TonyAus Posted April 23, 2022 Share Posted April 23, 2022 For some years I've put up with an engine vibration period in my 1925 roadster. I now need to know if others have the same problem. I appreciate that a large four cylinder engine without a counterbalanced crankshaft will suffer some degree of vibration. This fact is acknowleged in the DB mechanic's manual but feel that the width of my vibration period may be excessive. It occurs between about 20 and 35 miles per hour and can be driven through. Unfortunatly this is the speed range I find most useful. The result is an annoying resonance through the forward part of the body. After lengthy head scratching I think the gearbox can be eliminated as the cause as the period can be driven through. Bad bearings would probably continue to rattle as speed increases - or am I wrong? The flywheel was removed during restoration but replaced in the same position on the crankshaft to restore the function of the timing marks. It also showed evidence of factory balancing in the form of drillings. Can this also be eliminated as the culprit? Similarly, I can't think that the design of the clutch lends itself to be too far out of balance. In a past life the engine was fitted with a set of semi-finished aluminium pistons turned down to fit. all looks good from below with the sump off. The connecting rods appear to be original and I know for sure that no work on them or the bearings (which are good) was undertaken. I've also eliminated the starter/generator. Any ideas or helpful observations would be gratefull received. Link to comment Share on other sites More sharing options...
John McEwan Posted April 23, 2022 Share Posted April 23, 2022 My ‘23 had a what I thought was an engine vibration problem but it turns out it’s pretty normal. The engine being solidly mounted to the chassis only added to it. I ended up installing rubber engine mounts on the rear mounting ring and now no vibration at all speeds. The improvement is marvellous and is so much more comfortable to drive and be in.f 5 Link to comment Share on other sites More sharing options...
Machinist_Bill Posted April 23, 2022 Share Posted April 23, 2022 That is a great idea! Thanks for posting the photos! Link to comment Share on other sites More sharing options...
Mark Gregush Posted April 23, 2022 Share Posted April 23, 2022 The Ford Model A used rubber mounts at the rear and engine floated at the front. Wonder if Model A Float a Motor could be adapted at least at the rear, but would still leave solid mount at front; Snyders - Float-A-Motor Kit (snydersantiqueauto.com) Link to comment Share on other sites More sharing options...
Mattml430 Posted April 23, 2022 Share Posted April 23, 2022 I did similar to John on my 27 four cylinder. The difference is night and day. I used a Holden commodore engine mount in mine. It fits neatly in the original chassis mount. 1 Link to comment Share on other sites More sharing options...
TonyAus Posted April 24, 2022 Author Share Posted April 24, 2022 At this stage I am loathe to undertake such a radical change to the car. First I need to ascertain if the width of my vibration period (20 to 35 mph) is excessive. Can anyone comment please? Link to comment Share on other sites More sharing options...
Mattml430 Posted April 24, 2022 Share Posted April 24, 2022 1 hour ago, TonyAus said: At this stage I am loathe to undertake such a radical change to the car. First I need to ascertain if the width of my vibration period (20 to 35 mph) is excessive. Can anyone comment please? Try PM Rich tony he has a beautiful fast four engine. Link to comment Share on other sites More sharing options...
Minibago Posted April 24, 2022 Share Posted April 24, 2022 Well Vibration is perfectly normal with a four cylinder Dodge Brothers engine hard bolted to the chassis. Along with all the other design idiosyncrasies that is why we own a “Dodge” I tend to enjoy the individuality. In marriage you accept the faults as well as the attributes, so too with your car. You want a faster smoother more comfortable ride? Buy a Rolls Royce.😊 2 Link to comment Share on other sites More sharing options...
TonyAus Posted April 25, 2022 Author Share Posted April 25, 2022 Point taken Nigel. However, I still feel that the degree of vibration experienced would not have been acceptable when the car was new. With this in mind and taking into account the radical cure esposed above I took a hard look at the rear engine mounts. Mine are the later variety with two large bolts passing vertically through the chassis and engine mounting ring. Some time in the past these bolts must have been loose. As a result the bolt holes in the mounting ring show a degree of ovality which may allow the ring to move and rattle when attacked by engine vibrations. I'm hoping to resolve this matter by drilling and reaming the holes oversize in situ. Their original diameters could then be restored by turning up steel bushes to fit the holes and bolts. It could be worth a try to reduce rather than eliminate the rattle. 2 Link to comment Share on other sites More sharing options...
