Re: Bodyman needs Engine Advice
[Re: 70VERT]
#1289342
08/22/12 10:00 AM
08/22/12 10:00 AM
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Joined: Jan 2003
Posts: 75,326 A gulag near you.
JohnRR
I Win
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I Win
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Posts: 75,326
A gulag near you.
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Quote:
Just checked #1 and #3 cylinders there is just a whisker under 3/16" clearance from top of piston to deck at TDC. The heads are at the shop right now and I can't get any numbers, but they appeared to be stock cast iron heads---thanks ,bob
Sounds like you are using a ruler to measure ?
Anyway that far in the you'll got late model smogger replacement pistons , you'll have about 7.5 compression ratio.
Be careful not to over cam it .
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Re: Bodyman needs Engine Advice
[Re: RapidRobert]
#1289344
08/22/12 12:29 PM
08/22/12 12:29 PM
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Joined: Feb 2003
Posts: 21,318 Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Too Many Posts
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Posts: 21,318
Manitoba, Canada
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JohnRR is not joking. If those pistons are indeed that far in the hole, whoever rebuilt that engine used mid 70's 440 replacement pistons. Basically the worst possible piston to put in a 440. With stock open chambered heads, which I'm assuming is what you have, compression will be in the 7.5-7.8:1 range. This means you will want to be very tame on cam choice and you will be down on power compared to a 440 with proper pistons. To be honest, since you have the engine apart, in your shoes I would take this time to replace the pistons. You will thank yourself later. But if that idea does not appeal to you I do have a couple cam suggestions. I ran a lunati voodoo 60303 cam in a 440 with those pistons. 3.55 gear, headers, stock intake. It ran decent but needed more than the stock torq converter, with a stick shift I think you would be okay. Hughes makes two cam shafts for big block called the "whiplash" cam. They are specifically designed for 440's with smogger 70's pistons. I would take a look at their 440 whiplash cam. With your gear and stick shift I think it would do well. They are supposed to give you that lopey idle you want but still perform decent and drive well in a lower compression 440.
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Re: Bodyman needs Engine Advice
[Re: 70VERT]
#1289347
08/22/12 03:55 PM
08/22/12 03:55 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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I'd have them take .060" off of the heads' decks then a corresponding amt (there's a formula) off of the intake face of the heads'. Use a 6" small steel scale across the bore & feeler gauges stacked under it to measure down to the piston depth & that'll be plenty good enough
live every 24 hour block of time like it's your last day on earth
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Re: Bodyman needs Engine Advice
[Re: RapidRobert]
#1289350
08/22/12 05:54 PM
08/22/12 05:54 PM
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Joined: Feb 2003
Posts: 21,318 Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Too Many Posts
Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
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Milling those heads .060 will bump your compression some. You'll be closer to the factory advertised 8.2 compression than the real life 7.5 compression those engines were actually built with. My 76 440 measured out to the pistons being .150 in the hole. I've heard others have measured theirs as up to .180 in the hole. Doesn't sound like much, but in terms of compression, a piston that is flush with the deck versus one that's .150-.180 in the hole makes all the difference. Having the heads milled will help. If you mill them .060 you will need to have the intake flanges on the heads milled as well. As said there's a formula, it's not a 1:1 cut. Also keep in mind if you mill .060 your stock pushrods may be too long. If it was a .030 cut I would say you'd be okay but I think .060 will call for new, shorter pushrods. So by the time you have the shop mill the heads and buy those pushrods, how far towards the purchase of those new pistons are you? I've never personally ran one of the whiplash cams, but if I was to ever slap together another low CR big block, I'd give one a try.
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Re: Bodyman needs Engine Advice
[Re: 70VERT]
#1289353
08/22/12 08:16 PM
08/22/12 08:16 PM
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Joined: Jan 2003
Posts: 75,326 A gulag near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,326
A gulag near you.
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Quote:
Thanks for all the info, Daytona I'm beginning to rethink replacing pistons. Couple of questions here--how tough will it be to do with the block in the car? There is almost no ridge on cyl walls, will I need to hone or crosshatch? (there is about 1000 miles on this piston rebuild)and lastly what pistons should I install?
It's not a inline 6, you are not doing it with the block in the car, very easily, or very right.
Find a set of 915's and put in a cam.
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Re: Bodyman needs Engine Advice
[Re: DaytonaTurbo]
#1289358
08/23/12 01:50 PM
08/23/12 01:50 PM
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Joined: Jan 2003
Posts: 75,326 A gulag near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,326
A gulag near you.
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Quote:
For what he's doing, I think he would be better off finding a used edelbrock ch4b intake. With stock heads and low CR, the holley street dominator is less than ideal.
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Re: Bodyman needs Engine Advice
[Re: 70VERT]
#1289362
08/23/12 08:19 PM
08/23/12 08:19 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Yes there's been enough reported problems with the newer orange boxes (plus it's pricey) that I would highly suggest going elsewhere. Even tho there's many ways/options to go, a generic parts house ECU will get you up and running cheaply with more than enough ign power for now. The rest of your choices look good however I would mockup and check lifter preload before I committed to a particular pushrod length. I'd sure be nice if you could get some 915 closed chambered heads for the CR boost & even with slight milling (maybe a .030" truing cut) your pushrods (preload) may be good as is plus you could use the shortblock as is as opposed to boring/honing (& possibly balancing)for new pistons. Minimize the downtime.
live every 24 hour block of time like it's your last day on earth
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