Lotus Elan

Dyno results, not good

PostPost by: collins_dan » Mon Jul 09, 2018 6:41 pm

I wanted to update everyone and hope to get ideas as to where to go from here.

As a reminder, Q360 cams (rated at 135 hp at the flywheel) on stromberg head should make 100 hp at the wheels, only making 74 according to dyno.

Cam timing seems right. Exhaust gear on exhaust side. Markings line up perfectly (point at each other, perfectly level) and visually gears look correct. Intake lobe at 12 o'clock, exhaust lobe at 11 o'clock. Can't say for sure that offset dowels, or adjustable cam gear wouldn't help dial in a bit more, but certainly not off a tooth.

- Compression test:
1 - 115 lbs.
2 - 125 lbs.
3 - 120 lbs.
4 - 130 lbs.
1 - 130 lbs. After adding oil to cylinder.
Specification: 160 lbs. minimum.

- Leak down test: 1 - ~ 6% Sound of air escaping indicated all past the rings.

- Spark plug condition and gap: Found all between 0.028? - 0.030?
Reset to 0.025?

- Valve lash check:
Intake Exhaust
1 - 0.005? 0.010?
2 - 0.008? 0.011?
3 - 0.006? 0.012?
4 - 0.009? 0.010?
Specification: 5-6 intake, 9-11 exhaust

- Stromberg needle check: Found front carburetter needle recessed in
the piston by 0.007? and the rear carburetter proud of the piston by 0.009?.
Adjusted rear carburetter to match the front (richer).

Not sure where to go from here. The engine was rebuilt 10 years/10,000 miles ago. Properly broken in as far as I know. Not sure why rings not sealing better. I enjoy driving the car, but frustrated that its not making the power it should be. I will continue to drive and enjoy it for the rest of the summer. Let me know what you think I should be planning for this winter. Thanks, Dan
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PostPost by: Davidb » Mon Jul 09, 2018 7:15 pm

Dan, do you know if the rings were chrome plated?
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PostPost by: pauljones » Mon Jul 09, 2018 7:32 pm

Dan.

Great info there, i guess you could look at it in a few ways. Whats the limits in flow on that head? Etc Etc.

Id want to get that lash as correct as possible, too much on the intakes and the cam will be less effective. Too tight on the exhaust and the valves wont seal properly as it gets hot.
So id start on that.

Same time id want to degree the cams with the pistons to be sure. They may point at each other but at what degrees if crank rotation?

Rings may be a little poor, will a new set work or are you looking at a rebore?
A measure of bore vs piston would help.

As Rohan said before you may be needing a ported webber head to achieve the full asking figures the qed 360s are capable of producing. Is this realistic?

What exhaust do you have, perhaps a tubular system may help if you dont have it already.

If that pond wasnt in the way id lend you mine for a comparison, its on the bench collecting dust.

I'll be watching this with great interest, and im sure the others will be able to help you much more than i can.

Regards
Paul
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PostPost by: collins_dan » Mon Jul 09, 2018 8:28 pm

Davidb, I don't know about the rings and given that it was 10 years ago, I am not sure the installer will either, Why do you ask?

Paul,
The engine was rebored during the rebuild, so I can't imagine it would need it again after just 10K miles. I would really rather not do that again. Exhaust is a nice mild steel tubular header that was jet coated and installed when the cams went in 3 or 4 years ago. Valves will definitely get shimmed correctly and I would like to get the cams degree'd this winter as well.

I had the same thought about the head being the main culprit. My memory is that the car seemed quicker with the L2 cams, but who knows if that was really true or if it was just the difference in sound. The L2 cams had a great sound and seemed to rev very quickly, but it could all be an illusion. Could be the head just has bad flow characteristics.

Thanks, Dan
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PostPost by: Davidb » Mon Jul 09, 2018 8:39 pm

Dan, Chrome plated rings can be difficult to get to seat. I had a problem with an engine that I reluctantly fitted chrome plated rings to--I was living on an island and getting plain rings was going to take more time than I wanted to spend--instead I spent 10,000 miles trying to get the damn things to bed in! Finally I bought a set of plain cast iron rings by "Hastings Piston Ring Co" and after fitting those the engine stopped burning oil and produced the power it always should have! (The rings were intended for a Norton 650 Dominator and + 0.60" over...The engine was Aston DB2). I did NOT add oil to the bores or the pistons when refitting the pistons-just a haze of WD40. The bores get plenty of oil once the engine is running .

Assuming your engine was bored correctly replacing the rings may be the quickest/cheapest repair to attempt.
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PostPost by: collins_dan » Mon Jul 09, 2018 9:19 pm

OK, thanks for the explanation. The strange thing is that the engine burns no oil and produces no smoke. It doesn't drip oil either. Very tight. It's very odd. Dan
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PostPost by: Davidb » Tue Jul 10, 2018 6:12 pm

Dan, I think you need to check the cam timing properly.
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PostPost by: collins_dan » Tue Jul 10, 2018 7:28 pm

I agree, but everyone wants to pull the engine to do it, and as long as its out, they are going to want to pull the pistons and replace the rings, and porting the head will make a big difference.... you see where this is going, and based on the fact that all this work has been at least once before in my past 14 years of ownership, and apparently not done well, I am concerned that I will end up spending a ton of money and not having a lot to show for it. Frustrated right now. Dan
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PostPost by: rgh0 » Tue Jul 10, 2018 8:41 pm

There is no need to pull the engine to check the cam timing. If you have the lift specifications at TDC then it is a quick 1 hr job. A bit longer if you have to actually change the timing using adjustable pulleys or offset dowels.

cheers
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PostPost by: 2cams70 » Tue Jul 10, 2018 9:22 pm

Those compression figures aren't good. Especially number 1 cylinder that went up considerably with the addition of oil. I'd suggest taking the car for another run and retest the compressions just to confirm first readings as correct. Cam timing is highly unlikely to be the cause because of the variation in the compression readings across all four cylinders. I'd also try and poke an inspection camera down each of the spark plug holes to check the condition of cylinder walls and piston tops.
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PostPost by: collins_dan » Tue Jul 10, 2018 10:13 pm

Thanks, Rohan, that's what I am hoping for.
Thanks, 2cams70, sounds like I need an inspection camera! Just checked online and lots to choose from and not expensive. Open to suggestions. need to figure out the max diameter of spark plug hole.
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PostPost by: pauljones » Wed Jul 11, 2018 1:58 pm

I think you could probably make a reasonable accurate assesment on cam timing your self.

Find TDC an rotate crank to the 110? point.
At this point the intake lobe will be highest lift.

If its way out then im certain it needs resetting with a degree wheel.

Needs to be done on no1 cylinder.
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PostPost by: Bigbaldybloke » Wed Jul 11, 2018 10:00 pm

For info, I recently bought a cheap fibre optic inspection camera from Aldi for about ?25 and it?s suprisingly good, not sure if you have Aldi, but it?s just info that you don?t need to spend huge sums on one for that type of work.
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PostPost by: mbell » Wed Jul 11, 2018 11:54 pm

You can get one that plug into a phone for very little money too.
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PostPost by: collins_dan » Thu Jul 12, 2018 2:34 pm

I found one on amazon and should be here for the weekend. I think I am resigning myself to pulling the engine this winter. and having it gone over AGAIN. My only reservation is that even if rings are sorted and compression improved to 160-170, cams degree'd so getting the most I can from them, valves re-shimmed to correct clearances will it be enough? What if the head just has bad flow. Can the head be tested when its off? Advice appreciated, so that I don't miss the mark again. Dan
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