ti9ere

Hi

I have probably given up on the factory tri carb set up, its being recommended to me that I go 4 barrel.....question is what?

The engine is standard except for an L88 cam, can anyone recommend a 4 barrel intake manifold and carb set up that has been used and is proven as it can be to be a bolt on solution to give the car the best street performance that can be had. Or indeed if anyone has one to sell!

Advice appreciated, many thanks!

Lobzila

Not my area of expertise, but I can offer some advice. I set up my 68 to be an L88 clone. The engine my car came with was a 396 (orginial motor long gone) with a stock cam and it had an edelbrock performer carb on it. I changed it to a 454 with the Edelbrock Performer RPM top end which the cam is close to the L88 specs. Love me some lumpy cam idle! Anyway, the Edelbrock carb would not idle for crap on it due to low vacuum the engine made at idle (7-8") unless I turned the idle up to 1200 rpm. Ended up going with a Holley 800 CFM Double Pumper and put an electric choke on it. The Holley has way more adjustments to make it run better, I put a 3.5 power valve in it and it idles perfect. But, I am sure others will tell you a properly set up Edelbrock will do the same thing.
I always thought the Tri-power was the bomb, why can't your guy get it working? I would ask around on that and get a second opinion.

ddawson

For a stock BBC hood LS6 Clone intake and a QuickFuel SS850.

You still have to take the time to dial it in. I needed to jet down the primary's to 70, one size down on the fuel feed restrictions to get my A/F in line.

suprspooky

I have a Performer RPM for Rectangular Port Heads if you're really giving up. I'd rather help you get it going though. Check your other thread and get me some List Numbers (stamped on airhorns) and the timing info. (what Octane gas as well)

cv67

Call Jeff at AED performance (carbs) he can put one together that will be about perfect out of the box without fooling jets air bleeds etc. Maybe adjust idle speed....awesome after purchase customer service.

suprspooky

PM sent regarding carb vac data

ti9ere

Hi
just checking threads - I didn't see one that confirmed the vac data?
Re the intake, my car does have L71 heads as it should (checked the casting number) so would the manifold you describe be a port and total match? What do you want for it? It would need to get shipped to CT as although I'm in England it can be shipped inside a car that a friend is shipping to the UK.
Can you recommend a carb?

Thanks!
Paul

suprspooky

PM sent

TheSkunkWorks

With that cam I'd recommend nothing smaller than an 850 DP Holley style carb, tho I'd personally tend towards a 900-950 cfm unit from Pro Systems if you've still got ~11:1 compression.
Stock hood, the LS6 intake will be about as good as you can do, but if you're willing to move up to an L88 hood (with full cold air intake setup) I'd go with either an Edelbrock AirGap RPM or a Holley Strip Dominator, depending on whether you prefer a dual or single plane's characteristics. Or, you could just step on up to an EFI such as Holley's Terminator (which is planned to be topping off the Strip Dom intake on my own 427 redux).
Anyway, I wouldn't necessarily give up on the Tripower setup yet. I've run them on mild to fairly wild mills with very good results. YMMV

ti9ere

Hi thanks
I've seen an LS6 intake, will probably do that. Do you know how much of a base recess is needed with a 2" air cleaner - the stock 69 part looks like about 3"!! Can't find anything like that?
Most UK tuners I spoke to are saying go 750cfm...
But i'm through with the tri set up unless anyone can point me at someone who is the worlds expert and knows them inside and out. Holley even can't help me and I've got 30 years experience so I'm pretty sure I'm not missing anything obvious.

Thanks for coming back to me, Paul

ddawson

Under a stock hood using an LS6 intake and a Quickfuel 830DP

I have this heat-shield
https://www.summitracing.com/parts/o...9835/overview/

And a 4 hole 1/2 Spacer with room to spare before the stock air cleaner hits the hood.

GOSFAST

Hi "d", you my want to consider some longer R/A studs in those Edelbrocks now, before they become a repair issue?? Could get ugly down the road later.

Just a tip for what it's worth.

On a side note that's a very nice looking/clean build!

