Would siamesing the base manifold show any gains on a superram(plenum, base, runners) engine? This engine would have been treated to cam, heads, headers, etc. I recall seeing a gentleman's website (Mike Davis) where he was using non siamese LTR's and a siamese base with incredible results.

 

Interesting,
anyone?

 

I have yet to hear of it being done but would be most interested in finding out the results.


I've noticed however that it seems people who partially siamese the base (half the base runner lenght or less siamesed) are unhappy, while people who go all the way through almost to the head end up with good results (like mike davis)


Since we're speaking of that gentleman I'd just like to give a quick public thanks to him for what he's done for us..


I've used his site extensivly twice for ecm swaps and came out all smiles on the opposite end due to his leg work.

 

Mike Davis blew that engine up twice and figures it was teh intakes fault. His theory was that 5 was stealing the fuel from 7 since they are next to each other in teh firing order. Both times the engine blew 5 was dark and rich looking and 7 is the one that popped (ringlands). His theory makes alot of sense. Extreme siameseing is probably a bad idea, especially if you are going to run the tune on the edge. He doesn't even own the intake anymore, another member here bought it.

 

Lol, ok, nevermind I recall reading on corvetteforum that power was lost when a member siamesed the intake runners on his SR. I may remove the plenum dividers on the plenum but I doubt that will make any differences at all.

Any other ideas?

 

I dont buy Mike's theory. My 5 and 7 look just fine, and if it were really true, I would be experiencing the same problems. Besides that, the injectors are batch fired. If 5 was stealing fuel charge from 7, there would be problems in other parts of the engine as well, as the fuel has already been sprayed to all 8 cylinders and its just sitting there, waiting to be 'stolen' from others. He also mentioned about a leaking exhaust valve or intake valve, which causes excessive amounts of fuel and air to be lost on the exhaust side (mostly fuel I might add), or excessive reversion on the intake side and that can EASILY screw up a air/fuel mix. Also note that there are numerous single plane intakes out there that run short runners, and I dont recall anyone complaining about stolen fuel charges.

Thats my .04 on the stolen fuel charge theories.

As for siamesing a SR, I think thats unwise. The runners are already pretty good sized, and they are already shortened from stock. I think its unecessary.

 

I have no intentions of siamesing the SR runners. I've seen evidence that supports the fact that it doesn't work. It's the base I was curious about.

 

I was referring to the base actually. I still think its unwise, the SR already has the peak TQ and HP where it should be for just about any realistic street car.

 

Sorry Max, my bad. Do you have any recomendations on pulling more power out of a SR? The runners and base have both been cleaned up.

 

I've done research on getting more cfm out of the super ram, and have actually just finished porting my super ram. I've found out from a few guys on this board and the corvette board that the best way to gain power is to basically increase the diameter of the runners all the way to the heads. The most important area to work on though is the plenum to runner opening. This is what hurts the airflow the most, because the air has to make a 90 degree turn. What I did was take a did grinder to these port openings and angle cut the edges of the ports to around 45-60 degrees. I also cut a chunk out of the EGR ridge, which I don't use, so that cylinders 6 & 8 don't have problems getting as much air as the other cylinders due to turbulence. I don't know if that will help much, but I'm sure cutting the edges around the entrance to the runner ports and hogging out the runners and base will.

 

thats what i plan on doing. next time the engine is apart (soon) I'm going to hog out the base and runners and blend all the transitions I can in the air path.

 

Yep, MAX basically has the story.. My Exh valve
on #7 was leaking and was blowing the intake
charge back into the siamesed area of 5&7,
which #5 was getting most of because of the
firing order...

When the motor was rebuilt, I had to scrape
1/8" of carbon off of #5 because it was so
rich, and #7 actually melted a forged piston
it was so lean..

I don't tout siameseing the base any longer,
but mostly because I hate pulling motors
twice in 1 year.. 8-)

mike

 

My friends motor did the same thing after siameseing his base way into the intake

 

I would say just port the plenum and runners and thats it, good enough why need more, have a porter work it to match it all correctly.

 

Details, please.

 

he siamesed the whole thing and i dont remember what cylinder went.....but he took it to the track and it didn't go any faster, said the car wasn't running right

then the car just "exploded" while cruising.....just driving along (lol, this sounds like a lie already) and KABOOM

I can ask him to post to this thread when i see him online

 

LOL!

Well, I've had a car explode while just crusing too... Sad thing was, the engine was entirely stock.

 

ya well....his was a consistent 13.3@105 car that only had a ported plenum....everything else wasn't touched:

ie base, heads, etc

never had an issue with the car until he did the siamesing

 

Two guys I knew back about 15 years ago siamesed their 350’s base intakes. One fried #7 (similar to Mike). I actually tore the engine down and the rest of the pistons and combustion chambers looked pretty good. There was no valve problem. The other guy swapped to a carb in disgust and neither the siamesed base or the carb was as fast as the unmodified TPI base.

