Engine on the dyno

[RotoFlexible]

After many months, Bill McCurdy finally has my engine on the dyno. With these headers, Bill got a peak of 139 HP - he's since seen about 145 with larger bore headers and larger jets, but there are mixture issues in the low rev range. More experiments with chokes, jets and exhaust to follow. The engine is 1700cc (longer stroke in the stock block) at 10.5:1 CR, with a Dave Bean cam on the inlet side and Sprint cam on the exhaust. The goal is a strong, very drivable road behavior rather than ultimate peak power. I hope to have it in the car by late November.

[rgh0]

Andrew

The engine looks nice, always good to get a new engine on the dyno and see what it can do!!. I would love to see the dyno curve at some time. I have a long term plan for a similar engine for my plus 2 when the current engine needs a rebuild.

Did you do any head porrting work, what Dave Bean Cam did you use on the inlet.

cheers
Rohan

[CBUEB1771]

Andrew,
I am going down very much the same road with a long stroke crank in a Twincam block. John McCoy is converting my old Stromberg head for Webers. John has done his CNC porting and is setting the head up with his Stage III cams and valve gear. What diameters are the primary and secondary tubes on the two exhaust manifolds you have tried on the dyno? I am hoping to get my engine to Bill sometime in the next few months.

[iain.hamlton]

Hi

Out of interest how do you get a longer stroke in a standard block? 1600 cross-flow crank? Do you use special rods or special pistons?


best regards, iain

[RotoFlexible]

I would love to see the dyno curve at some time. I have a long term plan for a similar engine for my plus 2 when the current engine needs a rebuild.

Did you do any head porting work, what Dave Bean Cam did you use on the inlet.

When Bill has the engine where we want it, he'll print a curve and I'll post it. He did some rough porting (not his specialty) after which the head flowed as well as any he'd done. We sent it to a specialist (Curtis Boggs) in Virginia for a street port. When it came back it flowed a bit better - not a huge improvement but measurable. I think the inlet is Bean's 112 grind - the next step up (114) requires special valve gear and machining, and Bill didn't do that.

What diameters are the primary and secondary tubes on the two exhaust manifolds you have tried on the dyno?

The header in the photo is of unknown provenance. The tubes are not thin wall so it's hard to tell the inside diameters, but the header is holding the engine back in any case. We are currently running with a Bean SS header that Bill was able to borrow. It has 1.375" primaries and 1.5" secondaries into a 1.9" outlet to fit into a 2" int. pipe. The secondaries are very long compared to other headers we've seen.

Out of interest how do you get a longer stroke in a standard block? 1600 cross-flow crank? Do you use special rods or special pistons?

The crank is a Formula Ford 1600 crank (same as crossflow I believe) and the rods are FF rods, also crossflow. They are slightly longer than standard TC rods to maintain a reasonable stroke-to-rod ratio. (Bill would have preferred the yet-longer Cosworth rods but I put my foot down.) The pistons are custom from J&E, both to compensate for the longer rods and stroke and because the block was already +.040 and had to be bored a few thousandths to clean it up.

[CBUEB1771]

Out of interest how do you get a longer stroke in a standard block? 1600 cross-flow crank? Do you use special rods or special pistons?

Another approach is to use the 1600 crank and standard Twincam (125E) connecting rods, again with special pistons. I agree with Andrew and Bill that in general the longer the rod the better however we have competing interests if we retain the Twincam block. The shorter rods impose higher side thrust loads on the pistons. Longer rods force us to use pistons with further reduced compression height, possibly weakening the piston and reducing area for the rings. Using 125E rods with the 1600 crank increases the side thrust on the piston by about 3% compared to uing the 1600 rods. I am taking the gamble that this will be acceptable and plan to use 125E rods. Pistons for this application are available from Dave Bean Engineering. There probably is no right answer, just differing trade-offs.

[elancoupe]

Another approach is to use the 1600 crank and standard Twincam (125E) connecting rods, again with special pistons

This is the setup I have been using for 14 years. I bought a new crank from Ford, 125E rods, and Omega pistons from Bean. It has worked very, very well.

I have one of Rodriguez' Shankle cylinder heads from his national champ Europa-- back in the 70's. With Bean's 112 cams, it has shown 139 hp and 133 lb/ft of torque on the dyno.

For a pure street motor, it does a good job.

[mopho]

Looks great!!

I too just got my engine done after 9 months. It's back in the car now and I am having some fun, albeit with some minor, but frustrating teething problems

I am on the stock block but went a little more extreme on the valvetrain with Beans 114 cams and big valves, port and polish, balanced, .030 over pistons, Weber 45's yadda, yadda.
With race headers on the dyno, it measured 171hp @6000rpm and 150lb-ft @6k but with my current header and exhaust it is probably more like 160hp. It's quite lively


Of course I am now broke

[RotoFlexible]

Of course I am now broke

Thee and me, brother.

[cabc26b]

I am considering a long stoke option for my S1 and would find it helpful to get more info on torque figures. better to have as many dynos reporting in because my expereince here is that not all dynos or their operators report the same kind of stats.

would also find it useful to get input on exhaust systems - Factory header vs the larger size bean is suppose to have versus the TTR Bigbore

[msd1107]

Interesting commentary on connecting rod lengths.

A longer connecting rod forces the piston pin closer to the ring lands. This gives the opportunity to lighten the piston. There have even been designs where the piston pin goes through the ring lands, so that a specially machined button with ring grooves is necessary.

A longer rod is heavier and not as stiff. A shorter rod is lighter and stiffer.

However, one factor about connecting rod length that is not often discussed is its effect of apparent cam duration.

To illustrate, lets take a long stroke TC, a camshaft with intake closing at 60 deg ABDC, and connecting rod lengths from the Dave Bean catalog.

The longest rod is the BDD long rod at 5.48 in. With this rod and the intake valve closing at 60 deg ABDC, the piston has come up 19.7% of the stroke, meaning you have lost almost 1/5 of the cylinder capacity to late closing, a factor that is compensated for by converting velocity energy in the intake stream to pressure energy in the cylinder. So a 11/1 CR is effectively 8.83.

The shortest rod in the Bean catalog is the BDH Cosworth rod at 4.14 in. With this rod and the intake valve closing at 60 deg ABDC, the piston has come up 17.9% of the stroke. So your 11/1 CR is now an effective 9.03. Assuming the same amount of velocity energy to pressure energy conversion, the engine loses 17.9% of its capacity, versus 19.7% for the long rod. This is equivalent to gaining 1.86 cuin in engine capacity, together with the increased effective CR.

So a long rod appears more torquey because it runs out of top end more quickly, whereas a short rod appears peakier because it is able to rev higher. By the same token, a short rod could use a shorter duration cam for the same torque curve.

It is quite interesting to look at the changes in piston velocity and its shape, and piston acceleration acceleration and its shape as the connecting rod length is varied from a very long value to a very short value.

I would love to get a cam lift curve, either in a graph I could put into a spreadsheet of a tabular lift vs deg. If I get that, I will post the completed spreadsheet so everybody can look at the figures and gain what ever insights they can.

David
1968 36/7988

[RotoFlexible]

Bill is done. After much experimentation, he settled on 32mm chokes and the Dave Bean header with long secondary pipes. I just watched a pair of dyno pulls (and ran one of them myself, which consists of advancing the throttle and pushing a button to start the program). It sounds fierce as it gets into the midrange and all the way up to about 6800, where we ended the festivities. The average and best curves are below. He compared them to the best 1600cc street motor he's built, which has a stronger top end (at higher revs) but is down between 20 and 30hp to this motor in the midrange.

Now I have to get the car ready for the engine. I should have it in by the end of the year but it may be spring before I can put it through its paces and see how it performs in the real world.

[Vanden Perre]

Hello Andrew,

You mention your only contribution was the cam cover. Great! This is what I am interested about: what colour did you use? I would like to repaint mine as it was before (this pale grey blue metalic).

Olivier.

[RotoFlexible]

Hello Andrew,

You mention your only contribution was the cam cover. Great! This is what I am interested about: what colour did you use? I would like to repaint mine as it was before (this pale grey blue metalic).

Olivier.

Olivier,

It's Hammerite "hammered light blue" (41150). I thought Hammerite was a British product, and perhaps it is, but this paint was made in the US (Masterchem). It didn't develop the hammered effect as much as I'd hoped, but I think the color is reasonably close to the original.

[Vanden Perre]

Hello Andrew,

I kept looking for Hammerite hammered light blue in spray in Belgium until today when I got and answer from the importer saying this colour does not exist in spray unlike what I found on the web site.
Can you tell me if you bought it in spray in the UK?
Regards.

Olivier.