As an update for my commander 23, my engine is nearly done.. As I discussed earlier I want to be putting in a new cam... My engine builder seems to think there might be something goofy with the cam, something about a reverse grind or something. He said that sometimes with the gear drive they either made reverse drive gears or they actually ground the cam backwards, the latter would cause problems in finding a cam..
Again, I might be talking out of my caboose a little bit because I am used to engines with overhead cams..
So any information on a 327F would be appreciated. BY the way he offered me a trade for my 327 for a marine 454.. It took all my will power not to do that, but I gotta keep this thing original.. Apparently this was one of the good 327's with the steel crank, large journals, the good heads and all that fun stuff.. Go Chris Craft!!!!
I was looking at the firing order and distributor rotor direction on the diagrams Paul posted on a previous thread. The rotor rotation is clockwise which means the cam is turning the standard or left hand direction, which means the engine uses a timing gear on gear setup, no chain. The crank is turning CW, reverse rotaton. The cam is turning CCW therefore the distributor rotor is turning CW, as normal. The firing order is changed at the distributor by reversing the plug wires. The cam is ground to follow the reverse firing order.
I know this is confusing as heck!
Bottom line, this cam is not hard to find. Tell your parts supplier it uses a gear on gear cam drive. A Mercruiser 350 cubic inch/260 HP reverse/right hand engine uses this cam.
I can get you a part number if needed. This is a reverse rotation engine so just a reminder.
1.Rear main seal is different
2.Water circulation pump is different
3.If it has a timing pointer at front/harmonic balancer it reads backwards, so it is different
I'm not sure if a 327 is like this but on a 350 the pistons are installed backwards on the rods, with the indentation on top of the piston facing the rear of the block instead of forward, (reverse rotation engine only). This is because the piston pins are offset just a little. If you install them on the rods as you normally would the engine will run but you'll have piston slap and short engine life. Again I'm unsure if 327's are this way. I will try to find out. Both engines have a 4" bore, shorter stroke on the 327. If the pistons have not been taken off the rods yet it will be easy to determine.
The gear drive at the front of the Opposite rotation cam may change things, and since I haven't been into mine to see for myself, I won't give advice on something I know little or nothing about. I will say, however, that it is common for the distributors on the 427 standard and opposite motors to be turning in the same direction, due to the fact that the gear on the opposite rotation cam is designed to mesh with a special opposite rotation drive on the bottom of the distributor. This allows both motors to use the same distributor, and thankfully we don't have a world of standard and opposite distributors to worry about.
The cam, on the other hand, is an opposite rotation cam and these are always tough to find, not impossible, but you certainly won't be ordering one from your standard auto parts outlet. I checked a while back and found opposite marine cams available from some of the big names, I believe Comp Cams and Crane have them for the SBC.
Am I picking up a signal your engine builder hasn't done a marine motor before? Every grandmother, mother, and child above the age of 10 here in the South, and most of the men are able to disassemble and rebuild an automotive SBC blindfolded. Since NASCAR is a form of "driver education" here in the South, everyone knows how to draft at high speeds. Few know about the opposite rotation marine specifics.
If you need a specific "Cris Craft" opposite cam that will assuredly fit and work well in a 327F, get it from Robert at Chriscraftparts.com
My engine builder has done marine motors before, however based on the numbers I gave him he wasnt sure. This was prior to him actually looking at the cam... IM sure wont have any trouble now, that he has the cam in his hands.
So just to clarify, the marine cam has the reverse rotation which inherently makes it harder to find aftermarket replacements?
Wes, concerning the small block Chevy, reverse marine engine, the cam actually turns in the normal direction that it would in a non reverse engine. Why? because they use a GEAR ON GEAR cam drive, therefore the crank is turning reverse but the cam is turning normal. This keeps the distributor turning in the normal direction, clockwise, but more importantly, it keeps the oil pump turning in the normal, clockwise, direction! They do not make a reverse rotation oil pump!
The difference in the camshafts is not the DIRECTION in which they turn, it is the way the lobes are ground. The reverse cam has the lobes ground to match the reverse, 12756348, firing order.
