Increase displacement (1700 cc)

[Dieschelan]

Hello

Has someone experience increasing the engine displacement to 1700 cc using the lotus block? The gain is only in torque?

[seniorchristo]

I have a tall block installed in my S3 by a previous owner. Having not had the engine apart, I can't be sure of the exact displacement. If the tall block (M711) uses a 1600 crankshaft with stock Lotus pistons, the displacement should be about 1660cc. If the block is bored .040" oversize, then I think displacement works out to 1700cc.
My S3 has Sprint or slightly hotter cams and has substantially more power than my standard S4 did. I would guess torque is equal or slightly less.
Chris

[seniorchristo]

Let me clarify my previous post by saying low end torque is equal or slightly less probably due to the cams. Mid range torque is probably more.
Chris

[1owner69Elan]

I have a dyno run for a 1700 cc street engine with the Lotus block (short deck) constructed in 2012. Bored out to 83.65 and 77.6 stroke crank.

There was much more done to the engine as well (cams etc.). The engine makes 167 hp at 7200 (162 @ 6500). Torque curve is quite flat at 130-136 from 4200 through 6600. (Peak 136.6 @5100)

My street engine of a similar build is just being completed - see pictures above (plug wires being changed to black). This has a SAS head (street ports). Should be on the dyno later today.

[holywood3645]

interested in the spec for the 167 hp 1700cc street motor,.

QED have specs for a 1700 super sprint motor with 420S cam that has a claimed 150hp. I'm curious how you getting over 10% more on worse gas.

James

[bill308]

An increase in engine displacement (size) should result in an increase in both torque and bhp, all else being the same. Drivability at the low end should also improve.

Bill

[1owner69Elan]

Question about the spec for the 167 hp engine. I don't know the details as this was not my engine. The dyno results were shown to me as an example of what could be achieved for a stroker.

But, for my recently constructed engine, I will be posting the build spec on the main forum under the topic I started: "Engine hot off the dyno".

I would be interested in comparing the spec with the various QED configurations and why I am getting such superior performance. Where can I find the QED configs? If you have them, could you post them? Thanks.

I see your skepticism but to add to it further, as discussed on the main forum, my engine turned in 181 bhp and 143 ft-lbs on the dyno today (bit cooler than yesterday thus a slight increase) and at reasonable revs. I think these are legitimate numbers. See the discussion on the main Elan forum.

[holywood3645]

There are lots of posts here on the QED 420 spec cams and 1700cc engine build. I have some spec sheets from QED on there build that I will dig out and post. Its the road going part that confuses me, I think pretty standard part and 'not' race spec' parts such as steel rods, crank, heavily modified head with high CR race gas large 45/48 Webbers or Fuel injection etc.
What I do remember from the QED build spec' is it could use a twin cam or decked 711M block
83.5 bore
1600 (77mm ish) crank and 711M rods
10.5 to 11 cr
Slightly larger than sprint spec valves. lightly ported to match carbs
40 DCOE 151
QED 420 S cams and Q55 cam gear without any recess mods to head.
Electronic ign
Vernier cam or offset dowels;
This produced 150 hp and appeared to be the max you could go for a road spec engine on pump gas using pretty standard components. Think the rev limit was about 7K
High flow air box (larger at rear) from a guy in Aus'

I'm interested how you are getting the extra if you are using similar components.

James
Oceanside

[rgh0]

The SAS head and the other new head from Dave Bean and the McCoy conversion even in street port mode are a much better flowing head than most race ported original twin cam heads. With the right modern high lift short duration cams and right exhaust and carbs, 180 hp at 7000 rpm on a 1700 cc twink is certainly possible if built right with one of those heads.

In historic racing the original heads have disappeared very rapidly as the power advantage of the various new heads has become apparent

cheers
Rohan

[holywood3645]

Are you saying the head alone prepared to the same super sprint spec on a QED motor build say 5 years ago, is going give you 17 more hp.
Are you aware of any back to back testing being done on the SAS head on the same bottom end, cams and carb, all dialed in..
Very impressive if you are correct.

James

[rgh0]

Not the head alone but its a big factor - maybe 10 hp. There are better cams than the QED 420 worth maybe another 5 hp and lots of other little details that someone like Dave Vehger knows about that all add together maybe another 5 HP.

So yes the extra power is certainly there. I have done work on original ported heads, McCoy conversion heads and seen a couple of SAS head builds and the dyno testing on these while not back to back on the same engine and just changing the head casting and the porting possible with the different castings is what I base the numbers on above.

cheers
Rohan

[holywood3645]

Dear Santa.... I need to change my Christmas list, I would like
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Sounds these have been a mayor leap forward on twin cam tuning, making some equipment pretty obsolete

James

[Davidb]

This is interesting timing for me-I have just acquired a Formula Atlantic BDD crank and will be fitting it into a 84mm bore low deck block. The problem when doing this is that Everything has to be changed! It ain't cheap! Since the previous owner of my car froze the block and wrecked the steel crank I was looking at a major overhaul anyway. Its only money...

[elangtv2000]

Are you saying the head alone prepared to the same super sprint spec on a QED motor build say 5 years ago, is going give you 17 more hp.
Are you aware of any back to back testing being done on the SAS head on the same bottom end, cams and carb, all dialed in..
Very impressive if you are correct.

James

I am good friends with Dave Vegher, the builder of 1owner's new Twink, and in fact, was just at his shop an hour ago looking at it on the stand and discussing the build. I was also at the shop earlier when the head while Dave was working on the porting and chambers, and again while the lower end being assembled. I've also been with him during many dyno runs of different motors - all race engines.

Adding to Rohan's comments about the new head castings and configuration, a lot of the results for this motor are also attributable to the builder, who is very experienced and accomplished, and routinely builds race motors well above this output. In fact, he normally only builds race motors - BMW M12, Cosworth, Lotus and more, and considers it somewhat of a challenge building a "detuned" street motor.

I've got a Tony Ingram-built 1700 in my 1967 S3 Coupe, which was actually Tony's car for a few years, and it's definitely torquier than my ~1600cc motor I built for my S4 DHC. The cams have greater lift, however, so hp comes on a bit later, so the torque increase is helpful.