Cause everyone loves a build thread.... 1956cc

[FRNKNSTNGHIA]

So after some thought and advice I have updated my parts list:

After reading numerous threads, and looking at build sheets using these parts I feel that they will suffice for my 100hp build.

9.0:1 compression (93 octane)
AA SP heads with S/S valves, chromoly retainers, single HD springs. Intake ports opened to 31-31.5mm and exhaust ports opened to 32mm.
CB Rocker Shafts with 1.25 rockers only on the Intake side, stock rockers on exhaust side
Engle W100 Cam
AA 90.5mm Pistons B piston
AA I-beam rods 5.5 Rods
AA 76mm crank
AA L/W flywheel with gland nut
Dellorto FRD 34mm carbs (29mm venturies and jets to match)
CB performance Weber ICT Linkage and Manifold kit, modified to fit Dellortos
MST Serpentine Pulley System
Spring Loaded pushrod tubes with Silicon Seals
1.5" Sidewinder Exhaust
Pertronix Flamethrower III SVDA Distributor
Petronix Flamethrower 3ohm Coil
26mm pump with full flow
External cooler with fan and 180 thermostat (brand undecided)
All new engine tins (36hp shroud with no heat)

[bugguy1967]

You can't decide on a compression ratio before you select a cam. It doesn't work like that. 9.0:1 on a really low duration cam could require race fuel or with a high duration, 9.0:1 could be ridiculously low and need Only 87. Also, the more intake restriction you have, the more "safe cushion" you'll need. You'll want to keep compression conservative for the cam you'll select.

I won't talk you out of using SP heads, but since your top end will be limited to 5,000 RPM or lower, you should choose a cam with a matching powerband. If your selected cam makes power to 6,000, but your heads won't flow that high, you'll have a combo that leaves bottom AND top end power on the table. Another thing is 35mm intakes won't flow too much over .420"-.440" of lift. Lifting any higher will be a mechanical waste. A cam like the SCAT C20 or Engle 100 is about as big as you could go. If you end up upgrading to duals and better heads, there won't be huge gains with that small cam. You'll need to use a different cam or go with ratios.

Ooooor, you could use a FK7 with 1.1 rockers, which puts you near .400" lift with the SP heads, then swap to 1.4 rockers with the L5s. That would actually be a good compromise. 150-160? Definitely no. Maybe 125. It's going to be nearly impossible to find a cam that will work well with both heads.
_________________
"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[TinCanFab]

[modok]

Sp heads have limits
IMO cam max 240 degrees at .050, max cr 8.5-1 average

Of course, the compression will be too high. It could be brought down by 4 hours of work to the chambers but I hav3e a feeling you don't want to do that eh?
set deck as usual but use copper gaskets to space out the deck and drop the CR down, then later on can swap heads without upsetting the rings.

[FRNKNSTNGHIA]

I wasn't implying that I knew what Compression Ratio I was going to run, more so that I could run up to 10.1:1 if I could, since I have access to 93 and 100 octane easily.

Also for single port heads not flowing, Alstrup clearly has dyno-proven setup in the Engine Build stickies that Single Port heads ported to his spec with stock valves and 9-1CR making peak power from about 4500-6100 RPMs.

That setup from what I can see was using 34mm dual carbs, 90.5 pistons, and I assume stock crank. And that was using stock heater boxes with a bugpack 1 3/8" header.

Motor made peak 94hp at 5500RPMs and about 113ft lbs at 3760RPMs.

So I think with the 76mm crank, larger exhaust with J-tubes, should easily make similar numbers with most likely a better powerband.

So I would like a cam and rocker setup that would take me to atleast 6k RPMs but doubt it would see that range.

[modok]

Sp heads do have a few advantages often overlooked.
-Minimal manifold volume allows single carbs to work well.
-intake charge is not heated as much compared to DP
-smooth powerband due to different VE curves for front VS rear cylinders.
-the heads are slightly more durable
-with dual carbs "kadron idle" effect is also crude cylinder de-activation system for boosting MPG

CONS
-can't handle long duration cams due to charge robbing
-flows 15-20% less than DP heads
-engine runs unevenly

So, they flow poorly and can't use big cams..........so lets make it bigger and turn more RPM???
(Al Borlen sound effect) I don't think so tim

[mcmscott]

150 hp out of sp heads, yea right. Just dyno'ed a 2110 with clyde berg heads, matched tall manifolds, 44 idf's, 1 5/8 merged header at 8.8:1 c/r. made 155 at the crank
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[bugguy1967]

He never said he wanted 150 out of SP heads. You need to re-read his OP.

