SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: Rodbender on July 24, 2008, 08:57:24 AM
-
I have a 460 with stock crank, rods and cans. I am bolting on a set of C-9's which should bump the compression to 10.5:1. I am looking for a nice cam to run, but this is out of my scope of knowledge and i could use a reccomendation.
It is in a challenger jet, Dominator with an "a/b impeller, droop snoot, w/ diverter.
The goal here is to have a nice throatty motor that will get out of its own way, and I am not looking to win any trophy's, just tired of dragging my ass around.
Any thoughts?
-
Look at a Comps 270 or 280 hydraulic.
Sleeper CP
-
I have a 460 with stock crank, rods and cans. I am bolting on a set of C-9's which should bump the compression to 10.5:1. I am looking for a nice cam to run, but this is out of my scope of knowledge and i could use a reccomendation.
It is in a challenger jet, Dominator with an "a/b impeller, droop snoot, w/ diverter.
The goal here is to have a nice throatty motor that will get out of its own way, and I am not looking to win any trophy's, just tired of dragging my ass around.
If you have a bone stock 460 from a 1970's jet boat, then you have dished pistons and your compression ratio is somewhere around 7.9:1 as received from the factory. Removing the D3VE heads and replacing them with C9VE heads will raise compression to about 9.2:1.* Also, the valve trains that Ford utilized between these two cylinder head castings (D3VE & C9VE) will dictate that you upgrade your valve train to a full roller rocker valve train (hardened pushrods, guideplates, 7/16" rocker studs, roller rockers and tall valve covers) because the factory D3VE valve train will not fit the C9VE heads.
In regards to shelf grinds:- If the rest of your engine is essentially bone stock with thru-transom exhaust, then go with the XM270H.
- If your engine also has aftermarket carb & intake and/or also has OT tubular headers, then go with the XE274H
- (Either of these two camshafts will require the use of CompCams recommended valve springs and proper valve train/cylinder head setup.)
Please note that it would absolutely be in your best interest to port those C9VE heads prior to their installation, at the very least port the exhaust port. Not doing so will result in no major performance differences between these two cam suggestions once your engine is over 4500 rpm....
LO
* If you are certain that you have flat top pistons, then your compression ratio will exceed 11:1 with the C9VE heads.[/list]
-
Well, I was told the cans are 9:1 as stock last time I had the heads off. This came from the machinist that swapped my rods. They were casted with ford #'s (c-9) i believe. The block casting is C-9, but the heads are way different. I dont remember the #'s, but they are motorhome heads. I want to say they at T-6's, but I cant remember for sure. That is why i went to the C-9's. I have a tunnel ram w/ a 750 BP, but i can go to an 830 race DP as I have one in my garage. I have rewarder OT's, and MSD billet dist w/ a 6al box.
I planned on changing the springs but i wasnt going to spend the $ to port just yet. I am trying to keep this down as i will have to do my wear ring at the same time (it is shot). My thought was to run a new cam, lifters, springs and retainers, but use the original pushrods and guides. Am I screwed up in my thinking?
(http://)
-
...I was told the cans are 9:1 as stock last time I had the heads off. This came from the machinist that swapped my rods. They were casted with ford #'s (c-9) i believe. The block casting is C-9, but the heads are way different. I dont remember the #'s, but they are motorhome heads. I want to say they at T-6's, but I cant remember for sure. That is why i went to the C-9's. I have a tunnel ram w/ a 750 BP, but i can go to an 830 race DP as I have one in my garage. I have rewarder OT's, and MSD billet dist w/ a 6al box.
I planned on changing the springs but i wasnt going to spend the $ to port just yet. I am trying to keep this down as i will have to do my wear ring at the same time (it is shot). My thought was to run a new cam, lifters, springs and retainers, but use the original pushrods and guides.
So you have a C9VE block, OEM crank and rods, and pistons we still don't know what you have. Are they flat tops? Dish tops? If they are flat tops then you will likely be 11:1+/- (<---depending on boresize, etc) with the C9VE's.
Again, not much to go by in regards to your current cylinder heads, but I'll venture to guess that you have E6TE castings, which are single year heads that are essentially the same as D3VE heads, so everything that I noted about the valve train between D3's and C9s still applies.
With the tunnel ram and headers, I'd go with the bigger XE274H cam and spring package. And yes, install the bigger Holley in place of your current carburetor.
It's possible run the OEM valve train with the parts that you are adding, provided you keep the OEM rockers, rocker studs and pushrods...but even though people have done this successfully I think you are pushing the limits of the OEM parts because the C9VE OEM rockers are CAST iron and the oem pushrods are mild steel deals. Both of those items are now going to be subjected to bigger spring pressures and at sustained high rpms that the original application did not take into consideration. It will run and run strong, but your chances of engine (valve train) failure multiplies big time. My advice is to save up the funds necessary to do it right the first time, with all the proper parts upgrades.
LO
-
I definately want to do it right, i do not believe in being cheap when it makes the difference between swimming and driving!
So i will go with that cam * spring set up. The C-9's have 3/8 studs in them now, do i want to go to the 7/16 and go with rollers? I know that is the hot set up, but is it worth it for the $ ?
I have dish top cans, std bore, std rods. that i will not be changing as the low end is brand new.
-
do i want to go to the 7/16 and go with rollers?
I would.
-
So i will go with that cam & spring set up. The C-9's have 3/8 studs in them now, do i want to go to the 7/16 and go with rollers? I know that is the hot set up, but is it worth it for the $ ?
I have dish top cans, std bore, std rods. that i will not be changing as the low end is brand new.
You compression ratio with the C9VE heads, standard bore dish top pistons and that block will probably put you somewhnere around 9.5:1. (OEM Factroy 460 dish tops put you at about 10.5:1.)
The positive stop OEM rocker studs must be removed and replaced with 7/16 rocker studs. I suggest getting them in the BBF 1.900" effective length and not the 1.75" BBC effective length. You will also need pushrod guideplates, roller rockers & polylocks, and lastly you will need hardened pushrods. The length of the pushrods is an unknown until you investigate purshrod geometry which is dictated by the rest of your engine combination. Generally, the pushrod lengths will end up being longer than OEM, and the exhaust pushrods will be longer than the intake purshrods.
Tall valve covers (for rocker arm clearance) finish the job. Optimize the setup and the tune and you might be approaching 500hp with the bigger cam I suggested.
LO
-
I'm using the Comp Cams extreme marine 278 cam and kit in my 460. Flat top pistons, 95cc edelbrock heads, edelbrock air gap intake and 850 holley, mallory distributor, accel super coil and MSD 6AL box. Comp cams pro magnum roller rockers and elite pushrods. Topped that off with a stud girdle to hold it all together.
It can pull 5100 rpms with my 23 foot Glastron Carlson Berkeley 12JE and A impeller. I think there is still more there but I haven't pushed it. It's still to young for that.
The speedo shows 63 mph but who knows what it really is, it was near dead on at 56 but I haven't taken my gps out since we fixed the oil pan issue.
It has a nice lope but still idles down nicely, it pulls very hard.
Did you go to compcams.com and use their cam selector soft ware? You plug in your carb size compression, valve size etc and it pops up cam grinds and HP and torque graphs.
-
we ran it out a half mile today on the GPS, 60.5 MPH in a 23.5 foot boat, A impeller.
I think that's pretty good from the Comp cams 278 extreme marine cam in a heavy boat.