Gear drive, one gear turns with the crank, the other gear turns the opposite way: As you noted, in the opposite rotation SBC, the gear drive system causes the cam to spin in the different direction than the crank. In the SBC both cams spin the same direction, even with the LH and RH motors.
On the 427 motors, the cam always spins the same direction as the crank. The motors can use the same distributor and oil pump, due to the gear drive used.
That is correct, Paul, the early 327 had a smaller main bearing journal. They improved the later 327's with a larger crank main bearing journal, and then introduced the 350 using the larger mains as well and also the 4 bolt main block in truck, some marine, and high horsepower applications. There was never a 4 bolt main 327, contrary to popular belief, as you stated. There were some forged steel crank 327's as you know.
The "distributor assembly" (as noted in the parts manual) is basically the same distributor, but with the proper gear on the bottom to work with the opposite rotating cam. Even though the engines spin in opposite directions, the distributors on both motors spin in the same direction. As a result, I don't believe there is really any difference in the distributor itself, but only in the gear on the bottom of the shaft.
That's my take on it! I had mine out, had them rebuilt, installed them, got em running just fine. Only differenence I noted was the gear on the bottom. I think they use the tag on the distributor housing as the way to let people know what gear is on the bottom.
Well I got everything on the newly rebuilt motor ready to go, and i finally found the old owners manual and plates that were on the motor.
I found out this is a right hand (reverse rotation) motor, since the firing order is 1-2-7-5-6-3-4-8.. The guy who partially disassembled the motor also had arrows on the pumps showing their direction which would have been right hand...
I put everything on hold for the time being to figure out exactly what I have. I told my engine builder that I had a standard rotation motor with a gear drive... Im guessing that would assume a left hand rotation with a 1-8-4-3-6-5-7-2 firing order.
So, im guessing that I told him incorrectly, since i have a reverse rotation motor with a reverse rotation cam [installed in the engine], but since its a gear drive it needs to be a STANDARD rotation..
Im definitely going to have to call him back on monday and see exactly where we stand.
What do you guys think? this is kind of confusing. Might there be an easier way to doing this instead of taking the cam out and putting a different one in? The motor is all setup really nice and Id hate to rip it apart!! Im guessing though that IM going to have to take the motor apart and set everything up again!
Most SBC have chain drive cam. If it is a 2 drive gear setup, it would be obvious it was a counter-rotator. Why does it need to be counter-rotating? does the crank have the marks on the rear main seal reversed? When rebuilding a counter-rotator, the pistons should be installed 180 degrees from standard to compensate for the piston pin offset.
Something is not making sense here, proceed with deliberation
June 15 2008, 1:17 PM
First of all, if your motor has the gear drive, I would agree (being NO expert, mind you) that you have a reverse rotation motor.
We have to proceed with caution here, because I have long thought CC designated the rotation they posted on the motor in relation to how the crank turned when the motor was installed, and NOT necessarily whether or not the motor was actually spinning in an opposite direction to the standard automotive direction.
What REALLY complicates this theory is the fact that CC also turned these motors backwards on occasion, and I don't know at this time whether their designation referenced a deviation from standard automotive rotation, or whether their designation referenced the direction the output end of the motor and prop would be turning.
Looking at these images, one from our Chris Craft Power archives, and the other from Bill Policastro's identical 23' Commander, it sure appears the motor is installed backwards in the boat, being driven off the front of the motor (using the typical automotive installation designating what "front" means, with the distributor on the back or aft end of the typical SBC). If the motor is turning in the reverse rotation mode, which makes it a RH opposite rotation motor internally with reference still being in relation to the typical automotive front of the motor, and if CC turned it backwards, the power output end of the motor would be spinning in the LH (standard) rotation, but if the transmission maintained this rotation by the time you get to the prop you still have a RH prop. Depending on how the V-drive works, you might still have a RH prop, and I think you do. I don't want to spread bad info, so please be very careful taking this last paragraph as the gospel. I am hoping some others such as Mercrewser and Bill Policastro will chime in, since they are running this same setup and have been into the mechanicals.
