As some of you regular guys may remember, I have been fighting hood clearance issues and HP loss verified on the chasis dyno for a year and a half......This led me to put the car in what I called "race trim" when I wanted to go to the strip which consisted of bolting on hood latch extensions, the carb spacer and a homemade air cleaner base hold down..... This combination netted me 20+ rwhp verified on the chasis dyno. I always ran it at the strip in this trim...so I am not sure how much it really slowed down in "street trim", I just know it lost 20+hp. So what sux about all of this is, on the street, I always felt like it was handicapped(although no much, it still ate me up)... So I finally set out to resolve this issue and gain that power back 100% of the time....Here is what I did...



My old "race trim" setup...



Extended latches
Ghetto right?? it worked though...



Still VERY little clearance even with the hood propped like an inch...



Street trim....(no spacer, 2" drop L88 base w/ 3" filter, hood sitting on air cleaner lid and only 1" from the carb throat to the lid, less then that for the vent tubes)




The losses were:

-13 rwhp for having the lid and filter on

-7 rwhp for not having the spacer

-5 to -8 hp for having this hood closed (this was mainly if the air cleaner lid was not on an no filter..



My recent act of desperation to gain 20hp....






I had Vanacors make me an L88 high rise, "short" hood......Its a little more aggressive then I wanted the car to represent but......Its relatively easy HP so.....it needed to be done....Plus my old L88 hood was cracking all over and sagging in the middle of the scoop.

Its going to the paint shop next weds, hopefully once its the body color, it will be slightly less obtrusive...



Now to the mods..

After much internet research, it seems the L88 air cleaners still seem to be the top performers (according to speed talk, yellow bullet and other internet know-it-alls so...).. I decided to stick with it...But notice the big lip around the carb flange.





So I temporarily siliconed the lip/trench in until I decide if I am going to use a Sure Seal or epoxy etc and re-shape it..


Here is the base back on along with the 1" spacer that my motor really likes..


And to gain some clearance above the carb throat that I know was the major power killer on this thing, I went to a 4" K&N filter...I didnt want a taller/thicker filter because it kills the whole stock look thing but....I guesss thats out the window now anyway..



Thats a tall sucker





After everything is said and done, this is what I ended up with...

I still have about 3/8" of clearance so...I can add gaskets/Sure Seal or whatever....



As I mentioned, it kind of hurt my "sleeper" car image that it had with the lower L88 hood but....


But atleast now I know I am getting everything available that the motor can pull in...not to mention some heat insulation for the carb and better ventilation from the engine compartment. I will be track testing it in the Fall with and without the air filter/lid and see if it hurts it or not...as well as testing these new 28" Nitto DRs in comparison to my 27" MTs....Lots of stuff do try in the Fall..... 10.50s or bust IN FULL STREET TRIM...





Sorry for the long thread. I just spent about $1k to get this done and I needed to tell someone so I would feel better about spending $1k to get 20hp I already had....


Hopefully after I get the hood painted next week, it will be a lot less conspicous and most will just think its a stock L88 hood until they really start to look at it close...

 

Cool.

As for the lip, I use a piece of 14-gauge outdoor malibu wire to make an "O-ring" and that fills the gap. A couple small spots of gasket sealer keep it from coming loose. While I was in there, I made an aluminum "nose cone" to go over the air cleaner mounting stud eliminating the small flat spot.



It later occured to me that if I cover this piece with heat shrink tubing, I also get rid of any turbulance associated with the stud threads.

 

I love it!!......I had to sacrifice my 1" HVH Super Sucker carb spacer to fit everything under the L-88 hood, but hesitated to spend money for a 4" Vanacor hood. Looking forward to seeing that thing painted!

 

Had you thought about the K & N air cleaner top?

 

Looks killer!

Man I feel lazy when I look at your projects and attention to detail!!


