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SP vibration

Salmons
Posts: 355
Joined: Thu Feb 11, 2016 7:56 am

Re: SP vibration

Post by Salmons » Fri Nov 25, 2016 8:21 am

When in 1998 I bought my second SP250 I experienced a vibration at speeds over 45mph.

I took the car to Brian Hills a then SP250 expert, who lived nearby. He looked at the engine whilst it was running and suggested the shaft from engine to the fan was slightly out of true. We took the fan and shaft off and she ran like a sewing mechine.

I discussed with the previous owner who had taken the engine out and had it rebuilt. Whilst it was first out it was on the flloor and resting on the propeller shaft, which caused the damage. We fitted an electric fan and never replaced the original shaft and fan. Might this be your problem?

Dennis

pbrally
Posts: 15
Joined: Fri Mar 04, 2016 8:45 pm
Location: Australia Northern NSW

Re: SP vibration

Post by pbrally » Sat Nov 26, 2016 11:24 pm

The SP already has an electric fan otherwise that would have been a good suggestion.

Big Col
Posts: 330
Joined: Tue Feb 16, 2016 12:45 pm
Location: Leeds

Re: SP vibration

Post by Big Col » Sun Nov 27, 2016 5:00 pm

If you are going to do a rebuild it may be of some interest to stand the engine on the floor and run it without the fan on it. If the engine is unbalanced then it will wobble. If it is OK then it will run as smooth as silk, well the three I have tested like this did.
Colin,
I may be slow but I’m rough as well !

Soundmike
Posts: 36
Joined: Thu Mar 17, 2016 8:54 am

Re: SP vibration

Post by Soundmike » Mon Nov 28, 2016 11:35 pm

I believe in years gone by there were Australian produced pistons which were rather heavier than standard. My V8 saloon always had a tremor at about 2000rpm. I swapped the motor for another and now very smooth running. I have stripped our the old motor (+20 thou) and found the pistons much heavier than original, most of which I believe was the much thicker and heavier gudgeon pin! Should be rectified by doing a full engine balance. Maybe you have a similar situation.....

pbrally
Posts: 15
Joined: Fri Mar 04, 2016 8:45 pm
Location: Australia Northern NSW

Re: SP vibration

Post by pbrally » Tue Nov 29, 2016 3:56 pm

It is now a case of $'s and time will tell .

Dobbinridesagain
Posts: 103
Joined: Fri Feb 12, 2016 8:22 pm
Location: Gloucester

Re: SP vibration

Post by Dobbinridesagain » Wed Nov 30, 2016 11:17 am

Mission creep. It was OK before the mounts were changed. Do you still have the old mounts? Put them back.

Ivor

PS sorry if this has been suggested, haven't read right back through the thread.

pbrally
Posts: 15
Joined: Fri Mar 04, 2016 8:45 pm
Location: Australia Northern NSW

Re: SP vibration

Post by pbrally » Thu Dec 01, 2016 12:13 am

Hi Ivor, When investigated one mount was very soft the other had cracked. No point replacing bad stuff.Maybe the position of the gear box with the weak mounts had always been disguising the vibration. I know that sounds weird but all other avenues have been investigated so only thing left is the rebuild. Cheers PB

Dobbinridesagain
Posts: 103
Joined: Fri Feb 12, 2016 8:22 pm
Location: Gloucester

Re: SP vibration

Post by Dobbinridesagain » Thu Dec 01, 2016 2:26 pm

pbrally wrote:Hi Ivor, When investigated one mount was very soft the other had cracked. No point replacing bad stuff.
Not long-term. But as a means of eliminating the mounts from your enquiries, worth trying.

An article in this month's Classic & Sports car, a Merc, mounts replaced with pattern parts, vibration problem not cured, replaced with OEM and the vibes went away.

Appreciate we don't have OEM options, but I do think that aftermarket rubber components are an Achilles heel of our hobby.

Ivor

pbrally
Posts: 15
Joined: Fri Mar 04, 2016 8:45 pm
Location: Australia Northern NSW

Re: SP vibration

Post by pbrally » Thu Dec 01, 2016 8:26 pm

Unfortunately Ivor we are now past that point but your suggestion taken. I will give a little scream if the vibration is there after the freshen up. The engine has now been stripped and shows signs of needing a rebuild if not now but in the near future and we are doing the clutch at the same time. After that if vibration is still there I guess I will be looking for some old well used gearbox mounts to fix the vibration....hee hee. I will keep the forum updated. Pete

chrisrichards
Posts: 6
Joined: Sat Aug 20, 2016 11:05 am
Location: East Sussex

Re: SP vibration

Post by chrisrichards » Thu Sep 07, 2017 11:24 pm

Hello,

I appreciate that this thread was started some months ago but I was wondering if the problem was found.

My SP also vibrates from around 1300 rpm upward, I too can feel it through the seat of my pants and in fact through the whole car.

It idles smoothly at 500 rpm.

The vibration is severe and occurs whether in neutral or in gear, but will disappear when driving if I de-clutch and allow the engine to drop to idle, so not road speed related.

Here's the strange part though, occasionally the vibration will disappear, usually after changing gear, ie using the clutch. It will then run sweetly until the next gear change, up or down, when it will return.

I run an electric fan, and have replaced the gearbox mounts and propshaft uj with David Manners supplied parts.

The engine was rebuilt some 2000 miles ago before I owned the car and the oil pressure is always good.

Anyone got any ideas?

Many thanks

Chris

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