More HP Top end for 96 5.7 mercruiser

[FreeBeeTony]

Re: More HP Top end for 96 5.7 mercruiser

Think the 750 carb is an over kill............the Edelbrock 1409 (600CFM) is enough.

 

[HT32BSX115]

Re: More HP Top end for 96 5.7 mercruiser

whats a good set of resonably cheap heads? Or where is a good place to get a nice used set... Boat is strictly fresh water so aluminum can be considered.

There's cheap aluminum heads available? I want a set of those!! Get aluminum manifolds and risers too!

Sorry guys... I am running a turbo 21pitch ss prop, 5.7 350 not the mag (260hp) it has and edelbrock performer intake and a 600 cfm edelbrock 4bbl carb. Other than that it is stock. I can run 60 on gps currently on a light chop at 4800 rpm that was with 2 ppl and half tank of gas and a cooler full of beer hahah.

Jared, what is your drive ratio?

Is that engine really blown? or are you planning to supercharge it?


Cheers,


Rick

 

[John_S]

Re: More HP Top end for 96 5.7 mercruiser

Given the high HP and speed goals, would suggest staying with a 750cfm vac sec carb, over a 600cfm. While the 600 would be fine for a toned down approach, he may very well take it as a second step for more HP. That way he wouldn't have to buy another carb. Mercruiser has used vac sec 750cfm on all of thier carbed (Qjet & Weber) 350 Mag and 5.7LX offerings. ie you can tune them just fine, even though they could flow more than what is required.

 

[jared_blown5.0]

Re: More HP Top end for 96 5.7 mercruiser

sorry guys my boat is not blown I keep all my forum names the same and this mustang is blown thats how i got the id....

 

[Mkos1980]

Re: More HP Top end for 96 5.7 mercruiser

I'm running a 1409 Edelbrock with my combo and it runs awesome Plugs look perfect too. Why the 750? The 350 will never draw that amount of air in, unless your spinning over 6K

 

[John_S]

Re: More HP Top end for 96 5.7 mercruiser

Why the 750? The 350 will never draw that amount of air in, unless your spinning over 6K

The only difference betweeen Edelbrock carbs is the 600 uses slightly smaller primary barrels than secondarys. On the 750 all four barrels are the same and equal to the 600 secondarys.

He is playing with a go-fast boat and many of them will run the rpms above the 5K limit of reliable drive life. The VE formulas are mainly used to determine the best size mechanical sec carb. Using a vac sec carb that is larger than theoretical does not hurt anything, as evidenced by Mercruiser's carb selection when 4brl carbs were sold. Also, the 600 is used on 4.3LXs, without problems. Many people get too hung-up on that formula.

The 750 Edelbrock will allow a faster cruise speed without being into the secondarys. Theoreticly the 600 should have a very slight edge in throttle in off-idle throttle response. He will be probably giving the low-end torque up to get the higher rpm powerband he needs to hit the speeds he wants, anyway.

OK, so lets reverse the question, what does the 600 give you that you couldn't have in the correctly tuned 750?

 

[MikDee]

Re: More HP Top end for 96 5.7 mercruiser

OK, so lets reverse the question, what does the 600 give you that you couldn't have in the correctly tuned 750?

Uh, Better gas mileage?,,,

Personally, I'd go for the bigger carb, not saying it's right, but I would

I'm just fascinated by all this, and just gonna spin my wheels a bit here, jog my memory. The 1409 sounds like a Carter AFB- "D" carburetor # that I had on my old 62' Chevy Impala SS 327/300hp. I only vaguely remember that because, it was stolen, and I had to replace it. $70 New, back in the mid-60's I found that it was also used as the primary carb on a dual carb setup off the 409/425hp motor, hence the #1409! Ahh, but maybe my memory is a bit off, and it was #1469, and #1470 as a matched carb set? It was so long ago? but it had 1-7/16ths primaries, & 1-11/16" secondaries.

The Carter AFB-"E" carb. (2 of them) having 1-11/16' primary, & secondary, barrels, was used on my old 63' Plymouth Ramcharger 426/425hp. Nah, I don't remember the part #? But, a variation of this, a Carter AVS, also with 1-11/16" 4bbls was used on my 69' Dodge Charger R/T 440/375hp.

Finally, my son's 74' Nova SS 350 came to me from my cousin, with a slightly worked 350, and a new 780cfm Holley double pumper (that carb was nothing but a headache )

Anyway, I've had many Qjets over the years, and I believe they are basically a 750cfm carb, although on my ex-wifes 81' Eldorado 4.3 Buick V6 that computerized carb was governed from the factory so the secondaries didn't open fully? When I had to replace the TPS in it, is when I happened to find that out, I just left it that way, it had plenty of zip anyway.

I one time put a random Qjet on my sons 75' Chevy Monza Auto spt. coupe. 262V8, and it really woke it up! But, it had nice gearing according to the tach, similar to a 3:73 rear in the old Z28 Camaro, it was just like a mini-Camaro.

Please don't mind my old school blog, I'm just trying to entertain, hope it's not boring?

 

[MikDee]

Re: More HP Top end for 96 5.7 mercruiser

Oops! Meant to point out, the Carter AFB/Edelbrock/Weber, are all basically the same carb. Carter "D" series was the 600cfm model, "E" series was the 750CFM model.