The design of the TPI just does not complement high RPM usage very well,,,, regardless of how much you siamese the base. The base was designed to get long runners under the hood and has a funky entrance angle. The curved runners impedes flow and helps heat the air while being pulled against the sides,,, and the travel (heat up) time is the same from t/b to valve. Even if you don't consider the possible air/fuel distribution problem,,, the tuned effect the extra runner length gives is about all the TPI has to over come the basis design inefficiencies. The point of diminishing return occurs pretty quickly in regard to how much you can siamese,, and usually that’s somewhere within the RUNNERS,, not the base. Meaning at some point you'll take more midrange power than you can make up for on the high end,, and it won’t matter what gears or stall speed you throw at it.

Why it seems to work for some and doesn’t hurt others probably has a lot to do with the cam design / phasing, how well the heads flow, and the exhaust efficiency / scavenging (to some extent).

 

I siamesed the base on mine almost all the way through. I left about 2" on the head side just to help smooth the air flow into the heads. The car lost all of its off the line grunt. I slowed down by about 3 tenths on my 60 ft times alone. It was terrible. BUT... the top end was incredible! I accidently hit 7000 rpm a couple of times manually shifting it. The tach would just jump from 5500 to 7000 like nothing. Now granted, I have a supercharger so things are going to be different in my case. But it really seemed to like the single plane intake effect at higher revs. I think what killed me was too low of a stall. I just picked up a 3800 converter, so I'm going to put the siamesed intake back on and see how it does then.

 

I'm the guy Jimmy was talking about . #7 piston ate itself on mine . Honestly I did'nt give it a whole lot of though after it blew up other than the fact that a N/A stock shortblock , heads , cam runners and plenum car has no business blowing up like it did . That piston had a hole the size of half dollar in it . In the back of my head I was concered about air or fuel distribution problems and I guess that concer had mertit . Prior to the intake I never had a problem with the car . The engine wasnt a tired motor either , my Iroc had 55K miles at the time .

Interpret what u want from that . The intake ( siamesed almost al the way thru ) was on my car for one month before the carnage .
I improved from a 13.11 to a 13.10 and mph stayed the same right about 102 , which tells me I really want making anymore power .

---------------------------
Derek
95 Trans Am Convertible w/ 2001 front end
MTI stg. 3 LT4 heads , cc306 , hooker lt's , True duals with X-pipe and bullets , manual 700r4 w/ 3200 vigi multi disc and B&M hammer shifter wolfe cage ....and toooooo much more

Coan th350 w/brake , 4500 stall , spooled 9" w/ 4.11's and LOTS of chassis work

 

Well, that is definitely weird. I am not having any problems with mine, and I've checked the plugs 3 times now and the #7 is clearly not lean. I've had the intake on that car nearing 2 years now I think.

Dont know what to make of it.

 

Neither did I as I knew you werent have troubles , but I sporadically heard of distribution problems and actually found a shop that tried this way back in 91-92 and gave up because of too many problems . I think I went too far down in all honesty . All I left was a very small seperation in the head port side . The wall separating the cylinders was an inch long at best .

 

FWIW,
I just finished dyno'ing the car with the pistons
replaced and the Holley StealthRam in place
of the Siamesed base:

http://www.eecis.udel.edu/~davis/z28...age021105.html

That's more what I was looking for...

mike

 

Anyone have a good way to put the Holley Stealth Ram into Desktop Dyno? I would like to know just how it would act with my combo.

 

I modeled it as a tunnel-ram intake and
the DD2K model was pretty close to my
actual dyno curve and peak HP rpm..

mike

 

Why did you have to tell me that. I just pulled my engine file and swaooed the TPI for a tunnel ram, and oh boy. Is it a big difference. Now I want a Stealth Ram.

 

Mr. Davis, I think those are the dyno results that about 2000 people have been waiting for. I'm impressed. Did you ever dyno that combination with a SuperRam?

 

Saw this last night, someone posted the link elsewhere. I have to say that you are completely NUTS!


As for my base, I dont know what to do. Its working fine and I am quite happy with it. No signs of anything bad happening in the cylinder either. Maybe there is some sort of magic number of how deep to cut, and I hit it out of pure dumb luck?

Mostly, I did it because the Miniram is so expensive and I wanted to try an alternative. With the Stealth Ram though, and the results from both Mike and Jerod listed over on Tech/General Engine, I think there is finally a good and inexpensive alternative to the Superram and Miniram. Now that I've finally seen some good, solid results with the Stealth Ram, I might just go that way.

And on that note...

