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
