adapter plate

[old cars]

Wondering about using an adapter plate on square bore intake manifold , single plane in particular, to mount a quadrajet. Are they effective? Any issues?

[77cruiser]

I have a couple one open from Edlebrock & one I modified to a 4 hole from a cheap Ebay adapter. I'm running a Vic Jr. or square bore RPM.

[old cars]

I have a 454 with victor junior intake running a 780 holley I would like to change to a modified Quadrajet using an adapter plate if hood clearance allows.

[77cruiser]

How much room do you have now? What kind of car? Most adapters are close to an inch thick.

[old cars]

1975 Monte Carlo 454, 9.5:1 compression 500 hp (balanced and blueprinted, self built ) turbo 400, 2000 stall, 2.73 gears for touring. I have 1/2 inch clearance now with 14x3 GM drop base air cleaner. Adapter plates are generally 3/4 inch thick so I would have to use a shorter air filter ( not the best scenario).

[Cliff Ruggles]

The Victor Jr is leaving a LOT of power on the table for what you are doing.  Power in terms off off idle, low and mid-range. 

I'd change to a stock or Performer intake with a spread bore pattern and forget about spacers and adapters.

The reason I say this is that you are running a 2000 stall speed converter and 2.73 gears.  That keeps the engine WAY out of the efficient range of that intake most of it's life.

It will idle better, smooth off idle, and butt-tons more efficient in the "normal" driving range with greatly improved low and mid-range power with a low-rise factory, mid-rise factory or Performer intake on it.

I'm also curious as to the rest of the engine specs, heads used, camshaft specs, etc?.......Cliff

[old cars]

454 Mark 1V, sonic tested, bored .030 with plate, 0 decked, line honed mains, lifter bores grooved.

Pistons: icon 779 with Total Seal rings, 1/16 ring package file fit. 9.5 to 1 compression.

Cylinder heads: oval port 346263 (peanut port) 2.190 intake, 1.880 exhaust, pocket porting, runners and chambers cleaned up, 3 angle valve job with blending and cc'd  118cc. Comp roller tip rockers.

Camshaft: David Vizard spec'd, 273 duration, 107 LCA at 4 degrees advance, 227@.050 / .542 lift
                hydraulic custom ground on Lunati Voodoo lobes, Lunati springs
Rods: BBC oem, cleaned, magna fluxed,resized and fitted with ARP bolts
Recipcating asembly balnded
Fuel System: 780cfm Holley on Victor Jr replica by Profession Products

[Cliff Ruggles]

Cam isn't big enough and LSA too tight to see all the benefits of the big intake either.

Ya, I know, Vizard knows more about this that I do and loves that tight LSA stuff and quick ramp designs.  Nothing at all wrong with that deal, plenty of ways to skin the cat, but I'm NOT fond of the higher spring pressures they are recommending and using with a lot of these "modern" lobe profiles.  It's hard on EVERYTHING involved, pushrods, rocker arms, lifters, cam lobes and even drags the timing set harder.

I use and prefer much longer seat timing, wider LSA, bigger lobes and less reversion, plus I use at least a full point more compression for pump gas street builds.

The smallest cam I'd ever put in a 454 CID build would have at least 280 @ .006" and 230 @ .050" and not tighter than 112LSA.  Below is a dyno chart from a customer who only used me to purchase parts for his Q-jet.  The build is a 455 Pontiac, professionally ported iron heads, 9.3 to 1 compression and HR cam from Comp Cams (their recommendation) on a tight LSA and advanced with the ICL at 106.

It didn't make nearly the power they were hoping for, and some audible detonation when they tried throwing some timing at it.  They spun some bearings on the dyno, and of course EVERYONE right down to the guy taking out the trash was blaming the Q-jet.

I told him to replace the cam, provided the lobe numbers and positions, 110ICL and 114LSA.  He calls back after the changes, says it idles much better, and cranked out a butt-load more power, plus no "reversion" right off idle and improved throttle response, etc.........Cliff

[old cars]

I know lsa/lca is widely debatable. Cam durations even more so. My intensions were to build a 454 that was very street friendly and affordable to drive on todays fuel and still make good hp/torque.             10.5 to 1 compression with cast iron heads 
on pump gas is neither friendly to your motor or responsible. Long duration camshafts  with a  heavy car and cruising gears make for a pig on fuel and no torque where you need it. High stall converters that go with these cams will further decrease fuel mileage. We are not talking dragstrip as main use.

Most people love to overshoot duration on the  camshaft they choose. Peak dyno numbers are great but don't make for a great street motor unless those numbers are in the right range for the street.
I find most racers couldn't build a strong true street engine if their life depended on it. Rectangular port BBC heads , Ram AIR 1V cams , winding the engine  6500 to 7000 rpm to make hp numbers. Been there and done that.
I am more than happy with this build. Car idles great, almost smooth, drives like an electric motor, tons of torque for 2.73 gears, fuel milage is very acceptable, and it runs on 91 octane. Can you say that?
550 ft lb by 3800 rpm and 500 hp by 5000 rpm
They couldn't do this in the old days even with the higher octane gas .
Up here in Canada fuel was normally $ 1.35 a litre, thats $5.00 per american gallon for 91 octane.
My point being it is irresponsible to build  a true street car without without considering these factors.

[tayto]

where abouts in canada are you? im in vancouver, it was $1.35/L for 87 octane until covid....

