Indmar 454 Chevy

[biggraypig]

I have a 454 Indmar Chevy engine in my boat that I would like to get a few more ponys out of.
Block #14015445
Heads #14092360
Intake #333841
Don't have the cam #s
What I have found out is it is an 87-89 truck block, 85-89 open chamber heads (2.06 intake, 1.72 exhaust), and what looks like a 73-75 intake with the oval ports.
The boat is an 87, so I am assuming the block and heads are 87.
Am I in the right ballpark or not?
What I would like to do is cam it a little, upgrade the intake, and go to an HEI distributor to get a few more ponys. I don't need anything drastic, just would like a little more. (I know once you start it is an evil addiction that you have to feed. Could I run a blower on this engine?)
I run a Holly carb, and through transom exhaust.
Any suggestions on a combination that will work is appreciated. Thanks

[sdpm]

I have a 454 Indmar Chevy engine in my boat that I would like to get a few more ponys out of.
Block #14015445
Heads #14092360
Intake #333841
Don't have the cam #s
What I have found out is it is an 87-89 truck block, 85-89 open chamber heads (2.06 intake, 1.72 exhaust), and what looks like a 73-75 intake with the oval ports.
The boat is an 87, so I am assuming the block and heads are 87.
Am I in the right ballpark or not?
What I would like to do is cam it a little, upgrade the intake, and go to an HEI distributor to get a few more ponys. I don't need anything drastic, just would like a little more. (I know once you start it is an evil addiction that you have to feed. Could I run a blower on this engine?)
I run a Holly carb, and through transom exhaust.
Any suggestions on a combination that will work is appreciated. Thanks
If the heads have the larger oval ports, have some port work done to them, cam change (stay hyd), performer RPM oval port intake port matched, 750 dp carb., and install a droop snoot. You will be very happy with the results and not broke in the process.
Beautiful boat! I had one that was open bow and loved it.

[SmokinLowriderSS]

I THINK '360 heads are SMALL oval ports (peanuts), but my usual source site for verification is down at the moment. Small ovals don't breathe worth a damn above about 4,000 RPM, and also at anything above about .500" lift
If I am correct, you need new heads first off. Casting 353049 is easy to find these days, large oval port open chamber (basically, identical replacements for the '781 heads). Most have small valves and would bennefit a lot from having larger factory valves installed (2.19"/1.88") and a good stage 1 porting job. Nothing exotic or mondo-dollar.
Without this work, they still flow much better up to about .600" lift, and up over 5,000RPM.
My '78 Indmar 454 came with a cam lifting arround .460/.472", duration was in the 260* range.
I went to a very aggressive hydraulic ramping (custom grind HTP has had a lot of good experience with in "lake-boats" with my intended uses), .565" lift, 280* total duration, and, with the heads still stock, and the compression a still very anemic 8.?:1 (flat-tops under those open chambers), I get 400HP with my thru-transom headers.
Far more is available with a decent CR and some head work (head work is coming up this winter ).
Edelbrock Performer RPM Air Gap 2.0. Love that manifold.
There are dates on those castings, as I said, mortec.com is not responding just now. It also would tell you how to date those castings, block & heads.
A blower won't help much at all if those are small port heads.
If you have a cast crank, it's only good to arround 600-700 HP. RPM is the big killer of those. much more so than the pressure put against them. Keep a cast one below 6-grand for least risk.
Same limit goes for the 2-bolt block, arround 600-700 HP.
There IS a cool article in the how to do it section on modding a 2-bolt cap and block set into a 4-bolt block set, without buying caps and paying for an align-hone, and guys are running 900HP on those blocks apparently, successfully. (there is no dif. in the block castings normaly, just was or wasn't factory drilled for 4-bolt caps)

[SmokinLowriderSS]

Yep, those are peanut-port truck heads.
Dating the block:
The block casting date is usually found on the rear ledge of the block on the passenger side, but some later model blocks have the casting date on the driver's side of the rear ledge.
It is an alpha-numeric code.
The casting dates look something like this "E 12 7".
The "E" stands for the month of the year with "A" being the month of January, "B" being the month of February and so on thru the letters to December.
In this case the "E" stands for the month of May, the fifth month of the year and the fifth letter of the alphabet.
The "12" stands for the 12th day of the month.
The "7" is the year of the decade.
Now unfortunately this could be '57, '67, '77, '87 or '97
Some casting dates have both the year of the decade and the decade itself. They look like this "E 12 77",

[caribbean20]

Truer words never spoken than those by Biggray "I know once you start it is an evil addiction that you have to feed."
455Rocket, you ever want to know what impact those mods will have on your hull, I'm your huckleberry. I have a 1987 Hardin Marine Caribbean 20.5' that I swear is a splash of that Carrera of yours, or vice versa. Bought mine in 1991 in Colorado with the 333 H.P. Hardin Marine 454, and 16 years worth of multiple motor and pump mods later, could have bought my barge 4 times over, no BS.
Just down the street in Manhattan Beach if you ever want to hear what did and did not work.

