Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: Fred on Saturday,December 16, 2017, 06:26:35 AM
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Help I am into a full rebuild on my 821-30 the engine was originally built in 1969. The rebuild includes a re-profiled cam done by Crane Cams in Daytona before the closed up shop. 45 DCOE rebuilt, Headers, and the distributor has been modified with an optical switch. Looks like the head has been saved and the valves stems cut during a previous owners rebuild.
The main work started last May working with Renault USA in Springfield Oh. Had issues with the head bolts, fixed. Valve springs turned out to be way under spec at 200 Deg F, replaced with early !964-1967 MGB duel springs. Two rocker arms were damage, one was cracked, found a lightly used full set from Precision-Marine from 1965-1969 Mercury Marine 80HP inline 4 Renault engine, exact fit work great.
How the issue, in setting up the engine the number two cylinder intake valve is bending push rods at the proper lash setting from the Cam Data sheet .010. The issue is not immediate but after a number of Revolutions. If the lash is set to .014 no issues. Springs have been check for binding no issue, even went back to original springs and still an issue.
Anybody got an idea what is up? Maybe just a tolerance build-up that valve, spring and retainer combination?
Thanks
Fred
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G'day Fred,
Are the valves hitting the pistons?
That's what I'd be checking, particularly in light of your saying the head has been shaved.
Bending pushrods and breaking rockers could easily be from that same cause.
In normal service rockers and pushrods don't seem to be a problem.
That would be my 2 cents worth.
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+1 on Gavin's suggestion Re-profiled cam = greater lift and perhaps more duration. Shaved head = less piston/head clearance. Clay the pistons and see how much clearance you actually have. Measure your head to see if it is below the minimum thickness.
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G'day
Thanks for the comment it is a logical explanation, but that's what strange, there is no indication of valve to piston contact.
Just seems like opening the lash by .004 it works but make the standard Valve Lash noise. It seem to me that if it is not piston valve contact it is some kind of a tolerance build up on that valve,springs,retainer and keeper. Next will be measuring the other three intake valve combinations.
But we'll take a real hard look at the number two piston.
Ta
Fred
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Thanks for the comment it is a logical explanation, but that's what strange, there is no indication of valve to piston contact.
Fred,
Was the piston to valve clearance checked when the engine was dry assembled? (I'm presuming it was dry assembled)
I'd suggest if a .004" lash difference produces the breakages or pushrod bending you're experiencing and only in #2 cylinder, then it's quite possible #2 piston is a little higher than the others.
That is to say, #1, 3 and 4 may be only a poofteenth (engineering term) away from hitting their valves.
On the road, if you sink the welly in, they may all hit. Valve trains are designed with sufficient clearance to accommodate this.
What leads you to believe there's a tolerance stack happening on #2 cylinder and not the others?
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Are you saying that when you turn it by hand, you don't bend the push rod until it's turned several revolutions? I have no explanation for that, but I would still check the following areas: More lash = less valve lift. and duration, I think it might be worth putting some clay or other tell tale material or marker in the valve pockets of the pistons and make absolutely sure your valve isn't hitting your piston. Have you checked that your deck height is the same on all four cylinders? Next, I might also ensure that all your valves are the same length. Since you said they were shortened, it would be unfortunate if they weren't shortened properly. If an answer is still not found it is Less likely is that your push rods aren't the same length (is there any reason to suspect that your cam followers are not the same effective height?) and even less likely is that your rocker ratio is now off because of the replacement rockers you have but it might be worth double checking them. Probably the least likely is that you have a cam lobe that is too high.
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I think the discussion on piston to valve clearance makes a lot of sense. Let me get that measured and we can go from there. And, yes I think some bonehead did not trim the valves correctly, which is one reason why I want to do a tolerance stack build-up on No.2 Valve system. The engine was running when the push rod bent, and again no valve or piston damage can be seen. So one area we are looking at is spring coil binding if the tolerances are off.
Thanks again to all for the suggestions.
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Don't just increase the valve clearances to suit. You need more space than that at high rpm: at least 1 mm but I would be happier with 1.5 mm. Also, increasing the valve clearance changes the cam position on the lifter where it starts moving the valve. A cam has opening and closing ramps to "ease" the valve open and shut. Increasing the clearance moves the cam/lifter initial contact point off these ramps and can lead to severe stress/wear.
