any thoughts on a 351 Windsor engine?

[KenB]

I'm looking at a GT40 with a 351 Windsor engine in it, 11.2 compression and Holley carb. It knocks unless premium fuel is used. Anyone have any thoughts on the engine?? Thanks....

 

[DaveM]

Many GT40's have 351W based engines. Most of the Superformance ones use Roush, K.Craft, etc. stroker engines with a 351W block. How much of this engine is stock 351? I don't recognize the Holley carb. Usually the float bowls are front and rear. The 11.2-1 c.r. might concern me a bit. That's definitely a stretch for 91 octane fuel and probably even 92 octane. 10:5-1 is generally the limit for premium gas with aluminum heads.

 

[KenB]

I also thought the c.r. seemed a bit high. It supposedly dynoed at 480hp and has the Porsche g50 5 speed transaxle.

 

[Rick Muck- Mark IV]

Many GT40's have 351W based engines. Most of the Superformance ones use Roush, K.Craft, etc. stroker engines with a 351W block. How much of this engine is stock 351? I don't recognize the Holley carb. Usually the float bowls are front and rear. The 11.2-1 c.r. might concern me a bit. That's definitely a stretch for 91 octane fuel and probably even 92 octane. 10:5-1 is generally the limit for premium gas with aluminum heads.

Dave,

Carb looks like an Edelbrock (Carter AFB) to me. Would you run regular gas in a GT40? It would never occur to me.......

 

[Rod]

110 octane unleaded race gas from the pump is $6.39/gallon up here in NorCal.

And Sunoco 110 leaded in 5-gallon cans is about $9/gallon. 112 a bit more.

 

[Tom]

My 351W was stroked to 392 and came from Ford Racing--crate engine. I put 4 Webers on it. It has 9.5:1 compression ratio. You might try to find a special head gasket (thicker) to increase volume of the combustion chamber enough to reduce to 10.5:1. Good Luck!

 

[Jimmy P]

Now that the issue has been raised....is there any problem in running 100+ octane in an engine? I have a 347 stroker with webers. I use 93 Octane and it runs fine....what can I expect if I run a much higher octane petrol in the car. What about blending 100+ octane with 93. Any issues to be concerned with? Many thanks for your thoughts. Ooops sorry for the thread drift. Please move as required.

 

[Jac Mac]

My 351W was stroked to 392 and came from Ford Racing--crate engine. I put 4 Webers on it. It has 9.5:1 compression ratio. You might try to find a special head gasket (thicker) to increase volume of the combustion chamber enough to reduce to 10.5:1. Good Luck!

Using a thicker head gasket is NOT the way to reduce compression ratios. Either increase the combustion chamber size of the cyl heads or fit pistons with less dome [ flat tops ] or negative dome ( dish or bowl ) depending on what is currently fitted..

Fitting the thicker head gasket increases the squish distance @ TDC [Piston to head at closest points ] this will actually degrade the combustion process further .

 

[Mike Huddart]

It might stand more chance if they get rid of that pathetic air cleaner and bolt the carb on the right way 'round

I mean, if they can't even get the name of the carb right, it's a Carter, do you really trust them to give you the correct compression ratio.

Mike

 

[Kevin Box]

KenB

11.2 is too High for normal road use in my view
If the price is right and you like the car I woud factor in doing an engine disassembly to get rid of some of the compression.
You have the following options all of which require a tear down

1 Strip and machine a pocket in the piston to match the Cylinder Head
2 Strip and enlarge the Combustion chambers
3 Change the pistons for ones with dishes
4 Change the heads for ones with bigger chamber

IMHO #1 is the best option - may also require balance check

A word of advice on fuel - Dont run CRAP fuel in an engine over 9.5:1.
In the end Fuel is cheap comapred to a melted set of pistons !!
If you get stuck in the middle of nowhere regularly carry some octane boost in your car.

regards

KevinB :shocked:

 

[KenB]

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <woNotOptimizeForBrowser/> </w:WordDocument> </xml><![endif]-->Ok, so here's the current situation on the car I'm looking at purchasing;

The 351 on this GT40 is 11.25:1 compression. The current owner told me the motor was built by a quality shop that's been in business for 50 years and his car runs fine on 93 octane, though he has a friend that put the same engine from the same shop into a Shelby Cobra and it "knocks and pings like crazy".

I'm planning to drive the car a couple of times a week and put 1500 miles on it year, so I'm thinking I don't want to mess around with finding and adding racing fuel, because and I live in Southern California and 91 octane is about the best I can conveniently obtain for it.

