CR block decking

[nmauduit]

As promised the cam specs on my stroked engine (1692 cc).

From Kent cams.

Lift: .440"
Duration: 250 @ .050

thank you for following up : would that be the BLL42 profile (50/74/74/50 304? inlet on Burton's site which could be seat to seat) ? Kent website do not show any profile close to that (except maybe the PH4 of similar lift, but 314? ex duration 52/82 82/52)?

[1owner69Elan]

I really don't know if it is the cam you indicated on the Burton site.

My invoice indicates "camshaft, blanks, 450V". I thought the 450V referred to QED cams, but maybe this is something generic?

Blanks indicated so perhaps the grind was something the builder thereafter had done according to his spec.

I'll have to ask him next time we meet.

BTW: There is a further discussion on my build and twin cams in general on the latest episode (Mar 25, 2016) at http://www.vintageracingpodcast.com

[vstibbard]

Good pick up, they were a trade off.

We ended up using the 32 choke's as the car is intended to be driven on the road as well as track use, its very tractable with CR gear box and 3.77:1 differential, and does not foul plugs on hot days in traffic.

I was planning on 33's or 34's but the chokes supplied had one in each set had not been completed, with either slots or holes missing, and before anyone asks, they were genuine Weber and not after market!

I expect with the 33's it would remain quite tractable and have would have lifted final numbers, possibly at expense of the gently building torque curve though, 34's may have compromise off idea and transition but made better mid and top numbers.

Cheers
V

[nmauduit]

We ended up using the 32 choke's as the car is intended to be driven on the road as well as track use, its very tractable with CR gear box and 3.77:1 differential, and does not foul plugs on hot days in traffic.

I was planning on 33's or 34's but the chokes supplied had one in each set had not been completed, with either slots or holes missing, and before anyone asks, they were genuine Weber and not after market!

I expect with the 33's it would remain quite tractable and have would have lifted final numbers, possibly at expense of the gently building torque curve though, 34's may have compromise off idea and transition but made better mid and top numbers.

This is not far from my settings, though not fully tuned and tested yet, and based on webers 40 (1700cc big valve sprint cams, 3.77:1 diff):

I started with 33 chokes, and am looking into 34 now, to explore the high revs area - I have not noticed a radical change at low revs, but haven't driven the car much, hopefully spring coming will provide opportunities far back to back tests... I have a lambda sensor on the exhaust Y to help with jetting experiments (around Idle 35 - 40, Main 130 - 135, air 180 - 200, still too early to go into accelerator pump).
forgot to mention I'm now with F16 emulsion (from initial F2, deemed too rich but that was actually for a different reason)

I've seen a max flow for weber 45 according to choke in these ranges (though I don't have the source handy) :
choke 32 : 400 cfm
choke 34 : 420 cfm
choke 36 : 440 cfm

From that I should not be choke limited with my current engine up to 7000rpm (32 being good for up to 6700 rpm in a 1700cc), and if I used 36 I would not choke out until almost 7400, which is more than I would venture even with my next, stronger bottom end...

The effect of using 40 or 45 bodies for a given coke value (say 33 or 34, even 36) is not clear to me - I may try at some point if I source a decent set of 45 dcoe 9, but I've spent enough time (and money) on my currents carbs that I prefer keep using them for the time being.

[1owner69Elan]

The 181 hp @ 6900 and 143 torque @ 5100 on my nominal 1700 cc engine (actually a bit less cc) on Weber 40's has 32 mm chokes.

Pump gas (91 octane)
33 Deg adv.
F-16 E-tube
40 pump
45 F-9
165 Air
140 Fuel
2" air horns, stock
NGK plugs
Without air box, (stock air box decreased hp by 7 - instead larger box being fabricated).

Street use only.

Engine not back in car yet but expect it to be quite tractable with broad, flat torque curve.

[nmauduit]

thank you for the specs: always good to have reference points...

Without air box, (stock air box decreased hp by 7 - instead larger box being fabricated).

do you mean the banjo box? I've replaced it with a K&N filter, fitted up near the pod.

[1owner69Elan]

Not the banjo box. The air box that connects to the carbs. Stock S4/Sprint version too restrictive as per dyno runs.

The banjo (filter) box is being replaced with a K&N filter at the end of the trunking hose placed in the nose of the car.

[nmauduit]

Not the banjo box. The air box that connects to the carbs. Stock S4/Sprint version too restrictive as per dyno runs.

The banjo (filter) box is being replaced with a K&N filter at the end of the trunking hose placed in the nose of the car.

ok good to know, still more things to work on down the line...