PDA

View Full Version : 383 update



PaulO
08-07-2000, 05:00 PM
The rain stopped and I finally got a chance to pull the motor. Here is what I found when I dropped the pan:

2 small holes in the oil pan accompanied by many dents (from the inside out).

A big chunk and several small chunks of brand-new hypereutectic piston in the pan.

A big hardened bolt wedged inside the number 7 piston.

A bolt missing from the number 2 main bearing cap!!

Ouch!!!

Sent pictures today to the builder who is readying another engine for me. He did not question anything I did, simply began preparing another engine.

And, for all you readers interested in cam profiles; I discovered evidence of reversion when removing the exhaust manifolds. This cam is a 224 intake, 234 exhaust 109.8 degree lobe seperation cam.

Since I caught the builder before he installed the cam, we reviewed the cam profile and decided to go with roller setup on the new motor. We dropped the duration slightly and the builder feels that with the more aggressive ramps, we will get similar performance as the old cam ( not that I ever got to experience the old cam).

Will keep you posted. Hope to make the Lake George picnic. Chris, Alex, let's see if we can do this one together.

PaulO

RickR
08-07-2000, 05:17 PM
PaulO
Are you using stock manifolds?
What was the evidence of reversion?
Good Luck with the new motor.

------------------
RICKR
mailto:riggerb@aol.comriggerb@aol.com</A>

PaulO
08-07-2000, 05:58 PM
RickR,
Yes, one of the qualifications was that I wanted to use the stock manifolds/risers. Just too much damn money for anything aftermarket and, I don't believe that the stock stuff is too restrictive for small blocks. Anyway, while at idle there was a small amount of steam. Because of this, when I pulled the motor I specifically pulled the manifolds and looked. Sure enough, there was water in the center 2 ports and rust already on the ports in the heads. There is little likelyhood of a leak between the risers and manifolds as they are both brand new and properly gasketed.
PaulO

RickR
08-07-2000, 07:28 PM
Keep us posted. I am considering a 224/234 112 Roller Hyd for the Merc 454 and I would like to keep the Silent Choice and add a Gil Exhaust. I feel this combo could cause a reversion problem so I need some input. The Gils have a "Turbolator" which is supposed to eliminate some reversion problems.

Which cam are they using on the new motor?

After you get the new engine bring her up to normal operating temp, remove plugs from suspect cylinders and tap the electrode into the palm of your hand. You should NOT get any water out of the base of the electrode.

You may want to pressure check the new manifolds and risers just in case they are defective.

BTW I always use Hylomar(Permatex) on the manifold/riser gaskets and the hose/riser joint.

------------------
RICKR
mailto:riggerb@aol.comriggerb@aol.com</A>

[This message has been edited by RickR (edited 08-07-2000).]

Forrest
08-08-2000, 11:03 AM
Correct me if I wrong, and I know that there are other factors involved, but I thought that anything less than 112-degree lobe separation was just asking for reversion problems with wet exhaust.

------------------
Forrest

[This message has been edited by Forrest (edited 08-08-2000).]

PaulO
08-08-2000, 11:56 AM
Forrest,
My understanding is that it is a combination of things. I am no expert but it seems that for simplicity, there is a universal attempt to boil down camshaft profiles into 2 or 3 aspects such as duration, lift and overlap. The truth is that there is much more to cam profiles. If you consider that a lobe centerline is the line drawn through the approximate center of the profile of any given lobe and the lobe seperation is the # of degrees that the intake centerline and the exhaust center line are seperated, that is an indication of the overlap but, not the actual overlap. A camshaft with a 200 duration and a 110 degree lobe center seperation may have zero overlap but, when you increase the duration to 230, there may be 10 degree overlap. The Lobe center seperation didn't change but, because you increased the duration, you now have overlap. Also, as I am learning, ramp shapes make a huge difference. The faster you can get the valves opened and closed the more "usable" duration you have. Moving to a roller cam as I am in my 383, you can use less duration but have more usable duration because of steeper ramps. You may be able to decrease overlap and still maintain the performance of a larger duration non-roller cam. This, plus less frictional losses, is where the roller motors are a win-win.
PaulO

GeneD
08-09-2000, 09:43 AM
PaulO,
The water in your manifolds...
could it be that you do not have enough down angle on your risers going to the exhaust pipes?
I found this when I was building my boat, I had to go and get two 1 inch spacers.
Solved it.
BTW, if anyone is interested, I have a bunch of 3 inch spacers free for the asking. Pay only shipping.
Oh, Mercruiser only.

