Hillman Imp how to dial in a unknown race cam- GB 72

having just played this video back i realised there is a massive error in my settings!! see if you can spot it?

[@stevecmason-rs6vf]

Great video and explanation. I have to admit as you presented the dowel to the camshaft I was thinking, no don't drop it please don't drop it into the engine😮 as I have done similar! Keep the videos coming please, they are truly hands on engineering.

[@thehillmanator]

Thank you, ha ha yes i specifically put the sump on last after many an hour spent fishing with a magnetic ariel !!

[@LouKodge]

I remember back in 1970 in Sydney Aust. there was a a V8 Imp that raced in sports car category. It went like stink in the straights, passed everyone, but got caught in the corners because they couldnt get it to handle , sadly.

[@lotus-e-clan]

Back again. George Bevan consulted with Piper cams. So the BP cams on Imps4ever are Bevan Piper. I think the GB 72 lies somewhere between the BP 300 (fast road- comp) and the BP 320 (race) on the list. It's supposed to be a relatively torquey cam, that's why it works ok for me on the road. That said, I'm running a std box instead of my 1/2 Knight sc cr box on the new build and l preferred it with the cr box for a B road blast in the Dales! Just that 5800 rpm at 70 mph in top is a tad noisy for the road.

[@thehillmanator]

hi Pete, hope you are well, yes you will have to get some ear plugs !

[@stevehobbs2331]

Alright my mate, wish I'd have known the TDC trick a few years ago, loving the channel.

[@thehillmanator]

Hi steve, hope your all good, thanks for commenting 👍

[@chevyimp5857]

Wow ... Another gem of a video.. thanks for the lesson.

[@thehillmanator]

Glad you enjoyed it!

[@lotus-e-clan]

Hi Andy. You set the ILATDC to 168 instead of 158? I've run a GB72 in a 1040 with 11.9:1 SCR (Clan) since 2010. I've used several timings having initially no data to go on. Robin Human gave me some data about 10 years ago which I took at face value: cam timing 49 71 71 49; Full lift 101 degs in & ex; total lift 352; duration 300 degs; overlap 98 degs; ILATDC 157; clearances in 10 ex 10. I've just refreshed the 1040 and I'm running 145 ILATDC just to see how it goes. Had trouble burning off a BMW cooper S yesterday so I'm going back to 157 ILATDC! Also didn't like Robin's 10 thou valve clearances so went back to 8 in 13 ex. This will upset the Robins cam timing figures to something like 45 77 77 45 or is it the other way 53 63 63 53? A tutorial video on correct clearances and how it affects cam timing woul be useful to me at least. Btw. I thought it's called GB 72 because of 72 degs inlet closing ABDC? Loving your content and I regret not giving you any of my engine work over the years. Mostly done by Andy Chesmam (yes I'm that old), and recently Mark Maynard.

[@robertharrison990]

Thoroughly enjoying these (Imp related) videos but also puzzled as to why the final timing chosen was 167 inlet / 117 exhaust rather than 158 inlet / 140 exhaust.

[@lotus-e-clan]

Yes Andy realised he made a mistake with the 168 setting. In the description to the video he asked if anyone noticed the error. He only spotted it after playing it back.

[@thehillmanator]

thanks Pete, the engine i did for jonathan bevan had a gb74 and he said this was the engine from 1974 that won the championship. yes interesting to know if the ramp angle is different from the r series cams, i suspect not and that the bigger exhaust gap was to help servicing intervals, the new stainless valves don’t seem to suffer like the the old ones, after a season of racing i see no measurable recession, providing the guide/ valve was tip top condition!

[@thehillmanator]

thank you, yes tied my self in knots completely there ! attempting to dribble relevant content whilst doing the job simply overloads my brain 🤣🤣

[@gothicpagan.666]

GB72 Was a race profile for 850 class.

[@grantfuller2016]

Na , you lost me describing how to find tdc . So many degrees are lost in bearing tolerance. Best way is a positive piston stopper screwed into the spark plug hole . Turn one way until it stops , turn the other way until it stops, the actual TDC is the point between these two readings .

[@peterjohn3180]

Exactly what I was going to say. The inlet should open fully at the point at which the piston is at maximum speed. If you know rod length and stroke, you can work this out

[@nikaveyard1176]

And there is no account for piston dwell here. Not accurate enough. Our race cam gives maximum torque at xxx.5 - the .5 is far less than the dwell.

[@catnip4885]

A really useful video, great camera work to capture all of the detail but I think you mis-read the dial gauge and the exhaust figure was 135 thou rather than 140 thou that you recorded.

[@thehillmanator]

thank you , yes played back and couldn’t believe my ears ! i just cannot multi task ! also confused the inlet 157 for 167 !!!

[@RTC057]

Superb video and very interesting though quickly came to the limits of my understanding very rapidly 😂. Overall got the jist. Just out of interest, have you set up an Imp engine on throttle bodies and an ECU which seems to be derigeur these days? Use of throttle bodies that is.

[@thehillmanator]

thank you, the odd engline but most of my work is for historic race championships that require carbs and distributors.

[@chrispatten7619]

Andy, can I be your apprentice? I can make the tea :D

[@thehillmanator]

Deal!

[@bwautoian]

Very interesting and educational! Question about the weld on the head between 2&3, is that corrective or preventative/strengthening?

[@thehillmanator]

thanks, yes most cases preventative, they are prone to cracking here, extremely thin on the sport casting.

[@eweunkettles8207]

​@@thehillmanator is the simca talbot unit similar does it have a cast iron block and are any of the parts eg head interchangable they were raced succesfully in france " ugly little buggers"

[@havenview]

Love the camera falling over bit - you planned that all along right?

[@thehillmanator]

hi pal, yep not mastered the editing just yet 🤣

[@lotus-e-clan]

Oh yeah... Hoping you'll do a Dyno run so I can guess what sort of numbers I might be getting out of mine.🙂

[@thehillmanator]

coming soon pete 👍

[@lotus-e-clan]

Can't wait! If you have time to dick about, 145ish ILATDC compared to 158ish (or whatever optimum you arrive at) outputs would be really useful to know.