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I have read about the various bottlenecks in the 305 TBI engine: restrictive air cleaner, exhaust system, cylinder heads and cam. I have taken care of the first two and my plan is to install a set of rebuilt 081 casting heads and Comp XR258HR cam. In this situation, can I reuse the TBI intake or would I be better off with another intake (like Edelbrock 3704 or dual-plane carb intake with TBI adapter)?
Re: Is the stock TBI intake manifold a bottleneck?
I wouldn't think up to 250HP (which you wont reach with this combo) would be a problem with the stock manifold especially if you are still using the stock throttle bore.
Re: Is the stock TBI intake manifold a bottleneck?
Originally Posted by dmccain
I wouldn't think up to 250HP (which you wont reach with this combo) would be a problem with the stock manifold especially if you are still using the stock 43mm throttle bore.
Thanks, that is most helpful! My plan is more about the cost than out-and-out horsepower, so not having no to spend a few hundred bucks on an intake is a win.
Re: Is the stock TBI intake manifold a bottleneck?
Originally Posted by Schurkey
I'd like to see evidence that the air cleaner is restrictive.
I have heard--but not verified--that the OEM TBI manifold has terrible fuel distribution.
Sorry, it was a poor choice of words on my part: I meant that the air cleaner assembly, with the single snorkel, was the restriction. I have no evidence that this is the case, however I have read this on here on this forum and elsewhere. (It certainly seems believable.)
Thanks, too for your feedback regarding the intake. i have not read anything much about the TBI intake which is why I posted the question. Like I wrote, the 305 seems to have been saddled with a number of bottlenecks but wondered where the intake fit in the scheme of things.
Re: Is the stock TBI intake manifold a bottleneck?
Originally Posted by robertfrank
Spring for an Edelbrock RPM intake with a transdapt carb to TBI adapter plate. The stock intake sucks donkey *****.
Is the RPM intake with the carb to tbi adapter plate a better choice for his application as for overall performance? Would it be better than the 3704 TBI intake?
Re: Is the stock TBI intake manifold a bottleneck?
A friend of mine just put an Edelbrock Torquer2 on his TBI Yukon. He has a Vortec 5.7 shortblock with the Vortec roller cam and remanufactured 193 heads. He has a Volant CAI, shorty headers, custom exhaust and ultimate TBI mods.
He has not yet let me tune it and still has his base timing set to 0° with only 11 psi of fuel pressure. That being said his driving impression of the single plane intake were that it made a very notable change. He said he traded a little off-idle torque for a more linear throttle response and a much more sustained torque curve in the mid-upper rpms.
Re: Is the stock TBI intake manifold a bottleneck?
Originally Posted by robertfrank
I just saw this pic on Facebook lol
Probably so, he is a member of both Bowtie Kings and OBSsesed on FB and posted pics on both.
The Vortec cam in that engine is actually out of the GM goodwrench engine that was in my Express van.
We looked over the intake drinking beers in another friends garage on new years. The torquer 2 actually has an exhaust heat crossover under the plenum. We had a long discussion of TBI, intake choices and why he decided to stay with the TBI platform rather than a LS swap.
Re: Is the stock TBI intake manifold a bottleneck?
The Torquer 2 with Swirl port heads is honestly a better choice for a daily driver than what I ran. I have run both a Victor Jr 2bbl and Victor Jr 4bbl intake under TBI on Vortec head engines.
Re: Is the stock TBI intake manifold a bottleneck?
Originally Posted by robertfrank
Interesting, I've heard nothing but negative reviews of the Torquer 2 but have never had the chance to run one.
I have not seen negative reviews just heard people knock them with no real data for not being as good as a performer rpm HP/TQ wise. However having a tiny 2bbl TBI sitting on top that is not relying on vacuum to pull fuel through the venturis it actually works very well from off-idle up. In a TBI application I see the open/shared plenum as a huge benifit.
Re: Is the stock TBI intake manifold a bottleneck?
The Edelbrock TBI-MPFI conversion kits used a manifold that closely resembles the TorkerII in every way except a smaller plenum with a TBI flange and injector bungs drilled into the end of the runners. I have had a chance to play with a couple of those. The HT383 in a 1995 3/4 ton 4x4 lifted Suburban I tuned with one ran very strong everywhere in the RPM band. Ran MUCH better than that engine ever runs with the Vortec truck intake on it.
