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Topic Review (Newest First)
02-21-2013 05:55 PM
cdminter59
Engine

Quote:
Originally Posted by maxxman04 View Post
still going round n round with this. alot say to use pat kelly's calculator. so i did. this is results

scr-9.956
dcr-8.405
quench-.051

4.030 bore, 3.48 stroke, flat tops, 5cc valve reliefs, 4.166 bore/.039 head gasket, 65cc/1.94 valve heads ('810 casting, 350 truck heads) cam is. 218/224, 462/469 lift, 110 lsa. alum. intake, ruggles tuned qjet carb, headers.

trying to get away with pump gas, as this will be daily driven, not raced. i get mixed opinions in searches. some say quench too high, but if i drop that, then scr and dcr go up. some say i'm ok. just looking for others opinions on this setup. from all i figured, at my elevation, air temp and such, i should be fine.
So this means your deck clearance is .012 is this correct. With the 8.4 it should run on 91 octane at 36* total timing.
02-20-2013 04:02 PM
oldbogie
Quote:
Originally Posted by maxxman04 View Post
still going round n round with this. alot say to use pat kelly's calculator. so i did. this is results

scr-9.956
dcr-8.405
quench-.051

4.030 bore, 3.48 stroke, flat tops, 5cc valve reliefs, 4.166 bore/.039 head gasket, 65cc/1.94 valve heads ('810 casting, 350 truck heads) cam is. 218/224, 462/469 lift, 110 lsa. alum. intake, ruggles tuned qjet carb, headers.

trying to get away with pump gas, as this will be daily driven, not raced. i get mixed opinions in searches. some say quench too high, but if i drop that, then scr and dcr go up. some say i'm ok. just looking for others opinions on this setup. from all i figured, at my elevation, air temp and such, i should be fine.
This head is a version of the small chamber swirl port used on heavy duty trucks.

This is probably on the edge of OK with 91-93 octane unleaded. If necessary detonation can be controlled with less advance, richer mixture, cooler intake and/or operating temp, stiffer gearing, using 1.6 rockers. The latter keeps the valve open higher from the seat in the closing ramp which will bleed off compression faster and more total volume than will a 1.5 rocker.

Less advancce is very effective but usually isn't desireable as power output goes away at a faster rate and in amount when reducing the amount of igniiton advance than it does when reducing compression. Still it's a useful trick especially if you wire in a detonation sensor as the EFI engines use. That can be combined with an igniiton control box to back out some timing when it hears pinging, so it would only function at those times.

Water or water/alcohol injection is another trick that quashes detonation, there are kits on the market for this. With some electronics it can be used with a detonation sensor to switch on the system only when needed rather than manual control.

You can always open the chamber a little by polishing off sharp edges, genrally polishing the as cast surfaces, and/or by putting Singh grooves into the squish/quench pad.

I would not increase the squish/quench clearance to reduce compression by increasing chamber volume, this is like the dog chasing its tail as the clearance opens compression goes down but sensitivity to compression goews up. You end up having to add serious clearance to get the compression down where even with the additional clearance detonation ceases to be a problem, trouble is by that point the power output is long reduced.

Bogie
02-20-2013 12:38 PM
ap72 your quench, dcr, and scr are NOT the concerning factor, the heads are.

BTW, there are plenty of gaskets with a more appropriate bore diameter/thickness.

If its very well tuned you could probably run it on 93 Octane with those heads, just don't lug the engine.
02-20-2013 12:14 PM
vinniekq2 what elevation
what head material?
02-20-2013 11:48 AM
maxxman04
Scr/dcr

still going round n round with this. alot say to use pat kelly's calculator. so i did. this is results

scr-9.956
dcr-8.405
quench-.051

4.030 bore, 3.48 stroke, flat tops, 5cc valve reliefs, 4.166 bore/.039 head gasket, 65cc/1.94 valve heads ('810 casting, 350 truck heads) cam is. 218/224, 462/469 lift, 110 lsa. alum. intake, ruggles tuned qjet carb, headers.

trying to get away with pump gas, as this will be daily driven, not raced. i get mixed opinions in searches. some say quench too high, but if i drop that, then scr and dcr go up. some say i'm ok. just looking for others opinions on this setup. from all i figured, at my elevation, air temp and such, i should be fine.

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