------------------
GeneD
007
Melbourne, Florida

PaulO
08-09-2000, 11:11 AM
Gene,
Good point. I have been leary of the lack of angle since doing the mercrusher swap. Thing is, the new 18s are the same and I have no room for the risers to be elevated anyway. I have been looking at these setups for awhile and, it seems that since you need to put the through-transom hole above the power steering anyway, all Alpha setups without riser extensions are the same as mine.
PaulO

GeneD
08-09-2000, 01:12 PM
PaulO,
Yeah, you're right about the hoses going over the PS unit. But when I did mine, it did NOT clear the PS unit. I had to raise it 1.5 inches to do so. It wasn't until I found water in the oil that I wised up and put the spacers in there.
I do not know what the angle is supposed to be.
I'm thinking here...you didn't have this problem with the old engine right? So perhaps this point is moot.
My boat's risers now just barely clear the hatch. And I've noticed a bit of rubbing in that area.
This cam reversion thing has me concerned. I guess this is why all the race dudes run the dry exhaust huh?
I'm wondering if I am going to be able to run my auto roller cam in my 400. I would hate to go and buy a new cam.

------------------
GeneD
007
Melbourne, Florida

RichF
08-09-2000, 11:46 PM
Paul:
Are you using 4" exhausts? I had a reversion problem w/ old engine until we upgraded from 3-1/2" to 4"

PaulO
08-11-2000, 05:30 PM
More news:

The engine is assembled and scheduled to ship air freight Monday. Should have it Wed-Thurs. Went with the roller cam option and ended up with a duration of 215 deg. This should end the reversion and still keep the HP and Torque up. Doug's assembled 2 engines at the same time with the same specs and dyno'ed 1 to test the cam profile. Results were 415 HP at 5200 RPM and 458 ft. lbs. of torque peak. The torque band is wide. Surprisingly, these numbers slightly exceed the power of the original 224/234 cam!I am going to install mercruiser's discontinued exhaust extension kit that extends the center tube in the 4" risers just to be on the safe side.

Geoo,
Give us the scoop!! How did you solve the interference problem? How is it going? What did the dyno say?
PaulO

GEOO
08-11-2000, 11:03 PM
PaulO, We solved the injection problem 99% be using one common ground on the block.
The engine was Dyno'd with a carb first to check every thing out. Then he Dyno tuned the engine with the Fuel injection. (Carb 602hp @ 6250 rpms, 575 ftlbs) (Injection final set up as in boat with Stainless Marine Exhaust 575hp @ 6000, 560ftlbs with a real broad flat torque band.) The sheets are in my car but these figures are close. Idles at 750-800 but can go down to 600 for a breif time. GEOO

Riley
08-12-2000, 09:18 AM
PaulO, what size and type of prop are you planning on running with the new 383? Keep us informed on your progress....I'm betting you are going to be tickling the 70 mph range with that beast!....Chris Riley

PaulO
08-14-2000, 08:48 AM
Riley,
I have borrowed a 23 mirage re-worked to 24 but I have some doubts as to its condition. I can borrow a 25 mirage also. I will probably break it in with the 24 and see how it goes from there. I'm hoping that this thing can spin a 25 to 5000 RPM.
PaulO

Riley
08-14-2000, 04:13 PM
PaulO, just did some calculating here, and with 10% slip you should be running at 72.5 mph with the 25 Mirage. Cool! Good Luck, and keep us informed....Chris.