Camshaft for sprint engine?

[richard4040]

What would the best camshaft be for a sprint engine with twin 40 dellortos? Also where would the best place to buy it be:) thanks

[Dolly-Nut]

For what kind of use? You'd be better off with 45s considering the 40s aren't much better than HS6s.

[richard4040]

Well they are coming on an engine that I have bought so I'm just going to make use of them. Can't afford to be buying new things really:) it will be fast road/race. Cheers

[Dolly-Nut]

Have a look at this http://www.triumphowners.com/uploaded/3 ... sprint.jpg
The STR91 seems to be the most popular and provides good drive-ability and power but that's on engines with 45s. 40s will give slightly less top end power but increase drive-ability/torque in the lower rev range.
Remember to consider what you need to time the cam accurately.

[richard4040]

Thank you. What would I need to time it correctly?

[Dolly-Nut]

Not having personally done it I'm not the best person to ask, I'm sure someone else will be a long with the fine details but if you want to do it properly you'll need a vernier sprocket so that you can get the cam timing and chain tightness accurate, they're quite expensive for what they are though.
Alternatively you can use a standard cam sprocket and dowel it to the cam once you've drilled new holes for the correct timing position. Depending on which cam you get you may not need to do this, it all depends how it aligns when everything is together.
To accurately time the engine you will also need a DTI gauge (I think that's what they're called ) and some kind of angle dial on the crank so that you can find TDC precisely like so - http://img.photobucket.com/albums/v699/ ... G_2504.jpg

With a new cam new buckets should be used too. You will also need thicker shims to match the tighter tappet tolerances of most cams.
Also if this is going to be a race engine and will see north of 7k, heavy duty valve springs should be used. If the revs are going to stay below the redline for road use, new standard springs will be absolutely fine.

[mha447v]

Hello,I'm not too far away and I recently rebuilt my engine with a different cam etc. Pm me if you need a hand,
Jason.

[richard4040]

Thanks very much Jason! I will definately e in touch if things get out of hand:D

[paulsprint]

Maybe a standard cam. Or a Kent dms1 would be nice. Plenty of low down torque. The str091 is to wild in my opion for 40's. this cam need to rev with power coming on strong from 5k onwards. ( in my engine anyway). I would be tempted to sort the head , match the chamber volumes and raise the cr. the most important thing IMO is to sort the ignition with a programable system. Either the 123 setup or megajolt. Both replace the old and worn out dizzy

[bodgerben]

A standard cam with twin 40's would my vote. Lovely induction roar and flexibility. But potential setup fun and games.

The standard cam with a good engine build can liberate far more than just throwing a STR91 in. Spend your time/money on a vernier cam wheel (makes timing up a standard cam a doddle on skimmed heads) three angle valve seats, matched inlet ports and a good tune up. Been running with a 123 Tune on POE which I can heartly recommend.

Standard lump/HS6's with separate K&N's (for the sound) and a sports exhaust would be about the best road engine you can get. Don't forget Jerone gets 170 from a very well built standard lump on HS6's.

Flog the twin 40's and spend the dosh on K&N's and a good head refurb.

[soe8m]

If Jerone is Jeroen then it is 139. But in the Uk that's maybe 170

Jeroen

[bodgerben]

Oooops - sorry Jeroen!

You did say

On LPG it turns automatically to the advanced LPG curve. I'm also very curious what the output will be. With the std cam and hs6 fitted it had about 135 at the rear wheels and it should be more now.

I rounded that up to 170 at the flywheel. But 135 at the wheels on LPG is not to be sniffed at on HS6's and a standard cam

Edited to say - hmmm, you're right, I really don't know where I got the 170 from - I must have imagined it. 135 at the wheels does not equate to 170 flywheel. Still 135 or 139 at the wheels is plenty for a bit of fun - more like 158/165 at the flywheel.

[soe8m]

I think more a 150. I do not hope to have such a loss due to transmission.

Jeroen

[Mad Mart]

I think somewhere in the region of 20% loss between flywheel & wheels iirc.

[soe8m]

Noooo,

So Darren with his 600HP does loose 120 through transmission? Why should a std sprint loose less than the same sprint with 200hp and both have the same trans. It's not a percentage but about 10-15hp. Had a few years ago a 1971 landrover on the dyno at Hans and that one had a loss of 25hp.

Jeroen