Posted By: 69val6
G Van header info. - October 17th 2018 2:31 am
Hi, I'm new to this site and just purchased an 84 Chevy G30 chassis 22' Motorhome with a 350 v8 and turbo 400 trans. The previous owner decided he needed to install a new timing chain at 69,000 miles and installed it wrong. It bent all 8 intake valves so its in need of a valve job. It had the HD 350 in it so it had the 160hp engine which had the tiny 1.720" intake valve and sodium filled exhaust valves. I'm looking to up the perfomance of this engine because I will be pulling a car trailer behind it. I'm not trying to make a race motor, just a high torque engine that can go down the interstate at 70 mph without issues(4.10 rear gears).
I've purchased a different set of heads that should make more power (882 casting). I'm having them rebuilt now. I'm going to install an RV cam with 204/214 duration @.050" and .420"/.440" lift. I also have an edelbrock performer intake to install. My last performance upgrade is a set of headers and exhaust. I've searched this site and found that there are ones made specifically for this application. I've also read that 71-81 camaro headers fit right in. Ripper has posted that he's used these so I wanted to ask him what brand he used? I found a set of Thorley Tri-Y camaro headers locally pretty cheap but I don't want to buy them to find out that Ripper used a different brand. If he's on this site still please let me know. If anyone else has used the camaro headers and has pics they could post it would be great too.
One note on the exhaust on this RV is that it has the extra large fuel tank so the exhaust can only exit on the drivers side as there's no room behind the axle on the passenger side. It had factory dual tail pipes(2" OD) and they're dirt cheap new so I'll probably put a y-pipe in the exhaust and run 2.5" pipes from the headers to the y-pipe then a 3" pipe to the muffler then to the dual 2" tail pipes. It should be good for what I'm doing.
Thanks in advance for your help.
Posted By: frscke1
Re: G Van header info. - October 17th 2018 3:06 am
Welcome to the site Val ....
Posted By: CatFish
Re: G Van header info. - October 17th 2018 3:50 am
He hasn't been on here in a year but you could still drop Ripper a PM about the headers or reachout below.
His twitter link: https://twitter.com/customsbyripper
Or google customsbyripper
Posted By: shaggy
Re: G Van header info. - October 17th 2018 7:41 am
I have a 1979 G30 class B RV/campervan. I fitted Hedman headers and sidepipes. Hedman and other companies make G van specific ones and I'd advise you to get them as it's a tight fit. I also needed to switch to shorty plugs and heat socks on the plugs cos the headers were so close to them.
I got the headman headers to fit. I also painted them with header paint before wraping them with header wrap. It’s a tight fit for sure.
Posted By: 69val6
Re: G Van header info. - October 27th 2018 1:21 am
So after reviewing all the options, I've decided to stick with cast iron manifolds. I like the idea of more power from the headers but the headaches they create, especially having to run shorty plugs and cooking the fuel and brake lines, plus the extra cost just made it more than I wanted to deal with. So my plan b is to run later model g-van manifolds and y-pipe. I checked in the Walker exhaust e-catalog and found that 91-96 G-vans and savannah vans all use the same exhaust from the manifolds to the muffler. The advantage they have is that they have a 3" diameter pipe after the y. The original exhaust is only 2-1/2" dia. after the y. The 3" single pipe should be able to handle 300 hp with no problems. I plan on adding a hi-flow muffler with 3" ID x dual 2" ID outlets then using the original dual 2" OD exhaust pipes. It should flow well enough for my performance needs and not be too loud. I stopped at the junkyard today and found a 93 G2500 that had good manifolds and y-pipe(my old manifolds were cracked). The yard had already cut off the cat converter(which I don't need on my 10,500 lb. gvw motorhome) . None of the bolts were seized so the manifolds and y-pipe came off easily. I also have an 02 bung built into the LH manifold so I can add a wideband O2 easily without drilling or welding. So far I have a total of $30 invested in good used manifolds and y-pipe. All I need now is some straight 3" exhaust, the muffler and a pair of tailpipes. I should have the exhaust system completed for less than $200. Thanks for everyones input.