Re: Is the stock TBI intake manifold a bottleneck?
May I ask what you have to do to get the intakes to work on the tbi heads on edelbrocks web site they say they don't fit
torker 2 and rpm . Am I missing something
Re: Is the stock TBI intake manifold a bottleneck?
Probably the angle of the two middle bolts on each head--71 (?) degrees instead of 90 to the gasket surface.
I've seen manifolds that have the center two holes drilled-out, then they throw a bigass heavy washer on the thing for the bolt head to tighten down on. Great way to break the center two bolts...but guys do it.
I've got an Offenhauser cross-ram that has the center bolt holes hawged out like that. A shame, but also very inexpensive because nobody else bid on it on eBay.
Re: Is the stock TBI intake manifold a bottleneck?
Originally Posted by Schurkey
Probably the angle of the two middle bolts on each head--71 (?) degrees instead of 90 to the gasket surface.
I've seen manifolds that have the center two holes drilled-out, then they throw a bigass heavy washer on the thing for the bolt head to tighten down on. Great way to break the center two bolts...but guys do it.
I've got an Offenhauser cross-ram that has the center bolt holes hawged out like that. A shame, but also very inexpensive because nobody else bid on it on eBay.
Some of the manifolds are shipped that way by the manufacturer. Not like it is hard to find a tappered shim or make your own to correct the bolt angle/contact angle between the manifolds face and head of the bolt. I have gone both ways with this. Slotted newer TBI intakes to fit old style heads and slotted older intakes to fit newer heads. Neither way is a problem if you buy or fab up some angled shims.
Re: Is the stock TBI intake manifold a bottleneck?
Ok thank you for the reply
the reason I ask is I can get a torker 2 for cheep so I can just slot the middle holes and I can make it work
my thinking is marine 395 cam ported sp or ported 081 have both I have been collecting for a bit
I have order the ebl flash so I can run the tbi have stock and the 454
I am building a vortec 350 but was thinking if I have some parts I could do a budget 305 until I have the 350 the way I want it
or is the stock intake ok I like the idea of a single plan
Re: Is the stock TBI intake manifold a bottleneck?
I have always wanted to try a single plane intake since I started messing around with TBI. I'm finally getting the opportunity to do so. I have been away from TBI, learning how to tune a 3 bar speed density 6.0 LS swap with a S475.... I'm back to working on a TBI project and here it is.
Just fired my single plane 355 for the first time last night. Got LOTS of bugs to work out but it runs.
I need to install my wideband and start tuning this thing. I have a walbro 255 pump which is overkill probably but it's already here. I also need to figure out what injectors I can easily FIND that will be enough to feed this thing.
Re: Is the stock TBI intake manifold a bottleneck?
Originally Posted by Cdeez
I have always wanted to try a single plane intake since I started messing around with TBI. I'm finally getting the opportunity to do so. I have been away from TBI, learning how to tune a 3 bar speed density 6.0 LS swap with a S475.... I'm back to working on a TBI project and here it is.
Just fired my single plane 355 for the first time last night. Got LOTS of bugs to work out but it runs.
I need to install my wideband and start tuning this thing. I have a walbro 255 pump which is overkill probably but it's already here. I also need to figure out what injectors I can easily FIND that will be enough to feed this thing.
Find you one of the 30 psi marine regulators. Those with stock 61# 350 injectors should be sufficient for your setup. I have run the 61# high pressure marine injectors at 50 PSI for short periods of time on top of a Weiand 177 force feeding 10 psi to a TBI 350.
Re: Is the stock TBI intake manifold a bottleneck?
I was hoping you'd chime in Fast. I have been looking around for the marine pressure regulator, not sure I know what to search for to find it. Do you know a P/N or where I would find one?
Dominic mentioned in another thread I started that the Aeromotive 13301 would be a good candidate. What's your thoughts on this one?
That's good to know that I can use the stock 61# injectors though!!!
