jock

Cheers everyone,

Has anyone had personal experience with running 2v open chamber heads with stock ports and valves.
I am building a 351 Clevo, cam 214 deg @ .050"; .500" lift, stock 2v dual plane manifold, 600 or 750 vac sec carby, currently has 4v exhaust manifolds.

Car is XY sedan, FMX 1800 - 2000 stall, 2.75 gears.
The intention is for a mild usable street car which doesn't guzzle heaps of fuel. I was hoping for about 330 hp.

Do 4v valves make any difference to performance?
Do the heads need to be ported or can I leave them stock?

Thanks for help Jock

4vxc

I have them on my tow car, they are ok for everyday driving but the comp is quite low.
I wouldnt worry about porting them you probably would be better off with 2v closed chamber heads to bump up the compression (more hp and torque) even with the higher compression they are less likely to suffer pinging, detonation than low compression open chambers.

TruBlu351

Welcome to the forum Jock.

I have stock OC 2V's............bless their souls!! If you're budget conscious, you don't need to port the heads. With a cam that size, you'd be just fine with stock valves too.

750 holley, weiand xcelerator (single plane), 4V pacemakers, 2.5" twin system, bit bigger cam.

260hp at the treads. Nothing huge, but a fun daily driver.

__________________
XE Falcon
393 Tremec TKO 9"

clevo400

Some people recon use the 2V intake and 4V exhaust with all Clevo heads !!!
Some people recon just debur the head, clean up the exhaust port and smooth out the combustion chamber. And only let one person do ur head up his own way to guarantee performance. See Mick Webb at SVO.

__________________
regards
Stephen

davis

I ran factory 2V OC heads on a '71 Ranchero (ute) with an "RV" camshaft of about the same specs as you're describing. However, I ran the factory 2V inlet and a larger Holley 2V carburetor.

The "trick" is to leave it bone stock except as follows: before changing out the valves to good 1-piece valves, (while the old valves are in place) polish the combustion chambers until they glow in the dark. Start off with something like a 120 grit sand paper "flapper" wheel in an electric drill and go like mad. Smooth everything out. (Leave the spark plugs out and the stock valves in!)

Move up to about a 220 grit wheel after everything is throughly gone over with the 120 and do it all over again. (Much easier this time)

When the chambers look like mirrors, take the heads down to the local head shop for reconditioning.

Have them rebuild them with hardened seats in the exhaust and blend the bowl transitions to the ports. Use a good 1-piece valve and springs suited to your camshaft choice. I usually recommend having the head shop convert the heads to screw-in studs and guideplates, but your application probably does not require it. I haven't built a V8 engine without roller rocker arms in so long that I can't remember it.

I don't think that you need more than a 600-650 carburetor. In fact, a spread-bore might be a better choice if you can find one and an inlet manifold to suit.

I would recommend moving to something along the lines of an Edelbrock Performer inlet manifold. The stock manifolds are certainly nothing special. An "air gap" manifold is preferred.

:davis:

jock

Thanks guys,

How much bigger can I go with cam size before fuel economy gets worse and low down grunt or throttle response gets worse. I'll be staying with auto with this car and will use 2.75:1 diff with 14" rims/tyres for moment at least.

I'm aiming at 1500 - 1800 as starting rev range up to 4500 - maybe 5000 rpm tops. Lose too many points otherwise.
I'ts been long time since I've had hot streeter (it was 4 sp ); is this rev range close to mark?

Jock

Slabz

a 2.75 diff is a bit low for what you want isnt it? i would have thought that a 3.23 would be better suited to an acceleration concerned individual such as yourself.

__________________

jock

Hi Slabz,

Thanks for your reply.

Possibly. Gearing is going to stay as is for moment purely for finance reasons. After car is back on road and I have some time with new engine in I'll change gears if need be. It will be used on highway as well so don't want engine revving over maybe 2500 at 100 kmh.

Bottom line is I have no idea what gears will suit car yet.

Jock

TruBlu351

Here's a mild hydraulic I'm using which works great for a mild streeter. Kicks in about 2000 and tapers off around high 5000's. But the torque curve (pulling power) is quite strong from 2000 up 5000.

Do you have a budget? How much do you want to spend?

If you just limit yourself to 5000, your stock valve train should be fine (valves/springs/retainers etc). If you invest a bit in a set of stainless valves, springs, pushrods etc (as mentioned) you'd have a real fun machine.

Intake: 214@0.050 .512 lift
Exhaust: 224@0.050 .538 lift

__________________
XE Falcon
393 Tremec TKO 9"

jock

TruBlu351,

I have new 351 short motor, flat tops, decked (not sure of exact measurement yet- but approx. .005" using straight edge on block then feeler gauge to piston crown), have open ch. 2v heads (probably with 4v valves), stock 2v intake. Parts will include new hyd. cam, lifters, valves (haven't priced s.s.), retainers/locks, single springs, stock rockers/ pushrods.

Budget won't extend to port work I'm hoping to do rest of engine for about $2000, heads are about $1300 include fitting 4v's. Will keep stock exhaust manifolds on for originality (car is gt) - if its a slug, may put tri y's on.
What brand is your cam? What rev range did manufacturer say it works in? Just interested in comparison between their sales talk and your findings.
What gears do you run in your own car? Also how much convertor stall?