Minibago Posted April 25, 2022 Share Posted April 25, 2022 Hi Tony, I agree that when new the vibration was no where near what some of us experience today. My car a 1917 Roadster had been “restored” some years ago and a mixture of brands / ages / wear of pistons, valves etc had been fitted. The vibration in this is much worse than my 1919 Tourer before I pulled the engine down for a rebuild due to being well worn out. One of the drawbacks of the vibration is the cracking of the copper oil feed lines. When new various items were balanced to minimise the creation of vibration, when disturbed, mixed with other less worn parts and or using parts from other cars turned down to fit, (often other brands of cars) assembly of the original parts may not have been back to the original position (90 degrees out flywheel to crankshaft for example) so “restored” is an interesting description. As an example using several parts from a different gearbox will produce unmatched mating surfaces producing lots of noise and vibration. To minimise the vibration the major engine components, flywheel, crankshaft, clutch etc should be balanced individually and then balanced as a set. The pistons should be matched for weight, the con-rods should be checked for straightness and matched for weight and on it goes. Most folk do not have access to this equipment and I have experienced as well as heard many examples of work requested but not carried out satisfactorily by engine restorers. If you do it yourself (providing you have the skill set) the time spent is immaterial if you send it to a professional then the hourly rate and the time taken makes your eyes water. Many professionals won’t even take a vintage or veteran engine rebuild on. I have been fortunate to witness a true engineer at work on Dodge Brothers engine parts, surface grinding main bearing shims, trueing con-rods, weighing pistons to the gram, a work of art but you need the machinery, the skill and the time. So what often happens is they get put back together with minimal work so we can drive them. In summary, it can be done but it is a job as a whole not, sadly, an adjustment of one component. To return to your last post, eliminating wear in mounting bolts / holes etc is always a good thing, the chassis were made from a special steel so drilling will require cutting compound (Trefolex or similar) check for cracking emanating from any chassis holes and stop drill any you find. If the hole damage is only in the mounting ring and not the chassis then I have a spare in the shed you could have if it is in good condition for the cost of the postage. I will check on my return from Orange. Late next week. 2 Link to comment Share on other sites More sharing options...
TonyAus Posted April 26, 2022 Author Share Posted April 26, 2022 Thanks for the offer Nigel. However my intention in espousing the drill and bush method was to avoid removing the ring. As you would appreciate this is a fairly big job involving removal of the gearbox. If I decide to go with removal the ring could be welded and reamed back to size off the car. All this may or may not improve matters. In the interim I did notice that the bolts were slightly loose. Hopefully the brute force I applied to them may have pulled the chassis hard against the ears of the ring and eliminated some of the movement. The next run will see if I'm on the right track. If so, I will consider some form of locking of the nuts. 1 Link to comment Share on other sites More sharing options...
RichBad Posted April 26, 2022 Share Posted April 26, 2022 My fast 4 gets a decent vibe at bang on 29mph. A few people have told me it’s quite normal but it pretty much comes bang on 29 then goes - it’s only really a pain if your sitting bang on that speed (i.e in traffic going at the same speed). I had everything balanced, pistons, rods, crankshaft, flywheel, clutch & pulleys. what makes it worse is the vibration matches a natural harmonic in the horn at that speed so it sounds like the horn is going. I also had a few others that matched natural resonances in the car - doors, handbrake lever, air vent - but I was able to adjust all of them to eliminate/ damp the resonance. mine is a 4 point mount fast 4 - high tensile mount bolts done up very tight. I think the front mount/cross member could be a weak point easy to crack or loosen at the rivets. Back mounting is pretty solid with the huge mount and bolts going all the way through the main chassis. cheers, Richard 3 Link to comment Share on other sites More sharing options...
MikeC5 Posted April 29, 2022 Share Posted April 29, 2022 I think mine does the same thing (it's a sort of high pitched squeaking that seems to come from the forward part of the body but I can't pinpoint exactly where). The range is smaller than what you describe though. I'll have the car back on the road for the summer season soon and will pay more attention to what speeds it happens and report back. Link to comment Share on other sites More sharing options...
Mpgp1999 Posted May 6, 2022 Share Posted May 6, 2022 (edited) At 55 I can not see my hands on the steering wheel. It vibrates that much. They just look like a blur. I also have to re touque the head. It comes loose a bit every few months. But I drive this car well over 5000 miles a year. Edited May 6, 2022 by Mpgp1999 (see edit history) Link to comment Share on other sites More sharing options...
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