FRKNSTNGHIA, it takes a lot of work to make his heads flow well. Alstrup might even have flow bench access. All the power, in his case, came from headwork. If he would have bolted on a stock unmodified set, the numbers could have been over 20 HP lower. Home porting heads could go either good or bad. I'd try to contact him and find out where and how to port them.

Also, more CCs doesn't always mean more power. The heads on that 1776 will come close to perfectly complimenting his combination, whereas if those heads were bolted onto something else, the combo might not work as well together.

Hopefully, you can dyno the engine when finished. That's the only real way to know. Even I don't know what 100 HP feels like, and I've built all sizes of engines. I couldn't get it any one car and say that the car "felt" like it made x-amount of HP.
_________________
"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[Alstrup]

[Dan Ruddock]

[Alstrup]

Not nessessarily. You just have to think different. Something we more or less forgot in our quest for "easy power"

[FRNKNSTNGHIA]

[modok]

[Dan Ruddock]

Did not say it could not make some power but to drive something like that day to day with an obnoxious idle and as smooth driving as 80 grit sandpaper is not my idea of fun. I know I built some engines like that back in the late 70's when I did not know what I was doing.

I would be embarrassed to drive a car that idles like that. The hydrocarbons that a big cam sp engine puts out at idle pegs the meter. Two of the cylinders fuel mixture are so off at idle that it won't even fire the mixture. Gross polluter!!!

There is more to an engine than what it's peak torque it makes at high RPM.

Two way to fix it, separate each banks manifold runners from each other or do what VW did which was put in a very mild cam.

In a race car it does not matter because it's at wot almost all the time and if the rules say sp heads, why not.

VW's were designed to be cheap and a sp steel intake manifold was cheaper than the dp three piece setup.

Dan

[vwsb74]

You should buy my low mileage 77.5 dpr crank and my mahle 90.5 stroker p/c 1991cc . I made almost 130hp at 5.5k rpm with 256@50 duration 106 lobe center. I bet it make more hp With 86b.
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Xr310 cam =171hp@6k rpm sold so as the car😢

[FRNKNSTNGHIA]

I have been communicating with Alstrup for quite some time. Wish he was stateside, so that he could build my motor. For now his advice is GOLD. He has informed me of the dimensions to port the intake and exhaust, I would also have the manifolds port matched as well. FRDs will most likely get bigger venturies and jets.

Rough idle, if its 1k or less, no problem.
Gas pollutant, Florida has no SMOG test, and Alstrup's 1776cc SP at WOT had AFR of 12-13:1, perfect range from my experiences. Meaning off WOT it shouldn't be wasting fuel.

Car will be properly tuned on the dyno, if that is not a possibility it will be tuned with a Wideband AFR with data logging capability.

[Brian_e]

Along with Modok, I do like a nice little single port, but just don't get your hopes too high.
I spent a ton of time putting together a 1915sp. I have a flow bench in the garage, and I spent about a month of evenings getting my stock valve heads to right at 130cfm. It wasn't easy, and they are pretty much maxed out with the 35mm intake valve. I also moved the intake studs, and converted to a standard flange on the intake. I ran kadrons on custom built tapered manifolds.

I used a 218/119 split cam, and I can now say I wouldn't do it again. I wouldn't go past [email protected]. The idle is pretty rough.

Overall it's a good little engine, it makes some power, and it looks great, but for the time and money I would have been way ahead with the exact same engine but dual port heads and a set of 40mm idfs.

[modok]

I have a 1904cc sp in my buggy, single dellorto, cb2233 cam

The idle is pretty funny. It idles like a V8 with a hot cam.....lopety lopey, but it lopes along quite happily at 1000 rpm. Never stalls even when cold.
I just made a new intake for it and now it idles better WITHOUT a balance tube for some reason.

But....runs strong and a joy to drive. Throttle response is predicable and instant, and it will pull WOT from 2500 rpm!! it's quieter than any dual carb engine I've heard. TOrque curve like an electric motor, which is preferable for a lot of offroading purposes.

[vwsb74]

[Dan Ruddock]

I did a sync and tune on a mustang GT350 once with four ida carbs. Once I was done there was no rupity rupity and idled like glass even though it had a stout cam in it.

A V8 with a 4 Barrel carb and hot cam IMO is embarrassing and shows lack of tuning skils.

The V8 people could learn a few things from us and we could learn some stuff from them.

I like engines that run properly.

Dan