I was wondering has anyone seen any direct effects of different set ups on how the turbo comes in?

I know boost threshold is largely dictated by the exhaust manifolding and the a/r of the turbine housing.

With my 267 turbo it comes on around 2500 and thats fine. However my cam is a little large so peak power is still higher then I like (over 6k) and I am running a dual plane manifold.

I see people recommend a single plane typically. So If I go to a smaller, like stock or truck cam and run a single plane..how much could that affect my boost threshold?

 

what cam are you using now?? i think id look at something with about 210 dur at .050,, if you have a bigger turbine a 112 , or with a smaller turbine maybe a 114 lobe sep, i would think a cam of this size will have that little engine all in by 5k

usually when cams are rated they are tested used in a 350cid ,,, idle to 4500n ind a 350 could be 1500 to 5500 in a 267cid or idle to 3500 in a 400cid maybe something to keep in mind

 

I am running an edelbrock performer cam now, 204/214 420/442lift 112sep. I'd like to keep my rods intact and get my shift points from 6300 to more like 5-5500.

A stock 267 cam is ridiculously small at 178/194 350/384lift with a 108sep

This turbo seems to be a decent match so far.

Maybe I should leave the intake & find a smaller cam...maybe a GM 929 cam would work well

 

My 302 single plane with a 208/216 .550 makes peak tq at 4200. Divide cubes then duration by the same % and thats ballpark.

 

It’s no different than an NA setup. The smaller cam and longer runner dual plane manifold will make power earlier in the RPM band. Same deal with turbo engines. A single plane intake will shift the power band up in the RPM range. Which is not what you are wanting. Find a more stock like intake manifold to shift the power band down in the rev range. The more power the engine makes on its own early in the rev range the more quickly it will spool the turbo.

We need more info.

What engine?

267 turbo doesn’t tell me much. What is the AR size? Comp/Exh major/minor diameters? What kind of exh manifold was used? Hot side piping sizes? Cold pipe sizes intercooler? Etc…

 

https://www.theturboforums.com/threads/380749-turbo-chevy-267

 

Not knowing anything about the turbo, it's tough to make a call. Id measure the wheels and figure that out first. I wouldnt' change the intake at all. A stock cam would bring on boost sooner, but I don't know if it's worth the time/effort honestly.

Getting an IC, real fuel pump, and turning up the boost will make all the power you want earlier in the RPM range. Just don't rev it as high and run more boost. No reason that turbo shouldn't be able to make 15lbs well under 6k. If it's not doing this it's not the right turbo for the job, or you have leaks on the hot/coldside.

 

Ok thanks.

I do not know if the stock bottom end would handle 15psi. That would be insane!

I think ill keep an eye out for a deal on stockish cam. If not no big deal. I really should optimise my combo.

 

K.I.S.S u know what rpm ur turbo spools at so get a cam that has power range roughly same or little lower then spool rpm n take advantage of it.. LSA, overlap, back pressure.. why complicate it,??? Just like u build a N/A engine around the cam, I believe u should spec your engine around a turbo when it has one..its the primary power maker so let it do it job.. at most mid 220s duration n maybe little more on exhaust side

 

put a small exhaust housing on it with a tight LSA cam and it will come on fast and fall off earlier because of exhaust backpressure infecting the intake charge.

 

if your fuel injected and have some type of programmable engine management, you can spool the turbo faster by retarding the timing as much as possible and adding fuel. it works great for building boost for launching or right off the line.