The Stovebolt Site Forums The Shop Area Engine Shop Next engine project specs ....... comments?

Guys,

My next 292 is in the conception phase (mentally, that is). I'm expecting about a 30 HP gain over my previous build (which I've describe here on numerous occasions). Anyway, here's the planned new engine.

1. 292 bored .030 over, Badger LPG (propane) pistons for higher compression ratio.
2. Headwork to include pocket porting and stock sized valves. Screw in studs and performance springs and accompanying accesories. Still contemplating removing the 3 intake bolt bosses.
3. Clifford single 4 bbl water-heated intake and Edelbrock 500 cfm carb.
4. Schneider single pattern grind cam with 218 degrees duration at .050 and .490 valve lift.
5. Clifford shorty headers.
6. Stock rods and crank, reworked and balanced.
7. Stock type damper from "Damper Dudes" - single pulley.
8. Coil-in-cap stock type HEI distributor, possibly running an MSD-6A box if the cam doesn't allow good idle.

My only concern is the cam duration. Ideally I'd like to run about 210 degrees of duration because this will strictly be a street/daily driver engine. But Schneider has this grind in their catalog so I'll assume it's something they either have shelf ready or can make within a couple of days.

I'm going with this build because I have everything except the cam (and the engine block too, but a salvage yard ten minutes away from me had 4 or 5 292s a couple of months ago so getting a core won't be a problem.

What's your thoughts on this build? What would you differently?

Thanks,
-ftyler

Guess ur pleased with the previous 292--I'm curious about that lump porting business and removing those bosses--I had a 250 and those bosses seemed to me to be pretty poor enginneering but I never understood stickin the lump ports in--seems like that would be constrictive as well--angle of air flow I guess--maybe I otta read that Santucci book--after that came out was when the inliners seemed to get excited about it. I guess they remove the headbolts altogether--about have to with lump ports--short three headbolts makes me nervous...... :rolleyes:

I would suggest adding the 1.6" exhaust valves. They are standard small block parts and it won't cost anymore than a stock valve. On our air flow bench we picked up 34 cfm at .500" lift, and that's a bunch of cfm for not much work.

Watch out when working in the intake side. Those lump ports do work, but read at what rpm they are using them. I took modeling clay and added to the intake ports to match the lump design. I did not remove the center divider. The air flow stayed just the same from .050" up till .300", at .005" it was higher, 190.5 cfm with clay, 168.5 stock.

For steet use you want great low lift air flow with a high volocity air speed. To get that you need small well designed ports. The open lump ports are to big, it takes to much rpm to get the air moving threw them. The guys running them are only using a small range of rpm, 6000 to 8000.

I wish we would have measured the port volume on my head before I put together. I used a high heat epoxy and filled in were the clay was. It wraps around the center divider and tapers down to the back of the bowl area. I used porting tools and sandpaper to work it. I would bet we closed off 1/3 of the port and still kept the same flow, which means better throttle responce. It feels really good off idle even with a 3.08 gear and 28" tires.

Your HEI should be strong enough for this type of engine. Dad also has a distributor machine and we have spun HEIs to 7500 with out having them miss or jump around. I just regaped my plugs out to .060" and improved the idle a bunch.

You should invest in one of the computor engine analyzers. You would have a lot of fun with it. I use the Performance Trends base model, and dad uses the Pro model. You can spend hours changeing stuff :p :p Joe

Joe--

Always interestin to find somebody who has done the work--thanks. If I read you right ur saying that for a street engine a smaller intake port improves performance--by increasin intake velocity and removal of the bosses is of little utility except at hi RPM. Seems to kinda contradict the conventional wisdom--game is probably worth the candle on those engine analyzers.

on some of the chevy big block "Truck" engine(366 427) thay had small ports and made awsome torq under 4500 rpm
I had a set of truck heads right next to a set of reqtanguler Hipo heads and the ports were about a third smaller
on the BB im building for my 69 im using 366 truck heads and crank in 454 block wich will make about 430 CI, with short stroke and small ports it will make lotsa lowend tourq for street

Thats right, smaller ports make great low rpm torque! Big ports move a bunch of air at high rpm. You want high volocity at low rpm so the air actually overfills the cylinder. If you can move it fast enough, it will keep filling the cylinder even though the piston has stoped pulling in air.

In my case, we filled the ports with epoxy to redirect the air flow. If you look at a 250/292 head and compare the port floor to any decent V-8 head, you will see the differnce right off. There is no short turn in the 6 head. A "short turn" is a name for the turn the air makes from the floor of the port to the valve head. Air likes to follow a certain degree of turn. If the turn is to sharp, it will jump off and bounce around the valve stem or back wall of the port. By raising the port floor, I was able to blend a nice smooth turn in to the valve. Take a propane torch and blow fire thru the port, you will see how air flows thru the head. On a proper radius, the fire will follow it right around the corner, if its wrong, it will shear off.

Again, in my case, we closed off 1/3 or more of the port but still retained the same air flow up to .300" valve lift and from there to .500" lift it picked up air flow. So we got more air through a smaller port with out any major cutting or machine work. That will always make it run better. The lumps they install do the same thing, make the ports smaller and redirect the air up and over to a good turn in to the valve. They cut the divider out for easy placement of the lumps, not for a increase of air flow. The added flow is a by product of the lump mounting procedure.

In the racing manual, you will see the total port volume of a full race head is smaller than a stock head. Port volume is total area in the port. If you shut the valve and filled the port full of water up to the intake flange, the race head had 225 cc's and a stock head has 237 cc's. Yet the race head flows 264 cfm compared to a stock head of 169. Mine in stock form flowed 168.5 and modified was 191 cfm.

Joe