WTH is wrong with this combo?

[351Coupe]

I kind of don't really want to post this, but I'm up for some suggestions. The new dyno day thread got me thinking about my results from the last one. This is a mild setup but I thought it would make more than it did.

My 68 Coupe:
69 351w
TFS TW 170 heads, 1.6 RR
Comp XE284 cam 284/296 adv, 242/246 @.050, with .541/.543 lift
Performer RPM intake with Holley 780 carb.
T5 with 3.25 gears. Makes no power past 5500.

Last time it put out 288 rwhp, 342 rwtq. I was told on the last dyno day that the vacuum secondaries were only opening a little more than halfway, and I have put a lighter secondary spring in since then. It runs noticeably better now, but I still feel like it should run better.

It does have low compression pistons (not sure how many cc's the dish is, but they are huge dishes, I'm thinking mid 8.?:1), so I know that hurts it.

I don't know, just looking for advice. I have most of a wet kit. Maybe I should spray the fuck out of it? I know it needs gears too, lol!


I'm about to try something different for my 351w fox, some 11:1 pistons, Roush 200 heads, bigger cam, see how that works. I may end up with a similar combo for my 68 depending on how it works. I would like to maximize what I have for now in this car. Should I expect much more the 300/350 to the wheels? It runs okay in my sub 3000 pound car, but I still can't hang with a lot of cars from way out here in the sticks (Sherman) lol!

[5.0Thunder]

Might as well build a small turbo kit for it. put 6-7lbs on it and drive it till it gives up. you could handle some spray with that cam too.

[351Coupe]

Might as well build a small turbo kit for it. put 6-7lbs on it and drive it till it gives up. you could handle some spray with that cam too.

I had thought about that. I have another 69 351w on a stand with forged 8.5:1 pistons that would be perfect for boost. The heads I have are the O-ringed ones too.

[5.0Thunder]

well just boost this one and transfer the kit when it gives up. :P

[351Coupe]

I'm just wondering if money spent on boosting the current combo wouldn't be more effective towards something else.

By the time I buy the turbo/blower, carb enclosure (or blow through carb, $$$$$) piping, headers, all the fab work. It just seems like for that kind of coin I could maybe buy a better set of pistons, bigger heads, etc.

Hell I don't know, I'm just tired of being slow.

[Big A]

Though I don't disagree with boost, that will only mask the underlying issue(s), other than the lower compression. I personally would want to get it running 100% before adding a turbo kit, of for no other reason than maximizing the investment in the kit.

My first thought would be to make absolutely sure that the carb and fuel pressure are tuned properly, check the plugs/gap, and ignition.

Carbs are fairly simple, but "easy" to get right.

[Pro88LX]

Sounds like the compression is costing you a lot of power to me......well not a LOT but definitely a good amount.

[Big A]

I'm just wondering if money spent on boosting the current combo wouldn't be more effective towards something else.

By the time I buy the turbo/blower, carb enclosure (or blow through carb, $$$$$) piping, headers, all the fab work. It just seems like for that kind of coin I could maybe buy a better set of pistons, bigger heads, etc.

Hell I don't know, I'm just tired of being slow.

You could build the motor, but boosting your current combo running properly will make more power, and be more streetable.

[Pro88LX]

You could build the motor, but boosting your current combo running properly will make more power, and be more streetable.

gotta love them turbo cars!

[turbos66coupe]

That cam , heads , and intake combo should be good street combo. I think part of the problem is that cam has to much overlap for a low compression engine. I don't know the timing events but with a cam with a healthy amount of overlap and a low static compression that is not a good match.

[351Coupe]

You know what, I think I'm going to get up in the morning and pull that motor out, and pull the 302 out of my fox, and put this 351w in my fox.

I will buy the new higher compression pistons for my other windsor with Roush 200 heads and put it together and drop in my 68.

I have several reasons for this. I think my 68 should always be the quicker car with the better motor. Also my 68's current 351w will still run okay in the fox ( I have all the fox EFI swap parts already, 30# injectors, Trickflow upper/lower, all other swap stuff). And that will also free up my Foxbody's 302 to put in my 63 Fairlane.

Fuck it, I'm pretty sure that's what I'm going to do.

So what about 351w with TW 170's, XE284 cam, with EFI, Trickflow upper/lower, 70mm tb, 30# injectors, full bolt ons in my fox? It will still go back to the dyno day, just with efi in my fox.

Then the 68 will have a 351w, Roush 200's, undecided cam, 11:1 pistons, probably a single plane intake at that point. It should run a lot better.

[351Coupe]

Sorry, double post.

[Pro88LX]

You know what, I think I'm going to get up in the morning and pull that motor out, and pull the 302 out of my fox, and put this 351w in my fox.

I will buy the new higher compression pistons for my other windsor with Roush 200 heads and put it together and drop in my 68.

I have several reasons for this. I think my 68 should always be the quicker car with the better motor. Also my 68's current 351w will still run okay in the fox ( I have all the fox EFI swap parts already, 30# injectors, Trickflow upper/lower, all other swap stuff). And that will also free up my Foxbody's 302 to put in my 63 Fairlane.

Fuck it, I'm pretty sure that's what I'm going to do.

So what about 351w with TW 170's, XE284 cam, with EFI, Trickflow upper/lower, 70mm tb, 30# injectors, full bolt ons in my fox? It will still go back to the dyno day, just with efi in my fox.

Sounds like a solid plan to me.

[Big A]

Yep, solid plan, but I still think that the weaker motor will run stronger than it currently does, with little more invested.

Do a basic tune-up, check your ignition system and timing, and a solid tune should have it running at max capacity.

I'd do the same on the new 351 as well, with having the carb checked out and tuned. I still think that may be part of your current problem, which would affect the new motor as well.

[Chas_svo]

That cam , heads , and intake combo should be good street combo. I think part of the problem is that cam has to much overlap for a low compression engine. I don't know the timing events but with a cam with a healthy amount of overlap and a low static compression that is not a good match.

This is good info. If you do put itbin your fox, you will still have some what of of mismatched combo with that much cam and not having 10+ compression. Review the cam details, it should say this. Also if you do turbo this combo, the turbonwill overcome the low compression, but it will not be as great as it would be with 8.5 or 9:1 compression and a turbo cam.

I know it's not what you want to hear. Good luck.