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I am rebuilding a 63 motor with F.I. When selecting pistons at (.060" over), what is the best piston to use ? I realize, that originally, forged, 11:1 compression pistons were used. Would it not be better, to use flat top pistons, in order to drop the compr. ration, since the high octane fuels are no longer available, and octane booster would have to be used. What do most "experts" use ?
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Re: Piston selection for Fuelie engine
I am no "expert", but I have a 62 FI which is an identical engine to the 63. I currently have domed forged pistons, but I don't think they are in the 11:1 category, probably more like 10.5. Flat tops will usually yield around 10.0 Static compression is only one of the variables in combustion and detonation. Your cam will drastically affect dynamic compression, which is ultimately what can cause detonation. Bottom line is I think you can use pistons with a mild dome and run pump gas without problems. The 63 FI has a vacuum advance which allows you to run higher advance numbers at moderate throttle settings without risking detonation at WOT. -
Re: Piston selection for Fuelie engine
my 62 with fi still has the correct pistons & cam .I have no problems until the outside temp gets into the 90s ,but thats a gas problem not engine ,octane booster helps. with a 4:11 rear there is no pinging .Why have a F.I. that does not sound or run like one??? maybe someone with a 250 horse powerglide will trade?Comment
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Re: Piston selection for Fuelie engine
I recommend you use the Federal Mogul Speed-Pro forged pistons. These are essentially the same as OEM as this former TRW division was the original supplier. In order to yield the same engine sound you need these forged pistons fit at about .0035".
Prior to teardown, measure deck to piston crown clearance, and compute the actual CR of your engine. With typical clearance and a .040" composition gasket your actual CR should be about 10.5 to one. High overlap cam engines can take more compression because they have lower actual compression pressure at low speed, which is where detonation is an issue. Most '63 SHP/FI engines were assembled with TWO steel shim gaskets to reduce CR. You would have to deck the block and use only one steel shim gasket to achieve the advertised 11.25:1 CR. Most owners of SHP/FI small blocks report that their engines run without significant detonation on pump premium, and any light detonation can be handled by either small timing adjustments or blending some racing gasoline with pump premiu.
Assemble the engine with the LT-1 cam, rather than the Duntov cam. The LT-1 cam will produce a similar idle quality/vacuum, but will make more torque/power across the rev range. Special procedures apply to adjusting the valves on this cam. E-mail me if you want them.
If you still have the original '63 vacuum can replace it with the NAPA/Echlin VC1810. This is the replacement for the '64-up SHP/FI vacuum can. It provides a maximum of 16* at 8". The original '63 can did not provide full vacuum advance until about 16", but at idle the engine only produces about 12". The vacuum can must provide full vacuum advance at least 2" below what the engine produced at idle to provide maximum idle quality and stability.
DukeComment
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how much clearance to sound like 427
if i want my engine to sound like a 427-435hp do i give it .005" piston clearance?Comment
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Re: how much clearance to sound like 427
No, you just spend an additional 30KComment
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Re: how much clearance to sound like 427
The mechanical sound quality (has nothing to do with exhaust sound) of solid lifter SHP engines is derived from both both their loose clearance forged pistons and the mechancial lifter camshafts.
Some guys with new ZO6s whine about "valve noise". The 02-03 LS6 camshaft has constant acceleration clearance ramps (as opposed to the more common and milder constant veloctiy ramps) and lobe flanks that feature very rapid valve acceleration, so even with roller hydraulic lifters, they make a little more noise than most hydraulic lifter engines.
What's happened to the world? Back in the fifties and early sixties guys used to put Duntov cams in their 283s just to get that SOUND!
DukeComment
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Re: Piston fit
quote, in order to yield the same engine sound you need these forged pistons fit at .0035". duke, what on earth were you thinking???????? this has nothing to do with engine sound.Comment
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Re: Piston fit
Are you pulling my leg, John or do you not realize that high piston clearance adds to the mechanical sound spectrum created by a running engine? (I emphasize the mechanical sound, not the exhaust sound.)
It's usually referred to as "piston slap", and the looser the clearance the more of this sound the engine will generate. As engine technology developed over the years, piston clearance was tightened by OEMs to reduce engine mechanical noise, and cast aluminum pistons can be run in a 4" cast iron bore at about .001" clearance. The forged aluminum pistons in SHP engines need more clearance due to expansion issues and the higher clearance reduces piston skirt drag, which, along with the rings accounts for most internal engine friction.
Piston slap is usually more noticeable when an engine is cold, and to use the contemporary Z06 as an example, Chevrolet received complaints of cold engine noise in the '01 version. Turns out that the LS6 hypereutectic cast pistons were fit with a little more clearance than the LS1, which created cold piston slap that many owners noticed. Late in the '01 model year Chevrolet tightened the LS6 clearance to reduce piston slap and also added a polymer coating to the skirt to help prevent scuffing, which can be caused by tight clearance.
DukeComment
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