Warm starting of a RV8

[Norman Cook]

I have recently finished building a Pilgrim and passed the SVA second time (Note to all Pilgrim builders: make sure you fit the ETB speedo disk - It works first time) and I am delighted with the end result (Grins everywhere).

My problem is re-starting the fully re-built RV8 (3500). Starting it from cold is easy - Turn on ignition, two quick squirts on the 'GO' pedal (Weber 500), rotate engine and VROOOOOOM. Now if I run the engine at normal temperature for a while and switch it off and then try a re-start (say after 5 minutes), it is a devil of a job to get it going. The guy I had to tune it said that I ought to run a return fuel pipe back to the fuel tank from the Weber. I said that I would look into it but I cannot see how to do this. I am sure that other builders have resolved this sort of problem, so any helpful suggestion would be most welcome.

One final point of interest: when the tune-up guy did his bit on the car, he noticed that the vacuum advance was much too strong for the Lucas distributor and put a 'delay' valve between the Weber and the distributor (the valve appeared as if by magic from the back of his van) and made a tremendous difference to the running of the engine. I have no idea where this valve is usually fitted on production cars but it seems to be an essential addition to anyone's build if they are replacing the SU carbs with something a tad thirstier.

I hope this advice is helpful and would love to hear from others who have solved my warm start problem.

Best regards,

Norman Cook (no not that one)

[Purple AK]

Hi Norman. Do you have a Phenolic/insulating spacer between the carb and the manifold? The normal reason for bad hot starting is fuel evaporation in the carb due to excess heat. Never heard of a need for a return line.

[Andy S]

Norman, not sure if it helps but the Chevy has a similar trait. The solution is to fit a remote starter solenoid, cures the problem as if by magic. I've got 2 sources of info from the guy who built and fitted this to my chevy. 1 - streetrod stuff website go to tech stuff and its under hot start problems. 2 - gmguy89@netscape.net.
Basically you fit a Ford remote solenoid, 'dont scream', Chevy did it themselves.

[Norman Cook]

Thanks for the replies:

I don't know whether I have a Phenolic insulating spacer, I think there is a thin gasket between the carb and the manifold (I will have to check) - How thick is a "Phenolic insulating spacer"? I have seen another thread saying that "they" have fitted a Heat Iisolator Plate from Real Steel (Part # BY97 @ £13.73). Is this the same as a Phenolic/insulating spacer to which you refer. If so, then, no I have not fitted one but I will certainly get one. Please let me know.

Regarding the remote starter solenoid solution, I understand that this is the cure for low cranking speeds. I don't have this problem. In fact the engine cranks a lot faster when warm/hot than when it is stone cold. Please correct me if my understanding is wrong.

Best regards,
Norman

[Purple AK]

They come in different thicknesses, from 6mm up to 20mm ish, the 6mm is normally the sort of price of the Real Steel one, and works fine :thumb: Any thicker and you may have bonnet clearance problems HTH

[osgood]

Norman, Chris is right it's probably fuel evaporation for whatever reason a heat gasket will solve the problem I think, unless of course it is an electrical component breaking down once hot. As you say cranking speed is not your problem.

A return feed pipe to the tank is not required, only necessary on fuel injection items and if my memory serves me correctly the pipe must return into the tank a certain way or static electricity is created and bingo there will be a big BANG!!! Osgood

[STEVE G]

Norman
I think you probly have TOO much fuel rather than evap.The 500 is OK on the 3.5>I ran mine on one before changing to a 4.6.Get a Rolling Road test done and I'm sure you'll find you need to downsize the jets or needles.

[stevee8]

I agree with Chris & Eric that it's probably a heat soak problem. One way you might be able to test is to time how long after a hot shutdown your normal fast starting returns. Then repeat the test but take some steps to cool it down quicker - open the bonnet and maybe use water from a garden spray bottle to mist over the inlet manifold and carb. If you then find that fast starting returns sooner then the heat soak is your problem. Obviously be a bit careful where you spray.
I assume that when hot the motor still runs OK so it's not pointing to coil breakdown or similar.

[Norman Cook]

Thanks Chaps,

I think I will try the low cost option of adding a 6mm insulating spacer first before I go for the more expensive options.

I don't think it is an electrical breakdown as once the engine gets going it runs as sweet as the proverbial.

I was told by Chris at RPI that the jets supplied with the Weber 500 I bought from them were right for the 3500 but if the spacer mod does not work then I guess I will have to dig into the pocket and try the other possibles cures.

Once again many thanks for all your suggestions. I will endevour to let you all know how I get on.

Norman

[osgood]

Originally Posted by STEVE G

Norman
I think you probly have TOO much fuel rather than evap.The 500 is OK on the 3.5>I ran mine on one before changing to a 4.6.Get a Rolling Road test done and I'm sure you'll find you need to downsize the jets or needles.

Must say again this is another symtom and I have to agree with Steve this could be too much fuel 500cfm is far to big for road use on a RV8 3:5 with the exeption of track work. Osgood:angel: