Need some advice on intake and carb for 4.8L stroker

[pityocamptes]

Will soon be getting my engine, 4.8L stroker with the 1991 HO ported heads. Anyways, there is so many differing opinions on intake and carb setup. Some are saying dual plane offy with TA 470cfm Holley, while Clifford sent me this:

"Well, we are dealing with a single plane engine so our intakes are all single plane.
The thought behind the dual plane is to atomize fuel and air but it doesn't work.
This is why we install a water jacket and with our open plenum and oversized runners, 50% power gains are normal.
Check out our 6=8 combination. 70% power and torque gains are incredible for your stroker.
We use the Weber 38/38 DGAS for best performance and quick throttle response."

Now I'm confused. Can anyone offer a suggestion on what type of intake manifold, exhaust header, and carb (2bbl/4bbl) that should be used to get the most out of this engine? Thanks

[mountaineerjeff]

the one with the 6 little cylindrical thingies that sit down in the runners. I think those kids from the 20th century call them EnJeckTures.

Seriously though I have absolutely no helpful information for you. If it was mine Id figure out the Fuel Injection swap/conversion. But other than that, good luck, and free bump to the top

[CobraMarty]

Clifford has been around for a long time. Probably the most experience with non-fuel injected 4.0s. I would listen to them and their advice.
YouTube has some 4 barrel 4.0s reving to like 6,000+rpm and sound sweet.

[pityocamptes]

Thanks! I don't want to mess with FI, and would rather stick with carb.

I guess what I am asking is single or dual plane intake? Clifford says single plane, but a lot of guys on other sites are running Offy dual plane intakes. Also on the carb, some people are running 390CFM, other 450CFM, and still others 470CFM (all of them 4bbl), all of which are greater CFM than the Weber 38/38 2bbl...

Bump to the top... thanks.

[CobraMarty]

The Weber will have better street/mileage manners, 4 barrels more power and rpm.

[pityocamptes]

The Weber will have better street/mileage manners, 4 barrels more power and rpm.

I'd rather go with the 4bbl Anyways, do you know what CFM I should be looking at for a 4.8L stroker? I don't want to wash the cylinder walls with too much fuel. Also, any advice on dual or single plane intake? How about exhaust headers? Thanks again!

[El Stucko]

We've raced quite a few 232's, 4.0L's and 258's over the years. On every application including a stock cammed 232, the Clifford single plane out performed the Offy. I'd choose the Clifford over the Offy.

I used the Weber for a season and while it ran okay, there was a noticable power change going with either a Holley 390 double pumper or the Edelbrock 600, especially above 3500 RPM.

For drivability, I think the Edelbrock 600 would be about your best bet and still give you plenty of power. I'm not a fan of Holley vacuuum secondary carbs.

I really don't have any solid advice for a header. We've used the stock '95 headers and my brother recently switched to a Borla.

[pityocamptes]

We've raced quite a few 232's, 4.0L's and 258's over the years. On every application including a stock cammed 232, the Clifford single plane out performed the Offy. I'd choose the Clifford over the

I used the weber for a season and while it ran okay, there was a noticable power change going with either a Holley 390 double pumper or the Edelbrock 600.

For drivability, I think the Edelbrock 600 would be about your best bet and still give you plenty of power.

I really don't have any solid advice for a header. We've used the stock '95 headers and my brother recently switched to a Borla.

Thank you very much!!! So single plane, 4bbl carb. Would 600CFM be too much? Don't want cylinder wash or manifold pooling.

Also, could you explain why a dual intake is not as good as a single plane? So much conflicting info... any additional info would greatly be appreciated!!!

[str8-6]

I do use a Offenhauser intake with a Holley 600 vac. carb on my 4.5 liter,the 2-plane stuff is gone now since I milled the plenum to be a open one so You could say it's a single-plane intake,did that because I feel that a single-plane works better with a plate nitrous-system,haven't used that yet but I will do that next summer "just a 75 hp shot".

Since my carb is a 4160 Holley it has the stock jet-plate on the secondary,but that one should have been swapped for a slightly larger one,the primary has #66 jets but still a bit light on the sparkplugs,the cam is a Crane 216/228 dur. with .484/.512 lift,also has homemade headders 1.1/2 inch primarys going in to a full lenght 3 inch exhaust,runs good with VERY good pull in second gear (good enoug to toast the band and get the trans to slip badly under full power,"building a new one now...")Otherwise it's a stock engine no porting or overbore,stock 4.0 pistons 258 rods and every bolt and nut is the same as it left the factory with,I know it shouldn't stay together for my driving-style with 6000 rpm shifts and all but it does so far and has enough power (despite the use of the stock exhaust "headder") last year to go 12.94 on the quartermile with valvefloat at around the 1000 feet mark so it should be faster with some better valvesprings than the stock ones thats suffering in there right now...So all in all: with 4.8 liters You can use a 600cfm carb if You want power to be there even after You revved it beyond 3500 rpm's...But IF You really need 600 xfm's depends on what You are gonna use it for and in what car it will be in...

[pityocamptes]

I do use a Offenhauser intake with a Holley 600 vac. carb on my 4.5 liter,the 2-plane stuff is gone now since I milled the plenum to be a open one so You could say it's a single-plane intake,did that because I feel that a single-plane works better with a plate nitrous-system,haven't used that yet but I will do that next summer "just a 75 hp shot".

Since my carb is a 4160 Holley it has the stock jet-plate on the secondary,but that one should have been swapped for a slightly larger one,the primary has #66 jets but still a bit light on the sparkplugs,the cam is a Crane 216/228 dur. with .484/.512 lift,also has homemade headders 1.1/2 inch primarys going in to a full lenght 3 inch exhaust,runs good with VERY good pull in second gear (good enoug to toast the band and get the trans to slip badly under full power,"building a new one now...")Otherwise it's a stock engine no porting or overbore,stock 4.0 pistons 258 rods and every bolt and nut is the same as it left the factory with,I know it shouldn't stay together for my driving-style with 6000 rpm shifts and all but it does so far and has enough power (despite the use of the stock exhaust "headder") last year to go 12.94 on the quartermile with valvefloat at around the 1000 feet mark so it should be faster with some better valvesprings than the stock ones thats suffering in there right now...So all in all: with 4.8 liters You can use a 600cfm carb if You want power to be there even after You revved it beyond 3500 rpm's...But IF You really need 600 xfm's depends on what You are gonna use it for and in what car it will be in...

The 4.8L stroker is replacing my AMC258 in my Scout II, which is a heavy bastard. It will be driven in town, but offroad as well. The stroker is having valve work done, port, polished and comp cam.

[caveman]

I bought the clifford intake and the claims for performance is bogus. When i ordered it it took 9 weeks for it to arive and the quality of workmanship was less than i wouls expect from china. In my opinion the 99 and newer intake with an adapter for a carb is a better option.

[pityocamptes]

Is the 99 an oem intake? Will it fit the 91 4.0 HO head (cast 7120)? Thanks...

[pityocamptes]

Thanks again. So many conflicting advice, when looking through other forums on the net. Some say single plane clifford, others dual offenhauser, then carb size is all over the place... hate to spend the money, and get stuck with poor performance or not enough power... I wish an "authority" guru would chime in... I know engine building can sometimes be all over the place... thanks again...

[CobraMarty]

Some math as a guide-

CFM=CIDxRPMxVE/3,456 = 289x6000x.9/3,456= 451CFM engine's airflow at max engine speed assuming 90%VE

[pityocamptes]

Some math as a guide-

CFM=CIDxRPMxVE/3,456 = 289x6000x.9/3,456= 451CFM engine's airflow at max engine speed assuming 90%VE

Hey, thanks again! I guess another question I have, and kind of confused on carb cfm ratings, is, if the carb is too big, will it flood the engine, wash cylinder walls, or pool in intake? Or is the cfm rating based on max rpm, and keeping up with fuel demands for higher rpms? Thanks again!

So a 451 cfm with single plane intake would be the best choice? One more question on dual plane intakes, some people say they are crap and the engine never idled or ran correctly, while others say they are the next best thing to sliced bread. Thoughts on that?

Also, any recommendations on a carb at that cfm? Holley, edelbrock, etc. 4bbl or 2bbl?