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odd cam combo?

Posted: Sat Nov 18, 2017 12:28 pm
by Tony Z
I've been asked to rebuild a 2L bus engine and the owner wants a little more "get up and go" but using as many stock parts as possible to keep the costs down.
Our local cam grinders dont have any T4 cam profiles but only T1 profiles.
I did think of one of these two options:
1) regrind exhaust lobes to Engle 100 and leave inlets stock
2) regrind all lobes to Engle 100
I also thought about asking them to open the LCA a little to bring the overlap down (maybe 110deg).

anyone have thoughts, opinions or experience in something similar?

Re: odd cam combo?

Posted: Sat Nov 18, 2017 5:48 pm
by wreck
I've a GM hydraulic grind from a 70's 6 cylinder Aussie muscle car in my 102x71 engine that works well. you would have had them in SA maybe under a different name, Holden XU1 Torana . All the grinds a friend uses for the engines he builds are local Aussie grinds meant for either 6's or V8's . you just lose a bit because most are meant for 1.5 to 1 rockers . See if the local cam grinders have a selection of grinds for other engines and see if there is something close to what you want .

Re: odd cam combo?

Posted: Sun Nov 19, 2017 10:30 am
by Tony Z
thats not a bad suggestion. One more thing to look into....
Thanks

Re: odd cam combo?

Posted: Sat Nov 25, 2017 11:43 am
by raygreenwood
This is type 4 2L engine?.....dont play around with odd grinds and type 1 grinds. In fact.....with type 4 and its lifter contact pattern which is totally different than type 1....you are really rolling the dice playing with regrinding at all. These are case hardened only. Grinding them...eapecially to totally reshape the lobe removes some or all of the hardening layer.

The type 4 cams already have HUGE issues with oil quality and lifter to lobe hardness matching.....the results of which can bd catastrophic. Its common.
Do not cut corners or reuse parts in the type 4 camshaft department. There are excellent grinds and quality of camshaft out there.

You can easily reuse every single original part that specs out in a type 4.....except the camshaft and lifters. It just does not pay. Buy a new cam.
Ray

Re: odd cam combo?

Posted: Sat Nov 25, 2017 7:14 pm
by wreck
Ray maybe in Australia we get away with it because of the big selection of oils for flat tappet engines . I've a re ground cam in my 2.3 that is 15 years old with 100,000 km on it , my professional engine builder friend has only used re ground cams in all his engines for the last 30 years . In that time he's had only two type 4's with cam/lifter issues and that was caused by soft lifters not the cams .
He prefers to use hydraulic because he hates any sort of rattle and lot of people comment how quiet his engines are , There are very few performance type 4 hydraulic cams on the market but heaps of hydraulic grinds for other engines so he talks to the cam people about what they recommend for what the custom wants in the engine and goes with that .
On a funny note , he rebuilt his son's 100cc dirt bike and wanted a higher lift cam . the cam bloke wouldn't tell him what it was till he got feed back on how it went , the result was a bike with a lot more poke and a ford RS 2000 cam profile !

Re: odd cam combo?

Posted: Tue Jan 09, 2018 4:03 am
by dawie
Type 4 has 1:1.3 ratio rockers, and smaller lifter head diameter. Not sure if Engle W110, 100 or Scat c25 is compatible with the lifter head size. Total lift at the valve may end up more than you want at over 12mm.

Major difference between the "bus cams" and 411/412/914 cams seems firstly total lift at the valve. Original 411 cams roughly 10mm lift at valve? Bus cam dropped valve lift to maybe 8.5mm inl and 8mm exh. and duration is shorter than type 1 cam. (Never saw official specs for lift of various stock cams, but we have some info from those who measured original low wear cams).

If we use the intake profile from a standard type 1 cam, the T4 rockers puts us back at around 10mm total lift at the valve. Also more duration than stock "bus cam".
Near Web 142 spec. Just grind to your preferred lobe separation angle of 108 or whatever.

By the way, Web 142... if we compensate for difference between Imperial 0.05 and Metric 1mm spec using 6 or 7 degs, then Web 142 fits the early 411 "V" cam like a glove. (Stock D-jet cams are caracterised by eary opening inlet valve and more overlap, and the Web 142 is obviously different in that respect).

If owner would still want to move the power curve up higher, the Scat C20 profile "might" do the job if lobe still fits under the lifter. (12 degs more lift than Web 73, total lift slightly below if using T4 rockers.).

If using tight deck height, and seeing that 95RON is lowest octane available in coastal South African areas, Compression ratio of 8:1 would be nice. (Bus engine was designed to use 91Ron/ 87US-RON/MON i think).

If retaining 34PDSIT from 2L CJ engine, you could enlarge venturi from 26mm to 28mm and correspondingly increase main jet by 10 points as a starting point.

Re: odd cam combo?

Posted: Tue Jan 09, 2018 11:55 pm
by Piledriver
The t4 valvetrain is the absolute last place I'd try to save money.

SCAT has T4 versions of many of their cams if you must, just like there is a T1 and T4 version of the web86 series profiles.

I would still recommend a real Webcam and SLR reground/parkerized combo, the OG lifters can be reground if in good shape, the CB lifters are also viable new candidates.
(The "SLR regrinds" are usually new lifters with the proper radii and finish redone, as out of the box is frequently suck)

AFAIK no one (In the ACVW cam grinder world) other than Webcam nitrides their cams.

CB cams/lifters are also available.

If you must use T1 patterned regrinds, use T1 lifters.

Re: odd cam combo?

Posted: Fri Jan 12, 2018 12:40 pm
by Tony Z
thanks guys. You all make some very valid points and throw out some good ideas.
Unfortunately the guy who wanted his engine rebuilt has never shown up with the engine, so for now I am assuming that it isnt going to happen.