Merc-Intake Cross Drilling?

[blades280ss]

Alrighty then, I will get down to it... Has anybody ever heard of on carberated motors of cross drilling the intake? If so is it worth the effort in doing so?:confused: If it is, does anybody know the size of the hole your supposed to drill and the exact locatoin of where the holes are to be drilled? Any info on this subject will be appreciated!!!:thumbsup: Mr. Nibbles Out!!!:leaving:

[kb5050]

Mercury did it on the BP sst140 motors, I think it was a 1/4", connecting the adjacent cyl. not sure of the theory on it, the motors were spec'd with the drilled manifold so we couldn't use anything else so I don't what it improved...

[CharlieB53]

This is an educated guess.....

IF..... the intakes was drilled BEFORE the reed valves, then the crankcase would SEE a little more carb, i.e., a small but measurable flow from the adjacent carb.

HOWEVER..... at low RPM the signal being 'shared' any at all with the adjacent carb also lessens the signal to the original carb and you would some some small power loss at low RPM.

An example may be found in the Edelbrock intakes, the Performer vs the Performer RPM. The Performer intake is divided in two such that the intake signal from any given cyl only 'sees' one side of the carb where the RPM edition has a small section of the dividers cut out so that the intake signal 'sees' the whole carb and not just one half of the carb. The Performer has a stronger vacuum signal to one side, thus has a much crisper low RPM throttle response, where the RPM has a greater 'flow' potential for higher RPM speeds.

Same thing, only different.

[blades280ss]

Mercury did it on the BP sst140 motors, I think it was a 1/4", connecting the adjacent cyl. not sure of the theory on it, the motors were spec'd with the drilled manifold so we couldn't use anything else so I don't what it improved...
Thanx kb5050, I guess it is not a unheard of practice... I heard of this being done, but I have been skepticle until now thanx again. I am gonna research this subject further now.:thumbsup: Mr. Nibbles Out!!!:leaving:

[blades280ss]

This is an educated guess.....

IF..... the intakes was drilled BEFORE the reed valves, then the crankcase would SEE a little more carb, i.e., a small but measurable flow from the adjacent carb.

HOWEVER..... at low RPM the signal being 'shared' any at all with the adjacent carb also lessens the signal to the original carb and you would some some small power loss at low RPM.

An example may be found in the Edelbrock intakes, the Performer vs the Performer RPM. The Performer intake is divided in two such that the intake signal from any given cyl only 'sees' one side of the carb where the RPM edition has a small section of the dividers cut out so that the intake signal 'sees' the whole carb and not just one half of the carb. The Performer has a stronger vacuum signal to one side, thus has a much crisper low RPM throttle response, where the RPM has a greater 'flow' potential for higher RPM speeds.

Same thing, only different.
Thanx for the input CharlieB53, I am building a 200 carbed motor and looking for topend numbers only.:D So what I tying to say is I am exploring every avenue possble to get the results I am looking for!!!!:cheers: Again thank you for your input on the subject!:thumbsup: Mr. Nibbles Out!!!:leaving:

[fastcat300]

I remember back in the day,one of the best if not the best out board motor builder in offshore Albert Enzweiler [sp] almost flipped out when i picked up his intake and asked about the holes that were drilled in it.

[blades280ss]

I remember back in the day,one of the best if not the best out board motor builder in offshore Albert Enzweiler [sp] almost flipped out when i picked up his intake and asked about the holes that were drilled in it.
How ya doing fastcat300,:D Dont leave me hanging bro, what did he say???:reddevil: You know a little something,something or you would not have chimed in on this!!!:rolleyes: Tell a Nibble something...;) I wont tell anyone if you dont...:thumbsup: Its all good bro, you dont have to say anything, you said enough already!!!:cool: I know now this is worth me researching this futher...:cheers: Mr. Nibbles Out!!!:leaving:

[bobthebuilder]

we drilled them on 2.4's 5/8 inch holes done on a milling machine...... Fine T-rex on here and he can probably direct you to a pic. of one drilled..... I have one on my 2.4 now..... It seemed to improve mid rang acceleration...