Why would CC do this? Well it's still a puzzle to me why CC made ALL of their single engine true inboard boats with RH (opposite) rotation, requiring a special gear on the cam and special cam. Why in the world didn't they just use a more easily obtained standard LH motor? Since the V drive boats were generally pretty low production, and CC allready had a big stock of RH motors on order, perhaps they adapted to that
If you have gear drive which suggests you have the RH motor, and the pumps point in the RH direction, and you say you installed the RH opposite cam, you may not have any problem at all. Let's hope that's the case. I think I recall Mercrewser confirming his V-drive setup was using a RH prop. Comments anyone?
Paul is dead on about working your way through this confusion slowly. First of all, who dissassembled the engine? That person should know exactly what the original configuration was. Were the pistons installed on the rods with the indention facing the rear or bellhousing end of the block? Was the cam drive gear on gear with no chain? Both of these indicate a reverse rotation, right hand engine.
Then you can ask your engine builder...
1. What direction did you assemble the engine to turn
2. Which camshaft did you use in the engine. Trace the part number to the manufacturer to verify the intended application.
On a whim, I left my engine builder a voicemail yesterday afternoon. To my surprise, he returned my phone call about 5 minutes before I was getting ready to get into the car and leave the lake..
He apparently (somehow) realized that the motor was a right hand motor, and that the cam was CUSTOM GROUND to compensate for that. He only was concerned about the direction of the distributor, which means that the easy fix is if the distributor spins in the opposite direction as the firing order, we just have to flip the spark plug wires around. I'll crank the motor over and watch the rotor and make sure its going the right way.
The only thing he was concerned about (he apparently did a lot of his own marine-engine research, and he's built a few chris craft motors before) is if the motor was a bastard-child and the distributor was goofy, but he seemed to think that the cam was appropriate for the motor!
Bottom line is, I told him about the reverse firing order and all that stuff, and that the distributors spin the same way regardless, and he said that's how the motor was setup.
So, as I was about 5 mins away from stepping into my car, I decided to put my work clothes on and mount the blue giant into the boat. Got everything lined up, mounted in, now I just have to hook up everything... Ill have some pictures later today when I get home from work.
I'll have to get some info about the cam I have, but I know its not an off the shelf one, its made where the lobes are ground backwards for a STANDARD REVERSE ROTATION motor. Im not sure how he knew it was a reverse rotation motor, but he's the chevy expert, not me!
I didnt realize that all gear driven camshaft motors were reverse rotation. that makes a lot of sense, so I think I understand what he was truly asking me when he was asking for info..
He knew the motor was a reverse rotation motor, he wanted to know if it had the standard backwards firing order (1-2-7-5-6-3-4-8) or if it was weird and despite its RH nature still had a LH 1-8-4-3-6-5-7-2. So when I told him it was a standard motor, that meant it was standard for a RH motor! Based on what others have said, they just change the gear on the distributor and use the reverse firing order.
Whew, i think that clears everything up.. Im feeling pretty good, so next weekend we should have D-Day on our hands.
A note on ignition timing.. On the flyweel the only mark on the flywheel for timing is an "R" thats got a blue paint mark. Is that the one I want to set my base timing at?
All I have to do now is figure out where this whole mess of hoses and fittings go, which shouldnt be that big of an issue..
now is the time to mark TDC on the flywheel or damper. Put #1 cylinder EXACTLY on tdc, or go maybe 0.250" down both directions from tdc and mark the CENTER of those two measurements. You also need to determine at 30-32 degree advance mark to make sure you're getting full advance in the distributor. Don't worry about base timing..set full advance as needed. I'd start with 30 degrees and bump it up until it makes no more change in performance, then back off slightly.
All chevy distributors and oil pumps turn only one direction.
Apparently this was one of the good 327's with the steel crank, large journals, the good heads and all that fun stuff.. Go Chris Craft!!!!
Im guessing though that IM going to have to take the motor apart and set everything up again!
