Follow up on Strosek Ultra's heads
11-27-2012 | 12:09 AM
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From: MA
Follow up on Strosek Ultra's heads
There was a nugget of interesting info in another thread that had converged to a low level. I am picking it up here as a separate thread.
Strosek Ultra has a head recipe for us here:
Those are some bad a$$ cylinder heads.
Michael Mount from the NA 944 world has another recipe for he calls a "tame and dead reliable" street motor. This motor puts out more than 330hp from 3.2L:
Here's a race motor built for higher octane fuel by the same Michael Mount. It's making about 405hp from 3.2L:
https://rennlist.com/forums/924-931-...for-400hp.html
https://rennlist.com/forums/924-931-...nder-head.html
I have many, many questions for Strosek Ultra! To start with:
(1) How much power will those heads make on what size cylinder volume?
(2) Is the valve size difference between your heads and Michael Mount's heads simply due to you running a larger displacement or something else?
(3) Is there a demonstrable benefit from going to from 34mm exhaust valves to 36mm exhaust valves? That's a dyno exercise, right? The flow bench doesn't tell much about the exhaust shock wave.
(4) If the valve size is held constant, does reducing the exhaust valve angle by one degree help or hurt power?
(5) Are you running a stock size valve stem on the intake side?
(6) How many hours of welding on the heads?
(7) Why wouldn't you run a hydraulic lifter in a high performance street car? is it simply because of the RPM?
(8) I used to understand the cam-bucket geometry, but my brain has decayed. (I went as far as ordering one 37mm solid lifter from a Volvo tuner, before the day job took over.) How significant is the advantage from the 37mm lifter?
(9) Can your adjustable sprocket cams adjust the LSA (i.e., adjustable middle sprocket) or just the both cams together which is easy?
(10) Are you running these heads on a 928 or on a 944/951/968?
Strosek Ultra has a head recipe for us here:
Looking at the dyno chart of [Simard's] engine I would like to tune the length of the intake tract for 6000rpm (40cm or 16" from the open end down to the valve head). In order to get 100+ hp from one cylinder you need two 42mm intake valves which can be achieved without changing the spacing. In order to support the 42mm intake valves the intake port cross section area do not need to be larger than a diameter of 48-49mm (appr. 2.9 sq"). I prefer running 36mm exhaust valves in combination with the 42mm intake. This creates a small problem, the valves will interfere with each other during overlap. The inclined angle of the exhaust valves need to changed by one degree. Some machining is necessary, oversize exhaust valve guides must be custom made. We make them ourselves. We never cut the valve guides in the ports. Good support of the valves is vital. Oversize 37mm solid lifters also on the intake side will be installed. We use lightweight motorcycle lifters. I never use hydraulic cams in a high performance engine. The valve lift need to be about .500. We usually have WEB Cams to do our custom made cams. I have developed what I think a rather smart solution for an adjustable cam sprocket on the intake cam. In that way the cam timing can be altered as you wish. The intake port will flow about 240 CFM at 10" (400 CFM at 28"). Actually I need to invest in a larger flow bench for these big heads. These valves sizes are for a bore size of 4.250".
Michael Mount from the NA 944 world has another recipe for he calls a "tame and dead reliable" street motor. This motor puts out more than 330hp from 3.2L:
I'll address many of the questions:
-Bore is 4.155", stroke is 3.564. It's a stock crank offset ground and using Honda/NASCAR rod journal size. Rods are Pauters.
-The car in my avatar is my 'old' 924GTR that had a 3.0 NA engine in it. Ran PCA and HSR.
-Pistons are CP.
-Heads are ported S2 with 41mm intakes and 34mm exhaust valves.
-Cams are billet pieces with adjustable chain sprockets.
-Ignition timing on the dyno was 28 degrees.
-Fuel used was 93 octane bought at the Shell station up the street.
Cheers.
-Bore is 4.155", stroke is 3.564. It's a stock crank offset ground and using Honda/NASCAR rod journal size. Rods are Pauters.
-The car in my avatar is my 'old' 924GTR that had a 3.0 NA engine in it. Ran PCA and HSR.
-Pistons are CP.
-Heads are ported S2 with 41mm intakes and 34mm exhaust valves.
-Cams are billet pieces with adjustable chain sprockets.
-Ignition timing on the dyno was 28 degrees.
-Fuel used was 93 octane bought at the Shell station up the street.
Cheers.
https://rennlist.com/forums/924-931-...for-400hp.html
https://rennlist.com/forums/924-931-...nder-head.html
A 968 head is being used for this effort since the intake port cross section is most suitable for the power level. Both intake and exhaust sides will be ported, and 41mm intake and 34mm exhaust valves fitted.
A custom billet cam “girdle” will be used to stabilize the valve train and protect the head. These are necessary with radical cam profiles and high RPM. Otherwise, the head will crack at the spark plug bore casting. This isn’t necessary with hydraulic camshafts since they typically don’t load the valve train as badly.
A custom billet cam “girdle” will be used to stabilize the valve train and protect the head. These are necessary with radical cam profiles and high RPM. Otherwise, the head will crack at the spark plug bore casting. This isn’t necessary with hydraulic camshafts since they typically don’t load the valve train as badly.
Oil to the lifter bores is blocked off since the solid lifters get plenty of oil from the cam journals, and we want to minimize oil in the engine that’s not lubricating something.
However, since cam chains have been known to break and make quite a mess of things, there’s an oil jet positioned to lube and cool the chain.
However, since cam chains have been known to break and make quite a mess of things, there’s an oil jet positioned to lube and cool the chain.
(1) How much power will those heads make on what size cylinder volume?
(2) Is the valve size difference between your heads and Michael Mount's heads simply due to you running a larger displacement or something else?
(3) Is there a demonstrable benefit from going to from 34mm exhaust valves to 36mm exhaust valves? That's a dyno exercise, right? The flow bench doesn't tell much about the exhaust shock wave.
(4) If the valve size is held constant, does reducing the exhaust valve angle by one degree help or hurt power?
(5) Are you running a stock size valve stem on the intake side?
(6) How many hours of welding on the heads?
(7) Why wouldn't you run a hydraulic lifter in a high performance street car? is it simply because of the RPM?
(8) I used to understand the cam-bucket geometry, but my brain has decayed. (I went as far as ordering one 37mm solid lifter from a Volvo tuner, before the day job took over.) How significant is the advantage from the 37mm lifter?
(9) Can your adjustable sprocket cams adjust the LSA (i.e., adjustable middle sprocket) or just the both cams together which is easy?
(10) Are you running these heads on a 928 or on a 944/951/968?