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Fred,
I'm not sure where you're going with the valve trimming thing. Were the valves too long?
Anyway, let's suppose the valve is 1mm to long (or 1mm too short).
Given you can adjust the lash to spec, then there's no reason to suspect valve length as the cause of the breakages/bending.
NB: The valves need to be the correct length but for other reasons.
Another question . .
In your initial post you said:
. . Springs have been check for binding no issue, even went back to original springs and still an issue.
Do you now think it is an issue?
How do you propose to measure the valve to piston clearance with the head on?
I think you're going to need to remove the head no matter what the cause.
What do Renault USA in Springfield have to say?
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Thank for the help guys just fired up last night. This was a joint build I took the disassembled engine from my NC home up to Renault USA in Springfield Oh for the build. I had rebuilt the 45 DCOE Weber and Lumenition Distributor, had the cam reground by Crane Cams in Daytona Beach before they closed, and the pistons and sleeves reworked.
Looks like the boys in Springfield did have a valve clearance issue as you guys suggested which is now corrected by a thicker head gasket (the head was shaved somewhere in its life).
I developed a lot of data on valve springs/replacement if anybody is interested. We are using early MGB outer springs and the original inner springs.
Here is a run.
https://www.youtube.com/watch?v=gw5pMiL4AMA&feature=youtu.be
Thanks
Fred
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Very nice!
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Fred, that is exciting!
I'm in the throws of an 821-30 rebuild for my car so I'm really happy for you.
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Congratulations, Fred! :beerchug: I'm glad you finally got it all sorted!
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Congratulations Fred, Glad to hear what this block of metal should sound like.
Cant wait for the first drive video.
Dakazman
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Gotta love it when you can listen to the engine rev. 125HP? That’s great!
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Good result, Fred.
The engine sounds happy.
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I developed a lot of data on valve springs/replacement if anybody is interested. We are using early MGB outer springs and the original inner springs.
Hi Fred ,
I would love to hear about your vendor, part numbers , what year mga, engine size. I have two heads to rebuild . What size valves did you go with? Feel free to pm me if you like.
Dakazman
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I'm interested as well! Did you re-use the original retainers? Because I am starting with an 821 head without the double valve springs, and I don't have an original one. So I am looking to get new retainers that will fit.
Serge
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Let me pull together some notes on the valve spring process and try to post this weekend.
Should I keep it here or start a new chain?
Fred
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Thanks Fred,
Here works for me.
Dakazman
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The 821-38 S/N 0539 Valve Spring Story
As discussed earlier this build was a joint build between Renault USA in Springfield Oh, and me, in North Carolina. The Renault guys were twisting the wenches and I was providing “Lotus” knowledge. This motor is not on the road so there maybe future issues, I done not think so BUT!
The initial build surfaced issues with one head bolt not holding in the block. They like to run a 10ft/lb over torque and the bolt was losing torque when sitting overnight. After a number of trips to their machine shop it was fixed and the build continued.
The cam specs from the regrind see pictures
As can be seen the valve lift has increased to 0.434”. Unfortunately at that lift the valve springs started to float at a low RPM. The spring were removed and heated to 200 F and tested for strength. They were very weak.
So I started a search, over a three week period I could not find any OEM springs. Research was then started on vale spring specs on the internet. My guess was one of the 1960’s series European cars might be close or even use the same springs. The British valve trains looked similar so I took the valve/spring set to one of the shops in the area that specialized in old “Mature” British cars, Jags, MG, Triumphs, but not much Lotus work. This is one of those neat shops were the owner has been there many years and has two other guys and all they want to do is talk cars, and yes I would not call it a pristine garage just great work a great prices. They looked at the Renault valve and spring combination and pulled out an MGB head and said it look like an early MGB set-up. Turns out from 63-67 and onto 70 the MGB had dual Valve springs.
Below is from an MGB performance tuning manual: See pictures
Early MGB Service manual see pictures
The shop recommended I contact Moss Motors: https://mossmotors.com these guys are British car part people and have showrooms in Virginia and California although they do not list Lotus part if you can cross reference what you need there prices are ½ our Lotus suppliers.