To fix the situation, I was thinking of taking it up a notch and solving the CR problem at the same time, by turning the 351 Windsor into a 427! Can you please let me know what you think it would take to in terms of feasibility, procedure and price to do this.
Thanks for your input.........

 

[Jac Mac]

Why trash what is currently a complete running engine, sell it complete as it now stands & do your 427w buildup from scratch with all the right bits to suit your situation with regard to fuel available & intended use... that way you wont be tempted to compromise by trying to re-use any of the existing bits or have a garage half full of discarded parts that nobody wants..

 

[Howard Jones]

Jac, you beat me by a hour. Sell it as is and start over. A 351 stroked another 50-70 inches at about 9.5 to 10 with decent alum heads, running a nice streetcar friendly hyd roller cam will yield about 1.1-1.2ish HP per inch on 91 octane gas. A 408 windsor should be right at 425-450hp. Perfect for a nice strong 6000 rpm street motor that will last the life of the car.

 

[Tim Kay]

KenB,
I've been down this road and you can't get much better advice than Jac Mac and Howard have given. Take it.

 

[Seymour Snerd]

I've been down this road and you can't get much better advice than Jac Mac and Howard have given. Take it.

I trust you guys implicitly, but I'm puzzled by this response and so want to be educated. Suppose your end target is what Howard says "A 351 stroked another 50-70 inches at about 9.5 to 10 with decent alum heads, running a nice streetcar friendly hyd roller cam...". If Ken finds a local reputable engine builder, hands him the engine as-is and says "turn this into that, replacing anything that looks suspicious", why is that not the most direct and least-cost route? Maybe there's just something about the economics of crate engines I don't get.

My engine-building education aside, I see the KC or Ford Racing will supply something even more built than the above for about $10K, and Southern Automotive, who built my FE, have a 450 hp 408 for $7,500. What do you suppose Ken's engine as-is is worth?

 

[Jac Mac]

I'm looking at a GT40 with a 351 Windsor engine in it, 11.2 compression and Holley carb. It knocks unless premium fuel is used. Anyone have any thoughts on the engine?? Thanks....

Alan, I based my advice largely on Kens first post above: The car obviously already has compression ratio issues & been operated in this condition for some time, this may or may not have already be causing damage to the motor- gasket, piston, ring, bearings- from being operated with the 'knocking' problem, which we all know is a precursor to detonation etc, add to that we could presume that the block might also have been bored oversize in its current form & have wear, so if he was to use it as a basis for his 'new motor' this might compromise that new build which after all is going to be with a longer stroke & as such the rings would likely have to 'climb' over the existing wear step @ both TDC & BDC as the pistons for his 'stroker' kit will likely have a higher top ring position.

Now as aside, you do realise that by asking for this clarification that you have probably made it much harder for Ken to find a buyer on this forum for the existing motor, which of course might be a perfectly fine motor & have nothing wrong with it other than the compression ratio, just like your own car only needs a T44 to make it right, right!

 

[Seymour Snerd]

Now as aside, you do realise that by asking for this clarification that you have probably made it much harder for Ken to find a buyer on this forum for the existing motor, which of course might be a perfectly fine motor & have nothing wrong with it other than the compression ratio, just like your own car only needs a T44 to make it right, right!

Damn. Now where's my copy of "The Art of War"?

I had one other thought about Ken's engine: in an area of 91 octane gas he could just throw in some octane booster, right? I've never used the stuff so don't know how many points you can get with it.

 

[Jack]

Alan, simply do a google search for: Sun-Tzu

 

[Jac Mac]

Damn. Now where's my copy of "The Art of War"?
You probably loaned it to that guy that imports all those chinese parts in your motor's, let me know when you get it back, I wouldnt mind a read in case I ever get the notion to build & sell T44 replicas from NZ to Americans who seem to think they should only be made in the USA
I had one other thought about Ken's engine: in an area of 91 octane gas he could just throw in some octane booster, right? I've never used the stuff so don't know how many points you can get with it.

Ken made it pretty clear that he didnt want the hassle of that in his last post above, If it was me I would just get friendly with a local mate in the aviation industry & run some 100 LL @ about 25% with the 91, but thats me, not Ken

 

[Scott Calabro]

I agree Jac.

AVgas is the bomb... its 100% gasoline, not 90% gas 10% ethanol.

You can read plugs with it too!

Plus if you figure a nice 427 Windsor is say 10K and AVgas is $6 a gallon you can drive a sh*#load of miles before you spend 10K.