[Cliff Ruggles]

"I have 1/2 inch clearance now with 14x3 GM drop base air cleaner. Adapter plates are generally 3/4 inch thick so I would have to use a shorter air filter ( not the best scenario)."

Drop base air cleaners are power robbers right to start with, I've dyno and drag tested several varieties and they all lost power.   I see folks install "high rise" intakes, custom spacers and other "high performance" parts all the time, then cripple any potential improvements restricting air flow to the engine with shorter air filters and lid too close to the carb.

Related but when I was racing the Ventura a lot I went to an RPM intake over the factory unit.  It required a shorter Shaker assembly and I had to use a 1" shorter air filter moving the lid closer to the carb.  That deal absolutely KILLED the engine at the track.  It even induced a stumble/hesitation/bog anytime I went quickly to full throttle that would not tune-out.

So I removed the air filter and made a custom one for the opening in the Shaker, problem solved. 

A few years later I decided to remove the RPM intake and go back to the stock intake, stock air filter, lid and Shaker parts.  I was street driving the car more and racing it less. I also put the choke flap back in the carb and electric choke on the side of it.

Just for fun I took the car to the track after the changes and guess what?  It ran quicker in 60' and short times with the stock parts!  The engine didn't "feel" as strong on the street as the big RPM intake really shines in the upper mid-range and top end, but even with a stronger top end charge the loss in short times had the stock intake a winner over the high rise aftermarket unit.......

[old cars]

tayto ..  I am near London in Ontario,Canada. today 87 octane is 78 cents

I don't think I have ever seen a GM air cleaner that wasn't a drop base. Some more or less.
The one I am using is from a replica 1969 396 375hp bbc. It is identical to the one on my brother in laws 1969 Chevelle Copo 427 / 425 hp which he has owned since 1969.
I doubt it was a power killer.

Intake: Once you reach around 500 hp on a BBC single plane intakes come into play quite well and low speed torque suffers very little especially if we consider I am using a 780 holley instead of 850 or larger (even though my build could use more cfm). The smaller venturi ( 1.4 inch) of the 780 holley  keeps booster signal up. 850 holley has a venturi 1.5 inches. Add to that the small port heads I used which keeps velocity high. Result: Torque makers.

[Cliff Ruggles]

Have you actually tested anything being talked about here?  If so I'd LOVE to see the dyno sheets, or time slips......

[old cars]

That's a very good point Cliff. I do not have acesss to a dyno and I am not a racer. I put a lot of faith in David Vizards testing.

Would like to say that I have read a lot of your Quadrajet tuning tips and have your book . I am honestly amazed to the depth of your knowledge on quadrajet carbs. I enjoy reading your responses to people having tuning problems. I have a soft spot for quadrajets but I know my knowledge of them would never come close to yours.
We are all grateful you share your knowledge. Thank you Cliff

[Cliff Ruggles]

I wasn't asking to be critical but some of the responses sounded familiar to me.

I test EVERYTHING so don't just assume that what I read or am told is actually gospel no matter what the source.

Here are a few of the things I have tested back to back on the dyno.

Every intake that will bolt to my engine.

Every possible type of 1" spacer.

Three different cams, flat hydraulic, flat solid, and hydraulic roller, back to back but it took 3 days.

Every possible type of modern carb against my Q-jet, including an 850 Demon, HP 950 Holley, 4781-2 Holley, Thermoquad, Edelbrock 750 cfm AFB clone, and their Thunder Series AVS clone.

MSD with a 6AL box against a factory HEI.

Here are a few of the things I've tested at the track, on a car that doesn't spin and runs right on the dial in:

Every intake that will fit under my hood, Performer, Performer RPM, factory cast iron, factory aluminum, Street Dominator, Torker, Torker II, P4B, the P4B-QJ, and the Tomohawk.  I also added spacers to them.

All sorts of air cleaners, none at all, and the K & N XTreme lid.

Every carb mentioned above and on several private track rentals I've carried as many as 7 different carbs with us and ran them all day long on two different vehicles.

Every type of 1" spacer, fully open, fully divided, four hole, and semi-open.

Moved the same cam with a 9 keyway timing set four times and ran it after each movement, 107ICL, 109ICL, 111ICL and 113ICL  (you will LOVE those results).  I also street tested the different cam positions to evaluate off idle power/smoothness and how responsive the engine was in the normal driving range.

On the street and at the track I've tested 4 different types of DOT tires. 

I've also tested a LOT of torque converters, 13", 12", 11", 10", and 9.5", street and at the track.

You made mention earlier of "high stall converters" to go with larger cams.  That comment told me that you really need to do some testing in that area.  If you find a good converter guy you absolutely and for sure can "have your cake and eat it to".  My car uses a custom built 10" converter that so close to a stock full size converter you'd never know it's in there.  The trans engages firmly with some RPM drop.  Against the brakes it overcomes the tires at 1800rpm's.  Moves out with normal throttle right off idle, and very well coupled in the "normal" driving range.  You'd be hard pressed to see much past 2200rpm's heavy throttle in high gear climbing a steep grade at 30-40mph.

Take the car to the track, heat up the tires, and WHAM.....it leaves at 3500rpm's and runs 1.59-1.61 60' times and even better goes thru the traps with less than 100rpm's slippage!

https://www.youtube.com/watch?v=6zVdoLR-VzM

Continued......