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Old 07-27-2012, 12:51 PM
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chevy 350 piston advice

making a little hopped up 350 for a 89 chevy ... the guy wants a big cam and flat tops i tore the motor down and found a bent valve and dish pistons .. he has a set of heads with 1.94 valves .. now i am thinking the dish pistons will be better for the rebuild but .. want a little advice ..and i dont know what cam i should use

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Old 07-27-2012, 01:26 PM
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Quote:
Originally Posted by kennyhammond View Post
making a little hopped up 350 for a 89 chevy ... the guy wants a big cam and flat tops i tore the motor down and found a bent valve and dish pistons .. he has a set of heads with 1.94 valves .. now i am thinking the dish pistons will be better for the rebuild but .. want a little advice ..and i dont know what cam i should use
Are the pistons scored from the valves hitting them? If the pistons are fine maybe have the block and heads decked some and run a thinner gasket to get the compression up a little and then throw a cam in it. Can you get the four digit number off of the inside of the piston skirt? Then we can tell you what cc and compression height the piston is.
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Old 07-27-2012, 01:58 PM
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No the pistons are still in block.... no nicks or scuffs on pistons....what would be a good cam ...want that good ole lope idle... I am figuring it will have around 8.8 or so.... that should be good for a street motor with stock converter and high axle
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Old 07-27-2012, 07:23 PM
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lots of old time bump cams available.check your favourite grinder.Let them know about low CR,they might tell you to advance it when installing or recommend a cam with a lower intake centre line
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Old 07-28-2012, 08:44 AM
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Kenny, here's a "copy n paste" of an article I've been working on for the Wiki with suggested cams for 8.5:1-9.5:1 compression ratio SBC's.

Quote:
Small Block Chevy suggested camshafts for stock/near stock compression ratios (8.5:1-9.5:1).

First, a grind commonly known as an "RV cam". EVERY cam company has this, or an almost identical grind. Look for .420"/.440" lift, 204*/214* @ .050 duration, with a 110*-112* LSA (Lobe Spacing Angle). With a little more lift and duration than the ol' 350CI 300HP cam, this grind idles smoothly and pulls hard in a heavy vehicle. It's popular for towing and RV use (hence the name "RV cam"). The Summit K1102, Lunati 10000LK at Summit Racing, Speed Pro CL1014R cam/lifter kit at Northern Auto Parts, Elgin C923PK cam/lifter kit at Northern Auto Parts, Melling MTC1 torque cam at Northern Auto Parts, and the Howards #CL112561-12 at Competition Products are good examples of this grind.

2nd, one of the most popular grinds, if not THE most popular grind, EVER. The Comp Cams #12-210-2 High Energy 268H with .458" lift, 268* advertised duration, 218* @ .050" duration, 110 LSA 106 ICL (Intake center line), HE 268H cam/lifter kit at Jegs. Likely the reason it's so popular is precisely because it has the right combination of lift, duration, and LSA to work well with the millions of "smog era" SBC's. The HE 268H has a bit of choppiness at idle so it will give a nice "muscle car rumble". It works well with stock converters and hiway gears, but will benefit from higher-than-stock-stall converters and lower (higher numerically) gears. The Elgin E-1065-P grind is nearly the same as the HE 268H, a cam/lifter kit is part #CL-1065PK, and can be purchased at NorthernAutoParts.com. The Crane Energizer 272H10 is very similar to the Comp HE 268, with .454" lift, 272* advertised duration, 216* @ .050" lift duration, 110* LSA. The 272H10 is Crane part #10005, a cam/lifter kit is #100052, 272H10 cam/lifter kit at Summit Racing. A Summit branded version is part #K00052 K00052 at Summit Racing.

2 more popular cams for SBC's with "smog era" static compression
ratio's are the Crane 274HO6 (and versions by Summit and Elgin) and a grind referred to here as the "350HO", this grind is used by GM Performance Parts in the "350 HO" (350CI 330HP) and "CT 350" (350CI 350HP) circle track crate engines. Copies are available from Summit, Lunati, Elgin, Speed Pro, Howards, and others. Like the Comp Cams HE 268H, these cams have mild .050 duration figures to maintain dynamic CR for low end power. They will work well with stock torque converters and "highway" gears, but will work even better with "stall" converters and lower gears.

