I know this is the blower motor category, so easy on me! I have a twin turbo 350 Chevy small block.
I just melted piston #6. Would like to get some ideas on some engine specs before I rebuild. Anybody out there have a good recipe? Would a turbo engine block be built similar to blower or nitrous engine? Below are my current engine specs
written by the former boat owner.
Thanks!
Spec's on engine are as follows:
Heads are new World Products 67cc heads (standard
small valve versions with as measured 69cc combustion
chambers - chambers were close to 70cc when received
but I had to slightly mill them in order to true them
up and then I equalized the chambers @ 69cc). Valve
seats were multi-angled cut, and valves were "back
cut" and radiused/polished for increased flow. Valve
bowls were "ported/radiused". Valve size is 1.94"
intakes and 1.5" exhausts. Total calculated
compression ratio is 8.05:1. This is using head vol.
of 69cc, deck hgt. of +.008" (total quench hgt. is
.047" - .045" is considered minimum perfect for turbo
engines), gasket vol. of 9cc (Fel-Pro #1014 .039"
thick head gaskets), TRW forged pistons #L2441F with a
as measured dish vol. of -23.5cc (suppose to be
-21.1cc dish but measured -23.5cc). Bore is 4.030"
diameter and stroke is stock 3.48" = 355cid.
Rings are Childs & Albert Moly High Strength Plasma
coated (dutile iron) with wider 1st & 2nd ring end
gaps for turbo usage (.019" gap).
Complete engine rotating assembly was balanced.
Exhaust manifold gaskets are Fel-Pro with steel core.
Cam is Crane Energizer #10003 (204 deg. duration @
.050" tappet lift & with .427" valve lift. and 110
deg. lobe separation). Cam is normally installed
straight up with 5 deg. advance built in. This cam is
retarded via 8 deg. offset bushing in cam timing chain
sprocket for a total retard of 3 deg. (5 deg. advanced
-8 deg. bushing = 3 deg. retard). Timing chain is a
Cloyes Tru-Roller.
Rockers are 1.52:1 Competition Cams roller tip
rockers.
Ignition timing is 8 deg. initial advance with an
additional 24 degrees in the dist., all in by 2800 RPM
(max. advance is 32 degrees total). Initial timing
can be reduced to 6 deg. initial, but recommend not
going below that. Contrary to popular belief,
retarded timing (for long durations) does reduce
knock, but then it increases combustion chamber temps.
as well which then causes knock to return with a
vengence).
Note my thinking when building up this engine
initially was to increase low end torque (for better
hole shot), and use the turbo's to increase top end.
I know that I overdid this on the low end and this
caused the top end to suffer somewhat, and I told you
about retarding the cam (8 degree retard bushing) to
get back some of the top end. The new cam was the
next step (according to my discussions with the
experts- Gale Banks & Engle Cams), but I never
installed it. It depends upon how you are going to
use the boat (everything is a compromise). If you are
going to ski, tube, etc. and bottom end is more
important, then return the cam timing back to it's
initial setting of 5 deg. advanced (replace the cam
sprocket offset bushing with a "zero" bushing). If
top end speed and high speed cruising is where it will
be operated at, then leave it as is, or replace the
cam with the new one (your choice either way).
Frankly, as it is, I think it is a good compromise
with great performance in all catagories (but we
always want more).
New Engle cam spec is as follows:
#1002H (grind # TCS-2HYD). Duration @ .050" tappet
lift is 216 deg. intake & 210 deg. exhaust. Valve
lift is .458" intake & .440" exhaust. Lobe center is
116 deg. Description per Engle: Turbocharger Hyd.
Camshaft designed for modified engines with 8:1
compression ratio. Power band 2800 to 6000 RPM. This
cam will definately be weaker on the bottom end, but
would wake up the top end considerably!
You didn't mention if you had an EGT gauge or what kind of exhaust. If not this comes first to hotrod with a turbo. Get the EGT down and you'll stop melting pistons. Bigger more open exhaust from turbos back to lower EGT and still put the fuel to it.
[ August 17, 2002, 09:39 PM: Message edited by: zahndok ]
No EGT gauge.
The turbo system is set up for the old log type system. M&W is the manufacturer. They no longer make this kit due to not having a center rise system.
The boat has thru hull exhaust below the water line.
The boat has an old Carter Knock Detector, which goes off at full throttle. I dont stay into it over 30 seconds. I back off til it stops.
The kit came with a water injection system. The previous owner opted not to use?? I have heard that if I used the water injection system and mix the water 50/50 with ????? I cant recall?
Most melt downs are caused by problems in the fuel system. You made no mention of the fuel systems.
The cam you've got really should be changed. 110 lobe centers really doesn't work even with the short duration you have. The recommended cam is a bit small as well but not sure what you're trying to get out of the engine. What size are the turbos? The one upgrade on the heads would be to go with inconel exhaust valves. Other than those 2 things sounds like a good basic package.
Well what is the fuel system? Blow through or draw through? I gess draw through.
Is it intercooled?
Any plans to put some arm in it and get some more cu.in.?
Engle is the right direction and so is the inconel. JE Pistons has some Good slugs that hold up great aswell!
How much boost were you making?
How much HP do you whant?
The usual mix is water/alcohol.
You might also whant to think about locking the timing out at your desired total degrees.
What brand and heat range plug are running?
Thanks all
For the info and questions. I had to go out of town last week. I will try to post a pic of the engine.
Reccomended boost is 4lbs. Was running 5 lbs. ??
Low isnt it ?
Stock 4 barrel carb and intake.
Bosch platinum plugs
High output mech. fuel pump.
No intercooler. The turbos are water and oil cooled.
When I bought the boat I thought that when I first started having problems, the turbos must go.
But they are just way too much fun! I want a dependable engine that will last not necessarily be a demon of sorts.
Thanks again!!
KevinB
Another try at a pic !
[img]http://groups.msn.com/_Secure/0RACMDEEXx!9VTCRjjQ924jez4HOCmou0r8OrAyOfwk9XOBIpH m41jF7PyOyvM5K6Jhf2cNilRgEsxoxUjOnkyPbiXDGWcI1G2*d cVRTqKOo/CV-23ENGINESIDE.jpg[/img]
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