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GT6 front carb hitting bonnet.....

Lucky 13

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My car came with a 2,500 engine and although it was part dismantled and not running I could see that the rocker cover and front carb had been in contact with the bonnet when it had.

When refitting the engine I've lowered it as much as possible and made sure it's as far back as it will go. The front of the bonnet is raised to the max and the back edge is in line with the scuttle - so I don't really want to raise it any higher. I've managed to get clearance for the rocker cover, but the front dashpot is still in contact with the bonnet.

I understand that carbs from a Dolomite Sprint have shorter dashpots that overcome this problem.

There are 5 variants listed on the SU site - hopefully they all share the same shorter dashpot.

Any suggestions about where I might be able to get hold of a pair of tops and dampers? I don't really want to buy a complete set of carbs if I can avoid it......

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Couple of things;

Is it a GT6 inlet manifold (it looks like it)? The Saloon engine is tilted at 7 degrees, If the Saloon inlet is used then the carbs will be higher than with a GT6 inlet, You could have the inlet face where it meets the head, milled at an angle to drop the carbs.

Are they HS6's? If so they are taller than the strombergs that a GT6 has. You could consider 175CD strombergs. Yes I believe the Sprint HS6 tops are lower than the others.

Is the engine as low as possible? the GT6 sump has a shallower sump at the front. The 2.5 sump is deeper for the extra crank throw and also is canted over to acomodate the tilt of the saloon engine. The 2.5 sump needs a recess beaten or welded into it to go over the GT6 steering rack. This allows you to drop the engine by about a 1/4" - 3/8".

Its a squeeze under a GT6 bonnet but it can be done.

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I got a pair of SU HS6 Dolomite Sprints from Wins International for my GT6. I just used the dashpots and the pistons and replaced the taller ones that the previous owner had installed leaving me with a nice dent in the bonnet. I think they were about £90 for the pair and the bits I needed where in good enough condition for an easy swap.  

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I can believe that the front end of the rocker cover would be a problem, this one was already well worn on that corner and I took more material off before painting it. Unfortunately the engine wasn't in the car or I might have take a lot more off!

Glen, many thanks for the offer of a Dolly Top, but I've found a guy who can machine the top covers, pistons and damper arms, removing about 14mm from their height, which should nicely overcome the problem....

I'll post images once they're in place and pass his contact info to anyone who has a similar issue, just pm me.

Thanks                 John

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You can cut down the dashpot, damper tube and piston rod it takes very little to gain enough clearance, you only need to do this on the front carb (and cut all three by the same amount.) A lathe is handy for cutting down the dashpot but it can be done without one.

I have this done on my Sixfire.

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Here's the finished job - tops, pistons and damper rods all properly reduced and now there's plenty of clearance.

If anybody needs similar machining work done then let me know and I'll pass on the contact details of the guy who did this for me - he turned them around in 4 days and made a really nice job. No fuss and good value.....

Cheers          John

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What an interesting thread.  The comment about the rectangular engine tops impacting the bonnet rings true with me as our GT6 has a nasty crack in the paint where that very thing happened! Plus one of the front corners of the engine cover has been worn away. I will investigate the machining idea before refitting the engine.



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