Throttle body- DIY 48mm setup

DaviesDJ · Post by **DaviesDJ** » Tue Sep 17, 2013 8:36 pm

Hia guys
Been thinking hard about fuelling for my previously discussed track project (5.0 RV8) NASCAR rods, Buick 300 heads and cross over DCOE intake manifold. This is a track project and really want it to "shine". Chassis now rollig and engine in early stages. On the intake side I really have been torn between 4x webers or dellortos or jenvey a (direct fit)- but both have a significant cost attached and I was thinking about an alternative. Was thinking about buying 8x rover k series 48mm throttle bodies (10-20 quid each) - the alloy ones) and fit them individually with 4 bolts to the weber patter manifold plate - then modify and link up the throttle linkages and fit an injecto boss just after this directly into the crossover runner pipe (hope you can picture what I mean) - has this been done before? Could slash my cost for ITB setup - they also will all be fitted with an individual TPS - would I be able to use these?? If the pull of the linkage is going in the opposite direction then the link arm may need some adjustment, but I have started these sort of ideas and then realised its a waste of time and then end up buying the ready made kit??

kiwicar · Post by **kiwicar** » Wed Sep 18, 2013 10:06 am

Hi
I'm sure someone has done something very like it, I had a plan for a while to use 4X vauxhall red top throttle bodies on a plenum manifold for the chevy I can still see no reason for it not working and this sounds a lot simpler to me. My only observation is the a 48mm TB is a little on the large side for good throttle control, yes I see this is to be a race engine and part throttle response is not a first priority but 42 to 43 mm might be a little more controlable and offer no real restriction.
Best regards
Mike

DaviesDJ · Post by **DaviesDJ** » Wed Sep 18, 2013 11:39 am

many thanks mike, sound great, will buy one and have a look at it for size etc. What size TB are supplied in the 'standard' jenvey kit for the RV8?? are they 45mm??

kokkolanpoika · Post by **kokkolanpoika** » Wed Sep 18, 2013 12:14 pm

Jenvey recon 48mm for my 5.2l rover. At least 45mm..

And i fit 48mm, and engine run sweet. And it has got steady throttle control. Throttle control depends also your throttle cable bracket. Is that progressive or non progressive.

What kind hp readings you are expect?

ps Eales will run 50mm throttles on his 5.3litre race engine..

chodjinn · Post by **chodjinn** » Wed Sep 18, 2013 12:35 pm

How about running two banks of motorbike throttle bodies? You would only have to link the two throttle linkages then, not worry about individual. Also a lot less hassle all round, less wiring and tps worries etc.

kiwicar · Post by **kiwicar** » Wed Sep 18, 2013 1:32 pm

Hi
Generally 8X 48's are used for engines around 550+ BHP NA, you can use them and they are not in the region where they are "too big" in that throttle response if uncontrolable but ideal would be a little smaller as I said and there is no advantage to going to 48s.
Best regards
Mike

DaviesDJ · Post by **DaviesDJ** » Wed Sep 18, 2013 6:47 pm

Really hope to join the 400+ club with this build, 6 inch NASCAR rods and ford modular big bore pistons - minor mods to the rods and the offset grind to the crank at the smaller journal size - all work ongoing - heads now have the 1.77 inch inlets and 1.5 exhausts in - many thanks for the contributions from an old thread in guiding that. bike TBs are an option but the spacing is difficult and I wanted them to bolt on as oppose to cutting off the weber plates and clanging the runners to connect up with silicone hose ala bog brothers. Plus - can you get 45-48mm bike TBs??

kokkolanpoika · Post by **kokkolanpoika** » Wed Sep 18, 2013 7:15 pm

In theory ideal size would be ~43-45mm. But also inlet manifold lenght etc will make big part to choose size. Our "rule" is you need approx 45mm throttles for 43-56hp/cylinder and 48mm for 50-65hp/cylinder.

Off topic:
Just like why you need big valves to make power? You can get over 400hp with 43mm inlet valve, you do not need +50mm valves.. Theoritically 43mm inlet valve will flow approx +440hp..
And why they but 72mm plenum or triple plenum on rover engine? +70mm will flow over 500hp in chevy LS engine and rover triple 48mm will flow huge amount.
And why you need 45mm trumpets for rover efi manifold? 48mm throttle body will correspond approx 45mm straight hole.

There is no 100% answer without make measurements on the dyno..

chodjinn · Post by **chodjinn** » Wed Sep 18, 2013 8:23 pm

DaviesDJ wrote:Really hope to join the 400+ club with this build, 6 inch NASCAR rods and ford modular big bore pistons - minor mods to the rods and the offset grind to the crank at the smaller journal size - all work ongoing - heads now have the 1.77 inch inlets and 1.5 exhausts in - many thanks for the contributions from an old thread in guiding that. bike TBs are an option but the spacing is difficult and I wanted them to bolt on as oppose to cutting off the weber plates and clanging the runners to connect up with silicone hose ala bog brothers. Plus - can you get 45-48mm bike TBs??

Yeah Boggs brothers or someone else could knock up some custom manifolds. There was a guy on here a while back with a RV8 Vauxhall Chevette running two sets of bike carbs, the inlet manifold was a nice piece of work and wasn't crazy expensive I don't think.

Here we go;

http://www.v8forum.co.uk/forum/viewtopi ... t=chevette

Manifold looks great! Same set up would work with throttle bodies.

Kawasaki ZX12 uses 46mm throttle bodies and Kawasaki ZZR1400 uses 44mm throttle bodies, 1300 honda blackbird 45mm throttle bodies (according to google!).

Bonus of the Honda 1300 ones is the spacing, almost perfect!;

http://www.ebay.co.uk/itm/2003-Honda-CB ... 27c0047d63

Yamaha 1300 are nice too;

http://www.ebay.co.uk/itm/YAMAHA-XJR130 ... 2c682e08ab

Or ther relatively exotic (and pricey!) Hayabusa, tapered inlets 48mm>42mm;

http://www.ebay.co.uk/itm/39310-Suzuki- ... 4171236daf

SimpleSimon · Post by **SimpleSimon** » Wed Sep 18, 2013 8:56 pm

98/99 ww/wx Suzuki GSXR 750 Injected SRAD used 46mm TB's

have contemplated going this route on the RV8 but not before running full sequential injection though

DaviesDJ · Post by **DaviesDJ** » Wed Sep 18, 2013 9:09 pm

They do look nice:-) a good thing about the I series throttle bodies is they are cheap (10-15 quid each) and I can line them up one by one for perfect tract transition, rails and injectors on top of this obviously, but I am tempted by bike TBs.

DaviesDJ · Post by **DaviesDJ** » Sat Sep 28, 2013 7:42 pm

Bit of an update, am in the process of abandoning the K series throttle bodies as the spacing of the linkages etc is just too tight to be practicle, and am therefore thinking about giving in and paying for a proper jenvey setup, but the cost of 4 of these is quite eye watering (unless anybody has some reasonable second hand set) - but am thinking again about a hyabusa throttle body set up (99 quid ish a bank). But would the adaptor plates / steps caused by me bodging them on to my weber/je vey manifold may cause significant flow losses. Hmmmmm, could flog my current manifold and invest in a "bogg brothers" manifold made for a set of hay use bodies?? Just wanted to put this question to the room. Am also in the process of sniff ting my 300 head closer to the centre lines by drilling new dowel holes and ovaling the bolt holes / oil feed. Do you think this work is a waste of time (big valves fitted). Many questions, what does the floor think?.