Thanks, Gary in N.Y.

P.S. The set-screws in the poly-locks should be closer to the tops, there isn't enough of the poly-locks catching the stud threads?

wzschirnt

Hi,

You have probably already made your decision, but... what is the problem with the tri-power setup? I've had a 67 and a 68 with that setup on it and they ran crazy good! 4th gear and 35mph, stand on it and go to 150mph with no shifting!

People here are telling you to put a Holley 4-barrel carb on it. The tri-power carbs are Holley carbs. Just saying. Besides, 3 deuces look COOL!!

But, anyway, good luck.

walt z.

Jebbysan

I agree......nothing quite like a Tri-Power and they do very well for power apples to apples.....
I think you need to just step back and assess the situation. Once you get the end carbs to open.....all they have to do is meter fuel and you are in business.......
My Tri-Power worked excellent and it was the way GM built it minus some cleaning and gaskets.......
Keep trying.....

Jebby

crf311

I used a Holley 850 DP, on my 462 with a little more compression , roller cam and Brodix alum. Heads. Feeding the Th400 transl

TheSkunkWorks

In case it might help the OP or any other viewers, at the risk of having vastly oversimplified things and assuming there exist no major issues in need of repair or rebuilding, here are the very basics...

1) Disconnect the 2nds, confirming they are fully closed.
2) Tune the Primary as you would any Holley 2 bbl.
3) Only then reconnect the 2nds, making certain they are fully closed by the linkage at idle, but only just. (This can be a bit fiddly, but is definitely worth being as precise as possible here).
4) Operate vehicle under load (sitting static in the garage doesn't count) noting whether or not the engine bogs under WOT.
5) If it bogs, install the next stiffest pair of 2nd vac springs (always use the same in both ends) and repeat #4, else skip to #6.
6) If it doesn't bog, install the next weakest pair of 2nd vac springs until it bogs and then reinstall the next stiffest pair until bog is eliminated.
7) Happy motoring!

Notes:
You'll need two fresh (springs can die) Holley Vacuum Secondary Spring Kits, #20-13.
Do NOT attempt to reinvent or bodge up the linkage with non-standard bits. IMOE this is the biggest single mistake one can make when dealing with this setup.

Hope that's worth $.02 to someone.

TheSkunkWorks

FWIW, while I'm no expert on the matter, my experience with genuinely Hi-perf, rectangle-port 427 BBCs is that they tend to respond very well to larger than otherwise customarily prescribed carburetion. Thing is, a well cammed, healthy breathing 427 BBC is capable of generating as much of a vacuum drop beneath the throttle body as many of its longer stroke, larger displacement siblings, And, the higher the vacuum drop, the harder the engine must work to fill the cylinders, negatively impacting volumetric efficiency (VE%). So CID shouldn't be the overriding consideration as to CFM here.
Case in point from the BTDT files: I've personally run as large as a 1050 CFM Holley Dominator (progressive 2nds) on a rect-port 427 on the street with great result. Only downside was lacking MPG 'cause I never could keep my heavy right foot out of it, but otherwise it was grin city!
Bottom line: I'd caution against overly conservative advice or maths wind up having you leave some serious go fast potential on the table. That's my story, and I'm sticking with it.

7T1vette

I'll be more than happy to take those nasty, troublesome tri-power carbs when you ditch them.

You can put whatever 4-bbl carb you want on the car, but I would recommend that you put a well set-up/tuned Q-jet on it. It is a much better carb than any other you can buy (for all-around operation, performance and economy). But, a nice Holley, Quick-Fuel, etc. would be suitable, as well.

I would also recommend that you NOT get an Edelbrock carb that is just a remake of the old Carter AFB carb. It is a rather poor design and performance carb. Many folks buy them because they are less expensive and readily available.

7t9l82

A 750 carb is too small .I agree a quick fuel or holley. The chevy 3x2 setup is nearly identical to what chrysler used an should work well if set up properly. Skunk works pointed you in the right direction. Rebuilding them is pretty easy.

7T1vette

Doubt that 750 cfm is too small for a stock L-71. But, do what you must.