Advice needed - to rebuild or not

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redy
Posts: 23
Joined: Mon Nov 16, 2020 1:11 pm

Advice needed - to rebuild or not

Post by redy »

Hi All

I am doing up my jensen interceptor mk III (05/73) - and looking for a decision on rebuild

Compression test across cylinders shows PSI reading between 106-114(dry) - is this normal or below normal ?

With these PSI numbers would you do a cylinder rebuild?

I will rebuild heads - due a valve issue on cylinder 2

thanks in advance - Regards redy
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RockyUSA
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Re: Advice needed - to rebuild or not

Post by RockyUSA »

Those look low, but do a “wet” test with a squirt of oil in each of the cylinders to help determine if it’s the valves, or the rings.

Good luck!

Rocky
‘71 TVR Vixen 2500 - (M Series Tribute)
'72 Interceptor III - 133/5597
'73 DeTomaso Pantera
'74 Toyota Land Cruiser FJ-40
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redy
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Re: Advice needed - to rebuild or not

Post by redy »

RockyUSA wrote: Mon Jan 25, 2021 3:06 pm Those look low, but do a “wet” test with a squirt of oil in each of the cylinders to help determine if it’s the valves, or the rings.

Good luck!

Rocky
Hi Rocky

I did the "wet" test with some oil in the cylinders -as expected there was a increase in pressure - approximately 10 psi, but not more than that - would you think I need to look at the valve or does this increase point towards the cylinders?

Any experiences ?

Regrads Redy
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RayR
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Re: Advice needed - to rebuild or not

Post by RayR »

My Dodge manual says it should not be below 110 and a variation of no more than 40. Further goes on to say disassembly should not be based on comp test only, there should be some other issue as well.
On the other hand good compression does not guarantee a good engine. Are there any issues with the engine? power? smoke? etc.
My high mileage 73 MkIII meets the compression test and makes good power but burns oil a lot and has excessive blow by - I have elected to manage this as I am not ready for a rebuild yet.
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slotcarone
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Re: Advice needed - to rebuild or not

Post by slotcarone »

Some basic info is needed. Why are you checking compression? Is the engine running well? Oil pressure? How many miles on the engine? :)
1972 Interceptor III
133-5612
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RockyUSA
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Re: Advice needed - to rebuild or not

Post by RockyUSA »

Agree with this: "Further goes on to say disassembly should not be based on comp test only, there should be some other issue as well", and the very valid questions of SlotCar1.

Here's how I look at it... but obviously there's many other ideas out there.....

Are you SURE you want to get into the major project of pulling the engine? If the car is running well, you can get a lot of "bang for the buck" by pulling the heads, a doing a valve job, new gaskets, and a doing a frontal bay cleanup at a reasonable cost (probably in the $400 - 500 USD range).

IF more is needed - then all you are really only out the cost of time, and some gaskets. You have some of the work done if you want to pull the engine in the relatively near future.

Everyone would love a fire-breathing monster (as DaveV8 / Grant are dazzling us with)... I would love one! But I also wanted to drive my car this year (and after my recent engine bay update - I just returned from a 2000 mile road trip).

Anyway - it just depends on your priorities, the depth of your wallet, and the condition of your motor. Mine was a low mileage (~65K miles), generally in good condition. I opted for head work, and left the bottom end alone. If I blow this engine up (or if I win the Lotto), then out it comes, and we'll see what happens.

Rocky
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‘71 TVR Vixen 2500 - (M Series Tribute)
'72 Interceptor III - 133/5597
'73 DeTomaso Pantera
'74 Toyota Land Cruiser FJ-40
'95 Jaguar XJS Convertible
redy
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Re: Advice needed - to rebuild or not

Post by redy »

Thanks for all the responses

A little background - I am located in Denmark, bought the jensen on a car auction in Sweden as a runner with Swedish MOT ok at least in paper.

Not much documentation

Got the car home to Denmark - pretty in pics but in details many issues....

The car has a ton of electric fails - which I am tackling one by one..... :-)

Dead starter motor....

Falling brake system - so really NOT a runner :-/

After a oil change new filter and new starter - the engine started after a bit tickling but put into drive it takes a lot of rpms to get it moving....

