351 Long Tube Headers

alecracing · Mar 12, 2009

So, is there a difference between the 5.0 and 5.8 long tubes

Can i buy some used 5.0 long tubes and bolt them on my 5.8 and just change the x-pipe???

95Vert383AOD · Mar 12, 2009

alecracing said:
So, is there a difference between the 5.0 and 5.8 long tubes

Can i buy some used 5.0 long tubes and bolt them on my 5.8 and just change the x-pipe???

351 motor is taller....so swap headers are a little longer ....the lowering motor mounts may help a little. I will be going to the mid lengths and having someone weld them in.

Pokageek · Mar 12, 2009

"RWHP 25rwhp after all was said and done .."

I have to change this to 55rwhp now. Rick91 GT just got me another 30rwhp and I was at 425rw before and I am still running a bit too rich! Go LONGTUBES!

..as to the 3 1\2 to 2 1\2 I dont think it will matter much as the headers are the restriction. Mine go 3" all the way to the muffler and then 2.5" out.

95Vert383AOD · Mar 12, 2009

Pokageek said:
"RWHP 25rwhp after all was said and done .."

I have to change this to 55rwhp now. Rick91 GT just got me another 30rwhp and I was at 425rw before and I am still running a bit too rich! Go LONGTUBES!

..as to the 3 1\2 to 2 1\2 I dont think it will matter much as the headers are the restriction. Mine go 3" all the way to the muffler and then 2.5" out.

What long tubes are you using??? How are you tuning my car....not trying to derail my own thread but i need it tuned well and already paid a shop $350 to dynotune and it only made 265hp @ 4000 rpm and 497tq @ 2000 rpm

Pokageek · Mar 12, 2009

95Vert383AOD said:
What long tubes are you using??? How are you tuning my car....not trying to derail my own thread but i need it tuned well and already paid a shop $350 to dynotune and it only made 265hp @ 4000 rpm and 497tq @ 2000 rpm

Well, a 383 should be putting out waay more than than 265rwhp on any dyno

But your 4000RPM is a tell-tale sign that I had. It's not breathing at all.

First you need long-tubes. I went accufab 1 7/8" to 3" (IIRC) collectors, second you need at least an AFR 205 head and then you need a real good breathing intake. If it can't breathe, it won't use the cubes. FOR EXAMPLE: I had 210cc pro-comps on it before, the same intake Chris has and it MAXED at 4500RPM IIRC. I think it was putting out like 338rwhp on the dynojet. I was po'd. I changed to a quality head - AFR 205cc and an edelbrock intake, LT's and it revved to 425rwhp@5200rpm. Then I went to a better puter and a better tuner and they ran it with the SCT chip that was in it before, and got the dynojet equivalent of 425 and then ran the PMS computer in it and bumped it another 30rwhp and this time it didn't run out of steam until 6000rpm. They said it was running pig rich before.

So the moral is:
#1 have an excellent tuner,
#2 computer, meant to handle the power
#3 HEADS (as you can see the "cc" number doesn't matter - its the quality of the head)
#4 Intake that won't kill the airflow too early.
#5 I have a killer custom cam thats meant to rev to 6500RPM with a .589 lift.

Any one of these items missing will kill HP. I would recommend pm'ing Rick91GT because he is the one who got me there. You really need to ask someone experienced like him. He built my engine, tuned it and got the bugs out. It took a while but its there.

95Vert383AOD · Mar 12, 2009

What computer do you use??? and i have a trickflow box intake but the heads are 210cc pro comps i believe. said they flow 277cfm @ .600 lift. Motor used to rev to almost 7000 with an A9L computer and a smaller TFS r intake. but i realized that afr 185's flow about the same at .600 .....so the question is to ebay these and buy new ones? or would it be worth it to send these out to be ported???

I need to figure out the top end (Heads/ cam) and computer

Pokageek · Mar 12, 2009

95Vert383AOD said:
What computer do you use??? and i have a trickflow box intake but the heads are 210cc pro comps i believe. said they flow 277cfm @ .600 lift. Motor used to rev to almost 7000 with an A9L computer and a smaller TFS r intake. but i realized that afr 185's flow about the same at .600 .....so the question is to ebay these and buy new ones? or would it be worth it to send these out to be ported???

I need to figure out the top end (Heads/ cam) and computer

I think we found your issue. The pro comps are good for a 302 and a very mild 351 and SUCK for 400 c.i. So all in all, for the combo you have, they suck suck suck. They are EXACTLY what totally killed my HP. They have their place, but not on our cars. 185's will out flow them NP.

No, I would not have them worked. Sell them to someone who wants to run them on their truck or something. Even without the long-tubes I gained 60 rwhp at least going to AFR 205's. I didn't go 225 because I was concerned about keeping a lot of low end which is what I like, and I am not revving to 7k and the flow charts are nearly the same until where I rev.

I changed to a PMS and I got it used. New I think they are $600 or more. But the heads alone will be a major difference.

I also have 10:45:1 compression which is for N/A. Now you might be able to get away with a blower, keep those heads and FORCE that air through...you could try that first. Maybe someone PA can chime in. But I know for sure you will never get the HP NA from those heads man.

