Adamsy87

I have read many different things. Different people siamessing just intake on the runners, while others siamesse both ends of the runners!

What I am wondering is what is the Best all around way to port out your plenum, runners, and even base if some of you guys even go that far. And what kind of gain you noticed.

Measurements of bores would be nice to. I just want to do this right the first time. Also, when performing the siamesse, how far down do you go, and do you siamesse match the plenum?

Any info would be Greatly appreciated!
:hail:

mrr23

i siamesed the entire length of the base. haven't put it on the dyno yet. but no loss of rpm. there is another post where a guy did it and posted a dyno sheet showing what happened.

Adamsy87

wow thats awesome...Thanks! Does anyone know where this post is... i am looking everywhere and cant find it!

u r sofa king we tah did

holy sh*t! what rpm does that pull too?

mrr23

will have it on the dyno soon. so far it's been 5000 with no drop off in the seat dyno.

mrr23

https://www.thirdgen.org/techbb2/sho...threadid=47263

here.

BadSS

How much you "need" to port or siamese is dependant on head flow, cid, cam, weight of car, trans, gears, and converter - or at least your driving style or habits. Anyone that siameses the base without understanding all this may not be happy with the results.

Adamsy87

Thanks Guys ,

That is exactly what i was looking for! so far from what i've heard, would it be reasonable to say that porting/Siamessing the tpi, is more or less to "tweak" the power curve, by moving it to higher rpms. Or is done more for the power gains? To me it would seem that it would do a little of boths.

Adamsy87

Also, would it benefit to siamesse the plenum to the runners and the runners to the base? It seems like this would make the runners a lot shorter!

I got the base part down now....but what after that?

Thanks guys!

mrr23

i am still using the stock runners. my theory on that is so it will keep low end velocity up.

Beast5spdGTA

I siamesed the base ~4", put in a cam 214/220 in my 305, with stock runners it runs fastest times shifting at 5500(rev limiter), pulls great until then, no more 4800-5000 pause/stall. I went considerably slower with mildly ported SLP runners on the same set up( I may have lost some velocity?) not sure.

14.3 @96.8 mph at some elev.

14.6 @ 96 before cam and siamesed base, both used the same chip (SLP)

Adamsy87

Awesome!....that nice to know that you can make the same if not even more power using stock runners rather then a very expensive aftermarket large tube runner! Was that 14.3 before cam and other upgrades? or before. if before ....that means you made up 3 tenths of a sec. thanks for the info!

Do you guys think that a stock throttle body (kinda on a budget) with the two walls on the throttle body opening taken out a mild port job on the plenum to match the runners and then siamessing the base would be the best combination?...adn do you match the siamesse job on the base to the lower part of the runner? or just increase the exit of the runner with the diving wall in it?

For you guys who ported out your plenum, how big did you exactly port out the "holes". What is a suffecient size to keep that velocity up?

by the way heres the setup im thinking of running 350 TPI by the way with 700R4

stock size throttle body, ported plenum, matched runners,siamessed base....just a summit rebuild kit including the Hyper. 9.73:1 pistons, stock L98 heads mabey a mild port job and gasket match. Crane Powermax cam: Duration @ .050 Int. - 222 deg Exh. - 230 deg Gross lift .509/.528
For exhaust.....long story short: my dad is an old time hot rod guy and SWEARS against headers. He says I will be changing gaskets weekly and that i shouldnt expect his help if i get headers!!?!? but our good friend owns an exhast shop...so im thinkin he can make an awesome true dual setup! what i want to know is my dad right...or is that an old myth thats since been refined in the header industry?

Also one more question...are the stock rocker arms and valve springs suffecient...or anything else that I may need to change in result of larger cam?

Sorry about the long post....Im just a kid wantin ta hotrod!
Thanks any info would be AWESOME!

egmonster

I can't see why you would have problems with headers if they were installed properly...

RCR

Don't have TPI anymore, but this is what I did to mine before going to the LT1 intake.
http://mywebpages.comcast.net/rrabin...g/porting.html

Gruvin84SS

The problem with headers is that most people can't get the bolts tightened well enough. You need to tighten the header bolts to 25 foot pounds. Run the car for a couple of days and retighten them again after the gasket has been heated and cooled a couple of times. Then you should have no issues at all. I ran headers on my car for over 3 years before i pulled the engine apart to do head work and cam swap. Just get them tight and all will be good.

Adamsy87

Awesome! I can't wait to start on this one! All the info. was just what i was looking for. Thanks for your help guys!

Hodge

Just be sure to get good quality header gaskets. don't use the crappy paper ones. tighten them like gruvin said and check them about once a month for tightness after that. Or just get some stage eight fasteners and after the second tightening just lock em down

Hodge

Max_Maro92

another important factor to consider when dealing with hedders is the quality of the hedder. I currently run SLP hedders....great hedder and I don't ever expect to have to worry about them leaking for a few reasons. One the flanges used are really thick this means they are far less likely to warb due to heat. Two the flanges are individual for each port (except the center obviously) again an old school trick was to cut the heddr flanges in between the port. Third.....USE A QUALITY GASKET.......there is no substitute for a good gasket I recommend the fel pro performance gaskets. With hedders you really do get what you pay for, a cheap set of hedders will eventually give you problems, but if you wait and save your money than a quality set will last you for years.
-Mike

mrr23

when i did the porting on the plenum, i left all the holes the stock diameter. because i am using the stock runners and TB. but you remove the wall from the front right where the TB mounts. you'll see the hole on the left, at the bottom of it, i took then wall out. on the right the wall is still there. so you can see before and after. so far with what i've done ( ported l98 heads, plenum, base, lt1 cam) and shifting at 4600 i gained .5 seconds. went from 14.91 to 14.46. i was praticing my lauches at the track because i had new tires on. so, i forgot that i needed to shift higher. my 60ft before the porting and cam was 1.964. after i did a 2.000. so no loss of low end. will need to shift at 5700 to see if i pick up any more.

Beast5spdGTA

That gain of .3 sec was after the cam as well as the siamesed base.

It "should" probably be closer to 14.1 @98mph(after cam and base w/ no tuning), considering elevation changes between tracks, but I have no proof of that yet.

Headers, cheap paper gaskets lasted about 8-12 months, both started leaking. New quality gaskets still going. Spark plug wires is a totally different topic, make sure they don't touch. I've burned about 4 wires so far in a little over a yr.

Adamsy87

Ok.... I think i am starting to understand all this! Mr23 your info has been great, so when you did that did you match the bottom half runner to the base manifold when you cut that out? aka did you siamesse the bottom half of stock runners?

Thanks for the header info...it was helpful!

Later
Thanks

mrr23

no. i left the entrance and the runners alone. just to ensure sealing. plus couldn't get anyone with an aluminum welder to siamese the runners. metal is too thin to do it. so from the outside the intake looks completely stock.