Now to the engine part:

I have been working with other a few classic cars(mg, austin healey, range rover classic) and thought the idle and run as was some rough.
Furthermore it was pushing up the oil stick - on doing a fast - full on and off throttle

stated the investigation:

Checked ignition seems fine
Pressure test on cooling system - all ok
Did the compression test result: cylinder 2 - zero compression - 99% sure of a valve issue - so heads will be redone
A little exhaust smoke from the side of the engine with the failing cylinder....

looking for some advice on rebuild bottom end or not..... with the compression showing approx 110 psi on remaining 7 cylinders

regards René
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slotcarone
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Re: Advice needed - to rebuild or not

Post by slotcarone »

How many miles are on the car? Is the engine quiet when it is running? Is there any bottom knocks? Very tough engines. Not very common to have a valve issue. Make sure it is not a valve train issue. With zero compression you should be hearing some popping noise either out of the exhaust or out of the carb depending which valve causing the issue. :)
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AndrewP
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Re: Advice needed - to rebuild or not

Post by AndrewP »

Im going through a rebuild now, so I`ll add my thoughts and experience so far.

Firstly...as everyone else has said, approach it with bang for buck/usability in mind.
These are not daily drivers, they do minimal mileage most years and so even a 'worn' engine can carry on for a number of years.
Its not a small job to remove the engine (and gearbox) so factor in that. Everything will be caked in grease, mud, sand from the years of road grime
Its a great opportunity to clean everything and get to all those area that are otherwise inaccessible whilst the engine is in.
Access is a pain whilst its still in the car though...manifolds etc. are all a pig to remove especially if you snap a stud.

BUT...

As Slotcar has said, they are very strong motors, but this can mean that they will carry on working with a number of significant problems.
To my point, my 383 had good compression, blew no smoke, good oil pressure, plugs were a little oily on a few cylinders, no rattling and (what I thought) was decent-ish power.
On tear down, the crank was done (had been machined 040 previously and the bearings were scored and coppered), bores and pistons were worn/oval (one even has some debris damage on the top of the piston where something had fallen in), the cam was worn, lifters, timing gear (still had the nylon coated one on the brink of disintegration), water pump...all well past their use by date. Heads needed a rebuild and crank and piston end caps needed line boring to address some (what we think) was old poor workmanship/original tolerances in manufacture.
My engine is now basically new apart from block and heads...and I've gone for a 'budget' standard rebuild with iron heads, flat top pistons, flat tappet cam and a gentle skim on the heads and deck more to provide a good flat surface than to raise CR.
Don't underestimate what you may find once you start to tear down the engine. If you go looking, you will probably find it! so forewarned is forearmed as they say.

THEN...there's the other stuff AKA..while the engine is out.
Gearbox...now is a good time to rebuild or at least get it checked over
Hard lines (brake, fuel etc)...easy to get to while the engine is out
Bulkhead heat shielding...horrid job. Remember this extends to almost just before the rear axle so cleaning/scraping all the old underseal off, cleaning, fixing any rust. I`ll say again..horrid job
Cooling system - radiator is out at this point so an opportune time to get it flushed and/or rodded
Steering - you can get to the steering UJ's and flex disc..another job
If you are running standard cast exhaust manifolds, they will more than likely be cracked and need repair or sourcing a new/good second hand units. Then you start asking yourself...why not some nice SS extractors and a new exhaust system?....that's another $2000+ to the 'refresh' bill.

Finally, don't discount all the fixings/nuts/bolts you may want to change whilst its apart. You may snap some anyway if the parts haven't been apart since the car was built. Its a minor cost, but it can add a good few hundred $$ to the bottom line. in my opinion, it finishes the job off to a high standard and means if and when you pull it to bits in the future, you have nice new nuts and bolts rather than the old corroded and sometimes rounded old ones.

Anyway, thats my unadulterated view on my 'refresh' which is still ongoing as all those 'other' jobs take a long time to do. Only when they are done (and your own OCD levels) can you put the motor back in and cross everything that it all fires up and runs without any nasty noises or bangs!

Hope it helps, and happy to explain anything in more detail if needed.

