ronarndt

Yesterday I finally got everything back together on the 454 NOM in my 68 convert. Thanks to all for advice on selection of parts and trouble shooting on the mystery engine from the PO that came in the car. Final assembly: ProMaxx aluminum heads assembled by Shaw City Engines, Lunati Voodoo hydraulic cam (273/279 .542/.555 lift), Weiand Stealth modified dual plane intake, Cloyes timing chain and gears, CompCams push rods and guide plates, Holley electric fuel pump, Jegs ss roller rockers (from PO), Hedmann headers (from PO), QFT double pumper, mechanical secondary 780 cfm carb (from PO), flat top pistons .030 over (from PO), old school point/condenser distributor, Accel plug wires with ceramic ends, ARP head bolts and misc fasteners, FelPro gaskets, etc, etc, etc.$$$$. We got a break in the rainy weather here in northern VA, so I got to drive the car and it is noticeably faster than before. Will take it for a dyno run next week. Dyno run before starting work was 304 rwhp. I am hoping for at least a 100 hp increase. Fingers crossed.

7t9l82

Congratulations! I think your estimate is very realistic. I lived in.fairfax city and grew up in Annandale so I know your weather very well. It's nice to see a.big block Vette burning up the roads up there like I used. To. We used to street race on the Dulles access road and the airport cops would come out and bet on us. My 68 L-88 roadster beat a turbo Porsche so bad one night he just kept on going.
I wish you many miles of happy driving. Now take a run up the skyline drive!

ronarndt

" the airport cops would come out and bet on us" I don't think I would be so lucky. I got my one warning from the Fauquier county cops a couple months ago for doing 40 in a 25 zone, so I think I am out of favors.

ddawson

Awesome.

While you are getting the dyno done see if the 2.5" filter has an impact. If not I'd love to swap intakes and go with a lower filter.

ronarndt

I added a dropped air cleaner bottom piece (K&N part 87-3549) to give hood clearance. It drops 1 1/4 inch so the wing nut would not hit the hood. The PO apparently forgot about clearance, since there are spider vein cracks in the paint where he slammed the hood on the wing nut. I had this setup when I had it dyno-ed last time. Even with the bb hood there is not enough room for a three inch thick filter with the intake I have.

ronarndt

first dyno run with cast iron heads. November 2016


Car on dyno


printout of results


Well the dyno run was not as expected. Power curve was more aggressive than the run in November, but at 4800 rpm fuel starvation killed the power. Now I have to figure out where the choke point in the fuel delivery to the engine is located. Will change the fuel filter, replace the Mr. Gasket 1-6 psi fuel pressure regulator that came with the car with one that goes higher. The electric fuel pump is 130 gph, so that should be OK. Rats.

ajrothm

Did you remove the air cleaner for the dyno pull? That tiny air cleaner is KILLING you.. Having the lid sitting that close to the venturies and vent tubes will choke it to death.

And yes, the old mr gasket chrome **** fuel pressure regulators are complete junk, you need to get rid of that. IF anything, us a $25 Holley regulator.

ronarndt

I did have one run without the air cleaner and it did not cure the fuel starvation problem. I have on order a K&N air filter top with the pleated filter in it to add more filter area. The A/F ratio dropped like a rock at about 4800 rpm, like someone pinched off the fuel line. Holley has a regulator with a fuel return line port for about $80- think that is the one I'll get. I will also trash the fuel filter, which is a hose barb type like the stock Chevy filter with the return line built into the filter. It may not be plugged up, but may be sending most of the fuel flow back to the gas tank. I can run the return from the regulator and put a high flow filter in the line to the carb.


I did like the slope of the power curve, which is more aggressive than the previous run- until 4800 rpm.


Note that this is really all academic so I can see what the max power produced is with my modifications. (So far, I spent about $3500 to get one additional HP ) I don't plan to race the 50 year old car and driving on the public roads WOT with a loud exhaust is sure to attract the cops.

ajrothm

Things to check:

1) Fuel sock on the pick up in the gas tank. I actually just reached in there and tore mine off by hand it was so bad.

2) Fuel hose from the fuel sending unit to the hard line on the frame, make sure that hose is not swelled shut or plugged.

3) Fuel filter, especially if its on the suction side of the pump.

4) Some holley fuel pumps to not require a return line, and thus may not have enough volume to feed the engine if you are running a return line.

5) The Mr G regulator has got to go.

6) Maybe your pump is just weak.

You really need a fuel pressure gauge on the fuel line at the carb that you can watch while making a pull to see how bad the fuel pressure is dropping.

Lastly, make sure your floats are set right and working properly, verify the rear needle is not stuck closed. Remember the carb can cause fuel supply issues also. You need AT LEAST 3/4" gap between the vent tubes on the carb and the air cleaner lid.

FWIW, I dyno tested a K&N Extreme 14" air cleaner lid and it gained no power and actually chopped up the fuel curve some, it seems to create turbulance across the boosters or something, at least on mine it did.

