BBC performance intake manifolds

[Erland Cox]

I am helpong a customer build a ZL 1 engine for a historic racing Camaro from 1972.
I have tried the stock high performance 2 plane manifold and it gives good power on the first pull and the looses lots because of heating.
With a splash pan under and closed off heating.
What is the history on more isolated manifolds like the Victor JR and the Holley strip dominator.
When were the first ones made?

Erland

[gnicholson]

I remember the strip dominator coming out in 76. Im pretty sure thats right. Guys used to ice those dual planes between rounds

[Erland Cox]

Thank you!
This is road racing in FIA H1 from 1971 to 75.
So what I use must have been available 1975.

Erland

[pamotorman]

if you use this type of cold air intake system you will find the inlet air temp will be lower and lower intake manifold temp. my 68 and 69 Z/28 used this system.

[Old School]

I am helpong a customer build a ZL 1 engine for a historic racing Camaro from 1972.
I have tried the stock high performance 2 plane manifold and it gives good power on the first pull and the looses lots because of heating.
With a splash pan under and closed off heating.
What is the history on more isolated manifolds like the Victor JR and the Holley strip dominator.
When were the first ones made?

Erland

I have an old Honest Charley catalog from 1972 that I just looked through. The only intake that was not on the dual plane design was the Edelbrock Tarantula that the carb set on the approximate 45* angle. Best I remember it was McFarland's design trying to equalize the good/bad ports.

In a road race application isn't any intake going to heat soak and all will have about the same loss of power? I could see a drag engine being able to cool between rounds and minimize the loss.

If you can't cool the intake could you cool the oil? My experience is the oil runs 15-20 degrees hotter than the engine coolant, at least on street cars. I have never ran road race so I really have no experience to talk about what happen there.

Does your engine have the original ZL1 parts--074 heads, 180 cam, 12:1 compression?
It would be interesting to compare the Tarantula to the Chevy dual plane. The Tarantula didn't run too bad with a 2 inch spacer and the intake ported to straighten the runners at the head entrance, at least when that was all we had. Average power would be pretty close for both intakes.

[MadBill]

One of David Vizard's books (I thought it was the Holley one, but no...) details his extensive work to reduce manifold temperature on an SBF. He used spray foam on the underside with an aluminum shield, divorced the water manifold, used heat-rejecting paint, etc. I'll try to find the reference, but AIR, he picked up ~ 20 HP..

[F-BIRD'88]

The intake manifold will cool right down when run at WOT for about 20-40 seconds.
Due to the big amount of fuel being vapourized at WOT. Jet the carb for this average steady running
not rich jetting for a quick 10 second dyno blast on a cold intake manifold.

Jet it for the state it will be running at. As shown duct cool high pressure fresh air to the sealed air cleaner.

If you jet the carb for best dyno test power on a cold intake manifold it will be jetted wrong for how the car will be running in a road race, and the temp of the running intake manifold.
The vapourizing fuel eats a TON of that heat. And re-cools the intake right down from hot soak in a very short time of WOT and near WOT racing.

[pdq67]

I may be all wet, but I thought that Chevy never made a factory high performance BBC single plane intake manifold for two reasons.

1st. the stock engine production numbers wasn't there; and

2nd. the stock, high performance BBC dual plane after the divider was removed performed damned GOOD!

How far off am I??

pdq67

PS., and I would like to know how an L-88 engine would run with a tuned 3x2 intake system on it. A back to back test WITH good 4 tube, long tube, open headers dual plane vs trips.

[vortecpro]

I am helpong a customer build a ZL 1 engine for a historic racing Camaro from 1972.
I have tried the stock high performance 2 plane manifold and it gives good power on the first pull and the looses lots because of heating.
With a splash pan under and closed off heating.
What is the history on more isolated manifolds like the Victor JR and the Holley strip dominator.
When were the first ones made?

Erland

How much were you down after the heat set in?

[bigjoe1]

When the first manifolds came out with the air gap feature, back to back testing was showing about 5 to 7 more horsepower-- THATS ALL




JOE SHERMAN RACING

[gnicholson]

The intake manifold will cool right down when run at WOT for about 20-40 seconds.
Due to the big amount of fuel being vapourized at WOT. Jet the carb for this average steady running
not rich jetting for a quick 10 second dyno blast on a cold intake manifold.

Jet it for the state it will be running at. As shown duct cool high pressure fresh air to the sealed air cleaner.

If you jet the carb for best dyno test power on a cold intake manifold it will be jetted wrong for how the car will be running in a road race, and the temp of the running intake manifold.
The vapourizing fuel eats a TON of that heat. And re-cools the intake right down from hot soak in a very short time of WOT and near WOT racing.

This is a good point. Latent heat of evaporation effect from the vaporizing fuel .especially alcohol

[Newold1]

I think some simple ideas are the best here.

First , to my knowledge there were no air gap intake manifolds made for or used on PERIOD CORRECT BBC engines in 1968-1976.

Second, COOL the fuel, cool fuel cans were used a lot back then in racing. Use dry ice not regular ice and insulate the exterior of the can.

Use cold air intake period correct as shown in an earlier post here.

Use a thermal rejection type carb spacer under the carb to limit fuel warming in the carb. Colder fuel will remove some latent heat from the manifold when racing.

Build a bolt a heat insulator plate to the bottom of the intake manifold. I remember a post and pics here on Speedtalk where one was shown and discussed.

Cool the oil (oil cooler)to hold it at or near 180-200 degrees instead of normal 220-240 degrees seen with racing.

Use a solution like Water Wetter or same and try with a good sized radiator, higher performance aluminum water pump, a 160 degree thermostat and a good fan system to keep the engine water temp under race loads as close to 180-190 degrees as possible.

Things like these should help net 2-3% more power from a PERIOD CORRECT ZL1 engine that really made about 600HP in stock GM trimand thats about 12-18HP! We all know its small gains like this that win races and here thats one of the objects! Go win races!

[Keith Morganstein]

Edelbrock Scorpion and weiand X-celerator were out before 1975. Both single plane, neither is really an air gap, but you could make it air gap by cutting away some of the base and making a valley tray.

[tenxal]

For what it's worth: in conjunction with a lifter valley tray, an aluminum shield on top the lifter valley tray had a considerable difference in intake manifold temp (cast iron intake).

[Erland Cox]

Here is another BBC engine with stock 2 plane intake.
The 2 lower power curves are with and without the first exhaust system.
The brown curve is with 4-2-1 Burns designed headers and bigger sidepipes.



This engine loses more than 20 hp from the first to the second pull.
Manifold gets so hot that you can´t touch it.
Most tracks here are about 1,5 miles long and do not have very long straights so WOT will be less than 10 seconds.








This Corvette has a 427 engine based on a 396. Not bored fully to 427 but longer stroke than 3,75.
I do not know if it is allowed but it has the legal displacement but I did not want to make the block unecessary thin.

Erland