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Jensen Healey Moon Timing Belt Kit  Rating:  Rating
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 Posted: 04-22-2006 11:41 pm
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Dan Eiland
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I noticed a complete HTD timing belt conversion kit for sale on ebay and was thinking of seriously bidding on it. I have no idea who sells these kits new, nor do I know how much a new kit would cost. I'm looking for some input as to what would constitute a good and fair deal $$$, and who sells these kits? All input is welcome and appreciated.

Dan

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 Posted: 04-23-2006 06:49 pm
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Judson Manning
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I think I paid $300-$400 many years ago for my adjustable set of HTD sprockets from Dave Bean.  There are benefits to updating to HTD all of which have been questioned/debated in the past.

If you are putting in a set of 104 or 107 cams, they have a tighter lobe-center (104^ MOP) than stock cams (110^ MOP).  Make sure the HTD sprockets have the famous 'green' dot denoting 104^ MOP.

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 Posted: 04-24-2006 05:19 am
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Dan Eiland
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I'll ask about the green dot, but I would assume this kit would be for the 104 cam set-up since that is what he is selling on ebay along with the HTD kit. But I would rather be safe than sorry so I will take your advice and email him with this question. Thanks Judson for all your help.

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 Posted: 04-24-2006 08:41 pm
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Judson Manning
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The 104^ spacing isn't as critical on the 104 cams since they have the same overlap as the stock JH cam.  You can run them 110/110 no problem.  The 107 cam has less duration, hence less overlap on a 110/110 timed engine.

The hot ticket is the 104/107 combo which you can run on stock 110/110 sprockets.  Heck, the stock cam/107 combo is pretty good as well on 110/110 sprockets. 

If you run a 107/107 combo you'll probably want the 'green dot' to get maximum  top end breathing.  Running them on a 110/110 timed engine will produce more low-end grunt and better around town drivability.

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 Posted: 04-26-2006 03:19 am
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Esprit2
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Judson Manning wrote: The 104^ spacing isn't as critical on the 104 cams since they have the same overlap as the stock JH cam.  You can run them 110/110 no problem.  The 107 cam has less duration, hence less overlap on a 110/110 timed engine.

The hot ticket is the 104/107 combo which you can run on stock 110/110 sprockets.  Heck, the stock cam/107 combo is pretty good as well on 110/110 sprockets. 

If you run a 107/107 combo you'll probably want the 'green dot' to get maximum  top end breathing.  Running them on a 110/110 timed engine will produce more low-end grunt and better around town drivability.


W-e-l-l...  I'm not sure I agree across the board.

The 104 cam does have the same duration as the stock C-cam,  but the profile is revised to pop the valve open much more quickly,  has significantly more lift  and is generally more aggressive.   It hammers the valves open such that the full-open time is actually longer than for many cams with much longer seat to seat duration.   To complete that aggressive personality profile,  the overlap is increased 12° by setting the lobe centers (MOP) at 104°.

You can run the 104 cams at 110° MOP and they will function...  the engine will run.   However, they will not deliver the high end performance for which they are known.   At 110° MOP,  the 104 cams are more like high-lift versions of the stock cam.   Okay.   But no longer really "hi performance" cams,  and not very good as low-torque drivability cams either.   Why bother.   If you don't want the high end power,  then there are other cams that are better for producing low end torque...  like the 107.

What's meant by "hot ticket"?   The 104 int/ 107 exh set up is popular for the street,  and in some circles "hot ticket" describes popularity.   However,  the 104/107 combination is a compromise between more high end power and low end torque/ driveability and not a "hot" set up as in hotrod/ high performance.   Two 104's properly timed and complimented by appropriate compression and carburetion will produce more horsepower than the 104/107 combination.   However, some folk find the loss of low end torque to be unacceptable  (I have a pair of 104's in a Lotus Eclat and think it drives in traffic just fine).

Intake cam timing has more impact on the engine's personality than exhaust timing.   The exhaust has the advantage of "Critical Flow".   With sufficiently high pressure,  when you open the hole the exhaust gas WILL flow.   However,  the intake is only working with atmospheric pressure and needs all the help it can get.

The 104/107 combo provides much of the benefit of having two 104's with little power loss due to the milder timing on the exhaust.   The low duration 107 cam on the exhaust reduces the overlap which makes for a more mild mannered engine (compared to two 104's),  and the higher lift (compared to the stock cam) improves breathing despite the shorter duration.   As a result,  you get most of the power of two 104's (but not all) while maintaining acceptable low-end torque.   It's a good compromise for a massaged street engine,  but not a "hot" set up in terms of max power.

The 104/107 combination was Lotus' stock factory set-up for the 2.2 912 used in the Esprit S3 HC and the Excel SE & SA.   It met Euro emissions,  gave good low end driveability and made reasonable top end power -- 180 in the Excels and 175 in the Esprit (more contorted exhaust lost 5 Hp).