 

No, although I had one lined up, the
engine/head repair took most of the
Summer. I had a Holley single-plane
EFI intake on for a while, but ran into
problems with it and yanked it.. Then
the first HSR intake I put on was milled
incorrectly and had to be RMA'd which
set me back more..

Going to try and drive the car for the
rest of the year, maybe get back into
intake swaps again next season..

HTH
mike

 

What kind of problems did you have with the Holley single plane?

 

Congrats 85MikeTPI,
12.18 @ 109.5 !!!!! thats great!

 

I had it milled down to fit under the stock hood
with a Lingenfelter Elbow (used 58mm TB)
I had to have new vac ports tapped into it and
I used a large one directly into the intake
plenum area for the PCV.. The car would
miss/studder at cruise, and WOT was lackluster.

After several weeks of diag, I found out that
the PCV in that config was sucking oil right out
of the valvecovers and shooting it into the
intake ports.. I have it in the shop for porting
and reworking the vac ports now, maybe test
it again next year.

BTW, the 12.1@109 is my siamTPI data, I
should have HSR data tonight! 8-)

mike

 

Mike if you're going to cecil county tonight i could kick myself. I was planning on trying to sneak a few runs in, but decided to come into work for a little bit this morning, so i'd never make it north in time to be worthwhile now. Woulda been cool to meet you and check out the sleeper...

 

Sorry, I just made plans last night.. Things
are spur-o-moment when wife/kids take
most of your time..

I'll be going again to test the 9" rear and
we're planning an informal 3rd-gen outing
at Cecil on Dec 7th..

mike

 

Is Dec 7th a saturday Tnt? If so that would be awesome. I should have my scanner cable built by then and an inverter so i can burn on the road.
I wonder how close Trax's car is to driveable? I haven't talked to him much lately, but i think he did start putting things together on it again at least.

 

HSR data tonight:

11.83 @ 114.3..... I think my year-long intake
search has ended... 8-)

mike

 

What?!??!!? No more dyno intake testing? Shame on you!



Nice numbers Mike. Congrats!

 

Patience grasshopper ... patience.

Tim

 

Has anyone experienced sever lean conditions after the intake was opened up ? Mine was done about hlf way to 3/4 down like MadMax's in the photo, and I am sucking 2 tubes of intake runner air now. Anyone experience the same issues? How did you fix it ? I put a new 3 wire Os sensor in the header collector and it is reading about 885 - 900 mv at idel ~ 900 rpm. The car falls on its face past 3000 rpm and has no real oompf at this time. Help Please ! I have the Eprom out for a re-tunig to super rich, hope it helps. Suggestions ? Thanks, DaveB

383, big cam, 1.6 rockers, 11.3 comp, MAP system

 

This is a real old thread.
But it shows u are using the search button

NEways,
What kind of heads do you have, aluminum or iron, and what kind of gas do use (octane)? How big is your cam? Base timing?
I dont know if im offbase here, but 11.3 CR is kinda high, and im wondering if you are getting bad detonation.

 

885-900mv is really rich. What are you getting for O2 readings at WOT?

 

No.

 

The heads are Corvette aluminium. Timing is on 6 BTC with EST unplugged. When plugged back in, it jumps to around 14 - 16 degrees BTC. No evidence of pinging at all. 93 octane. At idle the header primaries are glowing a dull red. This car ran STRONG before the lower intake Mod, just started running out of air approaching 5000 rpm . No other changes made except the lower intake. Not sure why the O2 sensor is reading high, plugs are white hot, backfires out of intakes when tromped hard, some backfiring out tail pipe when eased up to 3000 rpm sitting still and backing off.
If others had to re-program the Eprom significantly for fuel, I guess I need to, just not sure if it is something else. Thanks for the suggestions. Dave

 

OK, I need to ask the embarrassing question....Would these symptoms be present if I had engine timing on # 6 rather than #1 when I placed the distributer back in the car ? Would it run this well at all ? Any other ideas ? Thx, Dave

 

It wouldnt run that way.

Curious, is maybe your timing off and you found out the hard way? I had that happen before. Check the timing mark.

 

Guess what ? I was convinced the timing had to be retarded with all the conditons I was experiencing. The balancer was custom balanced and the TDC spot no longer was the normal line found on a stock balancer. It was a drill divot about 20 degrees farther advanced on the balancer. I put #1 timing on that spot and it runs perfect.
On acceleration, no longer is there a flat falling off of the engine at 4500 RPM, it pulls hard right up to 6000 rpm where I stopped on the throttle. I'll say the lower intake mod works wonders. Finally !
Now for checking the O2 sensor......still running rich. It idles well but has 845-850 mv range. I'll drop the fuel pressure down from 55 psi to 40 psi and check again, that should help some. Thanks to all for your comments, it kept me going to get it right.