[caribbean20]

Biggraypig - one thing that I did not see mentioned here was exhaust. From the looks of the motor cover in your picture, you may be running the log style (also referred to as snail) exhaust system, Indmar or Hardin Marine. If that is the case, I would not mess with any motor mods until/if you do something about that restrictive exhaust. I learned that lesson the hard way (looks like my hull is identical to yours). In my hull, there was no free flowing exhaust that fit under that hatch, but that was 1998, and there may be other options today. I finally went with EMI Thunder exhaust and that is when I started to see some real gains, but also required complete redesign of motor cover to fit.
455Rocket, my hull is now at 72.3 MPH on GPS with a 502 and a bunch of other goodies. I will send a PM to you so as not to hijack this thread.

[biggraypig]

They are log exhaust. I would like to upgrade to a header that would go through the transom. Any suggestions? (I would like to build me a sundeck with a bench seat that goes across the back of the boat anyway)
I don't expect to reach blazing speeds, but 70+ would be nice.
Is this doable with a few mods?
Carib, have you ran a droop on this hull? This is what I have to play with.
Thanks

[biggraypig]

I would like to know about the goodies.
455Rocket, my hull is now at 72.3 MPH on GPS with a 502 and a bunch of other goodies. I will send a PM to you so as not to hijack this thread.

[biggraypig]

Found me some 049 heads, now I need a few suggestions on what to do with them for my setup. This is what I have.
358049 358049
GM10t GM9t
K28 72 K21 72
Both say PASS.
I plan on taking them in and having them redone.
I am looking for suggestions on what valves, rockers, rods, and cam to use. Should I port and polish them, or leave them the way they are?
I am going to run an air gap manifold with these.
Just looking for a good combo that will run good on pump gas.
Any input will be a big help.
Thanks

[SmokinLowriderSS]

Found me some 049 heads, now I need a few suggestions on what to do with them for my setup. This is what I have.
358049 358049
GM10t GM9t
K28 72 K21 72
Both say PASS.
I plan on taking them in and having them redone.
I am looking for suggestions on what valves, rockers, rods, and cam to use. Should I port and polish them, or leave them the way they are?
I am going to run an air gap manifold with these.
Just looking for a good combo that will run good on pump gas.
Any input will be a big help.
Thanks
For the heads:
A PROFESSIONAL PORTER, preferably with experience in boats/jet boats. Fortunately I have one here in Wichita Kansas. Saum Engineering.
11/32" valve stems, large factory size valves (2.19/1.88"). Stage 1 should be plenty of work on them. Total $$$ is going to run me arround $1300 with VERY good valves. According to them, they love working on those and '781 (same head, older casting) heads. Lots of HP hidden in them. Stage 1 gets most of it.
Edelbrock Performer RPM Air Gap manifold. My 454 loves it.
Cam I am running I spoke of earlier. Custom cut version of an Isky 280H with very aggressive ramps to maximize open time. .565" lift, 280* advertized duration (I think 232* @ .050"). Everyone has their favorites.
IMO, stay at or below 280* full duration, or you will push the power up into unreachable RPM land. You will have a hard time finding my lift at my duration on a shelf cam. A good guy on here who knows cams can make you a custom once you have settled on the other things. cstraub, professional cam grinder. From what I have seen, his long list of satisfied customers say he knows what he is doing.
Any good solid set of 3/8" pushrods and guideplates. My 454 had 5/16"ers in it. Has Speed-Pro 3/8"ers now, and is quite happy. 7/16" monsters would be overkill.
Go roller rockers, I do not like aluminums, period. Fact of life is Aluminum fatigues, and WILL break eventually. The only question is when.
I was going to buy Comp Cams Pro Magnum steel roller rockers ($290), but ran into a deal from a friend on a used set of Comp Cams Hy-Tech Stainless Steel roller rockers ($440 new), had them rebuilt, and just spent the same as the regular Pro Magnums. Needed Comp's matching locknuts and ARP longer set of studs to match it up.
1 guy on here I know broke a Pro Magnum, and was using it on a much harder core motor than mine. They should be indestructable on mine. I do not remember who it was, but he offered me his new replacement set they sent him, unused, when I had no budget to take him up on the offer. The offer was good too.
I tucked Lightning Headers under my hood, but they come all the way up to mid-carburetor height. If I had a dog-house-style hood, they would not have worked. As it was, I had to arch my flat hood slightly to clear the K&N air filter atop the taller Air Gap manifold (almost 2" taller than my stock iron cross-H dual plane).
Gained 50HP/200RPM from the headers alone, now the heads are a restriction point.
Get the comp ratio figured out to run arround 10.5:1, and stay on premium.
With the right work, well over 500HP is pullable at 5,500RPM from that 454, on 1 carb (800 CFM or so), perhaps close to 600, and on 91 octane.
I am managing 400HP, on only 8.?:1 compression, with the heads fully bone stock, and running 87 octane all day. 700CFM Holley, and the above listed parts.
My head work should make great improvement.
Eventually another rebuild will happen, to get 2 more points compression. That should be sweet too.