Injector hat to blower opening match.

At what point should a person consider using a spacer to adapt a hat to a blower opening? My blower has a 10.875" opening and the hat I have has a 10.5" opening. The front of the opening matches almost perfect but the rear is where the difference is. I can massage the rear a bit but not enough to get a perfect match. I understand a smaller hat on a bigger blower is better that the other way around but a $625.00 touch from DMPE for a spacer to gain a matter of a 1/4"-3/8" is that worth it?

Its going on a Littlefield HHR blower with the older K-8 rotors but its only got 12 passes on it, I was planning on running it up in the 45-50% range also. Just a weekend warrior car.

Thanks
Corey

 

My suggestion: Do what you can to match it and go.

 

I kinda thought that everyone was restricting the inlet size under the hat anyway to make the blower more efficient. Then the nozzles for the last four cylinders would go in the blower, not in the hat.

 

buzzard/blower match

hi all!
i have a question regarding a buzzard that i have,square doors,and a 13 3/8 opening:what is/was the use of such a big injector?
i see on most roots blowers mounting holes that are up to 15.250 apart in lengh,so my injector would fit,but the blower top opening is much smaller.
JR at RBS advised me to make a restrictor plate to match the injector opening to the blower,which all the answers on this thread confirm:so what is the point in building an injector with such a big opening?
at first i thought the opening on the blower should be machined to match the injector,but it seems you don t do that,so i m a bit lost...could someone educate me a little?

 

thanks for your answer,Mike!
so,having a blower top opening that is too big lessens blower efficiency?
JR explained to me that the pie shaped bottom opening is meant not to have air going back up in the blower:is the top opening size(depending on blower OD) meant to limit that as well?

 

thanks a lot Mike!
now i m beginning to "see the light"

 

blower setback??

so on my deal I am adding a SSI hi helix that previously had a non HH blower,where should I try to position the bottom opening?and do you accomplish this with a "set back plate"(I have never seen one myself} and is it even critical on my deal with a 30 over BBC w aj olds heads,running fast bracket stuff with it

 

blower setback

ideally the pie outlet should be in the middle of the intake runners. We had ours set back approx 2 1/4" last season but have just moved it back a further 2 1/4" so its closer to the centre of the runners, it will be interesting to see if we notice the difference. What amazed me last year was how close the egts were with this style of blower verses a standard helix/ standard outlet blower.

 

blower setback

sorry, we are running a 532 BBC, HH SSI-10-71 running 32% over, BDS comp manifold, dart 360 heads. You have to use a setback plate designed for this type of blower otherwise the front wont seal (just found that out the hard way !!). RBS have all the setback plates you could ever want. Watch out with the longer snout as the SSI blowers appear to need a longer coupler than other blowers (just found that out the hard way also)

 

Open my hole up!

talked to bob miner on this recently. I bought a 14-71 psi hi helix 2 inch rotor setback with delta outlet. his thoughts was for the price of all the snout, support,and extras, the cost of which doesn't really pay off for to put the delta smack in the middle of the manifold. the setback thing is more for top fuel because they are trying to get better distribution of fuel with the custom intake and such, whereas alky motors are trying to take away fuel with too big a pump to begin with, and not near as critical. my motor is a alky fc miner motor btw. keeping that in mind, I also have the erd intake setup that has 6 shoes to adjust the air into the blower intake depending on od. very nice, slick piece somebody put a lot of time thinking about. the psi is the king of high od, and this was made to make it a little better down in the lower od area. heres a link to the spacer if you guys want to see it http://www.erdengines.com/services/superchargers of couse its only 2700.00 for the spacer!

 

no delta opening on HH blower

i have a KHUL 8.71 HH blower,with a square bottom opening:would a plate with a delta opening (with or without setback)help optimize it?
current OD is 22% on a 413 cui wedge motor.

 

Blower opening

Hi Comax,

I used to have a LF k8 HHR and they are great blowers for on a budget. I bough a DMPE hat spacer for mine and it did not blend well presumably because they are made for Kobelco/DMPE blowers and hats so that probably isn't a good spacer for you. I am assuming you have a carbon hat.

I would say there are a few ways you can go. You can call someone like Rob Atchison who will add carbon to the back of the hat and sand it down to match the blower for the 45%+od or he may be able to add a carbon ramp to the back of the hat that goes into the blower some to blend the back, generally a 10.5" opening seems to be really good for 40-45% o.d.

or if you wanted to spin the blower at like 40-45% you could make a billet aluminum inlet plug and drill two small bolt holes in the side of the case like how the PSI blowers do it and machine that to blend but .375" may be too thin for the bolt holes.

Another thing you may be able to do is what I ended up doing, Sell the fresh blower w/ retro plate, and snout for $3250 (or somewhere in that ballpark as this was years ago) and add the $650 you would spend on a hat spacer and buy a better blower, the SSI D rotor HHR blowers can be had cheap and are everywhere and they have the setback rotors like a Superman, You may also find an old Kobelco K8 or K9 Superman. Sometimes you can even score one with some mod work too.

Just some thoughts that's I had when I was looking improving my old LF blower, hope it helps.

Trevor Sherwood

 

I should probably give an update on this. I actually was able to grind the opening of the hat well enough to give me a pretty good transition. I was able to get the engine fired and running but its getting cool around my neck of the woods so the season is over. This is a fresh engine so next year I will be doing a lot of learning and I feel the hat will work fine, I will have a bunch of other things to sort out I'm sure.

When I'm looking for more power I'll look at the mods everyone suggested. Thanks for all the advice everybody.

Corey