|10-07-2013 02:35 PM|
There's really not much to add to this thread that is over a year old, except to put in my two cents worth concerning max lift on stock L31 heads.
If a fellow is to use anything over 0.425" valve lift in these motors without mods, he's asking for trouble. Is there room to do it? Yes. Are you using up the safety margin? Yes. You don't put a motor together without some play (safety margin) between the bottom of the retainer and the top of the seal to account for an over-rev.
|10-07-2013 01:35 PM|
|vinniekq2||welcome to the forum Gator,maybe start your own thread with as many details as you know?|
|10-07-2013 01:30 PM|
I really appreciate the wealth of knowledge here guys. I just bought a 66 Chevelle the original 327 which has been upgraded in the following fashion:
-Double Hump heads
-268 duration 454 lift Cam
-Demon 650 Carb
-GM 373 ring and pinion gear set
He says it makes 350hp??? Not sure, but any ideas on boosting this up would be great. What would a different manifold and headers do? Thx-Gator
|08-04-2012 09:14 PM|
|jexrod||Great i wil try and make it work with 91 at around 9:4. The gas is available at Arroyo Parkway 76, the stand alone pump is red labeled with "racing fuel" 100 octane gas only $8.89 per gallon.|
|08-04-2012 09:06 PM|
|454C10||FYI, more overlap doesn't "bleed off a little cr". The engine isn't even trying to make cylinder pressure on that part of the 4 stroke cycle. The intake valve closing point is what effects the "bleed off", as this is the only part of the 4 stroke cycle that the engine is trying to make compression. And long duration cams will have a later intake valve closing point. In fact, the intake valve will be open long after the piston is on the rise to make compression, thus reducing the effective compression stoke which reduces cyclinder pressure.|
|08-04-2012 07:15 PM|
Is the 100 octane available at the pump, there? Just for my information.
Some of the gas stations in western NY have 100 octane unleaded at the pump.
Delta Sonic "Cam 2" (Sunoco)
This is very effective to blend with 91 or 92 when you need a bit more octane
to stop detonation.
|08-04-2012 06:36 PM|
|vinniekq2||91 octane will work with 9.5 iron heads.More overlap on the cam will bleed a little CR.make sure your cooling system is peak,..Is there methanol in your gas there?|
|08-04-2012 06:22 PM|
|jexrod||Just received the 700 trans any insight on the swap, would be appreciated. I will be searching for threads tonight. Also, regarding gas octane... I made a mistake 91 or 100 is all I have access to, 93 is not available in California.|
|08-03-2012 02:27 PM|
So you will not only have to insure the spring has coil to coil clearance usually no less than .050 inch per coil when the valve is fully open. But you've got to get inside the spring and measure the clearance between the top of the guide and bottom of the retainer with the seal installed. If using a positive seal this needs to become a measure from the top of the seal to the bottom of the retainer, this also needs to be no less than .050 inch.
Additionally when getting into really high lifts getting clearance between the side of the spring retainer adjacent to the rocker arm can be a problem. The need here is to grind on the rocker for clearance. Given this is an area of the rocker that sees the most stress, subtracting material can cause the rocker to break with easily imagined consequences. The best solution here and also one that helps these other clearance problems is the beehive spring which tapers in at the top and uses a smaller diameter retainer, thus the rocker doesn't need to be compromised.
With engine building, remember that the cheap way out of problems leads to expensive disasters.
|08-03-2012 02:06 PM|
Thanks, just got a lead on some springs i can drop in to Vortec heads without additional machine work. According to the vendor it makes them good 218 degrees durantion @ .050" w/ up to .550" lift.? Any input on experience using them would be appreciated.
DROP IN FIT VALVE SPRING KIT FOR VORTEC HEADS, HYD FLAT TAPPET CAMS, 110 SEAT PRESSURE
|08-02-2012 03:50 PM|
With a 9.5:1 compression ratio and the 700r4 you're going to want a cam around 210/215 @.050". It won't idle that rough but it will be very driveable and get decent mileage. On a well assembled 327 you could see an honest 325hp which for a daily driver is plenty.
|08-02-2012 02:53 PM|
|Ripper 410||is it the early '67 small jornal block or is it the late large jornal? if it is the small jornal not that it matters that much being it is a 327 I would not put anything smaller than 280 dur in it 327"s were notorious for not developing power til around 3000 rpms because of the small stroke if it is the small jornal you can rap it too 10000 rpm at the blink of an eye without doing any balancing or blueprinting if it is the large jornal you can safely hold 8000 before you need balancing and blueprinting for there time the 327's were screamers they love to turn and really were not designed for low end so as far as cam the bigger the better on this app.|
|08-02-2012 02:50 PM|
Will have to measure the "quench" again to be sure when I mock up the engine, shooting for .40 to .60 seams like the optimal choice. I will use the necessary gasket to achieve that.
Using the powerglide was more of a convenience because I know very little about engines, but I know a lot less about transmissions. That said, I have a lightly used rebuilt 700r4 (about 500 miles) being delivered this weekend from a friend of mine who totaled his car. Got a good deal on it so, i'm jumping into it.
I would rather not do any additional work to the vortec heads, ie... cutting the guides and the stud base for guide plates. Looks like making the 700r4 swap will be money better spent.
Should I stick to the 268 cam with the 700r4 now in the loop? I keep hearing .475 is max lift, does the fact that I have screw in studs help this, or is the clearance issue on the valve guide height?
|08-02-2012 11:42 AM|
As has been mentioned; the buildup of the piston crown to deck distance and the head gasket thickness is excessive for the best squish/quench. My calculator with your dimensions gives a fairly mild Static Compression Ratio (SCR) 9.1 to 1 which should be no problem for a Vortec head. You can lean on that a little and pull your squish/quench back toward the more desirable .040 inch by using a shim style head gasket these are available for .016 and .019 inch thicknesses. The .019 would bring the squish/quench distance down from .070 inch to .058 which is much more desirable for mixture agitation and detonation resistance. The .019 gasket would bring your SCR up to 9.5 to 1 which is quite good with these heads. The shim gaskets do require flat and parallel head and deck surfaces, it they aren't then some milling is needed and that depending upon the dimensions of material removed can drive a different gasket solution.
|08-02-2012 07:53 AM|
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