[TR] TR4 engine in a TR3

[tfansher at comcast.net]

My thoughts are this - and are based on what I understand about the dynamics.  I'll tell you what I know an let you do the measurements and get back to us....
The TR3 intake manifold is shorter than the later TR4 manifold.
The H6 carbs have a longer throat than HS6 carbs.
So a HS6 carb on a TR4 manifold is about the same length as the factory TR3 set up due to the lenth of the H6 carb.  Now maybe there would be more mixing on a H6 carb on a TR4 longer manifold. The only way to make that happen is to modify the TR3 inner fender - I tried and couldn't find any air cleaners that were thin enough. If the body isn't finished,  and that's what you want to do, modifying the fenders should work and be made to look nice. If that's what you decide to do, let me know and I'll send pictures of the choke set up on the HS6's on a three to use the "normal" choke.
I'm sure that better engineering minds than mine can explain this better...
Tom


----- Original Message -----From: Andrew Uprichard <auprichard at uprichard.net>To: tfansher at comcast.net, terryrs at comcast.netCc: triumphs at autox.team.netSent: Tue, 04 Feb 2014 13:54:49 -0000 (UTC)Subject: RE: [TR] TR4 engine in a TR3

Tom: are you saying the HS6s would be inferior to the H6s on a TR3? Myunderstanding is you can get a lot more horsepower from using the HS6s. Iam building a fast-road TR3 at the moment and, since I didn't want Webersthis time, I am going with HS6s.Andrew Uprichard

-----Original Message-----From: triumphs-bounces at autox.team.net[mailto:triumphs-bounces at autox.team.net] On Behalf Of tfansher at comcast.netSent: Monday, February 03, 2014 6:40 PMTo: terryrs at comcast.netCc: triumphs at autox.team.netSubject: Re: [TR] TR4 engine in a TR3

Hey, Terry, glad you're back. The intake manifold on the 4's is longerwhich with the longer H6 carbs impinges ont the inner fender. If you fit aTR3 intake, there's no issue. If you use the TR4 intake, use can use the HS6carbs from the TR6 and they are shorter, but you have to rig up a differentchoke set up. I did the change on my TR3A and probably wouldn't do it again.Not worth the hassle. The thought was that with the longer intake you havemore time for mixing of the "gases" - well, that might work if the TR3 carbwould work, but the HS6's are shorter so the net gain of length is minimalat best....just my two cents worth. If you just want another engine, then rebuild the engine and switch out themanifolds if and when you need to.Tom

----- Original Message -----From: terryrs at comcast.netTo:triumphs at autox.team.netSent: Mon, 03 Feb 2014 23:30:33 -0000 (UTC)Subject:[TR] TR4 engine in a TR3

Hi everyone. Been awhile since I've been on the list. Can someone remind meof the difference in size of the 4 engine in a 3 engine bay? I seem toremember the 4's head causes the carbs to take more space?Looking to rebuilda spare engine for my 3.

Thanks!Terry Smith (TS 58667)New Hampshire