Where would you limit compression with the Reverse Pattern Grind RV15M Erson?

Where will diminishing returns occur?
I'm thinking I'll be pretty safe with 10:1.

Yay, Nay?

CJ

_________________
Part of Tyrde-Browne Racing

10:1 seems like a lot for that short of an intake duration and, more importantly the early intake closing point. With the slant's open combustion chamber I'd shoot for 9:1 give or take. I think 10:1 is not going to allow full ignition timing.

_________________
Joshua

I am running the same cam in Twiggy with 9.18 static CR and I am not getting any spark knock with 10 degrees initial and 30 total timing on 87 octane fuel. The aluminum head may be helping my combo in resisting detonation.
DD

Hmmm. I may need to recam for next year then.

I can run my 52cc head with the small valves at Redding.
What's the Victor Reinz head gasket thickness compressed?

Time for some more cam then. With the low speed build I have, I need to watch how much bump stick I give it. Anything designed for over 5000 RPM is going to be wasted. Red Line is 5500. Theoretical comes out around 5800 I believe.

CJ

_________________
Part of Tyrde-Browne Racing

an aluminum head is good for a least .5 compression increase compared to an identical iron head.

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I haven't been pinging with ~9.5:1 and 10° base timing.

That may change though. we'll have to see. I need to dig up the info on my pistons for dish cc's. That should tell a tale.

CJ

_________________
Part of Tyrde-Browne Racing

Where would someone get the specs on the Erson RV15M camshaft. I don't see it listed in the manufacturers choices.

bwhitejr

_________________
'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

It's buried in the erson cam buy sticky somewhere (may have to follow a couple of links). There's also some special grinds buried there too.

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Isn't that almost a stock cam?

I would go bigger with 9.5:1. 225-230 deg @ 0.050" would be my pref.

Lou

_________________
Home of Slant6-powered fun machines since 1988

Where would someone get the lobe profiles for Erson?

bwhitejr

_________________
'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

Working on it Lou!

This is one of Doc's special grinds. I think it would be extremely happy in a pickup. The bottom end is phenomenal!

CJ

_________________
Part of Tyrde-Browne Racing

Here are the events for the 260 Intake / 244 Exhaust RDP design.
Ground on a 108 centerline.

http://www.dutra.org/pictures/engine/cam-260-244.jpg

It is a pretty mild cam design but it works well in a street performance engine.
In Twiggy, I reved the engine to 5200 at one point and the cam supported that RPM. (but the 1 bbl BBS was not keeping up)

I have to get-up the nerve to spray this engine... my guess is that it will handle 5500 RPM and run mid 14's with a 50 HP shot.
DD

Doc,

I looked at the cam sheet , but couldn't come up with the 260/244 durations. It looks like seat-to-seat is 286.7/278.2 and duration at 0.050 is 224.8/215.1.

Help!

bwhitejr

_________________
'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

The event plots are harder to understand, you need to subtract-out the lash.

Here is a link to a more general worksheet on the RDP RV15 / 244Ext. that is a little easier to understand. This cam was ground on a 110 L/C.
http://www.dutra.org/pictures/engine/er ... am60bd.jpg
DD