Inliners International Forums General Discussion Engines New Offy manifold and heat plate

I have a 250 with headers, a Clifford intake(no heat) and an Edelbrock 500cfm carb. I've always had a problem with bogging when opening the secondaries. I've been told that the runners in the Clifford manifold are too big and therefore are causing the bog. I recently bought an Offy manifold with a heat plate from Tom at Stovebolt. Here is my problem.
The brass fittings on the heat plate are very small (5/16 ID). My heater hose and fittings are 5/8 ID. What is the best method to hook up the heat plate?
Thanks, Al

You should be able to buy other fitings to step up the size to fit your heater hose.

The fact that you didn't have heat to the intake. would not have caused that bog when hitting on the secondarys. (Granted I live in fla.) And I never ran a heated intake. Offey ,Clifford, OR my own 3x4 tunnel ram intake. But even when I stomp on a 12pack (450 holleys) I have Never seen a Bog on the secondary side of it. 600 holley on a Non Heated Offey and still NO issues on the secondarys.
So my 2cent Oppion is you had other issues with the secondarys.

Al, I think what you're looking at is pipe thread, NPT = National Pipe Thread. I checked a few fittings here and I think you need 3/8 to 3/4 NPT adapters. On the manifold side of the block back were the casting flares out for the flywheel half way down there is a 3/8 plug that goes to the water jacket. If you can't find those parts (NPT) locally let me know.

Larry

Al, Mine had clear instructions from Tom indicating sizes and locations for hose and nipples. Didn't yours?

Thanks for all the advice. I'm having the boss on my lower thermostat housing drilled out and machined to accept a 3/8 inch nipple. I will connect this to the heat plate with 3/8 hose. The hose on the other side of the plate will T into my heater return line. I have found a T at the local hardware that will allow me to T into my 5/8 heater return line to the water pump. I'm hoping this will work.
Should have it all back together by Monday and I will post my results.
Thanks, Al

This may be a dumb question, but the Felpro metal manifold gaket I am using has a smooth side, and a rough side. Which side goes to the head?
Thanks, Al

The gasket will only fits one way.Match Bolt holes and Ports.

You're right! It will only go on one way..rough side to the head. Thanks, Twisted

Your Welcome.

when u find that bog on the secondaries,,, let me know what it is... lol i gave up looking for it on mine... same engine/carb... same bog...for now, ive got my secondaries disconnected., runs a lot better., i know its still lacking though, but for now, itll work...
ive been thinking its in the distributor, or coil (loosing voltage) but ive either had time and no money, or money and no time... (funny how that works huh?)

Question? Is that 500 Edelbrock a square bore Carb. or a speard bore.?

T~6 1.1
what's the difference between square and spread bores???

spread bore here twisted, and yes i run the changeover adaptor... why, could that be part of the problem???

Jim . . .

On sqare bore carbs the primaries are the same size as the secondaries. On a spread bore the primaries are bigger. Guys like edelbrock sell adapters to put either type of carb on either type of manifold:


The Rochester Quadra-jet is a spread bore - the Holley 650 double pumper is a square bore . . .

regards,
Keith

Finally got my car back together tonight. I took out the Clifford intake (no heat) and installed the new Offy with a heat plate. Big difference...the bog is gone!!
I can feel a kick when the secondaries open. The car also drives better at low rpm.
However,life is a series of trade offs. For some reason,the Clifford had a much throatier sound. The car seems more docile now. Maybe it's because it is much smoother running with no bog. I'm not giving up on the Clifford. If I can find some way to heat it, I think it will perform better than the Offy.
The install went smoothly except that the base plate (part of the new manifold) that the Edelbrock sits on was too thin. The throttle arm was rubbing on the top of the manifold. I used the one off the Clifford which is much thicker. I used 3/8 hose for heat from my thermostat housing, and connected the other side to my heater hose going to the water pump.
Al

This is not related to the sixes,
My f350 (351w) had a bog when I switched to a edelbrock carb and intake from the stock holley. My bog was from fuel starvation on hard pedal pushes.
Perhapse a bigger fuel pump might do the trick for you.

Odd thing, my mpg went up from 10 to 12 after the switch.

Personally,
I would not run the Clifford intake unless you have higher compression. Like 10-1 or more.
Plus you need a higher stall converter.Or if your car is like 2500 lbs or less.
If you do not have high compression or a loose converter,,, the car will run like a pig.
Running side draft Webbers gave me the most torque & horsepower over any Clifford, Offy, & the Webbers I had were too big, three 48 MM's & they still made more power everywhere in the torque band.
I had run Dual jet carbs 350-500, quadrajets 625-800,,Thermalquads, Holly Carter AFB 500, 625, AVS's 625 ,600 double pumpers, Holley vac 600-750 secondaries Holley2 barrel 350 & 500 & so on.
For a single four barrel,,, the 600 or smaller Holly double pump would be my second choice for carburation..
The Edelbrock carb is basically a Carter AFB, good carb, Good gas milage, don't have to mess carb, but I think a Holly DP is better for performance.
Just my two cents.

Hank

Thanks Hank.
I Don't have 10 to 1 compression, and my 52 Chev H.T. is way over 2500 lbs. I'm running a T5 from an 88 Camero. The Clifford seemed to perform alright until I put my foot into it. Then it bogged badly. The gas milage was also very poor. I'm running a Carter electic pump (5.5 lbs and new 3/8 line) and so I think the fuel delivery was OK.
I think the key was the manifold heat.
The Edelbrock is a square bore by the way.
Thanks, Al

If you want better gas milage I would go with the Offy.
If you want to go back to a one barrel, & get better torque & milage, I would try & find the Edelbrock S.P.2.P. intake.
With the Clifford intake the gas/air velocity is way down(slow) so your bottom end grunt will suffer along w/gas milage.

Hank