 50 with 19P at 4800 and not sure on 21 yet,I had a vibration start as soon as I started planing with the mirage,I let out and put the 19 back to finish the weekend,I did not want to break anything yet,long weekend!! I will try to find out what the vibration was this weekend.? I thought I may have gotten a tad more,it for sure planes alot better but I hear people going faster than me with stock motors!! boat empty is supposed to be 3800 pounds.

The only thing I did not totally check is enough fuel at the top end,I need to continue plug monitoring to see if they can get darker,pretty light right now,can a (new ) stock pump flow enough?
I am going to do a compression check to see if everything is cool.
What kind of power numbers can I expect?

Re: small block question heads/cam combo
 

Four MPH gain for what you did with a SB in a heavy boat is decent, I built a 383, Dart heads Pro Mod Lunati internals and a reasonable cam. I have a 22 Donzi 3200 pounds and gained four & a half, it takes a lot more HP then most realize to make big speed gains in any boat.

Phil

Re: small block question heads/cam combo
 

Curious what you have your top timing set at?

Re: small block question heads/cam combo
 

I figure some gain is better than none,I do realize boat hp/mph gains are totally different than a car,i have been boating with a friend that took years to get his formula 311 to a gps 80 mph,not easy,(for sale)!!! now has the a 353 to play with,anyway,I am maily trying to see what others have gotten for results,not alot of small block guys here!
If I can remember the timing is at around 30 total,I am going back to do more tuning this weekend,I did not want to mess with it much on a holiuday weekend,I am worried why the boat vibrated with the 21 mirage,I did not even let it plane to see,I put the 19 on and it was smooth,i kn ow the prop is ok because I ran it last year,I may not have had it seat right..??
I will try again on sat for the 21.

Re: small block question heads/cam combo
 

I brought up top timing as I went a bit conservitive at first running 30 degrees, bumping up to 32 degrees which gave me just short of 1 more MPH.

Phil

Re: small block question heads/cam combo
 

the cam seems small.

Re: small block question heads/cam combo
 

Mine? I figured I was going to try to keep some torque in it,I did a few different cams on desktop dyno and this seemed the best for my application,I could not get any good answers from anyone on the net or local engine builders so I did as much as I could,I will take any recommendations from people if they have them,this was the first chevy engine I ever built,I have all fords on the street.

Re: small block question heads/cam combo
 

I plan to play a little more with it,what cam do you have? what are the specs?

Re: small block question heads/cam combo
 

Im no expert by far, just looking at the specs, thats the first thing that came to mind. I would expect a little more duration.

maybe the cam experts will chime in.

Re: small block question heads/cam combo
 

I agree,not knowing alot about chevys I was trying to keep it simple,I can change cams fairly easy if I remove the seat,I may if someone can tell me what to run!!.

Re: small block question heads/cam combo
 

Again, I am not anywhere close to a cam expert, just what i have seen and HAD built, I would think about 15 more degrees on intake and exhaust would be closer, especially with the sportsman 2 heads. They flow 200cfm and need a bigger cam.

Re: small block question heads/cam combo
 

What did you have built and how did it run? Cubic inches?

Re: small block question heads/cam combo
 

I agree with Baja, I think the cam is too small.

Re: small block question heads/cam combo
 

A Lunati roller also a hi torque cam rather then an HP cam, it suits my needs better. Some of my Buds think I am nuts to have so much in the engine and still run a mild cam, I put together a pretty indestructable setup. A 383 with very good internals hooked to a BravoX diesel drive, I wanted a boat that would be very dependable able to haul 5-6 people with decent speed and economy I use it for both work and play, I am very pleased with how it worked it has done better then expected.

Phil

Edit forgot cam specs: RD D @.050 @.200
276 221 134
It degreed at 108 has .510 lift with 1.5 rockers pretty mild probably close to what we used to call a 3/4 race cam, it was ground for a tounament ski boat that anothe fellow was putting together he needed a lot of bottom and mid range to tow 8-12 skiers. It makes just over 65 @WOT and cruise at 40 with very good range, one day it would make a good tender on a yacht.

Phil

Re: small block question heads/cam combo
 

I talked to comp cams today,they said to use at least a 218/[email protected] (#12-262-4) maybe a little more lift,I sent a cam request to cam motion today,I will see what they say,I used them when I did a ford 306 and had VERY imporessive results,I hope whatever I do would be worth the time to pull the boat and bring it home for a week to do a cam swap and get it back in by the next Fri.!!!

Re: small block question heads/cam combo
 

what is the biggest without killing the low end torque?