If you run either the 104 or the 107 cams,  I strongly suggest timing them properly at 104° MOP.   A pair of 107 cams with 104° MOP is pretty mild mannered.   They give better power than stock due primarily to the higher lift,  but the personality is pretty milquetoast.   If someone needs the engine to be even more drivable at low rpm to the point of running 107's at 110° MOP...  ??...  why bother driving a sportscar?   Life begins at 3500 rpm...  it doesn't end there.

Regards -- Tim Engel

Last edited on 06-14-2009 06:21 pm by Esprit2

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 Posted: 04-26-2006 04:08 am
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Greg Fletcher
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Good post Tim, but I need to take issue with your conclusions. I, like many owners, live in an urbanized area- country roads are not quickly or easily accessible. Low end torque is very important and makes the overall driving experience much more pleasant since a large portion of time is spent in stop and go traffic. Good low end driveability and reasonable top end power is the Hot Ticket for me. Hot Ticket is not what is popular, it's what works best for my needs.

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 Posted: 04-26-2006 11:09 am
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Esprit2
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Greg Fletcher wrote: Good post Tim, but I need to take issue with your conclusions. I, like many owners, live in an urbanized area- country roads are not quickly or easily accessible. Low end torque is very important and makes the overall driving experience much more pleasant since a large portion of time is spent in stop and go traffic. Good low end driveability and reasonable top end power is the Hot Ticket for me. Hot Ticket is not what is popular, it's what works best for my needs.

?   If you have concluded I live in a rural area I'm not sure what I said to give that impression.   I too live in an urban area.   I leave for work early enough to beat most of the traffic and the commute takes an hour.   In the afternoon I can't avoid the rush and it takes an hour and a half to get home.   I'm in traffic two and a half hours a day.   Plus whatever running around I do for fun or errands.

I have three 907's (okay, one is converted to 2.2)  and a 4AGE (also low on torque),  all of which drive through clutches and 5 speeds.   I run two 104 cams in one of the nearly stock 2.0 907's and a pair of hotter DS2 cams in the 2.2.   The third 907 has two "Euro" cams...  whatever that means.   The PO had some shop install them and couldn't add more detail.   They're regrinds so the markings are meaningless and I haven't had them profiled.

Different strokes for different folks,  but I don't find any of the cars difficult to drive in traffic.   I could buy a Camry with an automatic if traffic was my primary focus,  but I own the sportscars for what they can do other than commute.   And it's my priority (I'm not selling it)  that I won't mortgage what they do uniquely well in order to tame them down to do what any ordinary car can do.   I have a Subaru SVX AWD automatic for the ordinary stuff.

Tim

Last edited on 06-14-2009 06:23 pm by Esprit2

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 Posted: 04-26-2006 04:04 pm
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Greg Fletcher
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Esprit2 wrote:
If someone needs the engine to be even more drivable at low rpm to the point of running 107's at 110° MOP...  ??...  why bother driving a sportscar?  


I totally agree that a 104 MOP (Maximum Opening Position) is normally the way to go, but I would be cautious about making blanket statements about that. Your proclamation that 107 cams set to 110 MOP is somehow unsporting misses the mark. My old Jensen Healey ran 107's at 110 (despite the fact that it had vernier cam pulleys), 9.5:1 compression, 40mm Dellortos and a 7 pound Tilton flywheel. I drove this car as a daily commuter for 16 years and enjoyed it tremendously. It was at all times very balanced and at home in stop and go traffic as it was at 90mph. It was far from ordinary. The car now lives in Minnesota and having spoken with several other people that have driven the car, they all agree it is a sweet ride. For myself, the 110 timing worked out just fine for the kind of driving I was doing. That timing can work nicely- to dismiss that out of hand is not an accurate assessment.

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 Posted: 04-26-2006 11:49 pm
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Dan Eiland
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Judson, You were correct in telling me to ask about the cam gears the green dot gears. According to the seller, the set for sale is for a stock 907 engine and not the 104 cam performance engine he has for sale in another auction. I called Dave bean and found out they have these in stock for about $350 for the kit and the oil pump inner and outer rebuild kit sells for about $229. All together you are looking at about $580 for everything selling on ebay in this auction. The adjustable HTD conversion set for the 104 cams would run about $585 without the oil pump rebuild kit. I think I will just save up and purchase the adjustable kit. Thanks for letting me know to ask about the green dot cam gears. Kept me from purchasing something I can't really use to it's maximum potential.

Dan

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 Posted: 04-27-2006 12:01 am
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Judson Manning
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No problem Dan....we're all here to help each other from wasting any more money than necessary.  Now ship your engine to ATL so I can build a monster for you!  lol

Now back to the Tim/Judson/Greg 104/107 debate and what I mean by 'hot ticket':

Tim, we really need to get your three engines on the dyno.  Perhaps then we'll figure out why you have great luck with the Spec9 Dellortos and my engines prefer Spec10?