95Vert383AOD · Mar 12, 2009

Ha yeah im looking at 225 afr's but thats $2000...Wish someone was selling some big heads on here. ill keep my eye on ebay. I already have Probe shaft rockers trickflow box intake....etc. i went cheap on the heads. BTW what Cam are you running??? With 1.72 rockers mine is 222-232 @ .050 .548/ .574 ...So maybe a cam is in order too. eegh...i need a cam & heads.

Pokageek · Mar 13, 2009

95Vert383AOD said:
Ha yeah im looking at 225 afr's but thats $2000...Wish someone was selling some big heads on here. ill keep my eye on ebay. I already have Probe shaft rockers trickflow box intake....etc. i went cheap on the heads. BTW what Cam are you running??? With 1.72 rockers mine is 222-232 @ .050 .548/ .574 ...So maybe a cam is in order too. eegh...i need a cam & heads.

I am not sure of the exact specs but the lift is .589 with 1.6's and it was made by Ed somebody, I forget. It's almost too much for street but the PMS toned it down.

95Vert383AOD · Mar 13, 2009

Ed Curtis??? Yeah i looked him up ....and ironically hes located in my state about 30Min. from my house.

Pokageek · Mar 13, 2009

Yea I think it was curtis.

BTW it was the Typhoon intake that KILLED my upper rpm too big time. I'll put it to you this way. I sure as hell know how to get the least HP out of a big c.i. engine lol.

95Vert383AOD · Mar 13, 2009

Ha that must have sucked....Im the person who puts a $700 intake on $800 heads. Guess its time to drop a couple grand on heads. I consider streetable anything that will idle at a redlight without stalling and full brake vacuum.

Pokageek · Mar 13, 2009

Yea, I tried to do the whole thing cheap and it was a 120rwhp difference. Now if you want a car that has wrecking ball low end then you don't need all those expensive components. It was still a blast to drive though. BTW, I LOST considerable low end at 1500-3000 when switching to the AFR's. Then at 3000rpm it blasted out like a turbo. The long-tubes fixed all that and went past the former low end grunt. Yep, I tried every short cut I guess.

You and I are reverse on driveability tho. I want tons of low end, idle like a BMW inside and sound like a beast outside..etc.. I even had to get rid of the drone and went with those new corsa mufflers. The ywork.

95Vert383AOD · Mar 13, 2009

Ha so where do you think i can unload these heads? They work perfectly fine ....they just act like 185's. I have a 2400 stall and like the power low. Im wondering if its worth the extra couple hundred for 225's over 205's. I want to make around 500hp with a redline of 6000-7000. The 383 is a very rev. happy engine.

Pokageek · Mar 13, 2009

I sold mine on ebay NP. If you want to rev to 6-7 get the 225's they flow almost exactly the same as mine but further out up top.

Here's the difference in plain site between the pro-craps and the AFR's:

You can see the ports squeezing together and cutting air-flow.

Not here:

Sorry for going so far off topic. but it is all about air flow I guess.

95Vert383AOD · Mar 14, 2009

WOW...wanna Come install my new heads...I hate removing all that crap. BTW are the rocker arms stud holes standard spaced??? I have Probe shaft rockers i want to use on the AFR's

Pokageek · Mar 14, 2009

"BTW are the rocker arms stud holes standard spaced???" I honestly dunno. I guess they are.

95Vert383AOD · Mar 14, 2009

Called AFR earlier today....Least amount of time i ever had to wait to talk to someone. They are standard spaced like a gt40. Guy said the Probe shaft rockers i have work very well with them. I think im going to contact Ed Curtis about heads and Cam.....Mite as well get it all out of the way at once so i get the best of it. I went to Pro Comps site....Those heads flow so horribly. I actually sold my Trickflow twisted wedge heads heads to buy those Ah well live and learn. When i get the purdy new heads in ill be sure to take hoards of pics with shaft rockers mocked up etc.

Im just deciding between 205 or 225. I have the AFR catalog and the 225's seem to have a little more lift across all rpms not just .700 or .800. But im not sure if i need it or not. If i dont need it i rather pay the $1800 than the $2000. Maybe ill find used ones on Ebay.

94gsl5.0 · Mar 19, 2009

I know i am late to this thread, but.... I installed a 410 in my SN-95 with CNC'd Highports and had a tough time finding headers to fit. The taller deck and raised ports made for some issues. I wanted to go the longtube route and actually got some fox BBK 351 swap headers... They did not fit at all. Then, I was turned on to the Anderson/Bassani 1 3/4" shorty big tube headers... Decided to try them out and they fit with some persuasion. Great quality and decent price without the headache and price of custom longtubes.

Just food for thought.

95Vert383AOD · Mar 19, 2009

94gsl5.0 said:
I know i am late to this thread, but.... I installed a 410 in my SN-95 with CNC'd Highports and had a tough time finding headers to fit. The taller deck and raised ports made for some issues. I wanted to go the longtube route and actually got some fox BBK 351 swap headers... They did not fit at all. Then, I was turned on to the Anderson/Bassani 1 3/4" shorty big tube headers... Decided to try them out and they fit with some persuasion. Great quality and decent price without the headache and price of custom longtubes.

Just food for thought.

Well i was thinking of trying the accufab mid length....then fabing pipe to meet my h-pipe

351 Long Tube Headers

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