Posted By: Don_F
Re: G Van header info. - October 27th 2018 3:43 am
The factory y pipe is awful for power. You are not going to get anywhere close to the full potential of your engine if you run it though that. TBIchips is a running joke on a few forums for their tunes, but this is one place they got it right. Also check your manifolds inside. I removed one today and the top part of the port had a huge iron glob in it. I can mill it out, but dang! Instant EGR.
I have a G30 350 and sometimes pull a 5000 lb trailer behind it thats similar in weight to a car trailer and medium car. I can't imagine a 350 that will power a 22 foot "barn door" motorhome and pull a loaded car trailer too. That is Big Block time. My mom had a 460 24' RV based on a E350 it was a dog with 110 more cubic inches.
Posted By: 69val6
Re: G Van header info. - October 27th 2018 8:54 pm
I've heard that before about the restriction at the y-pipe. I know that to be true on the c/k series trucks(I have a 94 GMC C1500). The design of the y-pipe on that truck looks like a lot worse design than the g-series y-pipe. I could just cut out the y and replace it with one of the high flowing aftermarket ones. I will look into that. I will look at the y-pipe again on the savannah/express vans to see what they look like. The y-pipe is on the correct side at least. I looked at the exhaust manifolds on a 96-up vortec Savannah/Express van while I was at the junkyard. They have what appear to be the exact same exhaust manifolds as what I picked up. I looked inside the newer manifolds and they have a lot bigger ports inside and the outlet is much bigger inside than my original manifolds. I've heard the stock late model manifolds are good up to 300 hp.
Posted By: Don_F
Re: G Van header info. - October 27th 2018 11:19 pm
Not trying to give you a hard time, just I know how disappointing it is to have a project fail because of a plan with holes in it. It's your money and time, just trying to save you a problem.
It's not the pipe size on the oem y pipe it the way the thing is joined and the crunched bends. You're getting a lot of bad info from somewhere... The factory 5.7 vortec engine is factory rated at 260 hp crank thats 210 to 190 at the rear wheels on a good day. A 350 is just not going to pull the 22 foot motorhome and a loaded car trailer with any sort of satisfaction unless you never hit any hill, not even little ones. There is a reason people with half the weight your pulling are still asking how to upgrade their 350 engine that is much better right from the factory than your current combo plan. I have 210 HP 350 in a 4000 lbs G30 and pulling 5-6000 lbs .. most of the time on steep hills I am in 2nd 40 -45, sometimes it's 30mph in first. Yes I am doing what you are trying to do weight wise without the 22' rv and its still not real good. In the middle of a lot of mods to make it a little better, still not a big block or diesel. That's what you need to have a reasonable chance of pulling your plan off.
Your cam choice is leaving a lot on the table too, as well as the 882 castings. Not duration, but its a old tech cheap grind with lazy ramps. I would at least look for a roller compatible 350 block and a 3.75 cast scat crank along with vortec style heads. Even then that engine will be very marginal with a car and trailer in tow. No way is it going 70 on any sort of hill pulling a car trailer.
Again just trying to warn you before you go too far. Its entirely up to you.
Posted By: 69val6
Re: G Van header info. - October 28th 2018 2:03 am
Don_F, thanks for your input. I have looked at the TBIchips website. I believe they got 25 rear wheel HP on a c/k tbi truck just by cutting out the OE y and replacing with an aftermarket. I wasn't sure if the same applied to the g-van tbi y-pipe. Luckily I don't have any major hills on the interstates near me. The worst interstate hills I go on are on I44 between St. Louis and Joplin Mo. in the ozarks. My 94 GMC C1500 gets down into 2nd gear(4L60E trans) on a couple of them at 50 mph and barely holds 3rd gear on several others pulling my trailer with car on it. That is with a completely stock TBI 350 putting out a whopping 190hp. I do realize the motorhome has the aerodynamics of a brick and weighs at least a ton more than my pickup. I picked up a set of either brand new or freshly re-manned vortec 906 casting heads while I was at the junkyard(they haven't been fired yet, junkyard score of the year). I was debating whether I wanted to put those on the motorhome or on my pickup. I already have an edelbrock performer rpm intake for them. That may not be the best suited intake for either one I know so if its a dud, let me know and I can probably trade it for a regular performer intake. It sounds like the vortec heads would be better off on the motorhome, I should look for another set and put them on both.