The data I've collected suggests there is little benefit to a 104/104 combo when compared to the 104/107 combo. 

Garry Kemp’s Creation (Erik Harkes Engine)

Cams:  268^ .425” lift Intake (modified 104)

            252^ .378” lift Exhaust (stock 107)

                                    210hp@6250rpm

                                    175ft.lbs@5000rpm

 

 

LotusBits.com Creation

Head ported from stock 126cfm to 170cfm

Cams:  272^ .410” lift Intake (stock 104)

            272^ .410” lift Exhaust (stock 104)

                                    218hp@7246rpm

                                    171ft.lbs@6232rpm

 

 

“Yellow Dog”

Richard Reyman’s 2.2Litre creation

Custom Cams

240hp@7000rpm

185ft.lbs@5500rpm


(If someone could post "Yellow Dog's" cam stats, or any other dyno results, that would be a huge help to us all).

We can be sure there are SIGNIFICANT differences between the 3 different dynos that tested these engines.  I'll assume they are all good to within ~5%.  If so, they all produce about the same amount of power, only at different rev points.

What I see is pretty simple:  Replacing a 107 Ex cam with a 104 cam only shifts Torque and HP up the rev range by ~1000rpm.  There are no appreciable gains.

While data doesn't lie, we really don't have enough of it to make a definitive conclusion.  One of these days we're going to do a 'dyno-days' so we can document all of these combinations instead of arguing about it....

 



Last edited on 04-27-2006 12:10 am by Judson Manning

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 Posted: 04-27-2006 12:40 am
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Ron Earp
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And to make it complicated those are all engine dyno numbers, which vary more than say Dynojet numbers. And, what we're likely to get in the future will be rear wheel Dynojet numbers since that is typically used and accepted about everywhere. 

Judson, what cams do we have in this thing you've built for me? I'll have some Dynojet numbers for it probably the weekend after Mother's Day, or, this Saturday if I can get the radiator/oil cooler in.

Ron

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 Posted: 04-27-2006 02:51 am
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Esprit2
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Greg Fletcher wrote: (Snip)...  I would be cautious about making blanket statements about that. Your proclamation that 107 cams set to 110 MOP is somehow unsporting misses the mark. My old Jensen Healey ran 107's at 110 (despite the fact that it had vernier cam pulleys), 9.5:1 compression, 40mm Dellortos and a 7 pound Tilton flywheel. Hmmm...  from the master of blanket statements I've been chastised about making blanket statements.   Wow.
I guess "sporting" is a matter of taste or opinion.   I know what a 907 with 9.5:1 and 40 Dellortos feels like...  I built several before moving up to what I consider "sporting".

Since we're obviously talking about different parts of the same elephant,  and since there doesn't seem to be much tolerance for alternate opinions here,  I'll just bow out of this forum.

Keep 'em on the road.   Bye.

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 Posted: 04-27-2006 05:04 am
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Greg Fletcher
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You're funny Tim. Clearly, I must learn from you about tolerance. I have a better idea- you stay and run the forum, I'll sell my JH and buy a Camry!

This is a JH forum, what do you expect? Sorry my timing isn't sporting enough for you? I'm not trying to be a jerk, but sheesh, when someone tells me why even bother drive a sports car because it's not as groovy a set up as you think it should be, well naturally I'm going to respond to that.

Please consider posting again, just because you find my comments annoying is not a good reason to bail out. Lots of very pleasant people on this board that appreciate what you have to say.

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 Posted: 05-15-2006 10:41 pm
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Joseph Mazurk
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TIM,

I also concur with Greg about you reconsider NOT leaving this board. I know Tim from another board and his knowlege is inexhaustable. It would be a dark day in JensenHealeyville to lose Tim. If we all held the same opinions what would be the purpose of this board. I like discord, keeps everyone honest. Personally, I call it mental masturbation. If I can use that word here.

 

                     Joseph Mazurk

                      Chicago, IL

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 Posted: 05-21-2006 04:33 am
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pbahr
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I can't say enough for the HTD system.  Have many track miles at very high rpm, and no problems.  Probable cost now would be in excess of $500.

What I know about YELODOG cam specs is:

1 - Exh lift = 0.4.65

2 - Intake lift = 0.4085

3 - Duration at 0.50 lift:

        Exh = 240>

        Intake = 235>

Intake opens 22> BTDC

Intake closes 39> ABDC

Exhaust opens 45> BBDC

Exhaust closes 10> ATDC

You can see dyno curves at: http://shorpac.com/v-web/gallery/album62

Hope this helps,

Pete

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