I knew you had done some pretty crazy stuff with TBI but never knew about a supercharged TBI you had? Got any pics or more details? I'd love to know more about your setup.
Re: Is the stock TBI intake manifold a bottleneck?
Originally Posted by Cdeez
I was hoping you'd chime in Fast. I have been looking around for the marine pressure regulator, not sure I know what to search for to find it. Do you know a P/N or where I would find one?
Dominic mentioned in another thread I started that the Aeromotive 13301 would be a good candidate. What's your thoughts on this one?
That's good to know that I can use the stock 61# injectors though!!!
I knew you had done some pretty crazy stuff with TBI but never knew about a supercharged TBI you had? Got any pics or more details? I'd love to know more about your setup.
Nothing crazy at all with the TBI supercharger. It was just a carb style Weiand mini blower on an otherwise stock 8600+ GVW 350 TBI with a water heated TBI-4bbl adapter and 454 TBI. I used 61# Marine high pressure injectors with an adjustable rising rate FMU after the factory regulator. My idle/non-boost fuel pressure was 30 psi, WOT hit 50 psi at 10 lbs boost. The MAP and FMU were referenced to the manifold under the supercharger. Ran it with the EBL and 2 bar map sensor. I did not keep the blower too long to be honest. It munched two very well built 700r4s in less than 10k miles a piece. Stock 8.75:1 HD TBI engine with 1.6:1 full roller rockers, upgraded valve springs, Thorley Tri-Y headers, 2.5" to single 3" Y-pipe, high flow cat and a 3" single in/dual out Magnaflow. The 350 made ~210 rwhp/300 rwtq with an edelbrock performer rpm, big block TBI, Holley projection adapter. With the blower and tuning changes it was about 50% gain in HP and TQ. Torque was over 400 ft/lbs at 2,000 rpm at the wheels. 450 tq in the 3,000 rpm and 300 hp @ 4,200 with a table top flat flat HP curve to 5,200. The factory TBI heads and pathetic TBI cam choked the supercharger at higher rpm and the boost would spike from 6 psi at 4,000 to 10 psi at 5,000. Atleast that is my theory as to why the HP curve just sat flat and did not nose dive after 4,000 like a stock TBI. With the OD and 3.08 gears my highway MPG increased by 1-2 mpg with the blower. Without the blower it was constantly kicking down to 3rd or even 2nd with the cruise set at 70 mph. With the blowers 6 psi of instant boost, if I kicked it hard enough to hit 3rd I was absolutely flying. My city MPG dropped by 4 because I loved putting my foot into it.
You would have to probably look on Ebay to find a NOS one or a marine replacement. Sierra marine might have an idea where to acquire one. GM once had a part number for them but it has been discontinued for years.
Re: Is the stock TBI intake manifold a bottleneck?
Well, I meant crazy as in "interesting"... But I think my context was lost as it often is over the internet hahaha. I've never seen a blown TBI in person, only on the interwebz. Do you have any pics of that setup? That just sounds waaay cool.
Re: Is the stock TBI intake manifold a bottleneck?
I can say now that after a few trial runs of the 355 I'm working on, the single plane intake DEFINITELY wakes up one of these TBIs. This thing just RIPS. Never seen or heard a TBI that sounds like it has such massive amounts of testicular fortitude as this one.
Re: Is the stock TBI intake manifold a bottleneck?
How is the bottom end power with that intake?
The one thing that the L03 does well is low end torque, with a peak that is just off idle. Swap the heads for some Vortecs, better cam, and go to a single plain, and it's hard do imagine that the low rpm performance doesn't get pretty soft.
Re: Is the stock TBI intake manifold a bottleneck?
I can't speak about the low end torque just yet as all I have done is run it in the shop for a little bit. I'm still building a 4L80 to go behind it. I can tell from the sound though it's going to be one strong mother.......
Yeah I know what you mean, there is probably better possibilities as far as torque goes, but I'm honestly thinking that the single plane won't be much (if any) loss in torque vs a dual plane. With all the rest of the goodies in this engine I'd guess it ought to make roughly 400+ FWHP and 450+ FWTQ..... Just a rough guess...... I'm thinking those numbers ought to be on the conservative side anyways....
08-15-2017, 10:35 AM