The best air cleaner setup is the factory/repro L88/LT1 2" drop base, with a 3" filter and matching lid. This will get you some clearance above the vent tubes but still fit relatively low. This will clear an L88 hood with a Stealth or RPM air gap intake.

ronarndt

"The best air cleaner setup is the factory/repro L88/LT1 2" drop base, with a 3" filter and matching lid" Thanks. I have a 1 1/2 inch drop base and there is only 3/8 inch clearance between the top of the filter and the hood (aftermarket bb hood). With this setup I'm stuck with the 2 inch x 14 inch filter. Will get the 2 inch drop base so I can use a 3 inch filter. I am going to re-plumb the fuel line in the engine bay and add a pressure gauge between the regulator and the carb. The PO replaced the lines from the gas tank to the previous mechanical fuel pump and also changed the in-tank pickup and plastic screen. I double checked them and they look good. The Holley regulator I have ordered splits the return line directly from the regulator and I found a filter that claims 90 gpm flow. Filter goes on pressure side of pump. The fuel pump claims 130 gpm. Will verify the pressure stays up even at high rpm. I also have a wideband A/F meter ordered and will check the ratio at various rpm before I go back to the dyno.
Unfortunately I kept some of the PO stuff in place when I added my electric fuel pump. The pressure regulator is AFTER that GM fuel filter with the return line. I suspect that much of the fuel was sent back to the tank. New plumbing should correct that issue. Plan B, if needed, is to just eliminate the return line.

ajrothm

Is your hood a repro BB hood or repro L88 hood? In the pics it looks like an L88 hood. The 2" drop base/3" filter "should" clear an L88 hood on the stealth intake. When I had my L88 hood, I had the 2" base/3" filter on an RPM air gap which is taller then the Stealth and I had about 3/16" clearance. The wing nut is recessed down into the lid for more clearance on a repro LT1/L78 lid.

Sounds like you are on the right track with your plans for the fuel plumbing.

Good luck. I'm sub'd for the updated numbers.

ronarndt

"The wing nut is recessed down into the lid " The lid I have does not have the recess for the wing nut. Before I got the 1 1/2 inch drop base, I had to grind the wing nut to make it skinney so it did not hit the hood. So far all of the air cleaner 2 inch dropped base plates I have found state they will not clear the carb if it has dual fuel bowls like my QFT (clone of the Holley double pumper mechanical secondary carb). I'll keep looking. My base plate has large molded "dents" to clear the carb. Guess I could re-form the shape of one of the available 2 inch base plates.

ajrothm

Here is a pic of the air cleaner. LT1/L78.



Just buy this and it will fit the carb, although you will have to trim/modify the breather tube for the valve cover if your carb is a double pumper. I just cut the tube off all together.
http://www.parts123.com/corvettecent...50g&ukey=10434

This is what the base looks like:



This pic shows the indentation for wing nut.




This air cleaner makes power, gives you decent clearance and won't mess with the vent tubes on the carb.

ronarndt

Alan- Thanks. The comments for the parts I found mentioned the problem with the fit with the rear double pumper fuel bowl and the air cleaner base. Looks like, as you suggest, I can just cut off the vent tube, plug it and it should work. Eckler's and a couple other places have just the base for about $60 and the whole unit for about $150. Looks like I'm in business. RA

USAFVeteran

Since I only have sticks and rocks in my home garage, This is what I did. That's a 10 gal pot lid, cut the way I wanted it. And it's fitted to the fiberglass L-88 hood, to make it functional. The air box is a lot bigger than the plastic L-88 cleaner box they you can buy. I wanted as much air capacity as I could get. The stock L-88 filter fits right in there too.


The A/F ratio stays as good as you can expect throughout the RPM range. However, I'm running a FAST fuel injection, not a carb.

ronarndt

"I can just cut off the vent tube, plug it and it should work". I'm getting pretty creative fabricating and modifying parts. Most recent was a brazed distance tube and custom tapered washer to make the alternator bracket fit the new aluminum heads. I have a large selection of plastic and rubber plugs and grommets to modify the air cleaner base.

ronarndt

Wow- that is really creative and actually a professional looking job when finished. Plus- if you saved the cut-out piece you now also have a lid for an 8 gallon pot! Not bad for using sticks and rocks.
RA

USAFVeteran

Thanks, I am retired sheet metal in the USAF, and then retired again from DoD doing the same thing.


I actually went to the restaurant supply looking for a pizza pan, but they didn't have one big enough. I saw that lid and ask for a tape measure. It is 14" across, so I bought it. Since I was across town from home, I went to the hot rod shop and asked to use an air cleaner. They were very inquisitive until I showed them the final pics too haha


I made all the fiberglass parts inside the hood too. Big piece of cardboard, some tightly stretched plastic wrap, and a release agent, and get busy. I used 2 layers of a light cloth first, and then 3 or 4 layers of the thick matt, then another 2 layers of light cloth. Trimmed to fit, glassed it in, cut the hole, made the piece so I could screw it in and out. And viola'.....


Thanks

ddawson

I have the same drop base on my double pumper. I had the squeeze the tube to clear linkage. BTW I thought the L88 base didn't have the PCV tube.

ajrothm

Thats pretty killer!!

At one time, I was going to do the L88 plenum but I questioned the volume it offered, especially around the sides and front of the air cleaner. After doing a lot of dyno testing and track testing, I figured out that the carb wants a lot of open area around it, on top of it and wants the air cleaner base sitting on the carb to straighten the air flow, even with no filter or lid.