jbcollier Posted October 20, 2022 Share Posted October 20, 2022 Crossflows in Lotus Seven S3s did not have thermostats fitted. Supposedly if you fit a thermostat they will overheat. I'm a retired, 35 year mechanic and I like thermostats. They provide quicker warm up and better heat dispersion while doing so. Can anyone confirm this is actually true? If so, any idea why? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted October 20, 2022 Member Share Posted October 20, 2022 Off to check some Assembly Guides...Who has suggested that they will cause overheating?ThanksJonathan Link to comment Share on other sites More sharing options...
jbcollier Posted October 20, 2022 Author Share Posted October 20, 2022 Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted October 20, 2022 Member Share Posted October 20, 2022 Thankyou.Do you have access to a copy of Weale?Jonathan Link to comment Share on other sites More sharing options...
jbcollier Posted October 20, 2022 Author Share Posted October 20, 2022 Yup, he says:"Lotus series 2 and 3 cars with BMC and Ford pushrod engines are not normally fitted with thermostats."No other details.Just looking for personal (not anecdotal) experience. Link to comment Share on other sites More sharing options...
Area Representative Golf Juliet Tango Posted October 20, 2022 Area Representative Share Posted October 20, 2022 My Crossflow is an AX block and installed in a '96 Caterham, so may not be relevant but it has a thermostat. May I assume you have a 711 block? Link to comment Share on other sites More sharing options...
rkeywood Posted October 20, 2022 Share Posted October 20, 2022 I run without a 'stat but with a restrictor plate fitted (711 block). My original 1989 Caterham engine had an 82 deg 'stat but that was a poor engine and ultimately unreliable when pushed so I wouldn't put much faith in what they did or say in assembly guides. A well respected FF engine builder put a new engine together fo me, fitted a plate instead of a thermostat and upped the water pump speed and it's run like that for 25 years including a lot of race use initially. The FF engines a friend and I had from other builders were also supplied like this. Hopefully Roger King will be along and bring some clarity (I believe he suggests a 74 deg 'stat with engine running at 80 deg) Link to comment Share on other sites More sharing options...
jbcollier Posted October 20, 2022 Author Share Posted October 20, 2022 Early crossfow, pre-711, with the vestigual combustion chambers in the head. Totally stock, Cortina GT tune. Even still has the 32DFM carb.I'm inclined to go with a 160F/71C stat but wanted to make sure I wasn't doing something plum crazy. Thanks for your thoughts so far. Link to comment Share on other sites More sharing options...
john g Posted October 20, 2022 Share Posted October 20, 2022 #6 ditto Link to comment Share on other sites More sharing options...
Roger King Posted October 21, 2022 Share Posted October 21, 2022 Probably a Chapman weight (cost?) saving thing. It's not good for an engine to run sans thermostat under normal road use, but the swirlpot probably has something to do with it. Link to comment Share on other sites More sharing options...
7 wonders of the world Posted October 21, 2022 Share Posted October 21, 2022 .....wonder if CC were trying to replicate this weight and cost saving on the 620....... Link to comment Share on other sites More sharing options...
Rhett Posted October 22, 2022 Share Posted October 22, 2022 I purchased a new 7 in 1983, 1600 cross flow, Sprint spec - twin webers. It was fitted with a thermostat. The biggest problem was the modified Hillman Avenger radiator (I think that is what it was) as the capacity/flow rate wasn't up to really hot running - as in, stopped in traffic with no airflow. A few times whilst touring in Switzerland I removed the thermostat - I always carried a spare Thermostat housing gasket. Mine was fitted with an electric fan & I fitted an override switch, so that I could pre-empt things and switch the fan on myself before the sensor (Otter Switch) kicked in. The car never boiled over on me, I just thought it was going to!! As a side note, my 7 was an only car for seven years so it was used all year. With a thermostat fitted it at least stopped the engine running too cold in the winter. From memory, the Thermostat housing, for the cross flow engine, accepts a fairly generic thermostat so you will have a range of thermostat temperature options to choose from. 82C should be a good compromise, but having a fan override switch should also be considered. Consider how you are going to use your car and hopefully that will help you decide what you need to do, if anything. Link to comment Share on other sites More sharing options...
rayjackson1950 Posted November 2, 2022 Share Posted November 2, 2022 I have a 1997 1.6 X-flow with thermostat fitted and don't get overhating issues Link to comment Share on other sites More sharing options...
DaveMorris Posted November 25, 2022 Share Posted November 25, 2022 JB, I've run a S/sprint type spec x-flow for last 20 years or so - have had a 74 degree stat fitted throughout (which the Academy boys from whom I purchased the car also had fitted ) and all has been fine.Engine is now 1700cc with quite a bit of porting, valve mods, roller rockers, injected, and still retains the 74degree stat., and no issues (apart from the longevity (or not) of the Radtec Alu radiators)),D Link to comment Share on other sites More sharing options...
jbcollier Posted August 9, 2023 Author Share Posted August 9, 2023 Long term update:Runs just fine with a 160° thermostat. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 9, 2023 Member Share Posted August 9, 2023 Is that 160° F or a typo?ThanksJonathan Link to comment Share on other sites More sharing options...
jbcollier Posted August 10, 2023 Author Share Posted August 10, 2023 160°F or 71°C Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted August 10, 2023 Member Share Posted August 10, 2023 ThanksJonathan Link to comment Share on other sites More sharing options...
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