Don Terrill’s Speed-Talk

Just a small pointer, motor should be cooled off between pulls & water & oil temps kept consistent for each pull.
A 20 deg change in oil temp can change power by up to 5hp.
So if you're looking for small changes its best to keep oil temp at the start of each pull within 5 deg of the baseline.

Cool! I was hoping something relevant to grandad's Morris 1000 was going to show up :p Got a few questions: How big are those exhaust ports? And how does that relate to stock size? What header do you plan on using? Is that combustion chamber shape better for combustion or was it mainly about flow? ...

hoffman900 wrote: ↑Wed Mar 13, 2024 8:02 pm

KnightEngines wrote: ↑Wed Mar 13, 2024 6:20 pm

Erland Cox wrote: ↑Wed Mar 13, 2024 6:18 am How much less hp will an engine with dual SU carbs give?

Erland

No idea!
All the ones I've dealt with have run a Weber.

Split Weber or single on a manifold with bends?

Single, splits may happen down the track, or maybe a pair of mikuni HSR42 flat slides.

Erland Cox wrote: ↑Wed Mar 13, 2024 6:18 am How much less hp will an engine with dual SU carbs give?

Erland

No idea!
All the ones I've dealt with have run a Weber.

Sounds like I'll be fine to replace at engine freshen around 15,000 miles.
Motor is a HD sportster Evo, most of the time it'll be street use, but will see the drag strip occasionally.

I'm debating the use of some 6mm stem Ti valves on a personal project.
170lb on the seat, 450lb over the nose, .600" lift HYD roller, 7500rpm max, but will mostly see sub 6000rpm.
1.84/1.5 head, 45 deg seats.
What sort of service life should I put on them?

Can you lift the valve to .700in or more safely? I only know them and other similar BMC / BL style heads to take 0.625” or so. The valvetrains are wet noodles on all these engines. Small journals, missing a cam bearing for the oil pump / dist drive, long pushrods, and because of their displacement,...

Fusion Works wrote: ↑Fri Mar 08, 2024 9:19 pm Can you lift the valve to .700in or more safely?

No, all it needs is .550" to support 9500rpm, a big reason for the effort to get a bigger valve in there.
I flow test well above lift to be used to make sure the port stays stable.

Rockers required .300" spacers to go with the longer valves. I did the intake as well, but that still has some more epoxy curing in it overnight, pics of that tomorrow. Motor is 1298cc, 13.5:1 comp on E85, Carillo A beam 6.125" rods, custom gas ported pistons. 264 deg scatter pattern cam, ...

Finished this one today, I've got around 70hrs in this head, about 20 flow tests etc. It's for a historic racing mini, restricted to 1300cc max & OEM head & block, but pretty much free internals. I started with a decent 1275 core head, not rusted badly & minimal core shift. Moved the ex ...

You got a spacer under the carb? They can help drop intake vac. But at 2" it definitely wants a bigger carb. 3" collectors are a definite. Looking real good so far! I wouldn't bother dialling in that carb, go for the biggest you got & dial that in, but do collector extensions 1st, they...

BLSTIC wrote: ↑Mon Mar 04, 2024 12:35 am About those headers, is there a reason to *not* have a merge collector and choke/cone?

Yeah, sorta - those headers exist already lol.
The gain probably wouldn't be worth the expense when there is still plenty of easier gains.

Just about ready to get wet.