JIM

 

Thats a really mean looking 'vette, Alan!, have you thought about using a fresh air box?, that would give the engine A LOT of fresh and cool air.

 

I did think about molding an original L88 air chamber onto the hood to fully seal the air cleaner to the hood...I looked into this quite a bit over the years...It seems there is two trains of thought on it... My way of thinking was it may not help much when its nice and cold out but it would probably help with the major power loss I get during the summer and high engine compartment temps...Basically force it to suck 100* outside air as opposed to 180-200* under hood air....I have read many other tests/opinions that the air induction from the base of the windshield doesnt really work and any REAL gains on the strip don't show up....especially if the air chamber is more of a restriction then an open style air cleaner...

One of the reasons I haven't done this yet though is I have found that my carb tends to not like anything on top or around the sides of it.....It seems like it wants to pull all of the air it can get in it from all directions.... Even running the little L88 chicken wire screen and mini lid killed 7 rwhp on the dyno vs. just running the base only....So I think that whatever I gained from the "cooler" air being pulled in, would be negated by the little lid/chicken wire screen and the fact that the 14" filter is now shrouded around 270* of its diameter but the air plenum. Now I COULD just not use the L88 lid/screen and just use my tubular air cleaner base hold down I made, (since the filter is in the hood chamber) but the down side is every time I open the hood, the carb would be open (like at car shows/cruises I go to every week) so I would have to cover it up with something.....all of that stuff just wouldn't show very well and damn sure wouldn't look like a stock 71' LS5.

So I am still on the fence about it....If I had a easy way I could test out the air chamber to validate its gains, I would try but...since it glues to the hood, once its on, its on....If I KNEW it would gain a tenth, I would do it in a heart beat.

 

I tested the K&N extreme top on the engine dyno, it lost 3hp.... The stock LT1/L78 lids are actually pretty good for power...the dip they have built in for the wing nut seems to help direct air downward..... I guess anyway..

 

sorta like this... wish I had a better profile pic.

 

I may try this -



http://store.spectreperformance.com/...3.0.0.0?pp=35&

 

The new hood does take away some of the "sleeper" effect. It looks like you could have a supercharger on top of the engine. But, it runs like you've got a supercharger on it, so its all good.

 

Just got it back from paint.....I think it looks great....Not NEAR as obnoxious as it was when it was black......I bet cruising down the road, people won't notice that it is not a stock L88 hood....atleast until they look real close from the back.... I'm happy with it now...



ITS STILL STOCK......







Here is a bunch of different angles.....How many people wouldn't think it wasnt a stock L88 hood?













You can still tell its tall from the back

















In the light

 

That is a very impressive car. Mine is black but if I were to go any other color, that green would be it. Simply beautiful.

 

What is your 1" spacer made from?

 

It is plastic for now. I may switch to a true phenolic laminate or wooden one soon for more insulation.

 

Thanks Ray!

Actually black is my favorite color on just about everything but the maintenance would freaking kill me and swirl marks drive me crazy so....I can't have it....lol

 

Do you have any problems seeing over/around that big of a hood lump? I cannot see my right headlight pod when it's opened and I only have the stock ZL1 factory hood. I'm 5' 10"

 

Alan, it looks tuff and nice at the same time. That sucker is tall. That is the 4 incher + hood I have seen on a few cars.
I guess you answered the question about the xstream element air filter lid. I am confused why you would lose HP, when its basically open and will allow air to flow thru the top of the air filter. They advertise that it doubles the CFM with these type of lids. Seems like a no brainer to me why anybody would not want to use these unless they are looking for stock/originality. I bet it is a little tuff seeing over that.
Great write up as always. Keep up the good work.

 

We've manufactured Woodfiber Laminate spacers for Edelbrock for about 15 years. If you'd like one, I could pull one from the shelf, send it to you to see how you like it. We make an open 1" for Holley.

 

It looks great, Alan. You're doing all the stuff I want to do to mine if I could ever get the motor back in.