Suggest you pull a spring with the heads on and have a shop pressure check and measure it with a good set of dial calipers. Then you will know what you have and if it will be OK to run with the cam you are thinking about.
I say this b/c some solid cams, (if it is a solid), run fairly aggressive springs, (which is what they need), that may callapse hydraulic lifters! pdq67
I'd suggest pulling the cam and heads if you are really serious. Then you can look at what pistons you have (to figure out the compression ratio) and install a new cam, lifters and springs all at once. then there's no more guesswork.
You can jack the rear end up, rotate the wheels in neutral, and count drive shaft revolutions to figure out the rear end gear ratio. You can also brake torque the car and read the tach to see what RPM the stall converter is.
Ok, I agree. Since the engine (327) is on an engine stand, I figured I would take off the heads and start from scratch to eliminate guesswork. I am buying a Comp cam kit that provides spinds, cam timing chain lifters etc.
The pistons have this stamped on top:
Anyone know what this means?
Can I determine the compression ratio from these numbers?
Thanks a ton!
[This message has been edited by Sgrouse (edited 09-07-2002).]
Are they TRW pistons? It looks like a TRW part number
I looked up that on summitracing.com using a TRW number it comes up as being a .040 overbore piston for a 3.25" stroke (327) and 5.7" rod.
It says this piston has a .125" dome
With 64cc chambers it'll have up to 10.35:1 compression (depending on deck height)
With 68cc chambers 9.87:1
with 72cc chambers 9.43:1
with 76cc chambers 9.03:1
This all depends on deck height and compressed head gasket thickness.
If you pull the heads when changin cams check your deck height. with a dial indicator stand and dial indicator. How far the flat part of the piston is in the hole at TDC is your Deck height.
[This message has been edited by CamaroNOTcamero (edited 09-07-2002).]
I dont know about that one, but i'm glad i could be of assistance with the other numbers.
Good eye with the numbers, it would be up in the air otherwise.
What are the numbers on your cylinder heads, maybe we can find out what size chmabers it has.
BTW since its an aftermarket cam shaft it should have a part number on it, we can see which company's number it looks like and go from there and possibly find out what cam is in there (might not be as big as you think).
Yes casting numbers off the heads would be next IMO.
If you have a small dome piston like CNC says, you don't want to go too small on the cam or you might have pinging problems. 10.3:1 is pushing it a tad with pump gas and 64cc iron heads. You kind of need a larger cam to bleed off a little cylinder pressure.
You may be able to use the Comp XE268. This would still have a little bit of an idle but would make good power and should be real steetable. Specs are: advertised duration 268*I/280*E, duration @ .050" lift 224*I/230*E, lift .477"I/.480"E, lobe separation 110*.
This combo should make about 300 HP at 5000 rpm with a nice smooth torque curve from 2000 rpm up. Idle will be a little sporty but it should still be fairly well mannered. I assumed you had GM 441 casting heads with 1.94"I / 1.50"E valves.
With stock heads you need a dual pattern. I dont know what you mean by a calmer idle but as eric suggests the xe268 would be good but the xe274 would be the next step up and could be a good idea imo. You arent going to run into any compression issue with 76cc and maybe if you dont mind setting valve last once every blue moon the 282S or maybe the 270S or a crower grind. Maybe the summit/ crane powermax grind that is a spilt 224 and I think 234 @.05. That would work very well and is a better idea than the before mentioned comp XE grinds. Im not a fan of the XE grinds, they are loud and durability maybe a concern in the long haul. plus that summit comes with lifters lube and cam for 71 bucks and you could get into some K-motion springs for 42 and 65 for the retainers. My vote is for the summit grind and yes your 292 must have a bad *** idle!!!