possible tuning issue, over carb'd maybe?

[Mattys1970C-10]

so ive been posting about this truck I got, its a 1970 c-10 long bed. 350 with rv cam, edelbrock intake and carb spacer, and edelbrock 650 carb. msd ignition, long tubes, duals to flowmasters dumped at the axle, stock heads. this thing runs like a raped ape, but off idle is pretty bad. if I hammer the gas from a dead stop, it barely squeals the tires and has a real delayed bog, and then comes on once it recovers from said bog. im no expert but this thing outa rip the tires off the rim from a dead stop, it has the power, its just not tuned or something. any thoughts? maybe a 650 carb is too much with stock heads??

[DreamRyder1963]

The bog could be caused by the wrong size accelerator shot.

[67 cst swb]

Get online and download the Edelbrock tuning guide for your model of carb (if you don't already have one) without a tuning guide, you are shooting in the dark. These carbs are not that hard to work on. but without that guide in hand you will never get it figured out.
I am assuming it is a 1806 electric choke. If it is not... let me know.
http://www.edelbrock.com/automotive/...&submit=search

[Mattys1970C-10]

ok I will check tomarro and get back with ya. ive done lots of efi, but never even touched a carb.

[geezer#99]

What's your timing set at?

[Mattys1970C-10]

Originally Posted by geezer#99

What's your timing set at?

no idea, I just bought the truck, and have never timed a motor before. had fuel injected mustangs until now

[CC69Rat]

Check the gasket under the carb, between the intake and the spacer. This intake / carb / spacer combo is bad to burn through on the passenger side secondaries and it will cause a huge vacuum leak. I personally have had one do this same thing to me and recently helped another guy on the board with the same problem.

Pull the carb and spacer and check the gasket I can almost promise you if you replace it the bog will go away.. look specifically at the edge of the gasket and mating surface on the intake.

I'll watch the thread to see how it works out. Good luck man.

[71tahoe]

Good stuff mentioned but there are a couple things you need to let us know.

What type intake? Single or dual plane.

What type transmission? If auto, what stall converter?

[Mattys1970C-10]

[QUOTE=71tahoe;6675894]Good stuff mentioned but there are a couple things you need to let us know.

What type intake? Single or dual plane.

What type transmission? If auto, what stall converter?[/QUOTE

edelbrock performer intake, no numbers on it though so I couldnt tell you if its a dual plane or single, ill be brutally honest and admit that I actually dont know the difference, or whats better lol take it easy its my first old school and first chevy

Tranny is a built th400, no stall, 3 speed auto

[Mattys1970C-10]

Originally Posted by CC69Rat

Check the gasket under the carb, between the intake and the spacer. This intake / carb / spacer combo is bad to burn through on the passenger side secondaries and it will cause a huge vacuum leak. I personally have had one do this same thing to me and recently helped another guy on the board with the same problem.

Pull the carb and spacer and check the gasket I can almost promise you if you replace it the bog will go away.. look specifically at the edge of the gasket and mating surface on the intake.

I'll watch the thread to see how it works out. Good luck man.

this would be awesome, ill check it today

[MidLifer]

Matt, if you've never touched a carb (which was basically me before I got my truck) then the tuning guide may look as Greek to you as it did to me. I recently called Edelbrock and talked to a tech about my setup, and within 2 minutes he told me how to tune the carb for my particular engine.

You should buy the calibration kit for your model, it comes with an assortment of metering rods and springs, they are about $50-60 online at all the usual places.

Edelbrock will want to know the lift and duration of your cam, hopefully you have a grind spec.

What they told me for my RV cammed 350 was:

- Set timing to 16 BTDC (I was at around 10)
- Accelerator pump rod in top hole
- Pink springs (each one in the set is colored)
- Metering rod part # 1455

My cam is 234 Duration 488 lift (one of the experts on this board said it's equivalent to a Melling in a previous thread)

Also, if you have a OEM mechanical fuel pump, Edelbrocks don't like a lot of fuel pressure, so you should add a regulator to bring the pressure down below 6 PSI. It will make it easier to tune (and run better). Most OEM pumps put out 8-9 PSI.

IMO it's worth the 10 minutes on hold with Edelbrock to have them advise you. Nice to get it right the first time. Though changing out the rods and springs is easy and quick - 10 minute job, don't have to remove the carb from the manifold to do it.

[Mattys1970C-10]

Originally Posted by MidLifer

Matt, if you've never touched a carb (which was basically me before I got my truck) then the tuning guide may look as Greek to you as it did to me. I recently called Edelbrock and talked to a tech about my setup, and within 2 minutes he told me how to tune the carb for my particular engine.

You should buy the calibration kit for your model, it comes with an assortment of metering rods and springs, they are about $50-60 online at all the usual places.

Edelbrock will want to know the lift and duration of your cam, hopefully you have a grind spec.