Cheers

Andrew
Andrew P
Perth, Western Australia.
Interceptor Mk3 #1284312
Basil McKinley
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Re: Advice needed - to rebuild or not

Post by Basil McKinley »

A cylinder lead down test may help you decide your course of action,

Regards,
Basil
1970 Interceptor MkII 123/3798
1973 JH MkI 1141/12698
money_one_four
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Re: Advice needed - to rebuild or not

Post by money_one_four »

Hi Redy , although you have low compression from the test this doesn’t mean the car will not run well. Mine has only 110 across the board and runs fine ,no starting issues no oil burning, although not quick away still pulls away comfortably.So am leaving it alone for now.
You are taking the heads off anyway todo the valves so you will be able to see and measure the bottom end to assess if it needs work.
Alan
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johnw
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Re: Advice needed - to rebuild or not

Post by johnw »

The car looks amazing. First off with the transmission, how much fluid is there in there? Sounds like you could be low on fluid. You are meant to start the car, foot on brake, shift through gears to fill valve body, then back to P and check the level, motor still running.

I would now take the heads off for a look as you suggest, and also the sump and timing cover. I would give the sump a clean out too. Look for bits of the old Nylon timing gear. Also pull the radiator and flush it out. I would do this before you order any parts from the USA. Who knows what the compression issue is, broken rings? These are great engines to work on. Great fun, and they really come up nice with some TLC. With the sump, heads, radiator etc off, you can change pistons, swap out cams, inspect the rings on the faulty cylinder if need be. Also pulling the engine, the heads, manifolds, WP housings, etc are very heavy. Much easier with those off if it needs a rebore. Search for the Dodge Polara/Monaco engine manual PDF free online. A great read. You will see everything with sump/heads off, then order parts, meanwhile clean and paint all the old bits, and tidy the engine bay while waiting for shipping*

My list of parts for a car is typically: Felpro full engine gasket set, water pump, mechanical fuel pump, timing chain, valley pan gasket, carb rebuild kit, distributor cap, rotor arm, set of black ordinary silicon HT leads, water pump belt, take the number off the old belt. That lot might be 300 to 400 USD for original quality parts. I then keep the old water pump and fuel pump as backup spare parts. You might order the wrong ones, if so fit the old ones back and try ordering again next time.

For the brakes, Rejen sell new FAG master cylinders. You might need new brake hoses too. 2 front 1 rear. I just woke up a Mk3 sleeper, someone had done the brakes 20 years ago, all it needed was hoses and master cylinder, 1 dodgy brake pipe. If the Callipers are dud, stainless pistons and a seal kit is very reasonable these days.

Even if I buy a "perfect" car, I like to take the sump off and clean it out. Look at everything from the bottom, check the timing chain, etc.
Have you seen our stolen Jensen FF 119/011 https://twitter.com/jensenffdotcom
Jon H
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Re: Advice needed - to rebuild or not

Post by Jon H »

Hi John,

Might be wrong but I thought checking the trans fluid meant getting the trans warm, cycling through the gears a couple of times then checking the dipstick in neutral not park.
Please advise.

Many thanks,

Jon
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johnw
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Re: Advice needed - to rebuild or not

Post by johnw »

You could be right there about testing fluid level in N. Maybe that is why they tell you to do it on level ground, the Interceptor hand brake can be marginal. 🤣. Jokes aside, if you are not used to automatic cars of this era then it might be difficult for you to know what is normal.

A poorly running engin, say running on 7 cylinders and with a dirty fuel system and poor idle, throw in a vacuum leak and dodgy brakes. It would be difficult to assess the transmission. It sounds like you have checked the fluid. I would also add the wrong (ie a wild hotrod) camshaft is enough to make a good transmission seem bad on it's own.
Could it have a high stall converter?
Have you seen our stolen Jensen FF 119/011 https://twitter.com/jensenffdotcom
redy
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Re: Advice needed - to rebuild or not

Post by redy »

Hi All

Finally a update

It ended up being a larger rebuild need - engine is out - something was dropped in trough the intake manifold og landed in piston 2....
440 block.jpg
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I need quite a lot of new part

Pistons and ring 0.30
Bearings main and
Cam and cam bearings
Lifters
Valves

I have been looking for options at summit racing seems to have good prices

Can anybody recommend parts(make) for the engine - and suppliers?

Regards
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