I'm putting a carter afb 625 cfm on a Edelbrock Performer 400 non egr. How much spacer do I need between the intake and the carb?? Will a 3/4-1" spacer found at the auto parts work well enuf? Their will be no egr valve so without a spacer it's right on the intake.
Also should I go with the one with 4 holes, the wide open one, or do they make one with a divider down the middle like the intake?
Thanks!

Truck is a 79 250 400 C-6 4wd

 

You shouldn't "need" a spacer, unless the throttle linkage hits the intake. A spacer may give you better low range torque, because it does increase the volume of the intake. However, the amount of this gain is often debated, without any real facts to back it up.
I would go with a 1" spacer, but not one of the swirl ones.

 

Thanks! The low end torque is what I'm looking for. I"ve got lots of top end.

 

Use a 1" 4-hole spacer, an open spacer will increase top end. I have had good luck with these over the years. They also keep the carb a little cooler.
Jimmy

 

I wanted a spacer to gain a little power plus keep the carb and a/f cooler comming into the intake. But I was told that too tall a spacer would kill the bottom end so I was looking at the shorter ones. The 4-hole also supposed to help more bottom end versues the open one helping the top end. Also the 'swirl-torque' or similar ones suposed to help boost power either more so at bottom end or throughout the whole rpm range. But I didnt want to pay the big bucks. So I got a cheap 1/2" thick phenolic spacer from summit racing (under $30 i think, and phenolic so it wont conduct heat as easily) and used my dremel and 'carved' out swirls to match the 'swirl-torque' spacer I looked at. My swirls werent quite as deep but because mine was only 1/2" thick I put a few more swirls in it. After putting it in my 351M I did notice that at ran a little better on the bottom end but there wasnt any other 'substantial' gains. Although I havent calculated my milleage since but it defenatley didnt go down... might have went up slightly. Truth is you wouldnt be able to tell a power gain much unless you gain atleast 10-20% and thats alot for just adding a carb spacer. But my motor was a little rough off - idle... probably because my carb was too big, but the spacer I put on seemed to make it run nice and smooth off idle. But as was said above you dont 'need' a spacer. Most folks I know with M-blocks dont use spacers.

Just my $.02

 

Spacer increasing low end torque???? As far as I know they will increase horsepower at high rpm, but take away from the low end. Spacers increase the open pleneum air of an intake. Most people know that single plane manifolds (large open pleneum) are for better for high end hp and dual plane manifolds (minimal open pleneum) are for lower end hp/tq.

 

Thats why (like I said above) that if your building a motor for a truck or heavy vehicle and dont want to kill your bottom end you should: stay away from tall spacers, and the ones that are completely open. Shorter ones like the 1/2" i used shouldnt do too much to hurt bottom end and might yet boost it too (you would have to probably use a 2" tall spacer until you noticed you lost bottom end). If you look at dyno figures, mid and high rise dual planes still have good low end torque. Even some single planes like my friend has a torquer 2 (edelbrock) and I couldnt believe how much low end power that thing had with a mostly stock motor. Race single planes and tunnel rams are what actually kill your bottom end, but your not gonna build a tunnel ram efect with 1/2" spacer. The 4-hole design is also optimized more for low end more than it is high end. And you have the benefit of reducing your carb and air/fuel charge temps comming into your intake which boosts power regardless of rpms (I dont know off hand how many horses per degree cooler it is). Plus the 'swirl-torque' style supposed to build power through the whole rpm band and increase fuel efficiency by better mixing the air and fuel as it goes through the spacer. The jury is still out on that but I made my own and it did help my bottem end slightly as I said in my other post. Without a timslip though you would probably never actually tell the difference except in my case where my off idle was a little rough being smoothed out by my spacer. Remember, spacers should be fine-tunning tools. Everyones motor is gonna be different depending on configuration and how you drive it. if your motor is tuned better without a spacer than dont use one.

 

They dyno test on a 455 olds in HotRod mag a couple of months ago showed and increase of low end torque when using a 1" 4 hole spacer. When using the open 1" spacer, the powerband moved up in rpm's. Have you ever looked at a 5.0 EFI intake? They have long runners. The trucks are even longer than tha cars. Then look at the 3 different Edelbrock EFI manifolds. The Performer has long runners, the Performwer RPM has shorter runners and the Victor Jr. has even shorter runners. It's not so much the length of the runner it is the design. As long as you keep the ports basically separated, the longer runner will give you more torque. But you don't want them too long or you will lose throttle responce. My 460 Makes the best torque with a Performer intake and a 1" 4 hole spacer. This has been proven on the dyno many, many times.
Jimmy