The Crane 274HO6 grind, (.450" lift, 274* advertised duration, 218* duration @ .050", 106LSA, 102 ICL), 274HO6 cam/lifters at Summit Racing The 274HO6 is an equivalent cam to the ultra popular Comp Cams High Energy 268H, but is ground on a tighter 106* LSA, which gives it a choppier idle than the other cams listed here. The tighter LSA makes the torque curve more "peaky" with a higher torque peak, but in a slightly narrower rpm range. This cam is one of the grinds that Crane used to classify as "3/4 race". If you want a real "rump rump" idle without losing all the low end power of your low compression SBC, this grind should be on your short list. Equivalent cams to the Crane 274HO6 are the Summit K00172 (supplied to Summit by Crane) - Cam/lifter kit Summit Racing SUM-K00172 - Summit Racing Street & Strip® Cam Kits - Overview - SummitRacing.com and the Elgin CL1785PK Cam/lifter kit at Northern Auto Parts Elgin Prostock Cams | Northern Auto Parts

Here's a YouTube video of the Crane 274HO6 idling in a '73 Nova with a stock Goodwrench 350, Performer intake, 600 cfm Holley carb, open headers. This Nova has hi-stall convertor, 3.73 open diff (no posi), and has turned 13.86 1/4 mile with drag radials Crane Energizer 274 H06 Cam Rough Choppy Lopey Idl - YouTube


Next, the GMPP "350 HO" cam, part #24502476 (.435"/.460" lift, 212*/222* @ .050", 112.5* lobe spacing angle), 350 HO cam/lifter kit at Pace Performance This is a modern split pattern cam, and has a wide flat torque curve. The idle is not quite as choppy as the 274HO6 but still has some choppiness so you can "hear the cam". Racers that compete with the CT350 crate engine have called it a "torque monster". Of the grinds listed here, this grind is likely the best all-round grind for a low compression ratio 350.

The Summit K1103 grind (.443/.465 lift, 214/224 @ .050, 112 LSA)
has just slightly more lift and duration than the "350HO" The K1103 cam/lifter kit is available at Summit Racing SUM-K1103 - Summit Racing® Cam and Lifter Kits - Overview - SummitRacing.com

These 3 cams are the same grind as the K1103. The Lunati Barebones 10001LK - available at Summit Racing
Lunati 10001LK - Lunati BareBones Camshaft and Lifter Kits - Overview - SummitRacing.com, the Elgin E-922-P C/L kit CL-922PK at Northern Auto Parts Northern Auto Parts: - CAM-LIFTER KITS by ELGIN INDUSTRIES, and the SpeedPro CS1013R C/L kit CL1013PK at Northern Auto Parts
Northern Auto Parts: - CAM-LIFTER KITS by ELGIN INDUSTRIES

Howards #112571-12 is another "350 HO" equivalent cam, with slightly more intake lift and intake/exhaust duration than the above grinds (.455"/.465" lift, 215*/225* @ .050", 112* LSA). A cam lifter kit is available at Competition Products

Here's Youtube videos with the "350 HO" grind:

'70 Chev C10 with 350 1970 chevy c10 with a nice cam - YouTube

350 with noisy gear drive 355 chevy with 272/282 cam and noisy gear drive - YouTube

As for "name" versus "generic" grinds, the main difference is the label on the box and the price. Most all cams, no matter who's box it comes in, are ground by 3 cam grinding companies. The only cam companies, as far as I know, that grind all their cams in-house are Isky and Howards (both very good cams). The Crane 274HO6 part # is 10017, 100172 for a cam/lifter kit. The last I knew Summit cams were supplied by Crane. The Summit part # for a cam/lifter kit is K00172 (looks kinda like Crane's number, huh?), but the part number for the cam only is 1785, the same as the part number for the Elgin boxed cam. Hmmmmmmm...
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Old 07-28-2012, 02:06 PM
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Definitely keep the compression under 9.5:1 for using 93 or lower octane.

As for big Ed's discussion on cams, there are more details that need to be brought out.

First, most flat-tappet hydraulic cams are actually ground by Camshaft Machine Co. in Illinois. They were the big supplier for the OEM before the advent of rollers. Crane, Comp, Crower, Isky, Lunati, Bullit, Howard's all have their own "masters" and the grinds are propietery, though ground on the same machines. Elgin, Melling, Summit, Wolverine, Edelbrock, etc. are what we refer to as "generi-grinds", where they're all based on "tried and true" grinds from days gone by. And I've heard before, some of the Summit grinds ARE old Crane grinds. Always be "on guard" against comparing them based strictly on "numbers". Most grinders have their own methods of measuring and advertising, so one "240" might mean something different than another... Harvey Crane retired MANY years ago, as did Joe Lunati. Not much innovation from those two since, except the Lunati "VooDoo" series designed by Harold Brookshire. Like the UD (Bullit) and XE grinds, VooDoo uses modern "fast ramp" technology. Good cams for lower compression.

I would recommend a Comp XE grind for this application. A mild one, probably XE256H, would be ideal. If you want more "attitude" from the sound, use XE268H. Nothing bigger than that, though, without changing converters. If torque is more important than "sound", use 265DEH.

Jim

Last edited by Mr. P-Body; 07-28-2012 at 02:22 PM.
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