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Camshaft info request https://www.ausmini.com/forums/viewtopic.php?f=5&t=90153 |
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Author: | deluxe67 [ Mon Aug 03, 2015 1:56 pm ] |
Post subject: | Camshaft info request |
Hi all. I just found the spec sheet for the camshaft fitted to my modified 1293 engine. I'd like to know what exactly it is. The info I have is below; Grind: Speco 4LA417 Cam lift 0.294 Valve lift 0.350 Duration: 290 for Inlet and Exhaust Inlet opens 38 BTDC, exhaust 76 BBDC, overlap 72 Inlet closes 72 ABDC, exhaust 34 ATDC The cam is street friendly with very good low down torque, pulls away from 1500 rpm. I'm curious to know what this cam is equivalent to as I'm tossing up whether to change it. (Gearbox has to come apart due to dodgy batch of synchros). The engine has a highly worked head (11:1) running with a 45 weber, LCB and close ratio gearbox so it should be suitable for coping with a hotter cam. Wondering what people's opinions are and what cams you are using for a similar spec engine. I don't want a pig of a car down low but would like to use a cam that is appropriate for the engines potential. (In a previous life I had a car with a 649 cam that was fun but tedious down low. I lived on a steep hill and the only way to get the thing going was to spin the wheels..) Thanks for any comments.. |
Author: | MiniVLT [ Mon Aug 03, 2015 5:18 pm ] |
Post subject: | Re: Camshaft info request |
I've got a fair amount of cam details but can't seem to find those exact specs. 290 duration is in the realms of a MD276 / 286. The 286 is said to be the max for road use with little traffic expected. If you encounter heavy traffic regularly then I think you should stick to what you've got, especially if your happy with it. Cheers Shane |
Author: | deluxe67 [ Tue Aug 04, 2015 6:00 pm ] |
Post subject: | Re: Camshaft info request |
Some more info that may be of use to those who know?! ![]() |
Author: | FNQ [ Thu Aug 06, 2015 10:22 pm ] |
Post subject: | Re: Camshaft info request |
hi deluxe Hoping to provide at least some thoughts,,,,, more in testing my understanding and using it as a learning experience in me "reading" a cam diagram , so WARNING this could be just utter rubbish but i will provide some comment , but these are fairly uneducated( sort of like tasting notes for wine from a beginner) The specs provided seem to point towards a lazyish cam... 290 duration but only 226 at 50 thous, so not an aggressive ramp approach.... should be long lasting for followers etc, but compared to more modern grinds, lesser total duration but more duration off the seat is possible ( more like 265-270t total duration with 235ish at .050) so, even though it is a 290 duration it is behaving more like a 270ish cam ( low down torque) . So , i think it is designed around older thoughts re head flow, where it is more about volume and less about velocity... ... getting valve seats angled and back cut (if not already done so) would probably make this cam act more at the top end of its spectrum, so if any improvements were planned it could actually make it less streetable.... it ( the current cam') has a relatively wide lobe separation angle and possibly could be set up offset also a degree or two,- both of which assist bring usable power down the rpms .... so this matches with your real world experience the lift figures are again probably aimed at getting fuel/air mix in using those S ratios but now with newer rockers, where (.350x Rocker ratio 1.24 = .434) or .350X 1.3/1.5 = .455/.525, the total lift could be overkill ...... in my understanding it is now more important getting air/fuel in quicker rather than just making the apex point as high as you can...... so you can do lower overall lift in newer cam profiles without sacrificing flow or area under the curve. so if not running taller rockers, think about the whole combo before just adding,, it may make it less streetable) So as above, if you are enjoying it now, hang on to it and continue as there are many ways to skin a cat ( tune for a particular use) but if you have upgraditis, look at cams in that 270 ish zone that have better lift at 50 thous figures and still have a widish lobe separation angle Doesn't help you identify the cam at all i know, but maybe adds some thoughts to whether to change it or not Please feel free to give feedback ( hopefully constructive) but if i m talking rubbish let me know , so i can learn too Cheers darryl ps not trying to tell you how to suck eggs at all, you probably have forgotten more mini knowledge than i will ever have so i just thought i would at least prod this thread as it was an area i was interested in) edit for clarification |
Author: | deluxe67 [ Mon Aug 10, 2015 11:38 am ] |
Post subject: | Re: Camshaft info request |
Hi FNQ, Thanks for your comments, made good reading and sense. I'm running standard rocker arms so now considering upgrading those (1.4's?), retaining the camshaft and getting the car dyno tuned (never been done) and then see what I turn up with.. Cheers 67 |
Author: | FNQ [ Mon Aug 10, 2015 1:14 pm ] |
Post subject: | Re: Camshaft info request |
67 sounds like a good and sensible plan, should you wish to replace your cam at a later date then the 1.4s won't go astray.... look forward to hearing how they go in the flesh Cheers Darryl |
Author: | deluxe67 [ Mon Aug 10, 2015 2:27 pm ] |
Post subject: | Re: Camshaft info request |
Will do FNQ. I seem to remember reading going beyond 1.4 rockers is unnecessary and creates extra stress on the valve train? What's your thoughts on that? |
Author: | FNQ [ Sat Aug 15, 2015 10:46 pm ] |
Post subject: | Re: Camshaft info request |
Plenty of more clever people than i could make better assessment, but from my limited knowledge... for a fast road rockers - 1.3 or now Mr calver has added 1.4 maybe these. the extra loads etc beyond that i i think can mostly worked through by good design (offset rocker arm) and set up shimming pedestals, but newer cams with quicker lift also mean not as necessary to go high lift to still attain good flow... .... i still think a good quality rocker shaft is important,- so look for wear on your existing |
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