Pre 94 351

[preppypyro]

I have been researching for awhile and thought I would just ask my own specific questions to what I want to know.

I have been searching for a 94 and up 351 for my project as some of you guys on here know. Im having trouble finding one, and have come across two pre 94's. Now I would love to try the roller out, but its looking like it may not happen.

So what is the big difference anyways? Can a person do a junkyard swap for the roller components from a 302? My goal in the end would be have around 300 horse out of the engine, and I would like to do it as cheap as possible, without getting a set of heads, but I understand heads I might have to get. So is it worth it for me to leave the pre 94 351's alone and wait for a roller one or not?

[HemiEater]

you don't need a roller block for 300hp, good cam, intake, and exhaust will get you there

[HemiEater]

you could swap the parts ,all but the cam. you would need a small base circle cam $$$$. the lifters are to tall for the short flat tappet lifter bores. the SBC cam allows the lifters to ride lower in the bores.

I would get some H-link roller lifters and run any roller cam out there instead of the few sbc cams they offer...or just run some solids, but thats just me...

[51dueller]

The reduced base circle cams aren't recommended as they flex under load. They also can create bad valvetrain harmonics at high rpm. Some guys have found they have cracked their billet timing gears running them.

[preppypyro]

So I guess is there any real advantage then for going roller? I gotta admit I dont really know what the advantage would be.

In the end I want a tough engine too. There would be nothing worse then lining my truck up against some young punk with a 51 merc dually with a hopped up 302 in it, and having the engine go boom!

I guess if 300ish horse isnt hard to achieve maybe I should set the bar a wee tad higher.

[Conanski]

The big advantage of the roller cam is the reduction in friction, but that may only get you 5-10 more HP overall on any particular combo, so it's not hugh. The heads are the bottleneck on these motors, and on the 5.8 in particular, without a better set of heads you won't get much beyond 300hp at the crank. Both Trickflow and AFR advertise 350-400hp with thier heads on a 351, so that should give you an idea of the potential. But you don't have to spend that kind of money to break 300hp, there are other options and though they don't flow as well they can be improved with porting. GT40's would make a good starting point and can be found pretty cheap, World Products iron heads are another option(if you found a used set)and have more potential. It's all too easy to spend a lot of money improving a set of heads though, so keep in mind that you can buy brand new Dart Iron Eagles for about $1000 a pair, and these flow near what the AFR and Trickflow heads do.

[bfletcher101]

I believe another advantage of the roller set up is increased fuel mileage. I had a 67 mustang with a 289 with a roller cam in it and I was able to get around 18 mpg. Although I did have to replace a distributor gear, but I think that problem has been solved now.

[preppypyro]

In the end I dont think the truck will be that hot on fuel, so the improved economy wouldnt be needed, although cool.

If it really is a matter of 5-10 hp then Im not sure if it is worth waiting around for.

I know the stock heads are really restrictive, and that might end up being a modification I end up doing yet. I have kinda been keeping my eyes open for a set of gt40 heads, but I have only found 5 liter ones, not 5.8.

Ive also researched alot on here and most guys say to port the heads out and whatnot is a 600ish dollar touch. If it did come to that I would spend a grand and get a good set of heads, but I would really like to do things cheap.

I think its neat when a guy can do those real life budget builds, and have always wanted to do one up.

[Chuck_Sloggett]

https://www.patriot-performance.com/...1&bestseller=Y

I saw these advertised in Hot Rod Magazine - anybody heard anything about them? -- Chuck

[Conanski]

Originally Posted by preppypyro

I have kinda been keeping my eyes open for a set of gt40 heads, but I have only found 5 liter ones, not 5.8.

So grab them!! All you got to do is drill out the bolt holes to 1/2", any monkey with a drill press can do that.. that's exactly what this monkey did.

Originally Posted by preppypyro

Ive also researched alot on here and most guys say to port the heads out and whatnot is a 600ish dollar touch. If it did come to that I would spend a grand and get a good set of heads, but I would really like to do things cheap.

A couple posts here recently have shown that even a porting novice can make significant improvements in the flow of these heads.. as long as you don't get too carried away. There are several here that have done a fair bit of this type work and I'm sure would offer some pointers, all you need is a dremmel or die grinder and a lot of spare time.

[preppypyro]

Well the spare time i got right now lol. I would seriously wonder about doing my own heads. I feel comfortable with alot of things, but Im just not 100 percent sure about the porting. I guess ya never know till ya try!

Thanks for the tip on the heads, I knew some parts were interchangeable, but didnt know if the heads would work or not.

Say a guy was to slap a set of these heads on, would porting be necessary then? Or would they provide enough flow?

[Conanski]

Originally Posted by preppypyro

Well the spare time i got right now lol. I would seriously wonder about doing my own heads. I feel comfortable with alot of things, but Im just not 100 percent sure about the porting. I guess ya never know till ya try!

I'ts no different than anything else, there are some basic rules you got to follow. Intake airflow follows the floor of the port, exhaust follows the roof.. primarily. A glassy smooth finish on the intake port is not ideal, some texture here actually inproves airflow by detatching the air column from the port wall. Gasket matching is good only if the port dimensions increase or decrease smoothly from either side of the junction. What you don't want to do is create a wide section in an otherwise smoothly tapered runner, this will kill velocity, produce eddie currents and ultimately kill airflow.

Originally Posted by preppypyro

Say a guy was to slap a set of these heads on, would porting be necessary then? Or would they provide enough flow?

Depends upon your definition of "enough". They will put the motor over 300hp with the right cam, but a set of AFR185's would put it over 400hp with the same cam.

[preppypyro]

Hmm very interesting. Just out of curiosity Paul, with your setup, what about are you running for hp and torque??

[Conanski]

Originally Posted by preppypyro

Hmm very interesting. Just out of curiosity Paul, with your setup, what about are you running for hp and torque??

I don't have a lot of hard numbers to show you but what I do will demonstrate how restrictive these heads are on the bigger Windor. Data logs with the Tweecer have shown that the injectors are running at 75% duty cycle at only 4000rpm. The heads I have are a bad design for making HP because the intake valve is badly shrowded, so even with the work I did to improve this I doubt these heads flow any better than a set of E7's... I didn't touch the intake ports on these heads at all. The E7's typically make about 275hp at 6000rpm on the 5.0, and that translates to about 90% dutycycle on the 19lbers. I think it's safe to assume I'll hit that flow rate at 1000rpm less.

TQ is very strong however, dyno software predicts about 350-375ft/lbs and it's believable, this motor has serious low end grunt. The stock truck intake will help TQ production but it will also become a HP bottleneck quickly too, it has smaller volume runners than the 5.0 truck intake if you can believe it.