cdrod

I have a 375cid stroker small block, built on an earlier Mark Remmel combination, before the stroker cranks were available. My question is about the exhaust system. I'm running Hooker 1-5/8" headers and a 2-1/2" Pypes stainless exhaust kit, but the tail pipes don't fit very well. They don't align with the bumper cutouts and the bends are different from the stock routing. I'm running 285-40-R18s for rear tires and the tail pipes are very close to rubbing on the rear tires. I have tried to purchase factory tail pipes from Gardner and Inline Tube, but they will only sell a complete system, not just the tail pipes. I have a chance to buy the Inline Tube exhaust kit at a good price with 2" tail pipes, but would I be leaving too much performance on the table by reducing my 2-1/2" head pipes down to 2" at the tail pipes?

Looking for some good advice before making this purchase. Thanks!

Rodney

68post

Check out the different varieties of flowmaster chevelle tailpipes to see if those work, they have plenty in 2-1/2".
I wouldn't downsize to 2.0" unless it was a dead stock smallblock (350ci or less), with iron manifolds. I've been building my own exhaust systems for more than 40 yrs, but I do buy pre-made tailpipes.

Fun71

I thought the pipe diameter behind the mufflers was not as critical due to the lower temperature of the exhaust gases and the restriction of the mufflers.

68post

This is true, but you don't want to take it too far of course.

bccan

As usual, 6 of 1 and half dozen of another on the Flowmaster Tail Pipes. Some have had nice results, my experience wasn’t as ideal, but they were usable as a starting point. Originally on these 2 cars I had better fit w/ Pypes tail pipes. Glad I could the water muddy for ya!

https://classicoldsmobile.com/forums...otches-141690/

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cdrod

Kenneth:
I was thinking the same thing and comfortable with a 1/4" reduction, but going from 2-1/2" down to 2" seemed like it could be too much.

Here's some pics.

Rodney


The RH tail pipe has an weird bend that seems to be un-needed. This has it kicking up and to the right side. The LH tail pipe has the same weird bend but not as much angle, it fits better.


LH side less than 1/4" clearance


RH side the tail pipe is touching the tire.

cdrod

Do muffler shops still bend their own pipes, if so, could they make me some 2-1/4" pipes? is it possible to reshape these tail pipes for better clearance to the tires and straighten out the un-needed bends at the bumper exit points?

Rodney

olds 307 and 403

So do, I was not thrilled with the tail pipes the local shop bent.

acavagnaro

Are you sure you can't adjust that out? I'd recommend loosening all of the joints and fiddling with it. I'm thinking you can push/pull things around to get the fitment better than what you're showing. That kind of thing usually happens when you tighten things down too early and the muffler exit doesn't allow for enough 'massaging' of the tailpipes. Twisting that right tailpipe would probably fix the misalignment at the bumper, no?
FWIW, I have the Flowmaster 409 stainless kit on my '69 442 and it fits like a glove - all the way to the trumpets.

On a different topic, what are your thoughts on that engine? I have a 350 in a '69 Cutlass and am planning to go the Remmel stroker route when it's time. I suspect I can make better numbers than the big block in the 442.

cdrod

I started my project back in 2013. I talked with Mark about a roller cam for a stock-ish .030 over bore, street cruiser. Then, in typical hotrod/car fashion I stumbled upon a smokin' package deal on some brand new ProComp heads, Lunati flat tappet cam & lifters & an Edelbrock carb. I sold off the cam and carb, kept the heads, and found out they had been prep'd by Bernhard Mondello and milled for a small block install (bonus). So I talked with Mark about my good fortune and he suggested going the stroker route. To do this, I had the crank offset ground to reduce the rod journals to 2" dia, this will fit early Chevy 327 rods, Mark recommended some Chevy 400 pistons from ICON to complete the rotating package. This was a few years before he started selling the stroker cranks, if i had to do it again, I would just buy one of his stroker cranks for even more displacement. I think his stroker cranks get you in 434cid range.

I don't have any street miles on the car yet (getting very close though), so I can't comment on the drivability of this combination; but it's very healthy with a nice throaty rumble but not too lopey. I had a TH200-r4 overdrive tranny from an '85 Buick GN built to handle 400HP and installed an Eaton Truetrac posi with a 3.42 rear gear. The TH200 has a first gear ratio of 2.74, combined with the 3.42 rear gear it is equivalent to TH400 with 3.73 rear gear. It should be a fun street package and be able to drop the RPMs low enough to get decent highway MPG.

Rodney

cdrod

I need to play with the tail pipe fitment, but I know I will need to straighten out the pipes at the bumper cutouts because they both have an unnecessary "hook" that pushes the pipes closer to the tires when aligning to the bumper cutouts. I'm having hernia surgery on Friday so it sill be a little while before I can crawl under the car and wrestle with the exhaust pipes.

bccan

I’ll soon be playing this game on a 69 el Camino that I just bought. Pypes 2.5” X pipe, Dynomax, but then comes the tail pipes. I want them like a 67 Chevelle SS but I can see the bends on the pre made pipes won’t nail it, Dynomax makes what I can see would be dead on, but only comes in 3”. So, will likely be spending considerably more $$$ to have custom tailpipes made. Can it ever be easy?

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Mr Nick

I have the same size tires and while I have more space between my tires and the tail pipes than you, there are witness marks from the tires touching. My plan was to use a hole saw bit and cut out a 2" hole from that area, flip the cut section of pipe around and weld it back in place so it's concave. Then weld up the center hole from the bit. Grind the welds and call it good. This way I'm only "restricting" a small section of the tail pipe, and not the whole thing.