When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
What gains to expect going from old Fast intake to Fast 102mm LSXR
I recently had some engine issues on my LS1, a lifter fell apart into the oil and scored some bearings. so engine out. Could have got the crank re-ground. Choose to go the 383Ci stroker route. New cam, pushrods, lifters, rockers, oil pump, cam bearings. Well everything that moves is being replaced. The 383 stroker kit should be on its way to me in a week as currently being balanced.
As I wanted something to do on the car while I'm waiting, I chose to paint the engine parts. Took my old F.A.S.T intake apart, had it over 10 years now, some seals look tired, it was painted. Starting to become a hassle cleaning it up. Then it hit me. Why not get a new intake.
Going from 346ci to 383ci, the engine could benefit from more air coming in. So looking at the 102mm Fast LSX, would need to get matching throttle body and perhaps MAF
The car as a 346ci pushes out almost 500hp at the flywheel, expecting around 570hp with the new mods, and perhaps the new intake will release a few more HP.
I guess what I'm asking it the nudge to go for it.
Thanks for the info.not looked at MSD before. That looks quite nice. Found a 103mm one that comes with big mouth throttle body for just over $1500. Tempting.
I will have to look into that. My next question will be sensors, with map, iac and tps from stock fit or does loudmouth come with new.
Will have to measure dimensions on outlet of whisper lid, to decide on changing MAF. It's a non stock maf currently but same dimensions as stock.
The MSD has shorter runners and a larger plenum. Everything a growing boy needs. But get it ported. Mamo did mine and made the runners 1/4" wider! Runners are straighter too, not curved like fast. On my 346, they crossed at 6400, but on LS7, MSD beat the fast at every rpm. I think that as you go bigger it makes more sense. Especially if your cam will have IVC later than 46 degrees.
As to sensors, it had 3 different places to run the map. You gotta drill out the one you want. I run rear mount. I ditched the maf went SD. I run the fbomb iat sensor out the front for accurate ambient temps.
NW 102 throttle bolts on.
If you got room a Holley 105 might also make sense.
id love to see the gains going to a ported msd from my ported fast 90. especially now with a 8" fti converter replacing my old 9.5" nitrous converter. not spraying more than a 100 shot any time soon so did not need to be a nitrous converter.
I think you'd benefit from it. Here's a direct comparison back to back dynos - well a few weeks apart, but no other changes. Just the manifold. This is on a 346.
Loads of interesting ready. Very nice post of comparisons. So I could have done issues with tuning. My IVC is 45 degrees on the new Cam which is the deciding point between the two intakes. I don't know what I will set my rev limit too yet, currently 6200rpm as entire bottom end was stock. Now it's all new and valve train is all new. Dual valve springs, new lifters, pushrods, rockers.
Loads of interesting ready. Very nice post of comparisons. So I could have done issues with tuning. My IVC is 45 degrees on the new Cam which is the deciding point between the two intakes. I don't know what I will set my rev limit too yet, currently 6200rpm as entire bottom end was stock. Now it's all new and valve train is all new. Dual valve springs, new lifters, pushrods, rockers.
Keep in mind, that was on a 346. Longer stroke will bring that crossover point down both in IVC and RPM. So, here is my best advice on it - be very honest with yourself about what your actual shift point will be. If you are going to shift at 6800, then get the fast102. The torque between 5200 and 6300 will be more valuable than the HP you gain from 6300-6800. If you are serious about shifting at 7200 or beyond, get the MSD. FWIW, I set my shift light to 7300, and I've done 7400 before. if you are a valvetrain geometry nzi, you can spin it. Mine is SBE, and I'm starting to get some smoke under hard acceleration, but i've got 160K on the bottom end. The last 60K have not been gentle. The bottom end is better than you might think.
What size is your old fast? I am using a fast 78 with a btr stage 4 cam for reference. Cam only though so I dont feel as if the intake is holding me back yet
if you are a valvetrain geometry nzi, you can spin it..
I would answer 'no' to that one, going by this...
Not sure what really caused it. This was after 3 years, so about 10k miles.
Oil pressure fluctuated, and a real bad ticking noise, got it to a workshop about a mile from home to strip it down.
My rockers are non adjustable, so hopefully my new push rods are the perfect length. No shims were put in last time. This time I'm gonna check for gaps when rotating the engine manually. It all seemed good last time, but obviously something went wrong. The lifters were 'comp cams' so its a name I trust even after this, I put it down to something else being wrong/failing.
Anyway, thanks for the info on the intake selection, to be honest I will be shifting before 7000rpm as this is whole new RPM range for me, so it seems the Fast intake would be best for me and my set up.
I will be using my same heads, which are patriot performance with dual valve springs. I picked up this list while I was visiting the states:-
What size is your old fast? I am using a fast 78 with a btr stage 4 cam for reference. Cam only though so I dont feel as if the intake is holding me back yet
My old fast is a 78mm, Its probably not restricting me. I was cleaning it up, as it looks very tatty now being over 10 years old, I painted it many years ago, and paint coming off. I could either spend time cleaning it up and repaint, or buy another. I usually like to improve if i buy something new and wondered if going bigger would compliment the increase in cubic inch.
I'm still on the fence, cleaning up my old one would save a lot of money, buying something nice and new is tempting as most of the rest of the engine is new or will be looking new.
Painted the block in Pontiac Blue (although I guess it is a Chevy based engine)
I started the thread about my issues on our local car club forum http://www.solent-renegades.co.uk/ge...am-engine.html
Had the start of the oil pressure issues.
The locals are egging me on to get a new intake too.
I guess I will make a decision by tomorrow morning so I can get it ordered.
Need to get the car running by April 10th ready for a car show. Things can take a week to get here.
Then a stg 4 cam was probably not the right choice unless you just wanted sound
Why not? The cam specs Is 235/242 I'm thinking. It's a big cam for a stock bottom end ls1 but once you do a stroker it's different. Stroke eats duration... All cam guys will tell you the same.
Why not? The cam specs Is 235/242 I'm thinking. It's a big cam for a stock bottom end ls1 but once you do a stroker it's different. Stroke eats duration... All cam guys will tell you the same.
Yup. That cam will be tamer in a 383. Honestly the thing I typically see is 383 get UNDER cammed and then don't do any better than a HC 346.
Yup. That cam will be tamer in a 383. Honestly the thing I typically see is 383 get UNDER cammed and then don't do any better than a HC 346.
But RPM=MPH
I strongly agree!! It's basically the same as the popular 408ci but with less bore. 64post on the other hand cammed his 383ci with a cam in the 240s duration and it shows at the track and the dyno.
Tusky, 243/251 but it's only used at the track. Why would he need to shift this new motor at 7200? I think he'll make peak power way before that, it just seems to over working his motor. iMO that 4" stroke and that cam is not going to make anything up there but noise. I'm very interested to see this build completed and tuned with an MSD intake.
Tusky, 243/251 but it's only used at the track. Why would he need to shift this new motor at 7200? I think he'll make peak power way before that, it just seems to over working his motor. iMO that 4" stroke and that cam is not going to make anything up there but noise. I'm very interested to see this build completed and tuned with an MSD intake.
64post, I agree. A 4" stroke motor seems to peak around 6400-6600 rpm most of the time especially when cathedral heads are in use. However, cam specs, headers,intake, head selection, etc all tends to play a role in where a motor peaks at.
03-25-2017, 09:33 AM
What gains to expect going from old Fast intake to Fast 102mm LSXR 