I ordered two MGB valve spring kits:
Product Name Part # Price
SPRING SET, valve 423-430 $23.11
SPRING SET, valve, double, uprated (20%) 423-455 $51.99
Here are my measurements with a digital caliper, maybe off what you would get on a machinist table? See Pictures
The MGB retainer stem diameter is too large to use on the Renault valves we keep the OEM setup. Renault Springs/Retainer 63-67 MGB Springs
During the head rebuild it was decide to go with the standard MGB outer spring (Above) and because of the extra length of the MGB inner spring to use the stock Renault inner spring. If when we get on the road and if we notice early “valve float” limiting RPM we may go to the MGB inner spring also, or the 20% stronger MGB outer spring time will tell.
REMBER I am not on the road yet so cannot tell if we will have any issues BUT I do not think we will. Everything is running great with about 2 hours on the bench stand.
There was a lot more work done to get to the MGB decision but I just cut to the chase to tell you where we are.
Questions??
Thanks Fred
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Thank you Fred , I have read your post several times . I will heed your warnings, and again I say
I know it takes time to put together a post with that much information concisely and to the point.
I’m sure I will have more questions about these 821 engines. Thank you again!
Dakazman
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Hi Fred,
Lots of investigation going on there, obviously, so that’s good.
Does your third pic describe the Lotus 821 spring rates?
I ask because I don’t recall the Europa manual having the full spec. on the stock springs.
I’m curious as to how you determined the MGB springs as suitable. As far as I can see, there’s no mention of the number of active coils in your 2nd pic so presumably you deduced suitability from the rate given?
So, no coil bind issues, then?
Did you calculate seat and open pressures so as to be able to make a comparison with the stock springs?
Is it too late to obtain spring recommendations from Crane Cams?
Just a couple of other notes:
Be careful if you’re proposing to use the MGB retainers that the angle etc. of the collet seat is the same. Also ensure the MGB retainers will maintain the same installed height. Don’t expect alternative retainers to automatically do this.
Remember too that the exhaust and inlet valves on the Renault use different collets IIRC . . I have no idea why.
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Thanks for asking, I am sure I still have left out details.
I tried to answerer your questions and did it in bold type not to yell just to highlight the answerer.
Lots of investigation going on there, obviously, so that’s good.
Does your third pic describe the Lotus 821 spring rates?I ask because I don’t recall the Europa manual having the full spec. on the stock springs. The third picture is from an MGB manual NOT a Europa, sorry for the Confusion.
I’m curious as to how you determined the MGB springs as suitable. As far as I can see, there’s no mention of the number of active coils in your 2nd pic so presumably you deduced suitability from the rate given? The second picture from an MGB tuning manual shows active coils 4 1/2 on the MGB outer spring, secondly the physical measurements and side by side comparison (See picture 4) led us to believe we had a winner.
So, no coil bind issues, then? We measured springs at the full 0.434" lift and had adequate spacing, no coil bind.
Did you calculate seat and open pressures so as to be able to make a comparison with the stock springs? We looked at the MGB spring rate in the shop and felt it was a little higher but not excessive with this cam we were comfortable with just the MGB outer spring as the starting position. AS I mentioned above we still have a 20% over spec MGB spring set if we need more.
Is it too late to obtain spring recommendations from Crane Cams? Yes out of business for a number of years.
Just a couple of other notes: We did NOT and could not us the MGB retainer the MGB valve stem is to large.
Be careful if you’re proposing to use the MGB retainers that the angle etc. of the collet seat is the same. Also ensure the MGB retainers will maintain the same installed height. Don’t expect alternative retainers to automatically do this.
Remember too that the exhaust and inlet valves on the Renault use different collets IIRC . . I have no idea why.
It is my understanding that collets are different so you cannot mix up exhaust vs. Intake valves, however the retainers are the same.
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All good, Fred.
It looks like I misread about the MGB retainers and misinterpreted that 3rd pic.
I probably need to drink more. :))
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You can buy compatible springs from Paeco in Birmingham AL. You have to use their aluimnum retainers. $160 for springs and retainers. I bought a set recently, but have not fit checked them yet. They advertise to have reground cams as well for $280 with exchange as well as gasket sets
http://www.paeco.com/Valve%20Train%20Equipment.htm
TonyWa