zimm Posted March 14, 2015 Report Share Posted March 14, 2015 for a 1976 L20B engine on a feller gauge Quote Link to comment
zimm Posted March 14, 2015 Author Report Share Posted March 14, 2015 what are the setting for the piston ring gap if anyone can give me that info it would greatly would be appreciated Quote Link to comment
67_1600 Posted March 15, 2015 Report Share Posted March 15, 2015 Someone may have the info off the top of their head, but a quick and simple Google search for 'L20B piston ring gap' returned this: http://vintage.mitchell1.com/PClubData/chassis/enis78/V2I785066.pdf Quote Link to comment
datzenmike Posted March 15, 2015 Report Share Posted March 15, 2015 On a stock bore L20B (per the FSM)Top ring gap......... 0.0098" to 0.0157"Second ring gap... 0.0118" to 0.0197"I found an on line site that specified 0.0044" for every inch of bore for the top ring... I got 0.0133" end gapFor the second ring 0.0055" for every inch of bore and I got 0.018" gap. Close enough for a stock use engine. Quote Link to comment
Stoffregen Motorsports Posted March 15, 2015 Report Share Posted March 15, 2015 For the top ring it's about .004" for every inch of bore. That's a rule of thumb. For the second ring it's less important, but the same rule can be used. Quote Link to comment
Doctor510 Posted March 15, 2015 Report Share Posted March 15, 2015 I use, .0035" x bore in inches for top ring, add .002" for 2nd ring. Quote Link to comment
datzenmike Posted March 15, 2015 Report Share Posted March 15, 2015 That will work as they all will. A tighter tolerance seals the compression better but on the down side if ever over heated, risk the gap closing and the rings or lands breaking. This would be an extreme case however caused by owner ignorance or running a turbo which isn't expected here. I've pulled many pistons with broken rings but usually they had either seized or had a rod through the block. Quote Link to comment
Jester Posted March 15, 2015 Report Share Posted March 15, 2015 I found an on line site that specified 0.0044" for every inch of bore for the top ring... I got 0.0133" end gap For the second ring 0.0055" for every inch of bore and I got 0.018" gap. Close enough for a stock use engine. This is the rule I have always used as well. Have yet to have a failure. Keep in mind that, like Mike stated, THIS IS FOR A STOCK ENGINE. If your are using any type of power adder like a turbo, super charger or nitrous, this gap will need to be bigger. Quote Link to comment
zimm Posted March 17, 2015 Author Report Share Posted March 17, 2015 thanks guys for the info have a blessed day 1 Quote Link to comment
Stoffregen Motorsports Posted March 17, 2015 Report Share Posted March 17, 2015 Also, if you're using a cast ring the gap should be slightly larger than if it's a chrome ring. Quote Link to comment
Draker Posted August 12, 2023 Report Share Posted August 12, 2023 Necro-posting a related question. I bought 85.5mm pistons and rings for an L20B. I got the block bored to match the pistons. The bore is pretty much on the money at 85.5mm. I got Hastings rings (Part#: 6872-020) which are for 020 over pistons and the top ring gap is coming in at .51mm. The stock bore spec is .25 to .40mm. Various websites state they should be between .0044 - .0065 per inch of bore, minimum. I'm a little over the spec for the max spec on a stock bore. Second ring and oil rings are within spec. How big of a concern is this? Should I try to locate 4 replacement top rings? This is just an NA street motor. Nothing special. Quote Link to comment
datzenmike Posted August 12, 2023 Report Share Posted August 12, 2023 Top ring is 0.0044 per inch of bore. For an 85.5mm bore that's 0.376mm Bottom ring is 0.0055" per inch of bore. An 85.5mm bore that's 0.47mm Perhaps you have stock 85mm rings???? they would be smaller and have more gap. I would prefer 0.37mm ring gap than 0.51mm. That just under 40% too large a gap. It will work of course but the wider the gap the more blow-by. Ideally no ring gap, but that 0.37mm is the minimum safe limit for expansion from heat. If there is no room for expansion the ring lands and the rings can break. Quote Link to comment
Draker Posted August 12, 2023 Report Share Posted August 12, 2023 1 hour ago, datzenmike said: Top ring is 0.0044 per inch of bore. For an 85.5mm bore that's 0.376mm Bottom ring is 0.0055" per inch of bore. An 85.5mm bore that's 0.47mm Perhaps you have stock 85mm rings???? they would be smaller and have more gap. I would prefer 0.37mm ring gap than 0.51mm. That just under 40% too large a gap. It will work of course but the wider the gap the more blow-by. Ideally no ring gap, but that 0.37mm is the minimum safe limit for expansion from heat. If there is no room for expansion the ring lands and the rings can break. I sent an email to Hastings tech support. The box is marked 020 over, but who knows. I was thinking the same thing.. maybe the wrong top rings. Quote Link to comment
datzenmike Posted August 12, 2023 Report Share Posted August 12, 2023 From the factory the stock bore can be up to 85.035mm. 0.5mm over would be 85.535mm and should be checked in case it was over, over bored by mistake. Quote Link to comment
Draker Posted August 13, 2023 Report Share Posted August 13, 2023 16 hours ago, datzenmike said: From the factory the stock bore can be up to 85.035mm. 0.5mm over would be 85.535mm and should be checked in case it was over, over bored by mistake. I measured it, but I’ll break out the precision tools to confirm the exact size. Quote Link to comment
Draker Posted August 14, 2023 Report Share Posted August 14, 2023 Well in a strange turn of events, Hastings replied to my email with an alternate part number for a file to fit top ring. They don't sell directly to the public to they gave me the phone number to Total Seal. I called total seal and after giving them the bore and the part number they confirmed the part to be SMALLER than the original ring, which would have given me an even bigger gap they said. So I bought 4 Total seal top rings (for the price of of more than a complete set mind you....) These rings are file to fit, so I'll get it them dialed in and all should be well. I hope. Could I have just bought rings for a 86mm bore and filed the end gaps down? Seems like it'd work also. Either way Total Seal was great, I'll have the part in 3 days. 1 Quote Link to comment
Draker Posted August 20, 2023 Report Share Posted August 20, 2023 On 8/12/2023 at 10:17 PM, Draker said: I measured it, but I’ll break out the precision tools to confirm the exact size. measured, it was spot on at 85.5. They took the measurements off each piston and bored to match. 1 Quote Link to comment
datzenmike Posted August 20, 2023 Report Share Posted August 20, 2023 That's the way it should be done and allow a thou or so under so it can be honed out to exact amount. The hone should match the type of ring you will use on it. Quote Link to comment
Draker Posted August 20, 2023 Report Share Posted August 20, 2023 $90 later I got the top rings gapped to about .4mm. Quote Link to comment
Ooph! Posted August 21, 2023 Report Share Posted August 21, 2023 Did you use Total Seals recommendation for ring gap? 1 Quote Link to comment
Draker Posted August 21, 2023 Report Share Posted August 21, 2023 I did, although I filed then a little too much. Still okay though. They recommend .0045” per inch of bore. 1 Quote Link to comment
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