What they told me for my RV cammed 350 was:

- Set timing to 16 BTDC (I was at around 10)
- Accelerator pump rod in top hole
- Pink springs (each one in the set is colored)
- Metering rod part # 1455

My cam is 234 Duration 488 lift (one of the experts on this board said it's equivalent to a Melling in a previous thread)

Also, if you have a OEM mechanical fuel pump, Edelbrocks don't like a lot of fuel pressure, so you should add a regulator to bring the pressure down below 6 PSI. It will make it easier to tune (and run better). Most OEM pumps put out 8-9 PSI.

IMO it's worth the 10 minutes on hold with Edelbrock to have them advise you. Nice to get it right the first time. Though changing out the rods and springs is easy and quick - 10 minute job, don't have to remove the carb from the manifold to do it.

this is actually something thats been buggin me so im glad you replied. Is there only one rv cam? or can you get any number of rv cam's all with different specs and different power ranges? I just know its an rv cam, no idea the specs

[Mattys1970C-10]

and I looked at the carb, the numbers are 1406 2094, dont know what this means but they are stamped right by the edelbrock emblem, hope that helps

[71K20chevy]

Dual plane intakes give you more low end torque. In this case, the Performer is a dual plane.

An RV cam is a loosely used term for a cam slightly bigger than stock. The stock 350 cams in the trucks were 194/202* @.05 if I recall, an RV cam would be somewhere roughly in the range of 200/210*.

[NoNeck]

Your carb is a 600 cfm square bore with electric choke. 2094 is a catalog number I believe. I have attached a couple of photos to help you understand the difference between a dual plane intake and a single plane as well as square bore versus spread bore.

The first picture is a SPREAD BORE, DUAL PLANE manifold. You will notice that the openings get larger at the back and the mounting holes are wider at the rear than at the front. This is a SPREAD BORE application. Also, you will notice the divider in the center, making it a DUAL PLANE.

The second picture is a SQUARE BORE, DUAL PLANE manifold. On this intake all the holes are the same size, and the flange is square. Again, there is a divider in the center making it a DUAL PLANE.

The third picture is a SQUARE BORE, SINGLE PLANE manifold. Again, the flange is square but on this intake there is NO DIVIDER, making it a SINGLE PLANE.

Welcome to the forums, and remember... there are no dumb questions. You have come to the right place.

POP

[GASoline71]

You need to nail down timing first. You need a timing light to do it. Also make sure the transmission kickdown is working properly (if an Auto tranny).

Gary

[Lee H]

Originally Posted by GASoline71

You need to nail down timing first. You need a timing light to do it. Also make sure the transmission kickdown is working properly (if an Auto tranny).

Gary

Plus 1.

Always dial in timing first. Make sure your vacuum advance is correct for your application, the mechanical advance is free and working. Post up your initial and at 2500 RMP (vac disconnected), and at 2500 with vac connected. Should be something like 14-16 initial, 32-34 at 2500, and then with vac connected 50-52 at 2500. Your engine may respond better at different readings.

[Mattys1970C-10]

thank you that is very helpful. I was under the impression that an rv cam was much bigger than stock, thats dissapointing to hear its a small cam....I tell you what it lopes like a beast, cant beat the idle sound at all

[Mattys1970C-10]

still tryin to find some time to check all this stuff out, goin to school full time but ill have some answers here soon

[CC69Rat]

Fellas I agree 100% on timing however the fact once it goes over the 'bog' on initial acceleration it's fine.. which kinda makes me think vacuum leak or carb, accelerator pump etc.

Let's just say I replaced my engine.. yes the entire engine with a 350/290 HP crate motor. When we moved the intake and carb over to the new crate motor.. The problem moved with it.. that's how we found the carb gasket I posted earlier. $5 fix. .. I fought with it for months. Dist, fuel pump, all new fuel lines, etc. We tried everything to get that stumble out of it. Mine was a 69 Camaro.

[Mattys1970C-10]

Originally Posted by CC69Rat

Fellas I agree 100% on timing however the fact once it goes over the 'bog' on initial acceleration it's fine.. which kinda makes me think vacuum leak or carb, accelerator pump etc.

Let's just say I replaced my engine.. yes the entire engine with a 350/290 HP crate motor. When we moved the intake and carb over to the new crate motor.. The problem moved with it.. that's how we found the carb gasket I posted earlier. $5 fix. .. I fought with it for months. Dist, fuel pump, all new fuel lines, etc. We tried everything to get that stumble out of it. Mine was a 69 Camaro.

crossin my fingers man ill know soon

[msgdsrf]

One more for checking initial timing! You've got to start there.

[Mattys1970C-10]

still gettin to it....who's idea was it to have kids anyway! lol

[67 cst swb]

Originally Posted by Mattys1970C-10

still gettin to it....who's idea was it to have kids anyway! lol

You know how that works right? Kids are usually the side effects of a sheets & pillows party. But then after you have 'em, you wouldn't trade them for the world... well, most of the time.

[Mattys1970C-10]

Originally Posted by 67 cst swb

You know how that works right? Kids are usually the side effects of a sheets & pillows party. But then after you have 'em, you wouldn't trade them for the world... well, most of the time.

THIS ))

couldnt have said it better myself