[blades280ss]

we drilled them on 2.4's 5/8 inch holes done on a milling machine...... Fine T-rex on here and he can probably direct you to a pic. of one drilled..... I have one on my 2.4 now..... It seemed to improve mid rang acceleration...
bobthebuilder, Thank you for your input on this.:cool: I will hopefully get to chat and get some pics from T-rex on this. Thanx again!!!!:thumbsup: Mr. Nibbles Out!!!:leaving:

[Scott in MN]

we drilled them on 2.4's 5/8 inch holes done on a milling machine...... Fine T-rex on here and he can probably direct you to a pic. of one drilled..... I have one on my 2.4 now..... It seemed to improve mid rang acceleration...

:iagree::iagree:

[fyremanbil]

It's very common on the HiPo Mercs, ModVP, Bridgeport, SST120, etc. As stated earlier, it allows each reed block to draw from 2 venturis.
I have seen manifolds with the divider cut completely out, and also some with a large plenum with all reeds and venturis open to it. These are difficult to start and get on plane though.

[mrcrsr]

if you want one eric i have several that are done already, i would tell you not to do it, kills the bottom end torque, screws w/ the idle, let alone the jetting nitemare

[T-REX]

In my opinion, X-drill'd manifolds are better leff on mod VP mota's...Mod VP iz gone, so let tha Xdrill manifold go wit them....Tha Xdrill'd manifolds work'd well on 2.4's for midrange punch(off turn power), but 9 out ov 10 2.5's don't work well with Xdrill'd manifolds...I have tried a bunch ov differnt type xdrill'd configgerationz...from 1/4" holes, ta 5/8", from 1/2" taper'in to 1/4", ta efi type manifolds...The problems created by tha xdrill far outweighs tha performance gains, unless U are only look'in for increased acceleration around 5K.......JMO

[DerStream]

on my Bridgeport Carb its drilled I believe 5/8

[blades280ss]

Thanx alot all you guys for the input on this subject.:thumbsup: After the responses I got from all of you, I am leaving this one alone!!!:D Thanx again for your insight on this, Mr. Nibbles Out!!!:leaving:

[bobthebuilder]

Well mine has 5/8 holes X drilled and I am building another motor copying the Cherry lil Motor by he byouboyz. I have had it on hold because of lack of work and $$$ but fixing to jump back on it again. I am not gonna use the X drilled intake on it though. The one on my boat now is very weak getting it on a plane. Sometimes it will barely make it on to a plane. I dont want the cherry motor project to be that weak on dead still take offs. But hey my boat screams from like 4500 on up. Actually it has to hit 1800 to 1900 rpm then it leaps forward but below 1800 it is super weak.. I definately want to cure that in my new motor if anyone has any new ideas????

[CharlieB53]

Vented Prop?

[T-REX]

Sum new additions to tha Cherry project, for bottom end iz to use a 1" spacer, and cut .050" off tha front half....These 2 procedures increase tha bottom/mid punch big time....

Also az Charlie said, yo prop will have to be loose on bottom...a mota(any mota) iz week at lower rpm...tha prop haz to turn it loose to git rpm above tha 2K-2500 range...:thumbsup:

[bobthebuilder]

Thanks,T- Rex I already cut .050 off front 1/2 but no spacer yet. I am still gathering parts getting ready to build it... I assume the spacer will hold the reeds instead of the front 1/2 likea stock mota right?

[T-REX]

The spacer goes between tha manifold and reed cages...U will have to have new bolts for tha cages, and mounting bolts...all will be an inch lomnger, if ya use a 1" spacer...Also will have to add to linkage:thumbsup:

[bobthebuilder]

Been figurin out today if I got room for the 1 in spacer and still run my cowl. I have a one piece cowl for it off a 2.5 offshore mota I repainted and had new decals by sign shop

[bobthebuilder]

It dont look like it will fit into the cowl with air box on there. I sort of wanted to run the air box and make a smoother sounding motor with less mechanical noise but no less exhaust maybe more exhaust noise....... I just dont see the extra 1 inch in there. Maybe without the air box on it.. any ideas??