Stock cams info

[joelyons50023]

I know that this question has been asked before but i was just wanting to know about the stock cams timing specs and lifts also the rod length. And also sean you said that thou can be milled from the block is that for the lip of the sleve to make it b/c i think that is gonna be the route that i go also what is the highest comp. ratio the quench/squish set 30-40 thou running on 91 octane with the heads ported and polished.

 

[TURBOVMAX]

Stock cam lift is .324 on the intake and exhaust. If your going to use adjustable cam sprockets I usually set them up at 104 intake-106 exhaust. Here's a link to available aftermarket cams and specs. WEB CAM click on the grind to see the specs.

There's lots of room valve to piston to take that .030 to .040 from the block.
Not sure how much it raises the compression ratio. But it's not enough to worry about the fuel octane.

Rod Length 124 mm (4.880)

Who's going to port and polish your heads?

 

[joelyons50023]

I am going to p&p my heads i was just wondering when the intake valve closes abdc to be able to get the proper dynamic compression. I done the math and taking 40 thou off with the stock head gasket thickness it will be at 11.9-1 when i measured stock it was right at 10-1.
Here are some pics to what i have done to my intakes before and after

 

[KJShover]

Looks great. Make sure you don't polish your intakes too smooth. The exhaust likes the mirror finish, but the intakes need some friction in there to aide in the fuel/air atomization unk:

 

[joelyons50023]

I sandblast the insides before it is done to help with the fuel atomization.

 

[KJShover]

I sandblast the insides before it is done to help with the fuel atomization.

I was just going to suggest that, LOL.. Thats what I did on my old XS head. IMO it turns out great that way :clapping: After milling the head, installing bigger low profile valves and big cams w/ slotted rotors, the power improvement was a huge upgrade. But, what I couldn't get over was the sound difference. It was flat out mean.

Some time down the road, I'm going to pick up a set of heads for my Max and give them the work over.

 

[TURBOVMAX]

Donno those numbers off hand. It's easy to just put a degree wheel on the crank and get them. Just curious.... what number are you using for the combustion chamber volume?

 

[joelyons50023]

Just what Sean gave 25-26cc but mabie tomorow I will cc them. I tell ya what I started on one head after I my shop foreman got me a spring compressor that would fit. I thought these heads would be better shape than I they are, the seats are way off and the casting marks are pretty pronounced also I am unshrouding the chamber around the valves. I am pretty excited about this project, with the head in this condition this leaves a good margin of improvement. I wonder what my numbers will be after with just P&P the heads and milling the cases. I can check it in the cylinder but does anyone know what the cc size of the stock piston is. I will take some pics as soon as I can. Also is there anyone who can do the degreeing the cams to get the stock cam specs my heads are off and part of the motor torn appart if not i will do so later on i was just hope some one would be at a better point to do that

 

[TURBOVMAX]

Don't have the time right now... maybe Sean has the numbers. The dynamic compression ratio will net a lesser compression ratio. That combined with the Vmax having a good combustion chamber design, is why you'll have no problem with detonation on pump gas. Do you have a flow bench where you work?

I can tell you from experience that your best bet, is to stick with the numbers for lobe centers that I gave you. That's the only way you can move the valve timing events around with your stock setup. I think Sean will agree that for a stock mild port with a stock cam it's not even worth the expense and effort to degree the cams. If your making radical changes to your engine (high flow porting, high compression, cams, long rods etc.) Then that's a totally different story and where the cam guru's (Web Cam) come into the picture. Then it's worth the effort and dyno time to move cams around.

 

[joelyons50023]

If I am decking the block i think that it would be a good idea to slot the rotors anyhow b/c i think the rear would be retarded and front advanced. no flow bench here, I don't believe in them much anyhow

 

[one2dmax]

Even with the shaved deck height it may not be worth the time but it's not all that hard to do either. Hardest part is getting the old plastic off the gears. You can get many of the cam specs off of the megacycle website. They do have specs for their regular grinds and stock specs for ref.

If I remember right I want to say 23-25cc's for combustion chamber volume.

Note that the exhaust and intake will fit like crap with the block decked.

Sean

 

[TURBOVMAX]

If I am decking the block i think that it would be a good idea to slot the rotors anyhow b/c i think the rear would be retarded and front advanced. no flow bench here, I don't believe in them much anyhow

Your talking turbo timing :biglaugh:... real horsepower. The cams sprockets are easy enough to do and it is lots of fun to play with the timing. I don't much believe in spending the money for flow bench work either. But in the right hands there's lots of power to be had. It's a science in itself.

I flow my heads with a garden hose and an intake adapter. Just turn the water on and set the valve height where you want and watch the flow... simple. Of course when I flow it's for max and that isn't what you want for street use. Your best bet for street and your particular setup is to just blend the ports nicely and if you want unshroud the valves.

Just my 2cents.

 

[Vinmax]

Anyone know the duration for the stock cams? I was just comparing to the web cams and see that they are 270 degrees for their most mild cam.

Vinnie

 

[one2dmax]

CAM VALVE DURATION LOBE INTAKE OPEN/CLOSE RUNNING
NUMBER LIFT AT .040" CENTERS DESCRIPTION AND APPLICATION EXHAUST OPEN/CLOSE CLEARANCE
274-00 .375" 257? 106.5? Designed for stock pistons, must check. 22 btc/55 abc .006"
.375" 257? 106.5? Improved mid-range, some added top-end. 55 bbc/22 atc .008"
Mini sprint 1/8 & 1/4 mile. Use #30-1017.
274-x7 .354" 254? 106? OK with stock pistons and springs. 21 btc/53 abc .006"
.354" 254? 106? Strong mid-range torque. 53 bbc/21 atc .008"
274-x2 .410" 250? Race only. Modified pistons, springs and shim under followers.
Stock .324" 241? Intake and exhaust same. For your reference.

 

[joelyons50023]

Just checking for sure the stock pistons are cast right?

 

[one2dmax]

yes

 

[joelyons50023]

I put up some pics of my heads on another post in motor section